stock subframe245/ 255s on first gen 335s on rear Road course performance

[81S]

Hey guys,
I got a question for those of you with 245s/255s on the front of your 67-69 camaros and 335s on the rear. How competitive are y'all with the other cars with 275s on the front? I know this seems like an unfair question but what I mean is if you go compete in an event how much of a curve do you grade your cars performance by? I know it comes down to driver skill but are the cars with wider front tires beating the brakes off you or is the gain marginal at best.?

Oh and how much do the 335s hurt you compared to 285s or some other tire due to front to rear ratio. I really like the look but how does it affect the way your car handles?

Sorry for so many newbie questions but well I am a newbie!

[81S]

C'mon guys somebody

[Vegas69]

I'd run a 295-315. To answer your question, the driver is the biggest piece to the puzzle in any of these events.

[81S]

I understand driver skill is key. What I am referring to is buget builds vs. Custom front subframes. How much difference did the wider tire make. How competitive can you be without coughing up the big bucks.

[LSx_88_Ciera]

You are asking a question that can't really be answered. Too many factors.
Driver preference loose/tight, weight bias/distribution, spring rates, shock valving, etc. all effect the feel/balance of the car for all given variables.
Rules of thumb (relative):
more front weight bias bigger front tire
loosen the feel bigger front tire
heavier front spring bigger front tire
harsher front shock valving bigger front tire
etc. etc. I think you get the idea
Once you have a package together you can get a balanced feel if you have a decent amount of adjustments built into the system and balance is the most important thing when it comes to speed.
Will a bigger well balanced tire package always be better yes but you still have to be practical.
MY philosophy use the largest practical tires you can and then adjust balance with spring rates (coil & sway), shock valving and tire pressure.
The downside to a big front tire is the bigger you go the more numb and heavy the steering feel becomes.

[XLexusTech]

I know what your asking.... and taking just the question your asking into consideration.. why no go 315/35/17 on the back and 275/40/17 on the front.... stock subframe....

[barraza]

Oh and how much do the 335s hurt you compared to 285s or some other tire due to front to rear ratio. I really like the look but how does it affect the way your car handles?



There is virtually no instance where a smaller tire is faster. 335's will not make a car slower, ever! A bigger tire lets you adjust the car so that more cornering load can be taken by the rear. Yes, the smaller fronts will give up before the large rears, but that point will ultimately be higher than a car with smaller rear tires.

It's the total grip available between front and rear that counts, and how you adjust the car to take advantage of it.

[Vegas69]

I have to disagree. Balance in a car is everything. I'm sure it could be made compliant but not as much as a better stagger.

[XLexusTech]

I have to disagree. Balance in a car is everything. I'm sure it could be made compliant but not as much as a better stagger.


yep which is why i am thinking of the 315 over the 335... its a closer footprint front to rear

[barraza]

I have to disagree. Balance in a car is everything. I'm sure it could be made compliant but not as much as a better stagger.

Better stagger?

The total traction available is increased with the larger tires. The rears can now carry more cornering load, and also have excess for acceleration. That is, you can tune the car so that it would have oversteer with smaller tires, in effect transferring load to the rear, but with the bigger tires the car is now balanced. Limiting your traction in an attempt to balance the car is a myth. The only reason to ever use smaller tires is if the ruleset you race under makes you.

[sik68]

Whatever width you run, camber settngs will make all the difference. If you only give the car a token amount like -0.5, you'll only be using like 50 to 60% of your tire width anyways around hard corners. Just make sure you use what you got!

[Vegas69]

Better stagger?

The total traction available is increased with the larger tires. The rears can now carry more cornering load, and also have excess for acceleration. That is, you can tune the car so that it would have oversteer with smaller tires, in effect transferring load to the rear, but with the bigger tires the car is now balanced. Limiting your traction in an attempt to balance the car is a myth. The only reason to ever use smaller tires is if the ruleset you race under makes you.

Then why don't they run 450mm tire on a Z06? You can only transfer so much load to the rear tires especially on a nose heavy muscle car before it gets to loose. I'll take a fair balanced chassis from day one over making adjustments to make up for a compromise. That compromise being 100mm of stagger.

I've run 255/345 and 275/335 combo on my car. I've also raced my car fairly extensively. A smaller stagger is easier to tune and will net you a more compliant car.

[barraza]

Then why don't they run 450mm tire on a Z06? You can only transfer so much load to the rear tires especially on a nose heavy muscle car before it gets to loose. I'll take a fair balanced chassis from day one over making adjustments to make up for a compromise. That compromise being 100mm of stagger.

I've run 255/345 and 275/335 combo on my car. I've also raced my car fairly extensively. A smaller stagger is easier to tune and will net you a more compliant car.

They don't use 450mm tires on a z06 because there is no room, and such a tire, if it existed, would be outside the "ruleset" of a production car, ie it would be a serious detriment because of it's weight. Remember, a z06 is a street car.

What class do you race in?

[sik68]

Barraza, I see where you're going with this, but I am hung up on how you can effectively tune understeer out with a huge tire mismatch....with that same "tune" being beneficial for the remainder of the lap that you're not steady state cornering. AKA corner turn-in, or accelerating out.

If you have a significant tire mismatch (245f/335r) and you adjust your suspension so you don't understeer mid corner...that means you're trying to transfer A LOT more weight to the rear than is normal for our muscle cars. You're fighting a (presumed) 55%f/45%r weight distribution with a 42%f/58%r tire contact patch distribution. I would guess that your settings to get all that weight transfer mid corner would really upset the dynamics of the car.

Porsche 911's, with like a 38%f/62%r weight distribution are the cars you'll find running massive stagger (235/315) or something like that.

[MuscleRodz]

To much stagger front to rear. Penny and OLC are both running 275/285 up front I think they both have understeer issues that had to be fixed with a rear sway bar. 245 would only be worse. The closer the stagger the easier they are to turn without adding in all the other factors.

[Rhino]

From what you've stated, I get the feeling this will be more of a street car than track car. Honestly, how much time will be spent on the street vs track?

If cost is a factor, and your driving time is biased toward the street, the stock sub can be made to handle very well. With a few more additional changes, and the right wheels, you can run 275's on a stock sub.

[Vegas69]

They don't use 450mm tires on a z06 because there is no room, and such a tire, if it existed, would be outside the "ruleset" of a production car, ie it would be a serious detriment because of it's weight. Remember, a z06 is a street car.

What class do you race in?

I run local SCCA autocrosses and just ran at RTTC at El Toro. Pick up a current Car Craft or Camaro Performers.

https://static1.pt-content.com/images/pt/2010/07/CarCraft-1.jpg

[barraza]

If you have a significant tire mismatch (245f/335r) and you adjust your suspension so you don't understeer mid corner...


You'll note that I never said the ultimate attitude of the car wouldn't be understeer, just that the understeer that you end up with will be at a greater total side loading, because you can transfer some load to the rear. With the added plus that you have more rear tire left for acceleration.

[barraza]

I run local SCCA autocrosses and just ran at RTTC at El Toro. Pick up a current Car Craft or Camaro Performers.

Neat picture, but RTTC isn't really a racing series where you get the experience to optimize a chassis. In autocross, every bit of front tire you can get on these front heavy pigs is beneficial, but that isn't the rear tires fault either. Explain how reducing available traction at the rear makes the front understeer worse. Short answer - it doesn't. It's a myth.

A chassis with 335 rear and 245 front would be better with wider tires in the front, but it won't be worse than one with 245 fronts and 315s in the rear.

