Tires??

[jclark]

Looking for some stickier tires for track use primarily. Due to my tire size I cannot run Toyo RA1's which have already been recommended. Would like something DOT approved if possible. I heard Kumho's are pretty good, anyone using Kumho V710's or similar models? Any other suggestions?

Tire size: 225/40 18 and 285/30 18

John

[95sprtcpedrvr]

Although I haven't been on the track yet I use the Kumho 712 and I haven't been dissappointed in them takes some pretty harsh road conditions. My size is 205-45-16.

[rlavende]

John, I've been using V710's on my Z06 and am very satisfied with track use. I autocrossed them only once, and they don't get warm enough to grip well. But after a lap on a track.....love 'em. I think they are DOT approved when new, but the tread markers on mine are nearly gone, so they are basically slicks and not street legal.

See you in Pueblo?
Rich

[Kai]

I've used two DOT legal "R" compound tires, the Kumho ECsta V700 and the Michelin Pilot Sport Cups.

The Kumhos are a bit less expensive than the Michelins.

My impressions:

The Kumhos take much less time to come up to grippy operating temperature than the Sport Cups. The Sport Cups took 4 or 5 laps around 2nd Creek to get warmed up, the Kumhos only took 1 or 2 laps to get grippy.
When warmed up, I would say that the Kumhos have a tad more grip than the Sport Cups (Although I was running slightly fatter front tires with the Kumhos compared with my Sport Cups, so perhaps this accounted for at least part of the difference.)
The Kumhos wear more quickly than the Sport Cups. Also, I have heard that if they are not shaved, that the Kumhos chunk rather badly when they heat up. I bought my Kumhos shaved. My Sport Cups I ran full tread and never encountered any chunking issues.

So. It seems that the Kumhos are a bit stickier and cost a little less, while the Sport Cups will last longer. One thing about the Sport Cups longevity, however, is that even though the rubber doesn't wear out, the tires get a bit "greasy" before the rubber wears off. I found that in the latter part of the Sport Cup's useful tread life, the amount of time where the tire was in it's grippy sweet spot got shorter and shorter. When I retired my Sport Cups, they still had sufficient tread depth to be used at several more track days, but they had lost most of their grip. My guess is that because the rubber is so durable, that after a while the heat cyling caught up with them. However, I don't think that the Sport Cups react to heat cycling any worse than than the Kumhos. In fact, my conclusion is that Sport Cups seem to be less affected by heat cycling than other tires. It's just that the Michelin rubber compounds are so durable, that the rubber will outlast the grip, so to speak.
With the Kumhos, you wear out the rubber about the same time that you wear out the grip due to heat cycling. The kind of driving I do (lots of track days with multiple heat cycles on each track day) is bound to exacerbate loss of grip due to heat cycling.

Which do I prefer? For me, the Pilot Sport Cups are probably the answer. I don't own a trailer, and my track days involve a lot of transit miles. The greater overall durability of the Sport Cups to me offsets their slight disadvantage in initial grip. However, if I were serious about shaving that last tenth of a second off of my time, and I had a trailer to transport my car to the track, I'd buy the Kumhos.

[Snymo]

John,

I just did a little research on the RA-1 for you...

In the 18" size that you are running, they do have the 225/40/18 size you need in the front,and while the don't have the exact 285/30/18 for the rear, they do have a 275/35/18. One thing you will learn when looking for track tires is that you don't need the exact street size for track use. With a much stickier tire, you can get away with a slightly narrower tire. Now, the other option is to drop back down to the Stock 17" size and get a dedicated set of track wheels/tires. The stock sizes are 205/50/17 and 255/40/17 (according to Tire Rack) and Toyo makes both of those sizes in the RA1.

As for Kumho goes, the V710 is a DOT rated tire, but it is as close to a slick as you can get. They are VERY sticky tires and just about everyone that uses them really likes them.

I don't know if the Kumhos will last as long as the Toyos though. I'm getting a lot of life out of my Toyos and they get faster with age. ;)

Rick

[jclark]

Rick,

Thanks for the advice. I assume the smaller 275/35 for the rears should not be much of a change? I have called around using NASA recommended dealers for the Toyos' and cannot get anyone to either call me back or give me a straight answer. Do you have a reliable source for Toyo's?

John

[Snymo]

We (NASA RM) have arranged to get Toyos through the Tire Source in Boulder. I've worked with Pete for over four year and he and is staff are great. Call Pete at 303-443-3021 and see what he can do for you. I know he'll ship tire too.

Rick

[BVinson]

Or give me a call for TOYO's at 719-633-1500x1011.
Brian

[FOXBAT]

Do not overlook the Nitto R IIs. They are very sticky, an A compound, and are DOT as well. If you go this way, I would recommend Discount Tire Direct and have the tires heat cycled.

I have run these at Miller, La Junta, and drove on them as I "arrive and drive."

All they do is make me smile.