rhneff

The following is a post I sent to the local SCCA region folks this morning regarding visible separation of the tread on a very new set of V710 tires. Thought I'd post it here as well, FYI. As an update, I just returned from having the tires dismounted and was told that actually three of the tires have a splice separation issue in addition to the butt splice separation - they're exhibiting a separation that runs longitudinally around the centerline of the tire exactly in the middle of the tread. The manager of the tire store, who supplies many of the local racers with tires, said the tires would probably not be safe for Solo use and especially not for track use.

So a word to the wise: check those tires, and be careful out there .

Post to Texas Region SCCA:

I thought some folks might be interested in the situation I discovered with a new set of Kumho V710’s after the Solo event last weekend and that as a precaution you might want to keep an eye on your tires if you’re also running this brand.

While washing my wheels after the race I discovered one front tire had almost completely separated at the butt splice, in exactly the same manner that caused last year’s recall on these tires. The other front tire seems to be okay for the moment but looking closely I can see the beginnings of the same separation so I suspect it will exhibit the same condition at some point.

I took the tires back to Todd Eaddy and he told me this is the second occurrence he’s seen in the past month or so. Unfortunately Kumho has refused to stand behind the product so I guess after only 16 runs I’m out $450 worth of rubber – I’ve sent a letter of complaint to Rudy Consolacion but am not expecting a more favorable response from him. As opposed to their splendid response to the issue last year, Kumho seems to be ignoring the problem at this point.

The problem could be attributable to the excessive heat during the event – the thermometer in the Z06 was registering 105 most of the day, and we were having to spray a lot of water on the front tires between runs to keep them within a reasonable temperature range. That may have combined with the longer-than-typical-Solo course to contribute to the situation. I suspect the issue is also likely to be more predominant in the larger sizes on heavier cars such as the Z06.

That said, you may not see any issues on your own V710’s but it would be worth keeping an eye on them. Not to say all current tires are defective but these were brand new, only used for Solo, only on asphalt rather than concrete, and the failure would I’m sure have occurred earlier and with potentially more disastrous results had I been road racing the car.

Bob Neff
93 SS

Vetracr

Its a slightly different problem but I ran Kumho Victoracers for years on my SS and BSP C4's. The Kumho butt lap seperation problem was common and well known 10 years ago. Scared the c**p out of me first time I saw the tread split transversely across the carcass. After many words from Kumho "not to worry" I wound up running them to the cord. Happened on most sets of Kumhos I ran but I never had a seperation. I'd be curious to hear others experience.

Larry

LehmanZ06

What was the date code (build date) of the tire

The 4 number code on the inside of the tire ?

Post a picture of what they looked like.


LeHmAN

SPIDEY

I had bought a new set for the front of my vette a month ago and after the first autocross notice the separation at the butt splice. I took pictures of both tires and emailed them to tirerack and called them also to be told that there was nothing wrong with the tires. I've ran four autocrosses since and have not had any problems with them, nor are the split getting any bigger. I've kept a check on them after every run. My friend's tires are doing the same thing. The guy at Tirerack said that the occurence isn't uncommon, that the split wasn't all the way to the core and that split will disappear. True or Fiction, who knows. Its a shame that Kumho, one of the main sponsors, isn't willing to do anything about it.

rhneff

I'll post a pic when I get a chance. Looked at the tire but don't find a 4 number code like you're referring to. There's a sticker with 20, some Korean characters, and then 43. There's also a molded-in MR13-20 A, if any of that makes sense.

My first thought was these might have been original design tires from last year's re-call, but they do have the correct construction molded into the sidewall including the additional polyester plies Kumho added to correct the original problem.

Gary2KC5

I used Kuhmo 710's for the 1st time this spring and after 6 sessions my right side tire tread was seperating at the splice and the left side was showing a splice line.

I called Kuhmo several times and after a few weeks finally got to talk to a person. I told them they had a safety problem and they said they would have an engineer contact me. NO email or call back after that.

I contacted the TireRack and they told me they would give me 50% off on a new set. finally I sent them a lengthy email explaining that they were new tires, they had a safety issue and after 20 years of buying tires from them I didn't expect the weak response. They sent me a new rear set of tires and issued call tags for the seperating tires.

The new tires they sent me also seperated.

I WILL NOT BUY KUHMO TIRES AGAIN!!

rhneff

Kumho may be correct - I'm certainly not a tire engineer and can't argue they aren't. My issue is what happens when I show up at an SCCA event and the Solo Safety Steward decides they're not okay to run? I spend too much money getting there, especially at national events, to take that chance. Hoosier A6's going on my wheels now.

XGRANDSPORTX

Had a similar problem with a front tire separating after a few de runs(The rubber on half the tire peeled away completly) Called Kuhmo and was basically told we wont do anything. So long Kuhmo will never buy your tires again. By the way I keep the tire in my garage to remind me never to buy Kuhmo tires again.

Alan

Gary2KC5

I talked with the TireRack again and they said you should swap them and the splice should close up. I wish I had know that on sunday.