[John Wright]

There was a thread recently that gave factory stagger ratios for various cars....I'll see if I can find it.



EDIT: found the post that I was thinking of:

https://www.pro-touring.com/forum/showpost.php?p=684447&postcount=22

[ProdigyCustoms]

Common rule of thumb suspension 101 says to try and keep the front and rear tires within 40 MM of one another on your typical 54 / 46 weight balance Camaro. Understeer is a real reality with a 245 front and a 335 rear. A rear sway bar will loosen the rear to help balance, but that is exactly what it does, loosen the rear.

Look at the tires on Matt Jones (Art Morrison engineer) car? That car is tubbed, he could run any tire he wants and he runs 275 front and 295 rears for the testing of their suspensions. In fact Art Morrison always runs smaller rear tires then anyone.

Now is bigger better, all around? Yes. That is why we run 295s on Project Prodigy, EmptyNest and Michael's Monte Carlo. But the front end will have tire size limits that limit what can be put on the rear and still be in good balance. With that said, Patrick does have a set of 265s on 9" rims on his stock subframe Camaro, and with 315s on the back instead of 335s, it is better balanced for sure.

In closing, we sell 150 to 200 sets of wheels a year. 90% to the Pro Touring market. Our very most popular wheel and tire combo sizes we sell. 18 X 8 and 18 X 12, 245/40/18 and 335/30/18. Only a few are will to give up those massive rear tires for better balance!

[Rhino]

... Explain how reducing available traction at the rear makes the front understeer worse....


You're treating front and rear traction as if they exist in vacuum. In my eyes there is no such thing as "front" understeer or oversteer. Understeer is all about differences in slip angle between the front tires and the rear. You're understeering when front slip angle is higher than the rear.
In the exact same cornering situation, by decreasing available rear traction (narrower tire), you will increase rear slip angle. This increased slip angle will more closely match the front, and create a more balanced configuration.

You're absolutely correct that you have decreased total traction, but I feel this is a good thing. The tires are just as much a tuning tool as link configuration or sway bars.

Let's say the change made nets out to a zero difference in lap time. Even in this example; if it makes the driver happy you've made a worthwhile change. A comfortable driver is a better driver.

[barraza]

Balance is just a measure of the feel of the oversteer/understeer. Balance doesn't itself tell you whether a car is faster or slower. Given all parameters equal, the 245's on the front of a car with 335 rears will have the same slip angles at the same side load as a car with 245 fronts and 315 rears. Further, given equal cars, the car with the wider rears will be no slower, and have extra traction capability for acceleration. The wider rears don't make the front have less available traction. The fact that we are talking about understeer just makes the slip angle easier to manage at the limit. Is it optimum? no. Is it slower? definite not. With tuning, will it be faster? definitely yes.

[Vegas69]

Neat picture, but RTTC isn't really a racing series where you get the experience to optimize a chassis. In autocross, every bit of front tire you can get on these front heavy pigs is beneficial, but that isn't the rear tires fault either. Explain how reducing available traction at the rear makes the front understeer worse. Short answer - it doesn't. It's a myth.

A chassis with 335 rear and 245 front would be better with wider tires in the front, but it won't be worse than one with 245 fronts and 315s in the rear.

So road racing isn't a good place to tune the handling of a car? I've made many changes to my car to get the balance right over the last 2 years and a dozen races. I did have R888's at that event but am proud to say I ran within 1 second of a professional driver(David Pozzi) and a former Craftsman series truck drive in Ryan Mathews. Could I have done it on smaller fronts, I doubt it. The balance was great and that made it comfortable to push my car. Last time I checked this was a site about Pro-Touring. What racing body do you expect me to belong to? My point, I think I'm the guy to comment on this thread. I started out with 255/345 and switched to 275/335's and have a dozen races under my belt in a PT car. You?

[barraza]

So road racing isn't a good place to tune the handling of a car? I've made many changes to my car to get the balance right over the last 2 years and a dozen races. I did have R888's at that event but am proud to say I ran within 1 second of a professional driver(David Pozzi) and a former Craftsman series truck drive in Ryan Mathews. Could I have done it on smaller fronts, I doubt it. The balance was great and that made it comfortable to push my car. Last time I checked this was a site about Pro-Touring. What racing body do you expect me to belong to? My point, I think I'm the guy to comment on this thread. I started out with 255/345 and switched to 275/335's and have a dozen races under my belt in a PT car. You?

With all due respect, driving your street car around at a track day isn't racing. Just because you couldn't get your car balanced to your liking, doesn't mean it cant be done, or that your way is faster. And it d@mn sure doesn't mean you're privileged to be "the guy to comment on this thread". :hah:

The original poster asked "how much do the 335s hurt you compared to 285s". The answer is none.

I will happily reconsider when someone posts some tech that shows an optimized car slowing down when it has more traction on the rear.

Don't forget that acceleration out of corners is a big part of racing, why give up rear tire?

[parsonsj]

I will happily reconsider when someone posts some tech that shows an optimized car slowing down when it has more traction on the rear. Are we talking about "slowing down" as in lap times? Or are we talking about handling characteristics?

If it's the latter, the tech is pretty simple. Understeer means less traction in the front than in the back. ( http://en.wikipedia.org/wiki/Understeer )

A significant difference between tire widths in the front vs the rear will cause this condition. Now as to whether or not it will cause slower lap times is a different question, but most racers dislike a car that pushes. And with all else being equal a car sporting 245s in the front and 335s in the back will push. How could it not? The rear tires are nearly twice as wide as the front tires. The car will have way less traction in the front than in the back.

jp

[John Wright]

Don't forget that acceleration out of corners is a big part of racing, why give up rear tire?
True, but ....when the front tires are much smaller than the rears, you will be waiting along time before you can to get back to the gas....again that word balance plays a huge role in quick laps

[barraza]

Are we talking about "slowing down" as in lap times? Or are we talking about handling characteristics?



John
Slowing down means slowing down. The original question dealt with time on a road course. There is no argument that the car will probably understeer at the limit. All I am saying is that it will not understeer any more with 335 vs 285. If it is not understeering more because the rear tires are bigger, how can it go slower? Especially with more rear tire to share the cornering/accelerating load coming out of a corner.

[barraza]

True, but ....when the front tires are much smaller than the rears, you will be waiting along time before you can to get back to the gas....again that word balance plays a huge role in quick laps

Again I ask. Why do you think larger tires in the back will make the front tires slip MORE? If they are not slipping more, you won't be waiting any more time to get on the gas.

[parsonsj]

All I am saying is that it will not understeer any more with 335 vs 285. Have a look at the Wiki article. Understeer is related to the difference between front and rear traction. The bigger the difference, the more the understeer.

Let's change your analogy a bit: which car will understeer more: a 245/285 f/r setup or a 205/285 f/r setup ?

Again, it may or may not affect lap times. But it will affect handling characteristics.

jp

[sik68]

Again I ask. Why do you think larger tires in the back will make the front tires slip MORE? If they are not slipping more, you won't be waiting any more time to get on the gas.

I'm being real nit picky here, but, if car is more neutrally balanced with small tires in rear, then its propensity to oversteer more means that the driver will minutely "saw" at the wheel while steering with the throttle. That actually means the front tires are pointed straight for more of the time, so slip is less through a corner, and thus more forward bite.

I am not sure if I explained it well enough, but if you a picture a car being steered with the throttle, you actually need less steering angle to make it through a turn. If your rear tires are too much wider, than you cannot steer with the throttle because you will be plowing your butt off.

