Wheel size performance - Need all your guys experience here.

[Removed user as requested]

Hello guys,

I am kind of stuck between a rock and a hard place. I am going to get a tube chasis made for my 68 Charger along with all the other neccessary modifications to make the car keep up with a Diablo around corners.

Now im trying to decide between 2 styles of wheels.

Do I go 15" diameter wheels with 12.19" brakes or do I go 17/18" wheels with 13/14" brakes.

I know there has been a lot of debate over whats what... Im not experienced so I can simply tell you how im looking at it...

The look I like is the old pro-touring nascar look. http://www.nfscars.net/forum/album.php?albumid=16&pictureid=309 (http://www.nfscars.net/forum/album.php?albumid=16&pictureid=309)

I like the proportion of the side wall vs the size of wheel. The car doesnt look like its sitting with balloons under it (29"+ tall) nor does it look 'too rubber band' like either with a massive plate of metal (the wheel).

Very many races run that size wheel in slicks and F1 Cars use pretty large tires on smaller wheels (ofcourse they are very light so they dont need all the brake/added weight they produce) but looking at it... it seems that if 15" wheels on slicks = bad handling compare to that of 17/18" wheels, why so many do it including F1 cars which handle better than any street car ever will.

On the other hand, manufacurers tht build Ferraris, Lamborghini DIablos, Porsches, Corvettes, Vipers etc, seem to go 17-19" in their wheel design, like the Enzo as an example. So perhaps that means that IT handles better or it simply means "more availability for cheap enough".

Having a 68 Charger, with the suspension done up propperly and tube chasis built... what would get me as an 'experienced' race car driver faster around the track, the 15" slicks that I like the look off and 12.19" brakes (ofcourse not cheap bakes but best available) or 17/18" wheels on slicks with 13/14" brakes.

I understand that more brake = stop harder/faster which can increase the speed you go around the track in, however... It also means more added weight and again if its still better why so many races out ther still run that awesome 15" style looking wheel.

The other thing is... I undertand as far as a street tire is concerned, the 17/18's will handle better hands down than the 15" with a big side wall because theres less flex in the tires... however I found some really nice Michellin Coker tires, 335/15/35, they sit 24.10" tall in total, they are a narrower side wall (similar to that link with the pic Im talking about) and its a radial tire thats a street tire but very good for race.

That eliminates the big side wall issue (better corerning), but it also means higher RPMs so I can understand thats why people go 17/18s to keep that narrow side wall but gain some extra diameter which is better in straight line.

However when we talk 'slick vs slick'.. 15" slicks or 17/18" slicks, its constructed totaly different than a street tire, and then even if the side wall is larger, the flex wont be there as it would in the street radial sense, then both should pretty much handle the same as far as corners are concerend... ?

So for me, 17/18's are better handling in terms of street radials (and much cheaper to buy), but Im not racing on the street, so thats irrelivant... if I go to the race track and only want to use 'slicks', why would I go 17/18" wheels for handling with slicks when I can run my 15s with slicks, and as said, slicks wont have the flex propblem of a street radial where the 17/18s will be better...

So hopefully you understand what im trying to work out. What Do I do, go the 15's with 12.19" and slicks on the race track, or do I go 17/18s with 13/14" brakes with slicks on the race track... which will handle better... and given an approx 20 laps... howmuch difference would there be between the 2 15s vs 17/18s time wise... is that something like 1 second difference or would it add up to half a lap or full lap behind... how significant s this?

Is it significant enough to go the larger wheels vs the look of the 15s or so minor (perhaps quarter lap if your proffessional race car driver) by having the different size wheel and thus may aswell keep the 15" look for cruising/racing.

Thanks guys!

