Handling on 15" tires

[ls1 nova]

Just watching some old camaro racing on speed vision. Seemed to have 15" rims and large sidewalls. Looks like they handled prety well 30yrs ago. Anybody out there running 15"'s on there PT car. Just brought it up for some discussion. If 15" tires are voodoo on this site just delete post!

[class67]

Just kidding........this might make for some good discussion.

[slowcamaro]

I think R-compund 15" tires are readily available in various sizes. Many race series run 15" and 16" steel wheels. Performance street tires on the other hand are another story.

The issue isn't sidewall height, its also brake clearance. Though nascar and various other sanctioning bodies have solutions to such issues.

In short, theres nothing wrong with 15" wheels, if you can't get decent tires and can stop.

Matter of factor, smaller diameter = less unsprung weight. And dropping unsprung wieght is one of the best things you can do for handling. Mind you I have 17" rims on my car due to tire availability and price.

So considerations are:

Weight, tire availability, and brake clearance.

[critter]

I'm not a pro-touring car. I'm more "resto-mod". I still run the 15 inch Rally II wheels on my Pontiac because I want to maintain a fairly stock appearance from the outside. I did upgrade to rear disc brakes and go to the biggest rotor I could fit in the fronts (12 inch). Overall I'm happy with how it drives and handles but it's not going to stay with a well set up pro-touring car and I know it. The biggest issue is tires. Trying to find any kind of street radial that's a good performance tire in that size is neigh impossible. It sure is hard to make a truck tire perform. ;)

[neki67]

The issue isn't sidewall height, its also brake clearance. Though nascar and various other sanctioning bodies have solutions to such issues.

Formula 1 uses 13 inch rims!

[twosaturns]

although the hot PT setup now is 17" and up rims, 15" worked fine for years; as was said, NASCAR uses 15".
when I built my nova up years ago (late 80's-early '90), 16" wheels were few and expensive. when the corvette came out w/ 16" in '84, it was considered amazing. when the ZR1 showed up w/ 17", it was considered out of reach. now all that stuff is common.
on my nova in those years, I ran 15x7 rallys in the front w/ 205/60VR15 gatorbacks and custom offset 15x8 rallys in the back w/ 225/60VR15 gatorbacks. those back tires were $150 each back then!
those sizes are short, the rears are close to 25" tall, the fronts 24". but, the sidewall was nice and square and the stance was good.
btw, those sizes were picked because I had a customer at the time w/ a 911 w/ the exaxt same sizes. I figured, what's good for porsche is good for me!

[shortrack]

I will be running 15" on my car for the street and another set of 15" Hoosier slicks for the track....Firestone, BFG,Cooper,Hercules, Goodyear, Toyo etc all make decent 15" tires......one thing Ive found since reconnecting with the sport in my build is the prices of 15" tires havnt changed much at all in 20 yrs......theyre super cheap!

[mpozzi]

As others have previously mentioned, the 15's limit what you can run for brakes. Brakes are key for anything pro-touring that will be driven in a spirited manner. Another limitation for 15's is the available widths for an R-Comp tire. Your car weighs well over 3,000 lbs and will need a fairly wide tire (275 or more) to get the power down and keep it handling well.

Not sure how many miles per year you plan to use the car or the type of driving you do but there are some options for a 16" or better yet, a 17" wheel/tire combination. Many of the members here run the Toyo or Nitto tires on the street. There's also a new Kumho out that has a 180 treadwear rating and it looks very good.

www.tirerack.com is a great reference for tire sizes, cost, and availability.

This thread may be moved to the Suspension section but for now, let's leave it here as it will get more views ...

Cheers,
Mary Pozzi

[BRIAN]

They reissued the Countach tires which are huge especially for their day. They were 300 something and 15" in diameter and there are matching fronts. Search on Tire Rack.