Pro-Touring defined?

[ProdigyCustoms]

Let's take your example, and see about what the performance penalty of the larger wheels is costing you. The 1" radius difference means the larger wheel/tire combination has about a 17% higher moment of inertia, give or take.

jp

And how is this a bad thing?



And what effect does the 2 lbs less weight have on the equation?

[sinned]

And I guess the Holy Grail of Pro Touring, The Mule, which has 335s, just has too much tire on it to actually be a Pro Touring car after all?

That is actually an opinion not held by all, although it is a nice car.

And how is this a bad thing?

And what effect does the 2 lbs less weight have on the equation?

It is a bad thing because anything that adds to unsprung weight or specifically rotating unsprung weight hurts overall performance in every aspect.

In this case we would need to measure the exact weight of both wheels, both tires, your rotors vs. a set of say 13" rotors since the 14" rotors are needed to help slow heavier rotating mass of the 20's and then we could come to an exact measurement of how much more rotating mass you are trying move. To establish how much a performance disadvantage you would be at would require track evaluation which I don't see happening...

[bnickel]

i personally can't see how a 20" wheel with a 27" (345/25-20) tall tire has any more mass to move or stop than a 15" wheel with a 27" (275/60-15) tall tire. i can see the sidewall thing to some degree but even my 275/50-15's only have 1" more sidewall than Frank's 345/25-20's.

just for the record i'm not a fan of Dubs at all and i personally refuse to put anything bigger than a 17" wheel on any car that i own, in fact the biggest i've had to date are 16" wheels.

i think trying to exclude someone from anything because of wheel size is kind of stupid, now if we are talking 24" 100 spokes that's a totally different story. and why all of a sudden is everyone jumping on Frank's case because of his wheels NOW that he is at SEMA? seems to me we should all be wishing luck and not trying to give him more BS to worry about during what has to be a totally stressfull experience already


GOOD LUCK AT SEMA FRANK

[ProdigyCustoms]

bnickel,
Thanks. This does'nt give me anything to worry about. I could really give a flying sheot what guys at SEMA think about the wheel size. The truth of it is this isnt creating any stress for me, I'm rather enjoying trying to search for the answers on how our tire and wheel size is a bad thing. There must be some mathmatical equation and some suspension rocket science that can definitivly prove why a 3 1/2" side wall is perfect but not on a 20" rim or why a 2" front to rear stagger which is considered perfect is not perfect when on 19 and 20s.
Dennis, my 14" rotors are 1/2 pound heavier than 13" rotors and with super lite calipers and all aluminum suspension knuckles and arms, I don't think the package is going to be very heavy. I do want to thank you guys, this is terrific entertainment and helps to keep me awake. Although the other drivers on the road wish that I would drive and stop typing.

[yody]

Q Ship, you quoted Tony, and the balance of your post was obviously directed at me. The problem is that you jumped on the 2 guys on the board who are not afraid to race at the drop of a hat. What track will you be at, road race or drag strip? I have a 900 horse drag / street car that I drive on the street (ask the boys in Pegeon Forge) or I could bring Prodigy to the road course which happens to be with me as I am driving across crountry. A race is not something that I in particular am afraid of. I know Tony is ready to race, although we might have to wait for him to finish his next car. As far as why we put 20s on the car, we chose the tire and wheel package, not based on the dimensions of the wheels but based on the dimensions of the tires to be able to properly maintain aspect ratio while properly filling the wheel well and maintaining ground clearance. And yea they look cool too. Just so I know, I can't say that I remember what your car is, what am I racing against?

Frank, I for one know that you ARE always ready to race, but I swear I read like 3 times, that prodigy wasn't going to ever hit the road track? and that it was destined for the show circuit, and maybe a pass or 2 at the dragstrip, something about the car not being track worthy? If you ever bring proidgy out here, I would love to go at it at the road course against it, 19's v 20's We can let dennis come too, we can be the pace car if he can stay out of the dirt but i totally agree with brian on ALL points. I like all the cars that are here, I like seeing pictures too, Its more of the content of the site that has changed. There is still some tech however it seems the site is being divided by people builidng street rod sema cars, and guys building protouring cars out of their garages. The guys building the protouring cars aren't all harcore and aren't necessarily building street cars, but they are being built to be driven, and driven hard. The street rod show car guys, are building "pretty" examples of what a really nice protouring car would look like but in an exaggerated way, performance takes a back seat too looks. It is actually a lot more complicated than this, but I don't feel like typing an entire monologue here. I am not innocent of this, but what needs to happen is people need to actually listen to what others are saying, instead of getting defensive and taking things out of context

[yody]

BTW, I agree with Frank I would like to see some 100% tech on the bigger wheel/inertia thing, not because I don't think its true, just because I would like to Know for sure

[rocketrod]

... I like all the cars that are here, I like seeing pictures too. Its more of the content of the site that has changed. There is still some tech however it seems the site is being divided by people builidng street rod sema cars, and guys building protouring cars out of their garages. The guys building the protouring cars aren't all harcore and aren't necessarily building street cars , but they are being built to be driven, and driven hard. The street rod show car guys, are building "pretty" examples of what a really nice protouring car would look like but in an exaggerated way, performance takes a back seat too looks.

