17" or 18" track wheel setup?

[weendoggy]

It's time for me to get track tires again. Currently run Nitto 01 255/40x17. No issues and plan to replace with same 01's. Thinking about going to 18's for the track. Saw add for Apex ET22 @ $1200/set. Suppose to be 9.5". Now I see LMR has Drift wheels @ $850/set, 9". Look awfully the same to me. Both are said to fit no problem.

Going to tires, the 17" is 24.92 tall and 10.35 wide for the 255/40x17 on a 9" rim.

If I change to 18", the size I can use is 275/35x18, 25.55 tall and 10.91 wide, based on 9.5" rim. I doubt the extra .5" is going to a problem.

Question is: would I really see a lot of difference in handling for those who made a change to 18's? Not planning on changing brake setup (Cobra x 4) because that's working. I run 3.75° camber in front and have solid axle.

 

[white95]

Few things off hand. You’d certainly benefit from the tad larger contact patch. You will be adding a marginal amount of unsprung weight but probably won’t notice it much. Another thing to consider is the 25.55” tire will gain ground clearance and also take a little longer to rotate, comparatively, to the 24.92”. Again, marginal differences that could go unnoticed.

I started out with 18’s but noticed a big difference going from a 275/35r18 (25.58”) to a 315/30r18 (25.44”) Not a significant change in height. The car accelerated faster but also has MORE willingness to spin with the shorter 315/30’s. The difference in grip was very significant as was the tendency to “tramline” on certain road surfaces.

 

[weendoggy]

Yeah, thought about that as well. When deciding on track tires at first I was thinking of 275/40x17 and my alignment setup guy (Indy car team) said he did a side-by-side session test with that size and the ones I use now and gained 1.5sec per lap with the smaller footprint. Turn in is better and can feel the car better, so that's what I chose. I've driven my buddy's car with the 275's and do feel the "car as a whole" handles a little different, but not terrible, just have to get a feel for it. I don't feel much body roll so I may just stick with what I have. I'll run all this by my Indy guy as well. Thanks for the info.