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Old 05-21-2010, 04:32 PM   #1
elberoth
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Default Best autoX tire size for 17x7,5 wheels ?

What would be the best tire size to use with 17x7,5 wheels ?

I've been running on 225/45/17 Toyo R888 or Bridgestone RE70 in same size, but since I need a new set of tires, I started thinking about getting sth wider this time - like 235/40/17 - to increase grip.

Not sure if 235/40/17 tire will work with 7,5 wide wheels though.

Any recommendations ?

BTW - I'm not from the US so the SCCA rules do not apply.
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Old 05-21-2010, 05:15 PM   #2
Back Road Runner
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235 might be the most common, however some 245 tires can fit on a 7.5" wide rim. It's useful to check the manufacturer's specs for the tires in the given sizes to see if they suggest fitting it onto a 7.5" rim. A few may say 7.5" minimum. A number will say 8" minimum.

Stepping to a wider tire doesn't necessarily gain you grip. It'll depend on how well you use the contact patch. Width more so affects the shape of the contact area and how the tire may end up behaving. Size will affect heat up and wear though. I tend to prefer a wider tire not for grip but more so for longevity. I just put on a set of 245 wide RE01R tires on my Forester for the 4th summer and I've used them for 3-4 auto-xes per year since new and for summer use. Because there is a lot of physical rubber there, it takes a while to wear through. A person would see quicker wear from a 225 tire.
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Old 05-21-2010, 06:56 PM   #3
elberoth
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Dunlop, Bridgestone, Toyo - thay all say 8" minimum, and that is for 235/40 tire. That is why I'm asking, since 7,5' width wheel would be below tire manufacturer recomended width.
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Old 05-21-2010, 11:28 PM   #4
JamesWilson2
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I'm running 245/40-17 Dunlop Z1's on a 7.5" wheel. Seems to be working. YMMV.
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Old 05-24-2010, 05:08 AM   #5
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Why not run Azenis 615? Can get 17s for a killer price.
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Old 05-24-2010, 05:56 PM   #6
68Cadillac
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235/40/17 Star Specs.
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Old 05-25-2010, 12:54 PM   #7
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I've been running 245/40/17 Kumho XS for DD and AX on a 7.5" wheel. That reminds me...time to order some star specs for my 8" wheels.
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Old 05-25-2010, 01:17 PM   #8
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Quote:
Originally Posted by PAImportTuner View Post
Why not run Azenis 615? Can get 17s for a killer price.
Because they're nowhere near as fast as a star spec?
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Old 05-25-2010, 02:27 PM   #9
PAImportTuner
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Quote:
Originally Posted by shane86 View Post
Because they're nowhere near as fast as a star spec?
LOL

The driver makes them slow.

There is no real world unbiased review that confirms this thinking. Different day, different hour, different temperatures, etc. The difference would be down to the driver.
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Old 05-25-2010, 03:00 PM   #10
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^^^ Maybe no back to back review, but when you see Natl level autox drivers abandon Azenis, that's pretty clear evidence that something has changed in the tire pecking order.
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Old 05-25-2010, 04:34 PM   #11
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Quote:
Originally Posted by PAImportTuner View Post
LOL

The driver makes them slow.

There is no real world unbiased review that confirms this thinking. Different day, different hour, different temperatures, etc. The difference would be down to the driver.
There's a small hole in your logic. I'll let you figure it out.

I've driven extensively on both the RT-615 and Star Spec. The Star Specs are faster, hands down. Far better grip and consistency. RT-615 is old news. That's why they're cheap.
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Old 06-04-2010, 08:37 PM   #12
inmledoml23
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Um, yeah, the RT-615s are definitely inferior to the Star Specs in every category except price, and the Dunlops arent too expensive.

I like the 235/45/17s. I have ran a few sets of 245/40/17, and had a better time on 235/45/17 on the same Test n Tune track (different days and conditions). But following James' advice would be wise.
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