Brand new Kumho delamination on 2016 ACR

[schulmann]

This is a 500mi 2016 ACR, after 15 min session in the morning (Temp 65F).

What is the problem with these Kumhos ??

18500

[canadian viper]

driving too hard on cold tires??

[38D]

Call Kuhmo as the tire shouldn't do that regardless of how you warmed up

[ACRucrazy]

One of the ACR owners at Viper Rendezvous Kumhos looked similar. 95+ degrees on a track that is 100% concrete.

[schulmann]

It was a cold day (65F) and it was during a warm up lap, didn't push it hard.

The fusion between the rubber layers is not complete, we can remove with our hand the different layers.

[Policy Limits]

500 miles? Thats like 300 more miles than the track wear rating on them. Lucky there was no property damage or injury. Tire rack it for 300 and change each

[kverges]

Was the car pushing? What was tire pressure? The tire looks like you drove through a big push with elevated tire pressures. I've done much the same and the dash
Pressure monitor is very delayed so you can have 5 psi more in tires than shown on dash. And if you have a push you can't just add more lock and grind or the tires will be destroyed. You must be gentle in warmup and keep them at 35 psi max hot. I start 30 cold and pit after 3 laps (under 6 min) and bleed back down. I see 10 psi increase in front tire pressure over a 30 min session.

[SilveRT8]

Was the car pushing? What was tire pressure? The tire looks like you drove through a big push with elevated tire pressures. I've done much the same and the dash
Pressure monitor is very delayed so you can have 5 psi more in tires than shown on dash. And if you have a push you can't just add more lock and grind or the tires will be destroyed. You must be gentle in warmup and keep them at 35 psi max hot. I start 30 cold and pit after 3 laps (under 6 min) and bleed back down. I see 10 psi increase in front tire pressure over a 30 min session.

No, I was there and can vouch that the guy is an experienced driver, running in our Pro group, he was well prepared setting-up suspension as per the book, checking tire pressure and lug nuts torque before and after each 20 min. session, saying he was taking it easy since the car was still new and on the track for the first time. The other front tire showing almost no wear and this one completly delaminated, worse than the pic shows when viewed on the spot.

[Policy Limits]

If it only occurred to one tire perhaps just a faulty tire. Hopefully that's the case instead of the kuhmo tires in general being the problem. Would like to know the answer for sure.

[VENOM V]

I've tracked with guys that have had chunking in the first session. They were going a little too hard on the first lap for this tire. However their chunking looked different than your case, they had small blocks that tore away. Maybe your tire is defective. Other tires like Hoosiers allow you to go hard out of the gate, but not these Kumhos. So even experienced drivers may inadvertently go too hard on the first lap.

What tire psi? I run 24 psi cold, 33 psi hot. I've never had any problems except that the fronts don't last as long as I'd like. I do a medium pace first lap then go hard on lap two.

[Policy Limits]

Todd what is the wear rating on these track and street?

[VENOM V]

200 tread wear street, which I believe because in the first 1300 break in miles wear was not appearant. On the track, there's no rating. A newer driver that isn't pushing hard should get a lot of track days out of the fronts. A hardcore driver may only get a day, or less if he pushes too hard.

[Policy Limits]

200 on the street? I couldve sworn someone posted 1400 street miles and 70% tire remained. Wow that's a bummer replacing tires once per month. That's 25k per year in tires. Are you sure u didn't mean 2000 Miles for street?

[ViperSmith]

200 tread wear does not mean 200 miles, it has nothing to do with milage nor are tread wear any accurate measurement

[VENOM V]

I would guess that they'd last maybe 5,000 to 10,000 miles on the street depending on how spirited a driver. But at the track the fronts lasted me 1 to 1.5 track days front and 6+ track days rear.

[Policy Limits]

Thanks for the clarification.

I've tracked with Pirelli's twice now and feel like they've held up really well.

[TrackAire]

Thanks for the clarification.

I've tracked with Pirelli's twice now and feel like they've held up really well.