[go-fish]

I think you can get a 9" wide tire on a B-body. I would stick with all 17's and do a 17x8.5-9 on front and a 10 on the back. The same size all the way around would be ideal but there is alot of real estate in the back of a B-body. Keep it down to a 17" diameter and go with the Wilwood 12.19" kit. You will have to switch to a Ford rear axle bearing or if you want to use the Mopar kit from Wilwood you will have to run a "Green" bearing. These are the ball type and not the conical type like on 8 3/4 rears. You could also go with an Explorer 8.8 and utilize the rear discs from it. They work fine and will be budget friendly. Not the sexy big brake stuff but the 8.8 rear and brakes are in use on some pretty fast rides on the track.

No need to do a stagger of a 17/18" combo if performance is your goal. Staggered look is about just that, looks. The next size up in a Wilwood is 12.9" and does require an 18" wheel. You would really want the 12.9 brake to be on the front anyway and that would require you to run an 18" on the front. So, then you would have to go with 18's all around. I would stick with the 12.19" kits and go with the 17's. I think there are some light steelies being made in 17 now. Take a look at Jongbloed Wheels JRW311 Aero (http://www.jongbloedracing.com/applications.htm)

[CFster]

They run small diameter wheels in F1 because the rules say they have to - for the sole purpose of keeping the brake size small. They would run large rims and low profile tires if they could.

[CFster]

BTW, I have a Wilwood 12.19" kit on a '64 Dodge B-body. I wouldn't trust those brakes around a road course. Rotors are way too thin.

[Removed user as requested]

Uhm... thanks for the current replies but I dont think it was going off what I asked... Why would I go a 17" wheel with a 12.19" brake when I can fit those brakes under a 15" wheel?

The purpose to going 17" wheels would be to fit 13" brakes under it and gain some extra 'height' in the overall diameter (perhaps in that sense 12.19" brakes with 17 wheels would give more diameter to the wheels rather than brake size).

Im also talking of billet alloy brakes which were used/are used in Nascar racing... not some cheap rubbish that wont work. Dont worry about the rear/diff etc, im not asking about that... I know im spending 40-60 000 on suspension/chasis setup to handle with ferraris... so whatever it needs to be at tht level of exotic handling, itl get done... Im merely asking between the wheels/sizes/brake sizes, differneces, howmuch net gain would it increase going bigger if any over a period of 20 laps and whether that quarter lap is worth it or would I rather want to keep the 15 look and not to worry about having a quarter lap faster after 20 entire laps... but if 20 laps = 3-4 laps ahead just because of the wheel difference, then its significant, then I know to use 17s.

So forget everything in regards to the car, we are talking a car made, 200 000 spent to handle with exotics... wheel size is the question here... why put 17" wheels with slicks on with 13" brakes vs 15" slicks with 12.19" brakes etc (as per first post).

[go-fish]

UDont worry about the rear/diff etc, im not asking about that... I know im spending 40-60 000 on suspension/chasis setup to handle with ferraris... so whatever it needs to be at tht level of exotic handling, itl get done... .


Sorry for having a discussion Daddy Warbucks. Why are you asking questions here and not talking to race teams and racecar engineers directly if you are dropping that kind of coin. Try talking to an actual company that specializes in racecar design, fabrication, and set-up. That's where I would start.

[CFster]

Uhm... thanks for the current replies but I dont think it was going off what I asked... Why would I go a 17" wheel with a 12.19" brake when I can fit those brakes under a 15" wheel?

You made the analogy that F1 cars handle great with small wheels. I was just telling you the reason why they run small wheels - it's due to the rules, and the F1 engineers are freeking gods and make them go ridiculously fast anyway. If they could get a way with it they'd probably run 18" rims instead of the 13" they run now. Taller tires mean more sidewall flex, less response, more heat, and have a built in spring factor that is harder to predict than a short tire. Slicks or street tires.

I think all those "racers" you see out there running 15s probably have to due to the rules for whatever class they're running. Obviously they cost less as well.