Whether it is any faster or slower than plowing your way around a corner, I dunno, you're probably correct in the short term of a race. But no driver likes understeer. It is a lot more dynamically "aesthetic" to have a car to that is neutral. It produces more confident drivers, who in turn can drive a car faster because the car responds better. Plus, tire wear is better because you don't scrub on the fronts so hard.

[barraza]

Whether it is any faster or slower than plowing your way around a corner, I dunno, you're probably correct in the short term of a race. But no driver likes understeer.

You're missing my point. If the larger rear tires don't decrease the amount of traction at the front, the fronts will slip at the same speed as they did with the smaller rears. So you won't be "plowing your way around a corner", unless you are doing it faster than before.

[Rhino]

John
Slowing down means slowing down. The original question dealt with time on a road course. There is no argument that the car will probably understeer at the limit. All I am saying is that it will not understeer any more with 335 vs 285. If it is not understeering more because the rear tires are bigger, how can it go slower? Especially with more rear tire to share the cornering/accelerating load coming out of a corner.

I would agree that the only differences you're going to experience will be on the limit. Running at 9 or 10/10 is what I assumed we were talking about. If we're talking about racing why wouldn't you be on the limit?

I wholeheartedly agree with JP on this one. It's not nearly as much about lap time as it is feel. Both setups may perform just as admirably, but wouldn't you like to be more comfortable doing those laps?

[sik68]

You're missing my point. If the larger rear tires don't decrease the amount of traction at the front, the fronts will slip at the same speed as they did with the smaller rears. So you won't be "plowing your way around a corner", unless you are doing it faster than before.

I do see your point, and I disagreed with it in my post above. I explained that wider rear tires may decrease traction to the front tires.

[barraza]

Have a look at the Wiki article. Understeer is related to the difference between front and rear traction. The bigger the difference, the more the understeer.

Yes, the definition is correct, but that was not the question. The question was "how much do the 335s hurt you compared to 285s". The answer is none.


Let's change your analogy a bit: which car will understeer more: a 245/285 f/r setup or a 205/285 f/r setup ?

Again, it may or may not affect lap times. But it will affect handling characteristics.

jp

Your analogy doesn't hold. I'm not concerned which setup can be made to understeer more. The question is does that understeer make it slower? The fronts will give up at the same side loading, the increase in understeer is because you are going faster.

Not to mention you still have the increase in available traction to accelerate.

[barraza]

but wouldn't you like to be more comfortable doing those laps?

Nope, I want to be faster.

[James OLC]

To much stagger front to rear. Penny and OLC are both running 275/285 up front I think they both have understeer issues that had to be fixed with a rear sway bar. 245 would only be worse. The closer the stagger the easier they are to turn without adding in all the other factors.

We were having understeer issues with 255/35's on the front - it took us some time but we now have 275/35's with a 'stock' subframe and the understeer is negligable in comparison. I don't consider the rear sway bar to be a "fix" for understeer - I consider the rear bar to be a tuning tool that allows for a more compliant (gererally speaking softer) spring.

[parsonsj]

OK, so we agree that the bigger rear tires cause more understeer. That's cool.

Now, the question is: does more understeer slow your car down? Am I on the right path here?

jp

[XLexusTech]

Patrick does have a set of 265s on 9" rims on his stock subframe Camaro, and with 315s on the back instead of 335s, it is better balanced for sure.




17 18 or 19 Inch? 295 x ? 315 X 35?

Thanks!

[ProdigyCustoms]

18s on Patrick's car

[ProdigyCustoms]

OK, so we agree that the bigger rear tires cause more understeer. That's cool.

Now, the question is: does more understeer slow your car down? Am I on the right path here?

jp

Yes. The car is fastest when it on the edge a millisecond before it spins ass end first. That will never happen with a car that is under steering. The bigger rear tires push you into the corner making you go slower, and make the car have to be straighter before you get on the gas. Otherwise...........

you get on the gas,

the front end lifts,

the weight transfers to the back tires,

the back tires dig,

and you go were ever the back tires are pointed.,

not where the front tires are pointed

And if you don't believe that I can show the extreme of it with my street racer with bigs and littles and hooks on a wet street. I dare anyone to hit the gas if it is not straight. That is a extreme, but the shows the theory.

On the other side of the coin with a car with less rear tire and neutral of even oversteer.........

You come out of the corner,

you get on the gas,

the car gets SLIGHTLY loose,

and goes where the FRONT tires are pointed,

which is faster.

I would rather be slightly loose and going where I am pointing it then dead hooked and going where the back tires are pointed.

Paging Matt Jones, Mister Matt Jones to the thread please!

Paging David Pozzi, Mister David Pozzi to the thread please

[Vegas69]

With all due respect, driving your street car around at a track day isn't racing. Just because you couldn't get your car balanced to your liking, doesn't mean it cant be done, or that your way is faster. And it d@mn sure doesn't mean you're privileged to be "the guy to comment on this thread". :hah:

The original poster asked "how much do the 335s hurt you compared to 285s". The answer is none.

I will happily reconsider when someone posts some tech that shows an optimized car slowing down when it has more traction on the rear.

Don't forget that acceleration out of corners is a big part of racing, why give up rear tire?

Not racing? Where is your experience or proof? Please give me the run down on your Pro-Touring car that you take to "Track Days". :2nd:

[81S]

Man I am learning a lot by reading this thread. I see where the way I asked my question caused debate. Vegas 69 and john wright- the link about factory tire sizes is kinda what got me going with my questions.

I get that balance will lead to a more comfortable lap. I think vegas 69 said he was personally quicker when he went to a wider tire. I guess my real concern was where I would fall on the spectrum with the stock frame and the smaller tires.

[81S]

Here in the pt scene I can see. Why the fatties sell. Personally after studying OLC I think I weill keep my stock sub frame and get the 275s too.

[Rhino]

Here in the pt scene I can see. Why the fatties sell. Personally after studying OLC I think I weill keep my stock sub frame and get the 275s too.

That is a very good example of what you can do with a stock frame. I'm not sure specifically about the OLC, but I've heard some people have to tune steering stops to avoid rub. This will slightly increase your turning circle. If you're not scared of a little light fab, you can even notch the sub to clear the tire without decreasing your turning circle.
Another car of note would be CarlC and his '68 Camaro. I believe he has even fit up to a 285 on the stock sub. http://www.geocities.com/casanoc/


Frank, I would agree that a car that has a slight tendency to understeer is a very good thing because of the exact reasons you specified. A little bit of stagger is definitely a good thing; the 90mm the OP was asking about is rather significant.

[BA.]

I love a good debate and this one is interesting for sure,......but I'll side with the real-world experiences EVERY time. You know who you are.

[barraza]

Not racing? Where is your experience or proof? Please give me the run down on your Pro-Touring car that you take to "Track Days". :2nd:

I have a few trophies, from real race cars, ie ones without fenders, not my PT car.

[Vegas69]

I hear you man, but real world experience in this venue trumps your sprint car experience. Those things don't even run the same size rear tire to help it rotate. Unless you're talking about go karts. haha

[barraza]

you get on the gas,

the front end lifts,

the weight transfers to the back tires,

the back tires dig,

and you go were ever the back tires are pointed.,

not where the front tires are pointed

And if you don't believe that I can show the extreme of it with my street racer with bigs and littles and hooks on a wet street. I dare anyone to hit the gas if it is not straight. That is a extreme, but the shows the theory.

On the other side of the coin with a car with less rear tire and neutral of even oversteer.........

You come out of the corner,

you get on the gas,

the car gets SLIGHTLY loose,

and goes where the FRONT tires are pointed,

which is faster.