The "200" tread wear rating means nothing since there is no standardized rating system put forth by the DOT or the tire manufacturers. It really is an arbitrary number picked by the tire manufacturer mainly for marketing to specific market segments. A lot of "street tire" race organizations use the number "200" to signify a street tire and not an R-compound type tire. I've got BFG Rival S tires on one of my track cars with a 200 tread wear rating and you'd swear they are R-compound tires when compared to Hooisers R7's, Nitto NT-01's, etc. But, with the 200 tread wear rating they can race in the street tire division of organized events. A very popular racing organization using the 200 tread wear rating is Optima's Ultimate Street Car Invitational. You can run any tire you want, as long as it has a manufacturers wear number 200 or higher.

To the original poster, that may be a defective or damaged tire due to off track environments.....do you know if it was ever unintentionally frozen? What was your starting pressure before the session began? I would definitely get contact Kumho for a potential warranty claim.

[allans]

Since it's in the center off the tire, I vote for high pressure coupled with heavy breaking. Or, bad tire. Allan

[kverges]

Just curious what pressures were and my personal experience is that you absolutely cannot run the tires for 20 min continuously without a pressure check and bleed down. I tried starting 25 cold and destroyed shoulders. Continuing to do at over 35 will destroy center. If you start a session with the door jam 35 psi cold front and have any pace at all it's easy to do that to the fire.

[kverges]

I'm an experienced driver too and have done that to tires. Just sharing my experience, not attacking.

[ACR Extreme]

To the original poster, that may be a defective or damaged tire due to off track environments.....do you know if it was ever unintentionally frozen? What was your starting pressure before the session began? I would definitely get contact Kumho for a potential warranty claim.[/QUOTE]

Go with defective and or unintentionally frozen.

Sounds like the guy knew what he was doing brings back memories of tracking at a high level can be a pia.

Adding spares to the order.

[ViperTony]

If the OP is that crazy Canadian I remember :D then yes he's a serious track rat and pushing these tires to the extreme. I'd venture a defect or they were frozen/stored in near freezing temps.

[schulmann]

The ACR was delivered from Detroit on May 10th 2016. This is a 2016 ACR. No winter ... And usually a short freeze don't make damage to tires unless you drive on them. 32PSI hot pressure, no agressive drive, the guy was testing his new Viper. This is his 3rd Viper and the owner is a highly experienced race drive.

[ACR Extreme]

The ACR was delivered from Detroit on May 10th 2016. This is a 2016 ACR. No winter ... And usually a short freeze don't make damage to tires unless you drive on them. 32PSI hot pressure, no agressive drive, the guy was testing his new Viper. This is his 3rd Viper and the owner is a highly experienced race drive.

Doesn't matter what year the car is - if race tires are subjected to cold temps when being shipped they can 100% be damaged most if not all race suppliers won't ship if the tires are going to be subjected to cold weather short freeze long freeze no difference.

Cold weather can easily create cracks - it's a good idea to keep those garages temperature controlled.

https://www.youtube.com/watch?v=64g4l2YIJWk

[Speeder88]

I tracked my new 2016 ACR for the first time last Friday at Circuit Mont-Tremblant, Quebec
. Outside temp 68 degree. After only 10 laps, the front left began to delaminate. Tire pressure hot was 33psi at the end of the session.18531

[TrackAire]

I tracked my new 2016 ACR for the first time last Friday at Circuit Mont-Tremblant, Quebec
. Outside temp 68 degree. After only 10 laps, the front left began to delaminate. Tire pressure hot was 33psi at the end of the session.18531

It would interesting to compare born on date codes to see if the suspect tires were made in the same week. Sorry, that does not look like normal track abuse to me if the hot temps stated are correct. I think this is an actual tire issue from the manufacturer or other issues outside of the track.

[Bruce H.]

The ACR was delivered from Detroit on May 10th 2016. This is a 2016 ACR. No winter ... And usually a short freeze don't make damage to tires unless you drive on them. 32PSI hot pressure, no agressive drive, the guy was testing his new Viper. This is his 3rd Viper and the owner is a highly experienced race drive.

