Kumho Tires

[glenn_993]

I missed the Kuhmo rep at the Nov DE. Was there any discussion as to what the differences are between the VictoRaces V700 and the Ecsta V700?

[ttweed]

I didn't go to the last one, but at the previous tech session at Discount Tire, the Kumho engineer said the Ecsta was a softer compound than the Victoracer, that it needed to be shaved for dry track performance, that it would last fewer heat cycles, and be faster, but less so than the V710 (except the V710 does not need to be shaved, as it comes with only 4/32" tread depth.) He characterized the Ecsta V700 as midway between the Victo and the V710 in most of the specs he displayed.

HTH,
TT

[Otto]

Tom:

Glenn poses an interesting question and your answer is encouraging. I have also looked into the V700 as an alternative because the wear rating is also 50 but the reviews on Tirerack.com are not as favorable as the Victoracers. Any comment on the performance of this tire vs the Victoracers and/or other comparable tires such as the Toyo RA-1?

[Jad]

Otto, I have only used the Toyos and Victoracers, but for me, there is no choice. The Toyos are indestructable. They just don't overheat, blister or chunk and they last at least 3 times longer.

While at their optimal couple of laps, the VR seem to be a few tenths faster at most, the rest of the time the Toyos are as good or better. Considering the wear differences, it means the Toyos cost 1/3 as much and have me convinced. If I want to go faster, I would buy real race tires like Hoosiers or slicks. To me, the Kuhmos are a lot of money for little if any improvement compared to the Toyo.

[Otto]

Thank you for the advice Jad. I have the Toyos (shaved) and used them for the first time at Pahrump this October. Your are right, they did not heat up much because pressure went up only to 37 psi hot (starting at around 30). I thought the shaving had something to do with it as it was the first time I had used shaved tires. I had been normally seeing pressures of 40 to 42 hot with my unshaven Yokohamas. Also I had a big slide (lockup) between Turn 8 and 9 and no blistering whatsoever. However, somehow I feel that they do not stick as well because I was understeering a lot in turn 1. That got me thinking that perhaps the V700 are more sticky but the reviews are not that good. You see, I cannot use tires with wear rating under 50 because of the points, so my choices are limited. I do miss the Yokohamas A032Rs. I was happy with them but they no longer offer my 245/45/16 size. Based on your advice, I might stay with the Toyos. Any idea how many heat cycles might they be good for? Is the "stick" quotient pretty even throughout the life of the tire? Again, I am using shaved Toyos (4/32).

[ttweed]

Any idea how many heat cycles might they be good for? Is the "stick" quotient pretty even throughout the life of the tire? Again, I am using shaved Toyos (4/32).

From what I have heard (never used them yet), the RA-1s just get better all the way down to the cords, and do not go away from heat-cycling. There were a lot of complaints about "chunking" with the Ecsta V700 at first, which probably affected the reviews of the tire. Many people ran them full-tread on a hot, dry track, and Kumho said they needed to be shaved for that. Right now, I believe the V710 is faster than any of the DOT tires, but if you can't use a 4-point tire, and want something that will last a long time, then stick with the Toyos. V710s don't come in a 245/45-16 yet anyway, and may not until after Oct., '06.

TT

[Otto]

Tom:

Your comments are appreciated. From your comments and Jad's, the shaved Toyos appear to be the way to go in the 50+ wear category. We'll see how they perform at Willow.

[Dan Chambers]

However, somehow I feel that they do not stick as well because I was understeering a lot in turn 1.

Otto:
I had the same experience with the shaved RA-1's at Streets o Willow. I actually found that increasing the tire pressure helped with the "push". I run my RA-1's at around 37-38 PSI hot; starting at 34 - 35 cold and deflating as needed. As opposed to the Azenis/Kuhmo tires I used to run (at 35 - 36 hot) the RA-1 seems to like slightly higher pressures on my 3100-Lbs. 944. Of course, every car is set up differently, and every driver inputs steering and peddle commands differently. However; overall, I was surprised to find more air was good .... at least for me and my tub.

Not to insult your years of experience and skill .... but have you tried experimenting with tire pressures and monitoring tire temps? I think the RA-1's are quite sensitive to pressure/heat relationships and grip, as opposed to other tires I've run.

Just my 2-cents.