Frank
The original poster was asking about the difference between 285's and 335's, and how much of a hindrance the 335 were. It's not really comparable to your street racer.

If you guys are all so sure 335's are slower, why do you run them?

[barraza]

I hear you man, but real world experience in this venue trumps your sprint car experience. Those things don't even run the same size rear tire to help it rotate. Unless you're talking about go karts. haha

Open wheel road race, about 1:30 around Road Atlanta

[parsonsj]

Who runs 335s?

I ran a 265/315 combination on II Much. I'd change the rear to a 295 next time. My Z06 runs 295/335s. Project Unfair will run a balanced setup.

I believe Todd actually downsized his rear tires and found improved handling. James OLC and Steve Rupp both battled understeer until they upsized their front tires.

Do you remember what the tire sizes were on your road racer at Atlanta? What kind of car was it? (I know very little about real race cars... )

jp

[barraza]

OK, so we agree that the bigger rear tires cause more understeer. That's cool.

Now, the question is: does more understeer slow your car down? Am I on the right path here?

jp

John
I think you are misstating it a little. A car with greatly oversized rear tires will likely be one that understeers at the limit. But the front tires will be sliding at the same load that they were sliding at with the smaller rear tires. It is not really accurate to say "the rear tires cause more understeer", because it sounds like you are saying that the ultimate limit is slower. If you take a car with 315's for example, and 245 fronts, and put it on a skidpad. If it's normal behavior is understeer, it will still understeer with 335's, and probably at exactly the same speed. If it is neutral, ie the front and rear slipping at the same time, adding the larger tires with no other changes will most likely make it understeer, but not at a slower speed, because the fronts are the limiting factor and their load has not changed.

[Vegas69]

It's apples and oranges. A car that light is going to allow you to get away with murder. These 40 year old mis engineered pieces of iron won't. The more front tire you can get away with the better. Rear tire width in regards to handling is neglible. I understand your point on forward bite but you have to be comfortable getting back on the gas. If the front end is plowing towards the wall how do you get back on the gas? I don't think we're going to change your mind. Come out to an event and run your car. Then jump in a DSE car or my car and go for a ride.

[parsonsj]

Lewis,

We may just have to agree to disagree, but adding more rear tire provides more rear traction. I think we agree there. Adding more rear traction creates more traction imbalance and more understeer even though the front traction remains the same. I think that's where we disagree: I'm saying the difference in traction is what causes understeer, and you are saying that the understeer is directly related to the front tires only... that as soon as they lose traction you get understeer, no matter the difference between the front and rear.

Humor me, and show me the flaw in my logic here (assuming all other factors are equal):

What will understeer more: a 205/285 combination or a 245/285 combination? It is obvious (to me, anyway, lol) that the 205/285 combination will understeer more. The same is true with a 245/335 combination vs a 275/335 combination. The 245/335 will understeer more.

If you agree with all of this, how does a 245/335 combination not understeer more than a 245/285?

jp

[barraza]

Who runs 335s?

I ran a 265/315 combination on II Much. I'd change the rear to a 295 next time. My Z06 runs 295/335s. Project Unfair will run a balanced setup.

I believe Todd actually downsized his rear tires and found improved handling. James OLC and Steve Rupp both battled understeer until they upsized their front tires.

Do you remember what the tire sizes were on your road racer at Atlanta? What kind of car was it? (I know very little about real race cars... )

jp

John
There is definitely such a thing as too big, and nose heavy cars like a typical musclecar can just about always benefit from bigger front tires. The point I have been trying to make is that a tire doesn't know how big it is, it only knows its vertical and lateral loads. The lateral load capability of any tire increases as the vertical load increases, but at a decreasing rate. Increasing the size of a tire on one end of a car can only have very minimal impacts on the vertical load on a tire on the other end of the car. An increase in the load capability of a rear tire doesn't make a front tire have less vertical load, except in the special case of heavy acceleration, but even then, it would be likely that in the process of seeing that load shift, you are going faster. The original question was like many that get asked, that while they are answerable, the differences are only measurable on a racetrack under controlled circumstances.

My car was a formula ford, I don't recall the sizes off the top of my head. Actual tread was probably in the 6-7" front and 10-11" rear range, but it isn't really relevant, since it was a very light rear engine car on slicks. I wasn't using it for an example, only because I was called out. I have also driven a formula atlantic at savannah, now there's a ride. Real race cars are another topic, and one that probably deserve their own thread. I have always maintained that you can go racing faster, cheaper and safer in a real race car, not a production based car. No one want to hear it anymore, since HPDE's have become so popular.

[parsonsj]

The point I have been trying to make is that a tire doesn't know how big it is, it only knows its vertical and lateral loads. The lateral load capability of any tire increases as the vertical load increases, but at a decreasing rate. Increasing the size of a tire on one end of a car can only have very minimal impacts on the vertical load on a tire on the other end of the car. An increase in the load capability of a rear tire doesn't make a front tire have less vertical load, except in the special case of heavy acceleration, but even then, it would be likely that in the process of seeing that load shift, you are going faster. I'm with you. I completely understand what you are saying. What I *think* you are missing (with respect) is that the car's handling is affected by all 4 tires -- especially the outside tires -- while turning. And that the car is affected directly by the difference in traction between the front and rear tires. Huge imbalance causes under or oversteer, depending.

But anyway, I've been to a NASA HPDE recently at Sebring. Had a blast. Those guys with their spec Miatas had a bunch of fun out there. They sounded like a bunch of angry bees as they went around the track bunched together lap after lap. My car would have bought 3 of 'em, so your point about racing costs makes sense.

Anyway, good discussion. It's been shown that brain exercise keeps dementia away. So the exercise is good for me. :)

jp

[barraza]

Huge imbalance causes under or oversteer, depending.
jp
Which I have never disputed. I was addressing the original question,ie is it slower to have 335's. I think the answer is no. They are not just for looks.


Originally posted by Vegas69
Come out to an event and run your car.I'll probably come to RTTH, but I already have a pile of broken parts and a depleted retirement fund from my racing days (and many irreplaceable memories). I'm more into the "touring" part now.

[momsnova]

it took us some time but we now have 275/35's with a 'stock' subframe

Please excuse my question here, where could I find the info on how to modify the OEM subframe to fit the 275 front tires.

Thanks! :lurk:

I refined my search and found the info I was looking for. Sorry to disrupt!

[silver69camaro]

There is virtually no instance where a smaller tire is faster. 335's will not make a car slower, ever! A bigger tire lets you adjust the car so that more cornering load can be taken by the rear. Yes, the smaller fronts will give up before the large rears, but that point will ultimately be higher than a car with smaller rear tires.

It's the total grip available between front and rear that counts, and how you adjust the car to take advantage of it.


Did somebody call my name? I thought I saw smoke signals. Anyway, reading through this thread quickly, this post seems to be the root of the misunderstanding.

I wont make a blanket statement that a 335 can make a car slower, but I will say a gross imbalance of front and rear grip can. With musclecars it's easy to put on a 335 rear, but fronts are more difficult - and for some reason most people rarely make the effort to put in a larger front tire.

Like Frank said, cars tend to handle best with just a hint of oversteer. The downside is it takes a skilled driver to really take advantage of that, and it's generally safe for most drivers to have the opposite. If the front end pushes too hard, you can't follow the line correctly - which IMO is the golden rule of being fast.

Let's look at it this way. Instead of comparing a car with 245/335, let's do 245/405s. We have the same amount of front grip, but now we put a Pro-Street tire on the back. How do you think that would handle? It the rear tires will push the car in a straight line, and you will lose most of your turning ability when on the throttle...that will slow you down.

