Chris

Here are the pics after I ran a 20 min session.
Pressures were a little low ( It was my first time on them) but later I ran 46PSI hot and STILL rolled the edge over

This was the drivers front, here is a map of the track (run CW)



These tires WERE NOT shaved and were poorly heat cycled by me.

Is this because I have no neg camber.. or did I overdrive them?

Willard

need more negative camber and try dialing it back a little bit...

Will

Warren

Too much tread. This is why shaving full depth r compounds is usually a good idea.

Warren

Honda318dx

DAMN!! never seen that happen, no matter what.. wonder if it was a bad tire

next time, get them heat cycled and shaved, they will last longer with a hard charger like you...

spoon_ek9

well, what size is the rim and tire? it seem like u put 205 tire on a 6" rim. if its true, then thats normal while u dont have enough - camber.

Honda318dx

Wheel/tire combo do not effect camber.. 6" wheel is fine for a 205.. but yes, more negative camber would help..

Chris

Yea Stock ITR wheels stock suspension.. 15X6 205/50/15

My Yoko A032R's never had this problem!

But my adjustable Upper A's are on order.

spoon_ek9

right, rim and tire size will not affect camber, but 205 is not fine on 6 " rim. i have a set of 205 on 6.5 rim and the center and outer block of the tire got more wear than inside(one day in street of willow, and its gone). and it actually got less contact pitch if u put more air pressure in the tire. since the tire is wide than the wheel, it reduce the contact area of the tire.

spoon_ek9

i believe A032R got stiffer sidewall and u could only buy hard compound in US(A032R), right? thats why.

Tyson

46 PSI is HOT HOT HOT!!!!!!!!!

I know this from experience. you must have been squirming all over the place. You gotta keep the pressures around 38 give or take 2 psi. What was your starting pressure?

oh yeah, and i also learned the hard way to get victoracers shaved when on the track, they accumulate too much heat. which is reverse for autox, where you want to build up as much heat for the short period of time.


[Modified by Tyson, 11:14 AM 5/20/2002]

Driven

wow... never seen that happen...

I bought a set of v700s on Jan 2001. Ran 19 autocrosses (with about 8-12 runs each event), and 4 track events... they still have some life in them. I bought them unshaven and un-heat cycled... I did heat-cycle them however (30 clockwise 50' circles, 30 counter-clockwise 50' circles, then jacked the car off the ground and sat on blocks for 3 days). I drive pretty hard as well...

Honda318dx

You don't have enough negative camber man, its not about wheel size, I ran 225's for years on 6.5" wheels and had VERY even treadwear across.. I also had almost 2 degres of negative camber.. of course a wider wheel is better, but its not going to keep his tires from chunking..

Also, 46 is VERY hot for Victo's like someone pointed out.. 40psi HOT is what I have used forever in the front of my prelude on kumho's..

DB2-R81

Most cars require 2.5 to 3.25 degrees negative camber to achieve a proper contact patch with Kumho V700's. Look at the inner tread blocks, minimal ware, yes shaving would have helped with the over heating and chunking. But at full tread depth they were over driven resulting in over heating, then break up.


[Modified by DB1-R81, 10:22 AM 5/22/2002]

Chris

Thanks all.

I did four laps and pulled in for hot pressures.. 46F 44R and I had them taken to 44F 42R and they still rolled over..

But yea.. more neg camber is on order. Live and learn..needless to say my lap times were the same as last year on the Yokos, I expected to ba faster...hehe

I will use these up and maybe try out the Hoosiers now that I can dial in neg camber.

Crack Monkey

Negative camber is nice, but the wear you experienced is due to improper tire pressures and temps, not alignment issues. 40+psi is WAY to high for Victoracers. Various Kumho reps have told me 35psi-38psi is correct. You probably overheated the tires, which led to the chunking. That, and you are probably driving WAY to hard. Is your car exhibiting monsterous amounts of push? If so, slow down.

I get pretty good tire wear with -1.25* camber (static) front and 0* camber rear on my RX-7. This is a 205/60-13 tire mounted on 13x7 wheels and at 35-37psi hot. The outer tread blocks do wear faster, but not so much that the life of the tire is compromised. I do not know how the camber gain on my McP strut car compares to your double arm suspension (anybody know?).

