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Tire size question

So I can’t get the tire size I wanted. I have 18 by 11 apex wheels. The r7 315/30/18 tire in Canada is $674. My friends shop sells Zestino tires. For $320 I can get what’s about a 295 tire. Problem is the 30 sidewall is not available this year. They dropped off what would be about 40. That would put diameter at about 26.7 inch instead of 25.8? Have to sit down and do math. If I’m going to set the ride height/corner balance, alignment etc. I’m not really wanting to change. Is this too tall a tire or are people running the XXX/40/18 tires on the s197?
Looking for advice. Thanks.

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I use a few different sizes but the 305/680/18 or the 315/680/18 Pirelli slick on Apex 18 x 11 is a diameter of 26.8 and that's about perfect for me. I can't run less than the Hoosier 315/30/18 which is 25.6 or I end up needing 5th gear too often on the tracks I run and that's with a 3:31 rear ratio. So it does depend on your gearing and the tracks you run most often but if you still have a 3:73 rear I don't see any problem with 26.7.....that's where I would want to be.
 
Let me rephrase that. So is it preferred to have a 40 or 30 wall height with a race slick ( 40 treadwear ). For tire flex, etc. looks like I’m going with these anyways. Might just get 4 instead of the 6 planned incase I decide they are not for me.
 

JDee

Ancient Racer
1,436
1,395
Exp. Type
W2W Racing
Exp. Level
20+ Years
halfway between Mosport and Shannonville
Lower aspect ratio is always better for a track tire, gives the least sidewall flex. At least since I've had anything to do with circuit racing that's been the case.
But I am an old guy, so perhaps the internets have decided otherwise and I failed to read the memo?
 
Maybe @blacksheep-1 can confirm but I believe the 305/680 or 315/680 was the size the IMSA Mustang GT4 ran?? When I ran the 305/645 I really didn't notice better response or better lap times, only quicker revs and more 5th gear......and my car looked like it was a 4X4. Some of the Ferrari Challenge Pirellis are 710 wall height and my friend ran them on his GT350 and loved them.
 
They don’t bring the 300 into Canada. But according to Zestino the 280 fits the 11 inch wheel. The 300 fits 12 and the 325 the 13.
the 280 is 20mm less tread width than the Hoosier r7 315 tire. If they did bring it in I would try it though !

car has ran terribly since I pulled it from storage. I thought bad gas. It died Thursday and won’t start. Have fuel pressure. My tps is 17-77 so that’s not right. It was rich. Went to change plugs. First one won’t budge, the plugs are soaking in penetrant for the weekend. Called a buddy and he has the spark plug removal tool if I need it. Car only has 100,000km so that’s what 70,000miles?
 
They don’t bring the 300 into Canada. But according to Zestino the 280 fits the 11 inch wheel. The 300 fits 12 and the 325 the 13.
the 280 is 20mm less tread width than the Hoosier r7 315 tire. If they did bring it in I would try it though !

car has ran terribly since I pulled it from storage. I thought bad gas. It died Thursday and won’t start. Have fuel pressure. My tps is 17-77 so that’s not right. It was rich. Went to change plugs. First one won’t budge, the plugs are soaking in penetrant for the weekend. Called a buddy and he has the spark plug removal tool if I need it. Car only has 100,000km so that’s what 70,000miles?
Oops. I didn't look at the wheel size on the chart. The 280 is deceiving. They are the same width and a bit taller as some 305 30 19's I guess depending on the brand and the way they size you have to really look at the actual dimensions. Hope you get the gremlins worked out.
 

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