Your car was shipped, delivered and stored in sub-freezing and below recommended temperatures for at least two weeks. The tires would likely have also been delivered in the dead of winter and may have been exposed to really cold temps, although hopefully the distributor and SRT knows to keep them heated at all times.

Check Kumho's recommendations and warnings. As an example, Pirelli warns not to subject the Corsa to temps below +10C, and no way below +5C according to a rep I spoke with. Sure there are guys here who have driven on them below that and say they're fine, but they probably aren't hauling ass around a race track on them afterwards like you did. I was also told by Pirelli that they sell lots of replacement tires to those who don't follow their warnings. Since both cars with this problem are in Quebec I'm suspicious that both are cold weather related.

Could be a warranty claim with SRT or the dealer if they exposed them to temps below Kumho's recommendations. Worth looking into.

[canadian viper]

are we talking about 2 different cars? or the same single car?

[SilveRT8]

are we talking about 2 different cars? or the same single car?

Same car, the owner Speeder88 just chimed in

[ACR Steve]

It looks to me like an overheating issue . However sometimes there's just a bad tire. That's defiantly delamination. If all the proper steps were taken with pressure and warm up then its possible that it was just a bad tire.

[Racingswh]

Ours were junk and showing signs of poor wear but nothing like that. Car would push immediately if coaxed but typically overheated after 10 minutes into a 20 minute session. We got 3 sessions out of the Kumho's before we went with an R7 295/30/19 which lasted the rest of the weekend which was 14 sessions. Rear Kumho's looked decent the whole weekend. Pace was ok, car was setup per the recommended track settings except I softened front bump and added rebound slowing some of the rearward weight transfer and off corner push seemed to diminish. I forgot to mention we monitored tire pressures religiously and bled off as needed.


We are considering an A7 in the front and an R7 out back for Watkins Glen in a couple weeks. We have 3 sets of fronts now. One factory 19" set and two sets of 18".

[cab33]

Do the rears ever have this problem?

[GTS Dean]

You guys need to be checking tread temps across the tires in addition to hot pressures. You may not be carrying enough pressure to support the belts adequately. They could be deflecting under load and causing a belt warp or stress raiser just outboard of center. Back in the early days of Vipering, BFG R-1's were known to exhibit "the groove of doom" which was caused by exactly the same underinflation problems.

[Racingswh]

You guys need to be checking tread temps across the tires in addition to hot pressures. You may not be carrying enough pressure to support the belts adequately. They could be deflecting under load and causing a belt warp or stress raiser just outboard of center. Back in the early days of Vipering, BFG R-1's were known to exhibit "the groove of doom" which was caused by exactly the same underinflation problems.

Absolutely true. 1st session Go out, get tires hot, pit in, bleed off excess pressure, head back out. Checked pressure before and after every session after the first. Had to AIR them up each morning from 20 or so PSI to 28. Repeated the same process each day. Too soft a tire will cause delamination. Especially when you're hammering on it from go at the low pressure. Know of two friends high speed tire failures where this was the suspected culprit.

[Racingswh]

Do the rears ever have this problem?

Our rears held up extremely well. We were shocked at the difference.

[bluesrt]

Check alighnment and give it more camber

[Darius]

You guys can talk temperature, pressure etc all day. In my 24yrs of tracking cars I've never seen tires come apart like this. I put a brand new front set on and blistered them completely in 1 session wasting my whole day and losing my money spent on the track day. Those tires are extremely sensitive, made in Korea garbage. I ran Hoosiers all day and they still look like new and I went half a second faster with just the fronts. I showed up to Laguna a day after they set the record, they had the Kumho big rig there, that's probably how many tires it took to break the record, the whole trailer full!! Quit wasting your time with them if you want to track the car, even Ralph G had Hoosiers on his way before we even got our ACRs.

[Bruce H.]