Another guy in our group put on a new set of Kuhmo 710's after the 1st couple of sessions and found a splice seperating after just a couple of sessions. He was swapping his tirs due to the heavy right front wear at HPT and he did say his mini splice had sealed up.

Mine's about 1/4 inch wide I don't think it will "heal" itself but I will give it a try.

RX7 KLR

The V710 recall was in 2004 not last year. I never had an issue with the old pre-recall tires and some ten or so sets later have yet to have an issue with the current tire. Proper care of your tires will lead to a long life. Not over driving a new tire is very important, if you don't heat cycle them you need to make sure you do not over drive them the first event. C6 Z06's roofs fall off, should we not allow those to autox?

gonzalezfj

The other solution is to throw the Kumhos in the trash and get a set of Hoosiers.

You will be faster and don't have to worry about tire failures.

Frank Gonzalez

John Shiels

When I started I ran Kuhmos. I was at Pocono doing 165 to the tunnel turn. That is faster than it goes now with the body kit. After I get home I see what looks like hundreds of 1/4" razor slits in the side wall. All tires were like that. I call tire rack they give me the race tires . I then stated I didn't want a dime back I wanted an answer to what is happening. They then call Khumo and agree to let me ship them back. I shipped a front and rear tire, I pay for they freight I don't care I want an answer.

I wait to hear back and call them after not hearing. They end up fighting with Khumo about who has the tires End result no answers from them. I then said I have two more I can ship but they refuse. Then they offer me 50 off new ones. I refused the offer. The Hoosiers or Goodyear's are better and last longer. The Khumos get greasy and spin and slide easy. Plus now my money stays in were I like to keep it.

Call Hoosier and see how fast a rep answers your questions

I finally got the answer from Mallet what happen. They told me it was probably sidewall failure.

Sidney004

What hot pressure did you observe prior to the thread separation?

wtknght1

Well, for what it's worth guys, I've run these (and even the recalled tires) down to the cord on many occasions and know many, many others who also have...with no problems at all.

These V710s are the most predictable tire I've ever run and they have the best support of any company I've ever been with.

It's of course up to you which tire you choose and run with...and which ones you feel comfortable with. A driver must feel comfortable and trust his/her equipment to be fast.

Phil Croyle runs the Kumhos and won the 2004 Southeast Division T1 National title, and I've won the 2005 and 2006 titles on these tires and have had no problems whatsoever. They grip...wear like iron...DO NOT GET GREASY...and they keep racking up new track records and division titles in many classes in W2W racing all over the country.

As far as Goodyear and Hoosier - they too are good tires. I think all my competitors should use them!

yellow01

Well sh*t... I just read this and have a track day coming up Sept 9/10th and will be out of town until 3 days before that... (i.e. not time whatsoever to get new rubber)

this is what both of my fronts look like (after 1 full weekend). I did notice the line mid weekend, seemed strange but figured it was normal... Is this something that should be worried about?

thanks...

TRACKMAN2

DOUBLE WARNING ON 710'S AT THE TRACK TODAY A GUY WITH NEW V'S HAD ONE JUST COME COMPLETELY COME APART ON HIM SENT HIM INTO THE TIRE WALL .... THE HOLE SIDEWALL CAME OFF AND THE TIRE WAS SPLIT IN HALF HALF HALF WAY AROUND. HE SAID IT JUST "LET GO" UPON INSPECTION HE DIDNT HAVE ANY UNUSUAL TREAD WEAR...I HAVE NEVER SEEN ONE COME APERT LIKE THAT.. IT LOOKED LIKE ONE OF MY ENGINES.......

Bill Dearborn

I have lines similar to that in some of my Kumho's. They don't seem to be any problem. What I have noticed with my front tires (275's) is a sort of blistering where chunks of tire tread are coming off the carcass. They started as spots where I had picked up stones at a previous event and then had removed the stones before storing the tires for the winter. After one autocross this season the spots started opening up. I used the tires for one HPDE and 2 or 3 other autocrosses and they have now gotten large enough I have to worry more about a puncture. I have over 20 heat cycles on this set so it doesn't owe me anything although I hate to give up on the remaining tread since there is still quite a bit there.

Bill

rhneff

The tires were heat cycled by Discount Tire before ever being run, then they were "rested" for two weeks, then they were run twice to scuff them and then weren't run again for another two weeks. They made six runs on the new asphalt in Topeka before the event here in Texas where the defects showed up. In between those events they were kept in an air conditioned tire room off my garage. I don't know about you, but I think that is taking proper care of my tires. The tires weren't over-driven, they simply failed in the course of normal use for their designed and intended purpose.

rhneff

I normally run the fronts at around 30 psi cold, but because the course was fairly long for an auto-x course adn the weather was really hot I started them at 29 psi. After the first sequence of runs they were up to between 32 and 33 psi, and were bled back down to 29 before each subsequent run.

XPC5R

rhneff takes very good care of his race equipment, certainly not a case of misuse/abuse. Race parts do break and fail, no question there. It's how the manufacturer stands behind them that makes the difference.

As for C6Z's, a smart owner would not run his when he starts hearing the roof pop and crackle, time to get GM to fix it.