[edit]More to think about....
The lower the COLD pressure entering the track, the more the tread will squirm. This in turn leads to big changes in tire temp and pressure. Finding a good cold pressure to start the day takes a lot of trial and error. Too low and the tire overheats, too high and the tire overheats. Just right, and you get pretty good wear, even with stock alignments.[end edit]


[Modified by Crack Monkey, 1:03 PM 5/20/2002]

Tyson

seriously, i hope you realize that those temps are way too high, and are probably a more leading symptom of your problem than the chunking. start off 32 all the way around. you want to be 38 all the way around at the end. so perhaps you should start 32f/34r, but thats the general rule with FWD.

Track rat

My guess is that a combination of things caused the problem. Improper pressure, need more neg camber, wider rims would help, and you have to take it easy on them. Even after you address the mechanical issues, you can't continously push the fronts beyond their limits. Understeer usually gets worse if you keep making it understeer.

shamun

I don't see much evidence of a tire that was rolling over. Maybe it is not apparent in the pics.

Seems like they were overheated and slid around on the outside edge a bit to much.

Austin

Trust me...they did, I took the pics, and was amazed at what they looked like...

Drew M

I will 100% wholeheartedly disagree with you here. I have been running 205s on a 6" wheel and have had ZERO problems. I have 5 track weekends on a set of 205/50/15 Ecsta 712s on the stock GSR wheels. They are fine. No cupping or anything of the sort.
If the 205 is too big for a 6" rim then how are people successfully running 225s on a 7" wheel? A 225 is an inch wider than a 205. A 7" wheel is an inch wider than a 6" wheel. If I add all that up I would be led to believe that a 225 is too big for a 7" wheel. So why isn't it?

Chris - In my experience the chunking comes from the negative camber that comes in under cornering. The track configuration is also a heavy bias of right hand corners which puts substantially more load on the left front. There are what appear to be 2 fast sweepers there as well as some slow, tight rights. Run more air on the left and dial in some more negative camber. You may even want to put a little more spring on the LF (raise up collars) to try and get rid of some of the suspension dip and subsequent camber change.


[Modified by Cobra, 9:13 PM 5/20/2002]

spoon_ek9

cool, if that dont bother u, thats good for u. however, my time in street of willow and big willow is better with 7" rim.
and u r right, in order to run right on 225, u will need at least 7.5 inch rim.

look, if u use wider tire on narrower rim, it will make your tire a "over inflat" like. if u know whats that mean, its not hard to understand that the center block of the tire take all the pressure. right, u can lower the tire pressure to reduce that, but it also make the tire become "weaker" to fight with the cornering force.

phat-S

FWIW to this discussion, we run 12 225 Hoosiers on 6" Borbet and AR rims and never see that kind of chunking. Also, we have never seen a cord on the center line of the tire (outside or inside quarter or third only) so whereas I'd prefer to run a 7" rim, we are not experiencing the problems of over inflation issues you describe. I have been running 36 fr/33 rr and 37 fr/ 35 rr psi.

Chris

thanks again all..

Let me tell you EXACTLY how the day went.

I had never run these tires before and asked a friend (Hybrid EG with a TypeR swap, Tien Suspension.. 400 pounds lighter). He mentioned I should run, IIRC, 24F 26R.. I was like WTF!?? Thats real low compared to my Yokos(32F 34R) but I tried it anyway... I went out and chunked them and rolled over the fronts pretty bad. The next session I upped them to 32F 34R and they "felt" a bit better but still rolled over and chuked a tad more. The next sessions were with the tires rotated and opposite direction.

In retrospect, now that I think about it, I was pushing in the front quite a bit, but only in the tight right hander (the "Off Ramp"), so I took it for being too aggressive and not the best line, something I could "learn" to fix myself.n And, yes, the turn "Riverside" is a huge 90+MPH sweeper..most likely where most of the damage occured.

All in all... based on comments from a passenger I had that day...I guess I was just expecting Hoosier-like performance, from the way these tires have been hyped up, when compared to the Yokos. I now realize how beginner-friendly the Yokos are and that I sitill have ALOT to learn.

Step by step...

Crack Monkey

Ahhh, those initial pressures are the likely culprit. That's way too low, even for the cold pressures. At the track, I start about 28psi cold front and 30-32 psi cold rear to get all four to 35-37psi hot.

With pressures as low as you ran, you overheated the tire surface. The low pressure allows the tires to move around (squirm) a lot. This movement generates heat, which caused the chunking. And, of course it also allowed some rollover.

Kumhos really need to be heat cycled before use. And shaving them for dry use also helps a ton (less tread to squirm, less heat build up, better tire wear and more consistent performance).

MaddMatt

I think you need to do the upper control arm swap ala Roger Foo and Karl Shultz.

That and slow the fvck down.