[Otto]

Dan:

I do not have a pyrometer to measure tire temperatures across the tire surface so I can only judge proper contact/camber by looking at the way the tire is wearing across the surface. With respect to pressures, I decide on the front to rear pressure stagger depending on the track and the desire to have more or less oversteer. Higher pressures in the front vs the rear will give my car a greater oversteer tendency, which is sometimes desirable if there are tight turns (which is not the case at Big Willow). I normally start with cold pressures in the 28 to 32 range depending on the expected track temperatures and measure hot tire pressures immediately upon finishing the first session. I then add or take out air so that tires have same hot pressures from side to side and the desired stagger front to rear. With respect to max pressures when hot, I try not to exceed 40 to 41 even though my shaved Toyos at Pahrump did not exceed 38. As you pointed out, maybe I have to start with higher cold pressures in order to achieve the 40 level, which might work better for those tires, particularly during a cold day in January at Big Willow.

I fully realize that different makes of tires require different pressures to achieve optimal performance, which is why we are always asking that question to the manufacturers. I wonder what that "hot pressure" target should be for the shaved Toyos.

[Jad]

As far as pressures, people are all over the board on the Toyo's. I think Martin tries for 30-32 HOT, whereas I was trying for ~39-40 hot. I don't know the right answer and they don't seem to effect times a lot either way. Martin and I both consistently make top 10 despite the 8-10lbs difference.

The toyo's do need to be shaven and even then they get better as they wear down. I thought my first set was done, so I bought another set, only to learn the first set was about 50% left and getting better. They started unshaven at Pahrump in 1994, 3-4 AX with 2 drivers, a QDE, some sessions at Fontana with 2 drivers and some play at the school so I expected them to cord at any time. This is twice the life I would have gotten from VR's and while they have hardened too much for timed events from age, they are still my street tires and did a few more decent AX's with no signs of cord.

If you are desperate for every 10th of a second, you may do better, if you want to have fun, save money are most likely have no excuse that better driving wouldn't have fixed, keep trying suspension and pressure changes and see if you can't make the Toyos just as fast would be my advice - which I am taking

[Otto]

Jad:

I am with you with respect to preferring a higher target hot pressure such as 40. Unless the factory rep advises differently, I believe it suits our purposes better than a hot 31 to 32 pressure. Martin, on what basis did you choose that low number?

Your comments regarding wear are encouraging so I am optimistic now that my Pahrump Toyos will still perform well at Willow in January. It is the track where I have noticed most the advantages of a fresh set of tires, particularly because they give you the confidence that the car will stick around turns 9 and 1 when you are pushing the envelope. The test for the grip you do around turn 2 and if the tires feel secure, you can go for it around 9 and 1. We'll see how it goes.

[martinreinhardt]

Otto,

I use different tire presures on different tracks. At the AutoX I use 28-33 hot and Buttonwillow per example I used 34-36 hot.

These low tires presure came from a combination of the Toyo RA/1 Usage Guide which recommends to start at 32 cold and end up in the 36-40 hot at around 160-220 degres. I followed that advice and used a Digital Pyrometer until I had an almost equal temperature across each tire after a run session. The front temp are usually in the 165-167 and the rears at 190-200 (I don't have a limited slip differenzial). It was also a suprise to me how low the tires pressures ended up, but it seems to work.

[Otto]

Aha! You go the more scientific way, with the pyrometer, which tells you if you have achieved the desired temperatures across the contact patch. You can also tell if your camber is about right. The resulting hot tire pressures are consequential and not your target. Along with you I am surprised that your tires go up to only 34 o 36 hot pressure while the contact-patch temp is in the 180 to 200 range. This might indicate that if we are seeing 40 hot then our surface patch could be overheated. You said you were reading a Toyo RA-1 Tire Guide. Do you know where to access that info? Do you also use shaved Toyos?

[MVZ944T]

Otto,

I have been using shaved RA-1's since last summer. I run only 34lbs hot and they work excellent at that pressure. I think most likely you may be using way too much pressure. My times with the Toyo's have been as good or better as slicks surprisingly enough, although they are 8lbs a tire heavier than Goodyears. I start out about 25-26lbs cold, that gets me close to 34 when they heat up.
I like them way, way better than any of the Hoosiers' or Kuhmo's that I have used. I agree with Jad also, they get better the more you use them, and they wear really good! Best DOT tire out there as far as I am concerned.

Mike

[Otto]

Mike:

Toyo would be mighty happy if they were to read all the comments but then, they seem to have a good product in their hands which I have only begun to test. We'll see how it goes and what I can add to the discussion after Willow. Thank you for your feedback.