This particular delamination instance was in cool weather, warm up and not pushed.

Are you SOL if you want to drive to the track and back? Tough to do on Hoosiers.

[Racingswh]

This particular delamination instance was in cool weather, warm up and not pushed.

Are you SOL if you want to drive to the track and back? Tough to do on Hoosiers.


If I drive my cars on the street which is very rare it's on Hoosiers or slicks. Never an issue.

I can't see how you could do more than a one day event on the Kumho fronts and expect to be driving it to and from said event on the same front tires. You may need at least 1 front tire per track day of an event. It's quite shocking how much better the Hoosiers wear over the Kumho's.

The reality is that everyone that stated the Kumho front is garbage and will not last is exactly right. I was extremely happy I listened beforehand to everyone's experiences and suggestions and went to my first event in the car well prepared.

[GTS Dean]

My friend SW in Austin took his ACR-E out to COTA right after following the break-in procedures to the letter. I do not know what camber or air pressure he was running, but this was a pic of his LF tire after 3 easy warmup laps and 6 shakedown laps (short-shifting). Temps that day were from 62F-85F.

18600

This was day 2 - assuming he made more camber adjustment here:

18601

After looking at the same wear pattern on all these cars, my suspicion is that you folks either aren't running enough negative camber for this tire, or too little air pressure to support the belt package. I suspect that the outside shoulders are overloading and causing the belts to flex up and bulge the tread in this wear area, causing localized tread overheating and the slip angle is scuffing the tread block off.

I realize that I'm just an armchair wannabe race engineer here, but that's my take FWIW. I've run Kumho V700s on my Gen 2 and have ruined a front at the track due to belt separation and I was paying very close attention to temperatures and pressures. My opinion of the brand is sinking lower all the time.

[bluesrt]

also seems to be the front left on all these complaints

[GTS Dean]

True, but the majority of road courses run CW, so the left side tires tend to get more loading. Although COTA is CCW, 16-17-18 is the long, fast, multi-apex right hander.

[kverges]

Dean and SW it's the inside shoulder of inside tire that has suffered worst in my experience. I am on my third set of Fronts. My experience is the car has a big push when set up per the supplement. I actually had the best luck because I was impatient and ran without the rear diffuser extensions that were not in my car at delivery. Since adding them I've ruined fronts.

My third set are faring better with 2 big steps. One, start 30 psi cold and never let tires get over 37 psi hot, with target of 35 psi. Two, never overdrive the tires and make stops at 5 or so minutes (3 laps max at COTA) and bleed them down because if you can drive they will be over 35, and stop again after about 10-ish more minutes. I get 10+ psi rise but my attempt to start at 25 psi ruined both shoulders.

And don't drive through the push, you will grind the tires off the car. I also suspect inside tire takes a beating due to Ackerman and/or the static camber and body roll dragging the inside shoulder.

[Policy Limits]

Is the TPMS indicator issues guys are having related to these tires as well?

[GTS Dean]

Is there a major reason why people keep throwing Kumhos at the problem that Kumhos are predisposed to experience? Is it price, or is it because there is a large body of factory engineering data based on the OEM tire?

[docwviper]

I've tracked with guys that have had chunking in the first session. They were going a little too hard on the first lap for this tire. However their chunking looked different than your case, they had small blocks that tore away. Maybe your tire is defective. Other tires like Hoosiers allow you to go hard out of the gate, but not these Kumhos. So even experienced drivers may inadvertently go too hard on the first lap.

What tire psi? I run 24 psi cold, 33 psi hot. I've never had any problems except that the fronts don't last as long as I'd like. I do a medium pace first lap then go hard on lap two.

So question. This is off topic from this and I'm sorry for it but this is a tracking thread. Have you guys noticed inner fender wall rub from the kuhmos in the rear? I have had this with lower tire PSI and lowering the vehicle. Other members of the IL VOA have confirmed they have had this to. I haven't seen this mentioned by other members on here which I'm surprised about. If you take off the wheel and look for it you can see it. Some people have rub all the way through the wall i've heard.

