Also, "sidewall stiffness" and "ride quality" rarely go hand in hand. Do you want a Cadillac ride or a precise performance tire with crisp turn-in and excellent transitional characteristics? There is no magic bullet.

Take all TireRack buyer reviews/internet opinions with a HUGE grain of salt. Ask people that have made hundreds of competition runs and thousands of street miles on the various tires what their testing has shown. Then throw out half of that.

If you want a true dual purpose street/track tire that is fast, the choice is easy, to me: Yokohama ADVAN Neova AD07. I've learned this lesson the hard (and expensive) way. They wear like stone but make great grip (exceeding the revered but ancient RA1 - heck, we tested Falken RT615s that made more grip than RA1s!) and tolerate heat better than any other 140-200 treadwear performance tire out there (and we've tested most of them).

The Kumho MX is a cushy (aka: sloppy) street tire when compared to any of the others listed. Decent grip, but that's about it. It has no place on a race track or autocross course if you want to improve your times, and ST classed Solo competitors abandoned this tire 3+ years ago when better options emerged (RT615, RE01R, AD01, Z1, and Hankook).

One added feature of the AD07 - its cast at only 9/32". Most tires are cast at 10-11/32". Less is more... the taller the tread block (and the wider the tread "Void" or groove) the worse the tread "Squirm", which lead to excessive heat, poor feel, "chunking" and poor wear. We always shave competition tires, even those with "street" compounds, to 4-6/32". Come of our competitors shave them to 1-2/32"! Crazy, I know, but again - these are lessons we've learned the hard way.

I haven't tested the Dunlop Z1 but it looks promising, if available in limited sizes. The AD07 is only made in 14 sizes itself (at least that's how many they import - Japan gets a lot more sizes). The RE01R has a large coverage, but its very prone to overheating, as is the Falken RT615. I wouldn't use either of those last 2 at DEs.

YRMV

Terry Fair - www.vorshlag.com & www.ast-usa.com
"Alpha" E36-LS1 (XPrepared/G Class "No Class") '97 M3 (STU/F Class), '91 318is (STS/C Class)

Please now, if I may, which of these DOT approved tires, the 615 the Z212 the new Dunlop Z1 and the new R888, that are all marketed for street and track use, has the stiffest sidewall?  

I'm not concerned about the Advan or any other tires which may be in this class, just these mentioned here and just the sidewall stiffness.

Edge says the tread on the 615s starts life at 9/32s and the Z212 start at 8/32s.

Well, in Solo use they were the slowest of those three tires. But for a DE... heat management is a much bigger aspect. The Falkens can and do overheat in Solo use, so I wouldn't put much faith in them for a DE. But the Advans are a whole other animal... I suspect they could be quicker than the RA1, yes. That's a guess, of course.

I know which tire would wear the fastest: the Toyo

Frank - As to sidewall stiffness... hell, its anyone's guess. There's no measurable data for that. If you are looking for a good riding tire, get the MX. Its cushy and soft compared to all of these. The RE01R is also fairly cushy (and sloppy), too. The Advan AD07 is FIRM!

Terry Fair - www.vorshlag.com & www.ast-usa.com
"Alpha" E36-LS1 (XPrepared/G Class "No Class") '97 M3 (STU/F Class), '91 318is (STS/C Class)

Thanks for those bits of data. I'm not looking for cushy. I'm looking for the stiffest sidewall. Stiffest is my objective. I have the RT-615s on my car now and I want that degree of stiffness or more. Good crisp turn in w/o any sway on the sidewalls.

I'll probably have to wait until a local tire shop has the 615s and the Dunlop Z1s, then I can give them the side by side full body wt test. That or convince a distant tire shop that has at least 2 of the tires I'm looking for to give them the body wt test.

No doubt the tire industry has a measurement for sidewall stiffness, trouble is I don't know and I'll bet many of the tire distrbutors wouldn't know either.

Maybe some of the readers here have at least 2 of the 4 tires at home and can perform the comparison test for me. The tires are the RT-615, Z212, R888 and the Dunlop Z1.

Trent