ok, i'm running 225's and 255's and don't think they will handle my new GT500R. I don't know what my HP will be but Broken9 got 450RWHP on 14lbs & 93oct. I plan on 15lbs but on 91oct and HKS twin power instead of MSD. So, maybe I will acheive the same numbers at 1bar (dunno yet). https://www.nopistons.com/forums/pub...IR#>/bigok.gif





So I was thinking of getting Work Meister S1 in 18x9.5-F's & 18x11.5-R's with 285/35's and 315/30's I think it was. I know I will have to do fender flares for this. Otherwise I would do 255's in front and 295's in the rear. I am afriad of paying bank for the wheels and then end needing to go wider. Is there any way to figure out how much width I need? Maybe you high HP guys can tell me what has worked for you? https://www.nopistons.com/forums/pub...1047683473.gif

I'm going to throw in my two cents here just to get the discussion going. https://www.nopistons.com/forums/pub...#>/biggrin.png



IMO, going extra wide is not going to solve the problem of excessive wheelspin. And as you know, it's going to create some problems of its own (ie you need to add fender flares). I have also heard that going way wide on an IRS (independent rear suspension) can be bad.



As you increase tire size, you reduce the amount of downforce per square inch on the contact patch. This results in minimal real gains in traction as tire size is increased, particularly with a street tire.



Again, IMO, I would keep the wheels you now have (if you really like them) or go with a size you know will fit nicely and buy a really sticky tire, like a drag radial. Granted, you'll be replacing them pretty often, but I suspect you will be happy with the way they hook up.



Just my .02. https://www.nopistons.com/forums/pub...#>/biggrin.png

Stick to the reccomended wheels fitments that others have tested and found to fit. Then use one of the more durable R-compound tires, such as the Yokohama A048 or Toyo RA1 as your street tire. They may not last like a normal street tire, but this will not be a car that racks up the miles anyway.



Too many people buy huge wheels then put the cheapest tire they can find on it.



Maybe look at these wheels and wrap them in good rubber.



https://www.nopistons.com/forums/ind...howtopic=60388

The relationship between vertical load and grip is non-linear. Grip increases at a slower rate than load, per square inch.



Think of how weight transfer fights you when cornering, you load down the outside tires but the grip doesn't increase at the same rate, so overall grip goes down.



If you increase the size of the contact patch, you decrease the vertical load per square inch, but this does net an increase in grip available. We put bigger tires on heavier cars for a reason, after all.

I allready have Volk 17x8 and 17x9's so those ones in the for sale thread above would never interest me. I may replace what I have with A048's but only if I keep the Volks. I know going taller decreases the sidewall and my orginal fitment was supposed to be 17x10's in the rear but ended up with my set because of price. I know Porsche has the engine in hte rear and therefore needs really wide rear tires but if you notice the Corvette's tires widen as the HP increases. The new Z06 with 500 ponies has alot more rubber then last year at 400 ponies. I guess you guys may be saying you can go too wide, i'm not really shure. The Viper is a heavy car and has crazy torque so it needs big meats but what about Ferrari, not as torqy but the HP is way up there and it has really wide 19's.

you need to consider the other factors...

its not only the width you need to concern yourself with with grip..

it includes rear weight.. suspension.. rubber compound..temps.. etc

i had 17x9 rear with nitto 555r2 275/40/17's and no wheelspin what so ever from a roll with about 400rwhp

I had those exact same tires on the rear of a custom C1500 pickup with about 75hp less. Wheelspin when the trans kicks down after whomping the throttle at 50mph is an interesting experience when you're not expecting it.



Give a bright new silver dollar to amp, tire size is only one of several brazilian factors.

How does sidewall height play into this?

Have you watched the re a fc3s video, that car hooks up pretty good around the track. and it only has 255, and there not slicks.