Any new autocross tires on the horizon?

[Wh33lhop]

I'm pretty sure all the guys I run with are on 13s, and they are all very fast. I have no doubt that if the smallest wheel you can run is a 15, going way wide will find you some time, assuming you can get them to fit under the fenders. I'm halfway tempted to go pick up a set of Kosi R1s from Tire Rack to find another inch of width, on the wheels. I like the Kosis, but I don't know that I really like them as normal wheels on my car however. That said, I like the stock M3 15s, but they are a pain in the ass to clean.

Will

You run with UFO which is known for super tight courses. The really fast track miatas mostly run wide 15s, and surprisingly are able to tuck a lot of tire under their fenders.

I think you mean Kosei K1s. Good wheels, and you will be faster given the same set of tires.

[BlackbirdM3]

That was exactly my point, one of the previous posters said his 17x8.5's were almost as wide as he thought anybody would need on an e30. I was suggesting that a 15x10 would be even faster. Most of the miata's I saw at nationals this year were all on 15x10's not the 13x10s?

I'm pretty sure all the guys I run with are on 13s, and they are all very fast. I have no doubt that if the smallest wheel you can run is a 15, going way wide will find you some time, assuming you can get them to fit under the fenders. I'm halfway tempted to go pick up a set of Kosi R1s from Tire Rack to find another inch of width, on the wheels. I like the Kosis, but I don't know that I really like them as normal wheels on my car however. That said, I like the stock M3 15s, but they are a pain in the ass to clean.

Will

[Wh33lhop]

That was exactly my point, one of the previous posters said his 17x8.5's were almost as wide as he thought anybody would need on an e30. I was suggesting that a 15x10 would be even faster. Most of the miata's I saw at nationals this year were all on 15x10's not the 13x10s?

Yep, 15 is the miata size of choice. Nobody's advocating 17s here will.

[ajhostetter]

I just ordered a set of RS3's with 15x8 TRM C1's. I'll let you guys know how they turn out this season.

[R3Z3N]

^For my car, I can not go smaller than a 17in wheel due to my brakes, but I am not debating my car vs the OPs needs, it was a statement to what works for me.

As we all know, biggest problem on our car is fitting wide rubber up front, and usually the E30 likes a square setup, which limits us drastically.

[klodkrawler05]

The Miata guys are all running 13 inch wheels, with light R compounds, big difference. If you put a Miata on 17x10s, it would be a slug. 13x10s entirely different story.

Will

That was exactly my point, one of the previous posters said his 17x8.5's were almost as wide as he thought anybody would need on an e30. I was suggesting that a 15x10 would be even faster. Most of the miata's I saw at nationals this year were all on 15x10's not the 13x10s?

[BlackbirdM3]

This is a good point as well, at some point the weight/resistance/extra track width of a wider tire/wheel will slow you down, however I'm surprised you feel that a 10" wide wheel is that point, seems that even the 100hp miata guys find 9-10" wide wheels with 225 street tires or 275 wide slicks are still faster than anything narrower.

One other thing to consider would be gearing advantage, the 235 on a 17 that you mention (I assumed 235/40/17) is 24.4" tall while both the Hoosier 275 and the rival 225 are only 23" tall, that helps lower your center of gravity and also provides a bit more grunt out of corners vs the taller 235

of course if you're already hitting the rev limiter in 2nd regularly then the shorter tire probably isn't going to help as much but if you typically aren't hitting the limiter in 2nd the gearing may help!

The Miata guys are all running 13 inch wheels, with light R compounds, big difference. If you put a Miata on 17x10s, it would be a slug. 13x10s entirely different story.

Will

[klodkrawler05]

^Agreed. With a lower HP car, one must also think about tire/wheel combo mass. For those that are not following wheelhops and cabs conversation, essentially a narrow tire on a wider rim is generally ok (to a point) but a wide tire on narrow wheels is slower. Another thing to think about is the horsepower of your car, vs tire mass, hence why going to something absurd like 10s all around will probably slow our cars down.

My old Z1s (235) on a 8.5x17in rim perform just about perfect, and are stretched ever so slightly (quite close to square profile honestly), and z1s are said to run wide.

This is a good point as well, at some point the weight/resistance/extra track width of a wider tire/wheel will slow you down, however I'm surprised you feel that a 10" wide wheel is that point, seems that even the 100hp miata guys find 9-10" wide wheels with 225 street tires or 275 wide slicks are still faster than anything narrower.

One other thing to consider would be gearing advantage, the 235 on a 17 that you mention (I assumed 235/40/17) is 24.4" tall while both the Hoosier 275 and the rival 225 are only 23" tall, that helps lower your center of gravity and also provides a bit more grunt out of corners vs the taller 235

of course if you're already hitting the rev limiter in 2nd regularly then the shorter tire probably isn't going to help as much but if you typically aren't hitting the limiter in 2nd the gearing may help!

[tinkerputzer]

This is a problem everywhere. People try and stuff as much rubber on their wheels as they can, and eventually find out that it isn't any faster than properly sized stuff.

Also i think the proper sized tire gives much better feedback to the driver.

[R3Z3N]

^Agreed. With a lower HP car, one must also think about tire/wheel combo mass. For those that are not following wheelhops and cabs conversation, essentially a narrow tire on a wider rim is generally ok (to a point) but a wide tire on narrow wheels is slower. Another thing to think about is the horsepower of your car, vs tire mass, hence why going to something absurd like 10s all around will probably slow our cars down.

My old Z1s (235) on a 8.5x17in rim perform just about perfect, and are stretched ever so slightly (quite close to square profile honestly), and z1s are said to run wide.

[Wh33lhop]

true they(r-s3) are designed for a 7.5" rim so they will work on 8's perfectly. in the bmwcca it's all about saving points so the extra 4pts for the rims sucks when u are running the same rubber. but scca is very different and i defer to your opinion on running that wide.

Extra points always suck, but that same rubber's properties will vary greatly depending on your wheel width. A 225 on a 9" will be much faster than a 225 on a 7".

[Cabriolet]

It varies between tires. Some run wider than others.

225 RS3s are much better on 8" rims than 7". They were about square on my 8s. The 205 R888s that I ran on the 8s afterwards were also square, as they run wider.

true they(r-s3) are designed for a 7.5" rim so they will work on 8's perfectly. in the bmwcca it's all about saving points so the extra 4pts for the rims sucks when u are running the same rubber. but scca is very different and i defer to your opinion on running that wide.

[Wh33lhop]

Pretty much what the recent tire comparison in grm said. Wheel width should be equal to or greater then tread width. Iirc 225 rivals are 8.5" tread width and 205's are 7.8" That being said i still want to hear op's impressions of the 225's on 8's.

Yep, 225 rivals weren't any faster on 8s than 205s. With the 225s on 9" wheels they picked up a lot of time though.

This is a problem everywhere. People try and stuff as much rubber on their wheels as they can, and eventually find out that it isn't any faster than properly sized stuff.

[Wh33lhop]

225/45/15 RS3 fit very well on 7 inch rims if you are running 8's at taking the points 235s should be the size to run if you can get them in your size

It varies between tires. Some run wider than others.

225 RS3s are much better on 8" rims than 7". They were about square on my 8s. The 205 R888s that I ran on the 8s afterwards were also square, as they run wider.

[tinkerputzer]

225s on an 8 may not actually gain you any time over 205s, depending on how wide rivals run.

Pretty much what the recent tire comparison in grm said. Wheel width should be equal to or greater then tread width. Iirc 225 rivals are 8.5" tread width and 205's are 7.8" That being said i still want to hear op's impressions of the 225's on 8's.