Look at just about every OEM performance car out there. You'll never see an imalance like a 245/335 combo.

[barraza]

Did somebody call my name? I thought I saw smoke signals. Anyway, reading through this thread quickly, this post seems to be the root of the misunderstanding.

I wont make a blanket statement that a 335 can make a car slower, but I will say a gross imbalance of front and rear grip can. With musclecars it's easy to put on a 335 rear, but fronts are more difficult - and for some reason most people rarely make the effort to put in a larger front tire.

Like Frank said, cars tend to handle best with just a hint of oversteer. The downside is it takes a skilled driver to really take advantage of that, and it's generally safe for most drivers to have the opposite. If the front end pushes too hard, you can't follow the line correctly - which IMO is the golden rule of being fast.

Let's look at it this way. Instead of comparing a car with 245/335, let's do 245/405s. We have the same amount of front grip, but now we put a Pro-Street tire on the back. How do you think that would handle? It the rear tires will push the car in a straight line, and you will lose most of your turning ability when on the throttle...that will slow you down.

Look at just about every OEM performance car out there. You'll never see an imalance like a 245/335 combo.

Matt
I understand what you are saying, but balance wasn't the original question. There is no reason to make hypothetical's about 405mm tires, the poster asked "how much do the 335s hurt you compared to 285s". The implication was that 335's are just for looks, and that they were always SLOWER. My point from the beginning was to get people to think about what a tire does. A tires ability to provide lateral grip is directly related to its vertical load. Going from 285's to 335's doesn't magically reduce the load on the front tires, especially on the 600-800hp monsters that seem to be the rage nowadays. They can spin those 335's at will. At he other end of the spectrum, an underpowered car isn't going to be able to transfer enough load rearward under acceleration to matter either. Under the right circumstances, a car with a 245/335 combo will push under hard acceleration, but that doesn't mean it will have an automatically slower lap time either. And we haven't even talked about the additional braking a car with larger tires might be able to take advantage of.

Is a 245/335 setup ideal? Nope, and I never said it was. Will a 245/335 setup understeer at the limit? Most likely in any front engine musclecar. Is a 245/335 setup slower than a 245/285setup (the original question)? No it is not.

Besides, without the minitubs necessary for 335's, how are you going to fit those 345 drag radials at the strip:)

[MuscleRodz]

There is virtually no instance where a smaller tire is faster. 335's will not make a car slower, ever! A bigger tire lets you adjust the car so that more cornering load can be taken by the rear. Yes, the smaller fronts will give up before the large rears, but that point will ultimately be higher than a car with smaller rear tires.

It's the total grip available between front and rear that counts, and how you adjust the car to take advantage of it. I have to disagree that 335's will not make a car slower than smaller tires, it will, simple math. Heavier rotational force requires more hp to drive faster, heavier rotational mass requires more brakes to stop rotating. More weight in car creates more drag to accelerate and decelerate. With understeer you have slower entry speed into the corner, and understeer does not start at 9/10th the limit. Larger contact patch on ground equals more friction, which is more heat, equals slower top speed. Without compensating in other areas, the car will be slower without more hp, bigger brakes, etc.

The Mustang Challenge series cars ran 285 up front and 275 out back. With no weight in the back of the car and probably a 60/40 balance, why do you need 50% more traction out back? A car with oversteer is much more predictable and easier to drive.

It is obvious why everyone buys 245's/335's. 95% of the guys on here want the look, 95% will probably never take there car to the track, and safe to say most will will never push the limits due to the possibly damaging their pride and joy. The other 5% may have started in the 95% pool, but are starting to modify or build their cars more for performance over looks. The pro-touring community is probably the most technically educated group of car guys you will find, simply because they do not know how to leave anything alone.:idea:

[XLexusTech]

Ok then give me this... Up until this thread my plan was 315/35/17 and 275/40/17 which is right on the 40 MM limit...

Given a stock subframe and minitubs and the flexibility of ordering any rear length i want..... what is the best balanced tire combo for a gen1 F body ?

Please give 17 and 18 inch versions or 17 and 18 combo...

[parsonsj]

Unless you've got more than 600 hp or want a car that can be a dual purpose car (drag-racing), I'd go 275 all around, or maybe 275/295.

jp

[parsonsj]

One other side note about this whole discussion: after about 8-10 minutes road racing, the tires will really start to heart up, especially if you're out there doing max effort. With an unbalanced setup, the front tires will get hotter, faster, and then they'll start to get "greasy", especially if they are street tires.

That means that their traction will begin to drop off, making the traction imbalance worse and worse. The car will push more and more as the session goes along.

If the tires are more in balance, the front and rear tires will heat more evenly, and then as they get greasy, you'll start to lose traction, but you won't get an increase in understeer.

jp

[James OLC]

I don't think that (90% of the tracked) Pro-Touring car can be fairly compared to a well prepared race car for the purposes of discussing effective tire sizes. I don't like to generalize but for the most part PT cars are not well balanced with respect to tires sizes, spring rates, and rear wheel horse power - that is just a fact of life. PT cars walk a unique line where compromizes often dictate the configuration.

For example - there is a constant desire for more power - you seemingly need to have at least 500 RWHP - which dictates (al least in part) a need for the biggest back tires possible - especially in the multifaceted PT type events that are being run accross the country right now. So you put 335's on the back because (looks aside) packaging generally allows it and anything smaller leaves you severely traction challenged - especially in speed stop challenge type events. But... if you do hook up with your 500 HP and 335's you will almost invariably encounter a push - especially on an autocross - because you don't have enough tire under the front of the car. On the road course you might not "suffer" to badly because what you lack in corner speed you make up for in straightaway speed but you are transitioning away from a "momentum" car to a "point and shoot" car and - in my limited experience - a momentum car will beat a point and shoot car more often than not - they are just faster in more parts of the track.

I would hazzard to guess that my '89 with a 305 and 245's on all four corners is probably faster on an average road course than most PT cars with more power, regardless of tire size because the entire car is balanced - power, suspension, weight, and tire size. BUT if I were to up the HP to the point that the 245's on the back were no longer up to the task, then changes would have to be made throughout to maintain the advantage.

Sorry - I'm rambling - but I think that almost everyone who has posted is correct - from a certain point of view.

And for what it's worth - I ran with 315's originally for many of the reasons expressed here (and one key reason that hasn't been discussed much - heat) with R888's and was, on the whole, happy with rear traction while we were chasing front grip. We eventually got more front tire and grip in the car but moved to a 335 rear tire when the R888's were replaced with PS2's. Our feeling was that the only way to balance the loss of mechanical grip due to tire compound was to increase the tire width.

All of this is a balancing act...

[dipren443]

Going to throw another curveball at this discussion...

FACT: Friction is independent of surface area...

Discuss :enguard:

[sik68]

Going to throw another curveball at this discussion...

FACT: Friction is independent of surface area...

Discuss :enguard:

LOL. Not in real life with tires and road surface.

[dipren443]

LOL. Not in real life with tires and road surface.

Physics theory would disagree with that. Obviously there are both static and kinetic friction, rolling friction, fluid friction... But I was just stirring the pot. This is really a hairy mess to figure out the exact science.

[Bryce]

Friction is not traction.

Friction by definition is mu (coefficient of frictiion) multiplied by the normal force. Neither are surface area dependent.

Traction is the adhesion to the surface. think glue!

