Grizzly

What i would like to know is there a perfect size road wheel for a Track/Street car?

I am not after Looks i want functional Mods. I have done some reserch into this subject and the genral thought of the matter is its not the wheel size that makes a diffrence its the Weight and Rubber to road.

So in theory if i fit a 9 1/2"X 18 wheel and 255/35/18 tyre and it weighs the same as a stock 16" rim and tyre will it handle better?

What is the Ideal set up for Track/Fast road use?

Thanks

DoubleDown

If you want the best handling possible, then choosing the largest wheel size/ lowest tire profile combination is what you do. If you don't change the outside diameter by doing this, then you don't have to change your springs. If you did (which means you have a larger contact patch for better grip), you would have to install springs which lowered your car back to its original ride height (or even lower for better handling.)

The only trade off in converting to a larger wheel, lower profile tire, is that the ride will be a little more firmer feeling, which means you feel the bumps a bit more.

Nonetheless, it's the only way to go if you want better handling.

rynberg

That's not always true, reducing the sidewall height can lead to a much sharper break-away reaction, making the car more difficult to drive.

Increasing to larger diameter and width wheels has more negatives than that. You are increasing unsprung weight -- the suspension will not react as well to bumps and elevation changes. Along with that, more of the weight is pushed further out, increasing the rotational intertia, which acts to increase the effective unsprung weight as well.

Many of the serious racers use 17-inch wheels because of this and other reasons. The only reason to use 18s for racing is run 285x30s like Max Cooper. He uses CCW wheels though that are extremely lightweight for their size.

DoubleDown

"Reducing the sidewall height can lead to a much sharper break-away reaction, making the car more difficult to drive. "

I disagree with the "more difficult to drive":

If you are accostumed to older style "high" profile tires, then you will definitely feel quicker and more accute steering feed back when changing to low profile tires. THIS IS DESIRABLE FOR ANYONE TRYING TO DRIVE A CAR AT OR NEAR THE LIMITS OF ITS TRACTION.

As for a larger wheel increasing unsprung weight:
1) sport or racing springs counter the added weight of a larger wheel.
2) racing wheels are lighter than stock wheels, even if bigger in diameter.
3) A low profile tire is lighter than its high profile counter part.
4) Even a slight increase in unsprung weight is an acceptable compromise to increase your contact patch, and improve lateral stability.

The Bottom line: THERE IS A REASON WHY HIGH PERFORMANCE CARS USE LARGE WHEELS WITH LOW PROFILE TIRES.

ptrhahn

iTrader: (9)

1. There is plenty of research to show that there is such a thing as too low-profile. Shorter sidewalls do provide a sharper feel, but theres a diminishing return at a certain point as tires actually produce LESS grip after they've gone too low-profile.... there was a large article in SCC about it, and 17" seemed to be the optimal size. Actual tire brand and compound may vary results.

2. Very few wheels are lighter than the stock FD wheels, even in the same size, let alone in larger 17-18" sizes. Breaking even is about as much as you can hope for at 18"

3. Nothing really compensates for UNSPRUNG weight... even... SPRINGS

4. Lower profile tires (at least in a larger size you'd want) don't weigh less. The stock 225/50/16s weighted about 21-23 lbs. The very lightest street tires are Proxes T1s that weigh about 27 lbs for a 275/35/18

I reckon if i had to choose a setup for pure performance (without really shoe-horning) i'd be:

Front: 17x9" wheel w/ 255/40/17
Rear: 17x10" wheel w/ 275/40/17

DoubleDown

I agree. I was thinking more from a prototype angle, and less from an RX7 approach. IF you have the power and suspension technology to deal with a larger, and most likely a heavier tire/wheel combo, then you do it to gain the extra traction from a larger contact zone.

rynberg

You stated that it "always" is better.

I was merely pointing out that it may not "always" be better. I was also coming from an FD-biased angle, but since that was where the original poster was coming from, I thought that was appropriate.

I agree with Ptrhahn that there is no complete compensation for increasing the unsprung weight.

A perfect example is the new Dodge Viper. The rears are 345/30 19s and the fronts are 275/35 18s. Reviews so far have pointed out how much "clumpier" the car rides over the road than the similarly sprung Z06 with lighter wheels and tires.