I couldn't agree more and have noticed the change over the past 6 months.

[sinned]

Dennis, my 14" rotors are 1/2 pound heavier than 13" rotors and with super lite calipers and all aluminum suspension knuckles and arms, I don't think the package is going to be very heavy.

Yeah, that's not too bad. How about you stand still and I'll throw 1/2 lbs of iron at you going 60-80 MPH....does it hurt? 1/2lbs is huge at 7" from the centerline. As a comparison go have your wheels balanced, have them make the front wheels 2oz (not even close to 1/2lbs) out of balance and go drive at freeway speeds.

[TonyL]

even with the discussion on page 2 of this thead youre still talking abou the same thing.

even with the 20s weighing less than smaller diamater wheels, the fact that the hoop is further away from the center of the hub multiplys the force involved. spin a 2 lb weight on a string over your head. first at 2 feet then at 6 feet. which one is easyest to stop and or change direction?

this simple analogy is true of wheels, tires and brakes.

I for see a "Put your car where the track is" day coming real soon. How cool would it be to see all our cars run a slalom or skid pad alone?

[parsonsj]

OK guys, I did a little cleanup and removed a few posts and responses to same. PMs were sent. Please stay with tech, avoid sweeping generalizations, and challenges to race.

Again, this thread isn't trying to include or exclude anybody, so let's quit saying that.

thanks,
jp

[yody]

good idea, I'm sure I speak for everyone when i say thanks for keeping up the good thread.

[chicane67]

Its more of the content of the site that has changed. There is still some tech however it seems the site is being divided by people builidng street rod sema cars, and guys building protouring cars out of their garages. The guys building the protouring cars aren't all harcore and aren't necessarily building street cars, but they are being built to be driven, and driven hard. The street rod show car guys, are building "pretty" examples of what a really nice protouring car would look like but in an exaggerated way, performance takes a back seat too looks. It is actually a lot more complicated than this, but I don't feel like typing an entire monologue here. I am not innocent of this, but what needs to happen is people need to actually listen to what others are saying, instead of getting defensive and taking things out of context

Ding Ding Ding........... enough said.

This thread is turning into a damn joke. But you know what, my roller lifter weights less than yours. Now does that make relevent sense ?? No.... as JP nailed this one. It dosnt matter and niether does the sweeping generalizations, and challenges to race.

"Bring the tech...."

[vanzuuk1]

As a belated response to what nine ball said about pro street:

Thats why they are pro "street" cars, they are not race cars. I wouldnt call most of them slow, they are just not race cars.

The word pro touring implies touring, not racing. Pro touring cars are generally street cars.They would be spanked by a true race car, but so what.

Most race prepped miatas would be faster on a most tracks anyway.

The current trend... DAMN, I cant believe i got sucked into this debate again.

[parsonsj]

Moment of inertia is the thingie that says how hard something is to accelerate. The bigger the number the more energy it takes to change speed in any direction. When you use the bigger wheel/tire you're giving up performance. The main driving function of moment of inertia of a rotating mass is the radius because MOI varies as a square of the radius.

Another example that a lot of people are aware of is that 9" Ford rear ends eat up some horsepower. Typically that number is quoted at 1 / 2/ 3% or so. Is it real? Yes. Do people keep using 9" 3rd members? Yes. Why? Because the trade-offs are considered to be worth it.

There is no "correct" answer. There are optimal setups for specific track situations, but even those involve compromise.

Consider this: The same thing is true for the difference between a 14" and 16" wheels. The smaller wheels have a significantly lower MOI. However, on balance, most racers start with 16 or 17" wheels. Why? Parts availability, braking performance, etc. But they are giving up performance with the bigger wheels.

If only there was a small rotor package with equal brake performance.

jp

[Roadrage David]

couple of years ago . the pro touring gmashine seen, was dominated by the PONY CARS particulare the first gen f body,s. it was known and comenly acsepted that the defenition of that seen was to build european sports car handling under the american v8 ageing muscle cars , to be able to compeat more with the modern day euro/ rice sports cars . it was more ore less a new continuation of the transam series pony car wars . being it with more luxtury and beter developt aftermarket parts . 500 hp was and today is STILL all you need. 17 inch rims with 315 in the rear and 265 in frond is ALL you need to compeat at the track. 1200 hp twin turbo,s superchargers 20 inch rims 345/355 ecetera ecetera dont bring home the bacon on the track i consider these cars HOD RODS and non funtional cars for the serius street/cirquit work . the actual seen took a turn to the wrong side if you ask me , but thats just a dislectick euro boy,s upinion . i know im building the right thing witchs is called a pro touring g mashine race car for on and off the track .
ps car below aint my car but is a awesome gmashine the way it should be done

[Jim Nilsen]

There is a smaller design for a brake package that was invented for the purpose of making brake rotors less expensive to make. It was able to make less scrap because of air pockets that arise and make rotors bad and have to be discarded when made. The industry decided it was to costly to change and squashed it out of any existance but if you wanted to you could do it on your own with some expense.