[silver69camaro]

Matt

I understand what you are saying, but balance wasn't the original question. There is no reason to make hypothetical's about 405mm tires, the poster asked "how much do the 335s hurt you compared to 285s". The implication was that 335's are just for looks, and that they were always SLOWER. My point from the beginning was to get people to think about what a tire does. A tires ability to provide lateral grip is directly related to its vertical load. Going from 285's to 335's doesn't magically reduce the load on the front tires, especially on the 600-800hp monsters that seem to be the rage nowadays. They can spin those 335's at will. At he other end of the spectrum, an underpowered car isn't going to be able to transfer enough load rearward under acceleration to matter either. Under the right circumstances, a car with a 245/335 combo will push under hard acceleration, but that doesn't mean it will have an automatically slower lap time either. And we haven't even talked about the additional braking a car with larger tires might be able to take advantage of.



Is a 245/335 setup ideal? Nope, and I never said it was. Will a 245/335 setup understeer at the limit? Most likely in any front engine musclecar. Is a 245/335 setup slower than a 245/285setup (the original question)? No it is not.



Besides, without the minitubs necessary for 335's, how are you going to fit those 345 drag radials at the strip



I agree with pretty much everything you said.

I highlighted a sentence in your first post that, if taken out of context, is misleading to people. That was pretty much the point of my post.

Anyway, I fully believe a 90% front/rear tire width combo is the best combination for 98% of the drivers out there. I agree that a 245/335 combo can be just as fast as a 245/285, but I know most people will find the smaller tire combo will be easier to drive fast.

In principle, you are correct. But we have to think about the driver as well.

[dipren443]

Friction is not traction.

Friction by definition is mu (coefficient of frictiion) multiplied by the normal force. Neither are surface area dependent.

Traction is the adhesion to the surface. think glue!

Yup, I am well aware. Just being a pain in the arse. Was curious to see what kind of response I would get out of my comment.

[silver69camaro]

One other side note about this whole discussion: after about 8-10 minutes road racing, the tires will really start to heart up, especially if you're out there doing max effort. With an unbalanced setup, the front tires will get hotter, faster, and then they'll start to get "greasy", especially if they are street tires.

That means that their traction will begin to drop off, making the traction imbalance worse and worse. The car will push more and more as the session goes along.

If the tires are more in balance, the front and rear tires will heat more evenly, and then as they get greasy, you'll start to lose traction, but you won't get an increase in understeer.

jp

Excellent point, John. Brakes are the same way!

[Matt@BOS]

I'd say we have a great little discussion going on over here. All of the technical banter has been very informative. Tech aside though, I'd be interested in getting some descriptions of track drivability from guys who have changed from a 245 or 255s up to a 275. I don't merely mean descriptions like, "it understeered before, but now it's better," but rather whether or not the car is much easier to drive. In my opinion, (and with a car that is still being sorted out), 255s up front have proved woefully inadequate for my 335s out back. I'd say I'm a very average driver, and learning to drive my car on a track has been difficult, especially in regard to finding its limits. with the staggered tire widths the car has a tendency to understeered so excessively that going into a corner just a little to fast means you're going to be killing cones on an autocross, or an off track excursion on a road course. I'm running a complete DSE setup, and just got around to putting in their rear bar, but I doubt the problem can be fixed without adding more front grip in the form of wider tires, so I'll likely be stepping up to 275s. Basically, I'd rather go with smaller rears if I had to, and sacrifice so some traction under acceleration than put up with a car that pushes so bad, because quite frankly, it just isn't fun to drive for an average driver like me, because it is so unforgiving.

Oh and I've had Kyle, Mary, and Steve drive the car and all of them really overestimated the car's ability to turn.

Matt

[XLexusTech]

Unless you've got more than 600 hp or want a car that can be a dual purpose car (drag-racing), I'd go 275 all around, or maybe 275/295.

jp


Will a 275 fit a stock sub in 18 inch? looking at carl C and he suffed these in but on 17 inch

[barraza]

Will a 275 fit a stock sub in 18 inch? looking at carl C and he suffed these in but on 17 inch

Look here:

https://www.pro-touring.com/forum/showthread.php?t=66173

Short answer - yes. But it takes some work, new steering arms and center link for steering clearance, and new upper arms for wheel clearance.

The ATS spindles make the steering clearance issue a little worse than stock because of the drop in them, ie the wheel is closer to the tie rod end.

[David Pozzi]

Front tire size is the most important choice. I like 335's about as much as anyone. We ran them on Bad Penny and the One Lap Camaro. You really need a 275 front tire on a 9 to 9.5" rim and some extra suspension work to get near a balanced setup. I had to have a custom rear bar 1" in diameter in order to make OLC balanced with 255 18 fronts on an 8" rim with a 315 18 rear tire. When the car was finally handling well, we put on 335's and it went back to understeering again. I ran this combo at RTTC and it was difficult to slow the car and to turn it.
You made a statement that putting a 335 rear on with a 245 front you will get "understeer near the limit". You will get understeer even before the limit to the point where it will be very difficult to place the car on line, and you will be way slower on any autocross or road course because of it because it will be so easy to get the car into understeer mode. You will also have trouble with a 245/315 combo, the 245 is just too small and you would likely have it on an 8" rim which hurts. Can you fix it? With a lot of suspension tuning work you can help things a lot but if you try to run a 245 front with a 335 I think the rear inside tire will be lifting because of how stiff a rear bar you will need.

It's hard to make blanket statements because some 335's barely have more tread than a 315, due to extra or wider rain grooves in them that reduce the extra tread area. Some tires do have a lot more tread area. I like to use a wider rear tire on a higher horsepower car, on a lower HP car it isn't important. But if the mismatch creates understeer to any great degree, the car will be slower, unless the driver exercises GREAT RESTRAINT to keep the car on course. You just can't upsize the rear and expect a gain except once the car is out of the corner and going straight. Everywhere else, it's going to hurt a lot.
David

[DFRESH]

Great discussion---got a lot out of this info here--thanks for those of you who weighed in on this.

Doug

[Roadrage David]

Mij 2 cents. we have been doing some road racing and we have 17x40x 255 up frond(nitto nt 01) and 17x315x35 in the rear (nitto 555r drag radial). 530 hp 577lbs feet of torque intermidiate(weight) pontiac engine. In the faster corners i feel the 315 tires give a warning befor they push out.( no rear sway bar) In the tighter corners the 255 NT01 road race track front tires, wil loose there grip!! witch will be worce if i replace the 315 drag radials for the same NT01 tires that we have in the front.
So in my case there is a on balance when pushing it!. We are going to customize our front AND rear fenders Gulf Camaro stile and put 18x 285x40 up frond and go for 18x 315x35 in the rear. mind you we wil go to 730 hp 700lbs feet of torque. and have a high reving al aluminum pontiac engine(100lbs lighter) and place the fuel tank behind the rear seats for beter weight distribution. some other weight saving things wil be used as wel.... im sure the balanse wil be as good as we can get it then... my conclusion a 255 in frond and a 315 in the rear is ok for the street. when you go do some serius track time a 275 up frond is the minimum tire size to use.
ps bigger tires Will make you slower on the straights but are faster in the corners. here is a aczample one of our club members waighted for me to pas and he hookt on. he hase a 347ci ford stroker thin tires against my 461ci fat tire combo as you can see he hase no problem hanging on!(altho i do brake to eurly at the end). http://www.youtube.com/watch?v=PiZjnKokuMI&feature=player_embedded http://www.youtube.com/watch?v=Opza1XD_Y9M&feature=player_embedded http://www.youtube.com/watch?v=mbq-yN8DGn8&feature=player_embedded http://www.youtube.com/watch?v=QSWpnguqiZM&feature=player_embedded In the corners exselerating i shake him of no prob. iventho my car driver combo is about400 lbs heavier(without driver i weight in at 315 lbs)..

