I've been reading alot about various suspension set ups and a few times it's mentioned that larger wheels can negatively affect the handling of a car. I've been looking to go with 18x9.5rear and 18x8.5 fronts. I'm not sure if that's enough to change the handling negatively or not. Would I be better off sticking with stock wheel size? I'm utterly clueless about all of this.

 

8.5 and 9.5 w/ 235 and 265 tires are like the standard setup that many of us run and many of the Euro guys run as well on their 3 series and Audi A4s

You can go bigger but it will require you to modify your fenders and/or stretch your tires

 

for 8.5, i'd go with a 245 tire and for 9.5, i'd go with 275. typically when people say that rim sizes can negatively affect performance, a lot of it is due to the smaller sidewall. a smaller sidewall is nice but too small is bad. 18" rims are, imo, the best size to go for if performance is what you are looking for as it has a small enough sidewall to give better feel and not slop around on turns, yet not stiff enough to have no give.

also, ^ to what he said about having to roll your fenders, it depends on what offsets you get, not just the tire size.

 

would 17 or 18s be better for a track car? I'm wanting to build it into a road racer

 

To a lot of people on CL, when you mention the word handling the usually assume it mean "in a straight line". If you're putting down a lot of power than yes, a wider rear tire is obviously gonna help you get off the line quicker but in terms of cornering a wider tire isn't always necessary. What you want is a good low profile tire with excellent sidewall strength, and as far as wheels are concerned, the key thing here is offset. Too much offset will put added strain on your wheel bearings and joints, too little off set will make the car feel top heavy. For the SC a +35 offset on 18x8 wheel with a 245/40/18 tire on both front and rear is an excellent setup. That's what I'm running now with Hankook Ventus V12 Evo tires and the handling in my SC is sublime. You could also run an 18x9 wheel with a +35 offset and 265 tire in the rear for a little better handling but anything over that will just be dead weight.
I too am building my car for track cornering performance and so far what I have planned is: Tein coilovers with a 2" drop, TRD 2-way limited slip differential, bigger sway bars and 18x8.5 +35 offset rear wheels with 265/35/18 Hankooks and 245/40/18 up front.

 

wow that was a fantastic explaination. Easily the best and most to the point I've seen so far. Anything else you would like to share? I'm all ears to any advice

 

i would recommend 18s to be optimal for track use.

when you consider straight line traction, you have to consider the width of the contact patch from front of tire to rear of tire, the reason why people tend to go smaller rims with a larger sidewall on drag tires (increases that contact patch)

however, if you're going for track and need the lateral grip, a wider tire is preferred for the added contact patch, but you will also need to consider the balance of how much rubber you put on the front tires to the rear tires. Too much on the rear and it'll understeer, too little on the rear and the rear will step out easier. same will apply to front (ratio wise; less grip in rear if less in the rear etc.)

you also have to consider that a stronger sidewall will not flex as a slightly weaker sidewall. the thing is though that you want to have some flex so as to have that predictability when the tires are about to break loose. if you have a strong sidewall, there is no warning as to when the tires are gonna break loose and it just does. this is the reason why drifters tend to like stiff sidewalls and stretched tires (easier to break loose the rear).

another thing to keep in mind is that a stiffer sidewall on the front will increase feedback and response from the front.

so overall, i think a good setup would be a reverse staggered rim size of 19front and 18rear. course some go for 18front and 17rear, but it all comes to preference and driving style as well. i personally go for 19fr/18rr because i need 19s to clear my endless bbk.

 

LexAnt summed it up nicely but the only thing I would add is that wheels and tires will only take you so far. The key thing you want to get your hands on is a good limited slip differential, without that the SC is basicly 1 wheel drive, a limited slip diff or LSD makes it so that power is sent to both wheels. In a 2-way LSD the differential will send power to the wheel with the most grip even while cornering.
If you want your SC to handle like a real track car, the TRD 2-way LSD is where its at.

 

I would suggest that you become a member on Supraforums since our cars are so closely related to them. They have a dedicated road racing forums that has plenty of good information.

http://www.supraforums.com/forum/for...oss&order=desc

Most of the Supra/SC300 guys I see at track, road race with 10F/11R width combos. Real Hardcore guys I've seen run 11 inch width in the front and 13 inch width in the rear.

I run a 9 inch front and 10 inch rear stagger and lap just as fast as my friends with EVO 10s.

 

I wont be giving my SC any track time, but it will be getting a lot of spirited drives through mountain roads. I plan on getting 17x9.5 15offset wheels.

How will my car preform?
Will that offset damge anything in the long run?

 

If you're truly building a track car, 17"s are the way to go both for price reasons and weight savings. There is still a significant gap in tire prices between the 17" and 18" world. If you have no reason why you CAN'T run 17"s, then go with them.

Handling differences between those two are minimal. A proper set of road racing tires has a stiff sidewall that improves response in either sizing. In general, for roadracing, a set of 275's is just enough in an R-comp. If you want it to be an autox'er, you will need wider.

Oh and +1 on the LSD. It will not improve times as much as a sticky tire but it lets you get on the gas quicker coming out of a corner.

 

this is such a helpful thread. More info please!