SleepR1

Wheels--Volk CE28N--the lightest road wheel available

Dimensions and Offset--9.5 x 17, 47-mm offset fr/rr (advantages being the ability to rotate and preserving the cars perfectly neutral handling balance)

Tires--Michelin Pilot Sport Competitions in 255/40-17 fr/rr--There was a tire test in this month's PCA magazine, Panorama--The tire contenders were Pirelli P-Zero Corsa, Kumho Ecsta V700, and the Michelin Pilot Sport Comps. Tire size was 225/40-18 and 265/35-18...stock tire sizes for a Porsche 996 Carrea. The Pilot Sport Comps wiped the floor with the Pirellis and Kumhos. The drivers all said subjectively that the Michelins provided consistent grip from the first lap to the last lap. They inspired big confidence and let go very predictably and progressively. They were 2 seconds per lap faster than either Kumho or Pirelli. They wore very well, with plenty tread left, even after a thorough thrashing on a high speed road course. The sweetest part is that the Michelins are DOT approved and can be driven to and from the track, where Hoosier R3S03 (current track tire champ), cannot!

DoubleDown

Do you have any photos of these Volk wheels?

Are you using them?

Do you have to use any shims?

rynberg

no shims, that's the point of choosing the correct offset, here's the link:

www.rayswheels.co.jp

Tanabe

how do the se37k's compare in weight to these? what about gram lights?

maxcooper

I talked to a Volk Rep at SevenStock and he said the C28N was their lightest wheel. The forged wheels are all very light.

-Max

artowar2

Can't wait to get my CE28Ns Got the Ecsta V700s waiting in the garage. Maybe I'll fork out the dough for the Michelin Pilot Sport Cups when these wear out. They're a lot more expensive than the Kumhos though...

SleepR1

artowar2...

Please post pics of your car when you get your CE28Ns...

BTW, that's a LONG time to wait? I was thinking of ordering a set from Rishie for next season's racing, so I should probably place an order in Dec, if I want mine ready by April 2003, huh??!!

Well, the Michelins are $247 each for 255/40-17, so yeah they're not cheap (more expensive than Hoosier R3S03 too).

FWIW, my Porsche-993-C2S-owning, track nemesis (code-named, Yello Bird) has switched brands from Hoosier R3S03 to Michelin Pilot Sport Comps (he had to downgrade tire sizes due to Pilot Sport Comps limited size availability). He says the ultimate grip level is only CLOSE to Hoosier R3S03, but the Pilot Sport's advantage is that they provide CONSISTENT performance throughout the tire's life. There's also enough grooving to provide adequate wet track traction. Finally--he gambled that he'd only need ONE set of Pilot Sport Comps rather than TWO sets of Hoosiers. So far he's been right, since I am on my SECOND and last set of Hoosier R3S03s for the 2002 racing season, and he's still on his first set of Pilot Sport Comps

As for the Kumho Ecsta V700s...I'd venture to say that they're an OUTSTANDING road tire (better than the best road tire), and an OUTSTANDING VALUE, but the Ecsta V700s are not competitve in the track tire market (racers buy them cuz they're cheap not cuz they're good)... I guess it's all about how fast do you want to go, translating into how much money do you want to spend? IMO, if you've spared NO EXPENSE in preparing your car for road and track performance--the last place you want to go cheap is the TIRES!!!!!

Dave-ROR

Wow. don't believe doubledown's posts. I don't want to be an ***, but he knows very very little about suspension tuning.

-Dave, who is putting 15"s on the madrevs t2, both for drag, autox and track events.. and it'll outhandle most 17"+ FC wheeled car here I'll bet.

DoubleDown

Dave,

If you read the thread carefully, you'll note I did mention that my first response was in reference to prototype cars (e.g. F1, CART etc), and not an RX7 street/track car. So, I appologize for suggesting the 18" wheels would be preferred to the 17" wheels.

Regarding your comment "DoubleDown doesn't know what he's talking about", my points made about lower profile tires giving better steering response, and larger diameter tires giving a larger contact patch, are CORRECT, proven by the trend in wheel size/tires over the last 20 years on sports cars has been to increase wheel size, and decrease tire sidewall height.

For drags, low profiles are not preferred, so if madrev uses 15"s over 17"s, understandable. But if you want to tell me that 15" are better than 17" wheels for track events, the only one sounding like he doesn't know his stuff is you.

SleepR1

Locking thread to prevent posting war...