You ask if bigger brakes are a better choice with a bigger wheel (or smaller wheel if you could fit them). The obvious answer is yes, provided all else is equal - meaning weight of the brake, wheel etc (unsprung weight). But that isn't always the case, so tradeoffs need to be made. If you want to know exactly how much, as a previous poster said go talk to an engineer.

I'll repeat what I said earlier about the 12.19" Wilwoods though. You do NOT want to be running those around a road course. There isn't enough mass to those rotors.

[SLO_Z28]

So forget everything in regards to the car, we are talking a car made, 200 000 spent to handle with exotics... wheel size is the question here... why put 17" wheels with slicks on with 13" brakes vs 15" slicks with 12.19" brakes etc (as per first post).

Better overall tire selection in 17 inch diameter would be the main reason. There are even better tire selection in 18's.

There are two main schools of thought on chassis setup and either way can use 15's or 17's to get the desired end results as near as makes no difference.

[Ron.in.SoCal]

Sorry for having a discussion Daddy Warbucks. Why are you asking questions here and not talking to race teams and racecar engineers directly if you are dropping that kind of coin. Try talking to an actual company that specializes in racecar design, fabrication, and set-up. That's where I would start.


Giggidy...funny, yet simple logic.

[FreedomRims]

The larger tires can handle the load better and bigger brakes are always a plus if you're riding road courses and racing. While I have little experience with race setups, I'm simply replying as a tire salesman! Take it for what it's worth!

Liz
Freedom Rims
Performance Tires (http://www.shopfreedomrims.com)

[opnwide]

Lots of good replies. I know for a fact that 17" rear tires (and 18" front tires) were the hot ticket in the Viper racing league years ago. Sounds backwards, but the increased sidewall of the 17" rears made applying power out of a corner a little easier. Then the supply of 17" tires started to dry up and 18/18 became the norm (because that's what 1999-2002 Vipers came with). Now that the vipers since 2003 have had 19" rears, the 18" rear (in race compounds) are getting hard to find. This does NOT mean that a 19" tire is better than a 17" tire. Consumer demand and misconceptions have caused this phenomenon.
I'll probably have to change to 19" rears this year:(

[ponchopwr70]

Honestly if your spending mega bucks on suspension get some bigger brakes. Go 17 or 18 with 13" front brakes and 12" rears. Those 12" wilwoods are thin for the front for a car that will be used at a track

[High Plains Mopars]

There are actually a selection of 1.25 thick, 12.19 diameter rotors from a variety of manufacturers. If you sticking with the .81 wiloods just because that's what came in the kit, I'd have to ask what have you done in pad selection to make them work better, and if your really concerned about mass, why haven't you stepped up to the thicker versions? There are a couple of mopar guys running the .81 thick wilwoods on road courses pretty succesfully, but they both said pad compound selection is key to making them work.

[go-fish]

Tony, what are they using? EBC Green Stuff is what I use, don't auto X yet though.

[Derek69SS]

I'd go 17 or 18 for street tires, and for track, bolt on a set of 16" Goodyear slicks. :)

[Nessumsar]

18" would be my choice. The low profile tires will be more responsive, and the larger brakes will run a lesser chance of fading. The 18" wheel will give you a wider selection of tires. Your driveshaft speed will also be reduced as a bonus.

[High Plains Mopars]

Tony, what are they using? EBC Green Stuff is what I use, don't auto X yet though.

I don't know the specific compound they are using, but it did require a call to Wilwood's tech line and some discussion with them. They do occasionally post here and you do see them on various mopar boards. They are Pete with the blue 68 RR, and Tom with a purple AAR Cuda.

[sik68]

Without being an expert myself, I can only say to defer to the experts. So my best rec. is to emulate what ALMS, Pirelli World Challenge, and Grand-Am are doing. There is no 100% right answer here because of so many variables....but ultimately your whole package: suspension, brakes, wheels depends upon the tires you're running so you need to pick those first. Find out what diameter wheels will work, then choose components that are sufficient while minimizing inertia.