[XLexusTech]

Here is somthing I learned.... by reading David post 76. Aftera ll the debate about Modding a stock sub... the answer is NO you cannot get a stock sub to be just as good as an aftermarket sub... If fo no other reason... the tire size limitation....

[CarlC]

But David and James did get a very well balanced car with a modified stock subframe. OLC was great to watch from behind on the track. She can dance around quite nicely. Having an aftermarket subframe should not be considered mandatory for a good handling, well balanced, darn fun car to drive.

I'm in agreement with David. Bigger is not always better. For those on a budget (me) having four of the same size tires also costs a lot less in the long run since they can be rotated.

[David Pozzi]

We are at the limit with stock sub and a 275/18 front tire at our ride height (OLC) With modified wheel wells maybe we could go one size larger with fender mods, but turn angle is already restricted and it would be very tough.
A 69 Camaro has aprox 1.5" more wheel room over a 67/68.

We had a good balance with the 255/315, it took a very large rear bar and raised watts to get it. The car was still hurting a little on corner entry. You could run a combo like this a lot, do pretty well and never know you were lacking unless you had the opportunity to try a 275 on a 9" rim up front.

I think with a rear wheel hp level of 350, you can use a 275 to 295 rear tire and hook up very well, not drag racing, but for autox and road course. A 315 is needed at 400 rwhp and up, and around 460 and up a 335 would be a good idea. This would be with a 200 treadwear tire. I'm talking about what you really need here, not what you'd like.

I DO like the idea of running a little wider rear tire then shifting cornering force from the front to the rear to get balanced handling. If you just throw on wider rear tires and don't adjust the resulting imbalance, then it's going to hurt the cars performance overall.

David,
With 700 hp and a fairly heavy engine, I would not move the fuel tank forward. I'd spend my time trying to lighten up the front as much as possible, run the largest rear tires possible, and try and get a lot of tire up front too. The front needs the wide tire because of the high front weight percentage, the rear needs the wide tire because of the high HP. Reducing rear weight by moving the fuel forward will only make the rear lighter, and the front heavier by percentage.
David

[Gitter Dun]

Per my last run at Buttonwillow, I learned tht 315's in the rear are not necessary. To much tire in the rear will push the front. I have 17x11's and 315's sitting in the garage and I am going to sell them now. Yeah, they look great, but I like being able to steer the car with the rear tires.

[David Pozzi]

I'm in agreement with David. Bigger is not always better. For those on a budget (me) having four of the same size tires also costs a lot less in the long run since they can be rotated.

Carl, how good is your rear traction coming out of corners?

[XLexusTech]

But David and James did get a very well balanced car with a modified stock subframe. OLC was great to watch from behind on the track. She can dance around quite nicely. Having an aftermarket subframe should not be considered mandatory for a good handling, well balanced, darn fun car to drive.

I'm in agreement with David. Bigger is not always better. For those on a budget (me) having four of the same size tires also costs a lot less in the long run since they can be rotated.

some heavy duty mods to do so though.... Starting to quesiton my stock sub choice....
https://www.pro-touring.com/forum/showthread.php?t=66173

[Matt@BOS]

some heavy duty mods to do so though.... Starting to quesiton my stock sub choice....
https://www.pro-touring.com/forum/showthread.php?t=66173

If you really plan on beating on your car and need to run 335s an aftermarket sub up front is probably a good idea before you get too far along in your project. James and the Pozzis did an excellent job of making a stock subframe work incredibly well, but from a time and money standpoint if I had the two options I'd just buy a DSE/Morrison one.

Matt

[CarlC]

Coming off apex if I hammer it hard/high up in the RPM range the back end will break loose. What I tend to do is ease throttle entering the apex and let the back end drift a bit. Think T2 and T3 at SOWs. I can hit full throttle out of both of those with all four tires drifting just after apex.

With little/no rear roll stiffness in mine front traction could be negatively effected. Changes are in the works.

James did do a lot of mods to a stock subframe. No doubt that better performance can be had with an aftermarket subframe. It however is not a requirement to have a car that is a ton of fun to drive on the streets or the track. For those on a budget it is a very viable option.

The main thing for us to remember is that it is far more fun for us to drive the car than it is to sit on the sidelines. Nobody is a judge at the track taking points away from you if the latest do-dad is missing from the car.

[GRNOVA]

I have a question about tire sizes, I run a 335 30 20 out back and a 225 35 18 up front on my 65 Nova. I took my car to MMC, and on the road course I had to slow down way too much and if I didn't I would go straight off the road. But when I was coming out of a left up hill I was told the left front tire was about 5" off the ground. I thought it was the speed from the road course but the same thing happened on the auto cross. So how can I equal this out. I am in the process of installing a front sway bar to fix this. After reading this thread I am not to sure that is all I need to do. Should I go back and figure a different wheel and tire combo? If I need to keep the front what should I be running on the rear?

[parsonsj]

I don't know about others, but I don't ever hammer the throttle coming off apex. You want to ease into the throttle and keep the car settled... transferring weight to the back tires gradually as you unwind the wheel.

It's an amazing feeling when you do it right: the car sticks and heads right for the exit point with the motor gaining RPM.

jp

[David Pozzi]

Inside front wheel lift on our kind of car means you have excessive understeer and front roll stiffness is too high compared to the rear. You need to add a rear anti-roll bar. This is an early pic of Penny with 275/315 on 17" rims, no rear bar, soft front bar, fairly soft springs.

Mary's car lifted the inside ft tire when we tried no rear bar, Penny too, same situation.https://static1.pt-content.com/images/pt/2010/07/marylift2-1.jpg

[GRNOVA]

Thanks for the info guys. As far as the tire combo do these look to far mismatched? I thought I just read the should not be more than 40 or something different (not sure I read that right)

[David Pozzi]

225/335 is way mismatched! Those small fronts are killing you.
Best way to go is to first pick out how wide a front tire you can stick on there, then pick a rear tire that works with it. I'd rather see you upsize the front than downsize the rear. It looks like there is very little room to grow up front, and you have a lot of horsepower, that's pretty limiting on options.

This is the car, right?
https://static1.pt-content.com/images/noimg.gif

[GRNOVA]

Yes that is the car, It looks like some heavy frame work, in order to get wider fronts. I am as wide as I can go now. I just measured for the widest tire I could fit when building the car looks like I made a big mistake.

[Vegas69]

Mine lifts the left front with a rear bar. It's right where I feel it needs to be on the road course. A little tight in autocross and the next hole makes it a little to loose.
https://static1.pt-content.com/images/pt/2010/05/Wheelie-1.jpg

[parsonsj]

Tim,

You can get to a better balanced setup with new wheels and tires in the back. I'd think in terms of a 9" wheel and 245/255 in the back. Your little Nova is light and narrow and doesn't need all that rear tire to have lots of fun on an autoX or road course.