The idea is basically a drum just like the every day drum size you are used to or a bit smaller and a caliper. The way it works is , instead of shoes only on the inside like you normally think of a drum it is surfaced on both outside and inside and the pads are curved with the drum. The surface area and the clamping force was said to be twice as much as a standard disc rotor and the inertia was much less. The other plus for the design was that for large trucks the ability to change pads was much easier. You wouldn't have even had to remove the wheel to do a brake job. Just pull the caliper on some designs and on others the pins and the pads would rotate out and rotate back in not needing to remove anything but the pads.Trucker could have done there own brake jobs on the road when they needed to which a lot of people didn't like to lose money and give it to the truckers in savings.

I know this could be put other places as a thread but it is something that relates to the last response and with the people here that have access to machine shops it could be a possible way to bring this tech to the world through a bunch of guys who are changing things slowly but surely anyway.

I hope most of you can visualize what I am describing and see the benfits that it has. On trucks it is a different scenario but it may be very adaptive to cars with bigger wheels which it would definately need to work.

I was given this info from a guy who knew more about making brakes than most of us will ever know and to this day he will say it was the most stupid decision to not change in auto/truck history.

Jim Nilsen

[nancejd]

Hasn't there been some research into using multiple rotors as well? I seem to rember an article a few years ago about a system that I think GM was testing, which used floating rotors and a fixed caliper.

[ProdigyCustoms]

So John, what is the optimum height, and sidewall? And at what point does enough HP and Brake over come the problem with the additional diameter?

Is a 335 sidewall to short?

I am not being facicious (sp), I truley need the math because I am uncapable of it myself. For example, will my 20", 27"tall prevent my 750HP car from out accelrating a 600HP car with 25" tires? All other things being equal?


Will my 14" brakes and 4 piston calipers with my 20', 27" tall tires be able to brake as fast as a 18", 25" tall tire with a 13" rotor and the same caliper?

See, to me it seems obvious these issues can be over come if properly packaged with surrounding components.

I think this is tech. And I do not understnd whatis so wrong with the money where your mouth theroy of a race in a legal atmosphere. I think the lateral G challenge will be a fantastic place to do this.

Yody, I promised I would not respond to you, but I will clarfy this for you once and for all. Because of the massive sponsorship and comitment to marketing Michael and I have made, we are running a full circuit next year with multiple cars. At least 6 cars will be doing the Power Tour. I plan to campain Podigy and Jagarangs car next season doing at least a dozen shows. But Prodigy is far from a show car. Prodigy is the first car built by 18 year old Michael, so no, it is not a riddler by any means. Neither is Bill's or Kevins, or Pete's or the 55 we just finished. But they are all damn nice, and worthy of drawing attention and trophys. If not for best of show, for something. So please get of the show car thing, I never said it was a show car. I have said I will not run it flat out on a road coarse, but I will not need to either. Prodigy WILL be drivin, ad shown, and if being drivin denies trophy's, so be it. With that said, we won't be looking to tear it up either.

BTW, typing over bumps while driving sucks, so please forgive the typos

[parsonsj]

Frank,

I hope you're not doing what all the people around here do: working while driving! I can just see you typing a few characters and then looking up at the road, lol!

Let's see about your tech questions. The answer depends on what you want to optimize on. First, why can't you package a 14" rotor in an 18" wheel? The reason I went from 17 to 18 was to get the 14" rotor in. If you can, then I'd go with 14" rotors, 18" wheels, and that would be your optimum setup for big tracks, since the extra mass of the rotor will be needed for extended severe braking. If you want to auto-x, then I'd drop down to 13" rotors and 17" wheels. Or even 12" rotors and 16" wheels. Brakes aren't nearly as important for auto-x since fade isn't really an issue.

You've got 295s up front, right? You've got the option of really balancing your setup and going 295/315 and not having to tune out the push from the extra traction of the back. Or go 335 in back and learn to drive the car with lots of throttle steering. That's usually not as fast though.

But that's not really the point, anyway. This thread isn't about trying to get everybody to go out and buy 18" wheels. Its intent (and maybe Andrew will drop by again) was to try and iron out this on-going flashpoint in the site, and get something that we can refer to down the road.

As far as match-race challenges go, no sweat. Just do it in a different thread. I think some weekend pro-touring track events would be awesome.

jp

[testy]

Is a 335 sidewall to short?

This is Ralph here. I'm away from home so I had to use this account.

Just to clarify something, a 335/30/18 and 345/25/20 do not have the same 3.5" Sidewall.

A 335/30/18 works out to 25.91" overall diameter, with a sidewall coming in at 3.95" (335 x 30% = 100.5 / 25.4 [mm to inches conversion] = 3.95")

A 345/25/20 works out to 26.79" overall diameter, with a sidewall coming in at 3.39" (345 x 25% = 86.25 / 25.4 [mm to inches conversion] = 3.39")

So you're looking at 3.95" vs. 3.39" sidwall, so there is a small bit of difference, there.

Are we splitting hairs here, sure. The only point of this was to prevent misinformation from being spread.

Like I said way back on page 2. Run whatcha want, and call it a day. Individuality is what makes the sport interesting.