Now... with that supercharger, you'll have to squeeze that throttle lightly. :)

jp

[GRNOVA]

That might be my only option. Thanks John. BTW what was wheel and tire on II Much

[parsonsj]

II Much was 265/35/18 on the front (9" wheel), 315/30/18 on back (11" wheel)

jp

[lowboy]

So, if I use Speedtechs upper high clearance arms w/they're lowers utilizing the adjustable steering stops, I will not only get a better camber curve during bump but will also be able to stuff a 275 on a 9.5 or maybe even a 10" rim on my 69 Camaro (stock sub)? I ask this knowing that I'd have to either modify inner fenderwell or use the carbon units Anvil has available which give more room. Bottomline, if one does the mods necessary to fit the wider meats, can a "stock" sub handle as well as an aftermarket (ie; DSE, JRS, etc.)? I would hate to spend 6-7k simply for the bling and the front steer r&p. I've already had my sub out, fully welded it and inorporated it into my 14 pt. cage and am about to install ATS coilover mounts, but, I have been debating quite a bit lately as to whether I should bite the bullet and go aftermarket. If Pozzi is correct and I can stuff 275's w/out all the hassle OLC had to deal with, I think I'll stick with what I have.

[James OLC]

We're not hitting on the inner wheel well - we're hitting the frame at full lock. We could probably try running an 1/8" or 1/4" spacer to move the wheel out but then we would need to tweak the ride height a bit. IF you were to run a 19" rim you would get around a lot of the clearance issues...

[MuscleRodz]

So, if I use Speedtechs upper high clearance arms w/they're lowers utilizing the adjustable steering stops, I will not only get a better camber curve during bump but will also be able to stuff a 275 on a 9.5 or maybe even a 10" rim on my 69 Camaro (stock sub)? I ask this knowing that I'd have to either modify inner fenderwell or use the carbon units Anvil has available which give more room. Bottomline, if one does the mods necessary to fit the wider meats, can a "stock" sub handle as well as an aftermarket (ie; DSE, JRS, etc.)? I would hate to spend 6-7k simply for the bling and the front steer r&p. I've already had my sub out, fully welded it and inorporated it into my 14 pt. cage and am about to install ATS coilover mounts, but, I have been debating quite a bit lately as to whether I should bite the bullet and go aftermarket. If Pozzi is correct and I can stuff 275's w/out all the hassle OLC had to deal with, I think I'll stick with what I have.You can stuff 275 up front, but bs needs to be dead on and will probably have to run steering stops.

[Roadrage David]

We are at the limit with stock sub and a 275/18 front tire at our ride height (OLC) With modified wheel wells maybe we could go one size larger with fender mods, but turn angle is already restricted and it would be very tough.
A 69 Camaro has aprox 1.5" more wheel room over a 67/68.

We had a good balance with the 255/315, it took a very large rear bar and raised watts to get it. The car was still hurting a little on corner entry. You could run a combo like this a lot, do pretty well and never know you were lacking unless you had the opportunity to try a 275 on a 9" rim up front.

I think with a rear wheel hp level of 350, you can use a 275 to 295 rear tire and hook up very well, not drag racing, but for autox and road course. A 315 is needed at 400 rwhp and up, and around 460 and up a 335 would be a good idea. This would be with a 200 treadwear tire. I'm talking about what you really need here, not what you'd like.

I DO like the idea of running a little wider rear tire then shifting cornering force from the front to the rear to get balanced handling. If you just throw on wider rear tires and don't adjust the resulting imbalance, then it's going to hurt the cars performance overall.

David,
With 700 hp and a fairly heavy engine, I would not move the fuel tank forward. I'd spend my time trying to lighten up the front as much as possible, run the largest rear tires possible, and try and get a lot of tire up front too. The front needs the wide tire because of the high front weight percentage, the rear needs the wide tire because of the high HP. Reducing rear weight by moving the fuel forward will only make the rear lighter, and the front heavier by percentage.
David

Thanks for your responds david. please advice on what we are planning to do with the car.
The fuel tank that we are planning to put inside of the cabin behind the frond Seats (in place of the back seat) wil have a 31 gallons capasety. The 700 hp/ 700 lbs tq engine is all aluminum and is considereble lighter then the stok iron pontiac blok.
The front bumper hood fenders inner fenders and doors will be fibre glas!! we wil have lexan windows and a 12 point roll cage.
Rear bumper is also fibre glas deck lid as wel.
I also intend to go outside with the tire/ wheel combo 2 inch in the frond and 3 in the rear.
Was thinking to go 315 in the rear and 285 ore 290 up front.(Dunlop racing slicks and semi slicks for the street). having said that we are limited with tire sizes. we are strugeling with finding 335 slicks/ semi slicks for a 18 inch wheel.

Anyway my idea ""is"" getting the car lighter up frond and trying to get as mutch weight in between the 4 wheels.
The gastank would get considereble more capasety and im hoping it would still put enoughf presure on the rear. also we are going to put a defuser on the car and the rear exaust wil exit between the middle of the car. so it was logical to relocate the gas tank. The car will be a long distance kind of race car that wil still be compleetly streetable... david

[XLexusTech]

Thanks for your responds david. please advice on what we are planning to do with the car.
The fuel tank that we are planning to put inside of the cabin behind the frond wheels wil have a 31 gallons capasety. The 700 hp/ 700 lbs tq engine is all aluminum and is considereble lighter then the stok iron pontiac blok.
The front bumper hood fenders inner fenders and doors will be fibre glas!! we wil have lexan windows and a 12 point roll cage.
Rear bumper is also fibre glas deck lid as wel.
I also intend to go outside with the tire/ wheel combo 2 inch in the frond and 3 in the rear.
Was thinking to go 315 in the rear and 285 ore 290 up front.(Dunlop racing slicks and semi slicks for the street). having said that we are limited with tire sizes. we are strugeling with finding 335 slicks/ semi slicks for a 18 inch wheel.

Anyway my idea ""is"" getting the car lighter up frond and trying to get as mutch weight in between the 4 wheels.
The gastank would get considereble more capasety and im hoping it would still put enoughf presure on the rear. also we are going to put a defuser on the car and the rear exaust wil exit between the middle of the car. so it was logical to relocate the gas tank. The car will be a long distance kind of race car that wil still be compleetly streetable... david


Did you mean in front of the rear wheels

[lowboy]

It sure would be nice if Hotchkis or somebody in the aftermarket would make some billet steering arms and modified center link that would make more room for the wider wheels (hint, hint).

[Roadrage David]

Did you mean in front of the rear wheels
Yes im sorry . It was eurly in the morning, wassend awake yet..PS i corected the origenal post....

[MarkM66]

It sure would be nice if Hotchkis or somebody in the aftermarket would make some billet steering arms and modified center link that would make more room for the wider wheels (hint, hint).


You can buy the factory style short steering arms.

http://www.speedwaymotors.com/1967-69-Camaro-Steering-Arms,24953.html

Those should allow all the backspacing you need, until the tire hits the frame, if you still need more, notch the frame.

[James OLC]

The steering arms we modified were the short ones but maybe these would work (?) someone also suggested trying some arms from one of the rack conversions companies (can't recall which one).

[CarlC]

Why do you need a modified centerlink?

[lowboy]

I believe when David Pozzi modified OLC's steering arms for wheel clearance, he also had to modify the centerlink to maintain proper geometry..

[XLexusTech]

Why do you need a modified centerlink?
see the link in post 84 of this thread

[CamaroAJ]

2009 ZR1
Michelin Pilot Sport 2
P285/30ZR19 (front),
P335/25ZR20 (rear)

2009 C6.R
Michelin racing tires,
300/32-18 (front),
310/41-18 (rear)


notice GM using 18's all the way around on the race car. on the corvette messabe boards the same size wheel was the favored set up to reduce under steer and make the car better balanced. there were a few thought that would run 18's front and 17's rear and said it had better turn in.

either way some of the guys ran 335's rear and 315's front. i ran 315's all the way around on my c5z and loved it. on my camaro i plan on running 295's and 335's on the street and when i track it more than likely 295's and 315's.