[bluesrt]

keep in mind also with these tires don't think they are really made for balls out hard core ass ripping trac times, they were made for spirited driving on the roads, I bet they could make a tire to hold up if they were told to do so.yes the sport cups didn't do this,but different car and different times,era/things change. buy a better tire

[VENOM V]

So question. This is off topic from this and I'm sorry for it but this is a tracking thread. Have you guys noticed inner fender wall rub from the kuhmos in the rear? I have had this with lower tire PSI and lowering the vehicle. Other members of the IL VOA have confirmed they have had this to. I haven't seen this mentioned by other members on here which I'm surprised about. If you take off the wheel and look for it you can see it. Some people have rub all the way through the wall i've heard.


On the quarter panel or just the plastic liner? None on the fender but a little on the plastic liner occasionally. I will take a closer look, thanks for the heads up.

[VENOM V]

keep in mind also with these tires don't think they are really made for balls out hard core ass ripping trac times, they were made for spirited driving on the roads, I bet they could make a tire to hold up if they were told to do so.yes the sport cups didn't do this,but different car and different times,era/things change. buy a better tire


I think they are made for balls out track times, but more of a qualifying tire rather than for a long race. They remind me of Hoosier R7s in this respect. Very fast for the first five or so laps, then you have to back off a little for one lap to let them cool, then go hard again.

[docwviper]

On the quarter panel or just the plastic liner? None on the fender but a little on the plastic liner occasionally. I will take a closer look, thanks for the heads up.

on the plastic liner. I'll take a pick if my lift is working this weekend. It's killing me, been down for weeks. Just wondering why it's doing this and the noise it makes his awful when going into a corner when it hits.

[VENOM V]

I suspect the noise is actually the diffuser extensions scraping, which is normal.

[bluesrt]

If its actually rubbing the liner may wantto check ride height on that side .dont take much

[SharpMan]

If its actually rubbing the liner may wantto check ride height on that side .dont take much

According to SRTs videos the diffuser extensions are designed to rub the asphalt.

[bluesrt]

True, but only if your haulin ass. People lower these cars and sometimes dont get all 4 ride height sqare

[VENOM V]

If its actually rubbing the liner may wantto check ride height on that side .dont take much

True, I just had my ride height, alignment and corner weighting readjusted after 7 months of tracking. I found that the alignment and corner weighting were still within spec, but rear ride height dropped 3/8" after a bunch of track days. I imagine rubbing will now be minimal.

[SharpMan]

True, but only if your haulin ass. People lower these cars and sometimes dont get all 4 ride height sqare

I just realized you said "liner" and weren't referring to the extensions. Sorry.

[dadgoneracing]

Guys - I have a track day tomorrow at Laguna Seca. I had a similar experience with Khumos last fall at Laguna Seca in my ACR E. Front left delaminated on the inside. I saw the piece come off in 2.

I'm going to run Hoosier R7's tomorrow. Thanks for the tip to adjust ride height - done.

One thing has me stumped. The Hoosier tire care and safety guidelines for a 3000lb+ car, say recommended pressure hot is 40-42+, cold 30-34 + add more cold if the car has aero. That is in contrast to my experience and most of the pressure levels guys are running on this forum.

https://www.tirerack.com/images/pdf/warranty/HO0914.pdf

Is this a case of manufacturers not knowing how their products are to be used? That seemed odd for a racing tire company!

I would appreciate any advice.

Thanks in advance.

[1ststrike]

My best luck to make Kumho's last was start with 33 psi cold. That will save the outside till they get warmed up. I used nitrogen also to help limit pressure increase during heat up. Didn't push to hard first lap or two depending on track length. Then adjust pressure by the line where the tread and sidewall meet compared to the road surface marks. Also changed my driving style and suspension setup a little to make them last longer. I could make Hoosiers last longer no matter what. So I run them unless I'm driving on the street.

[BlueAdder]

Guys - I have a track day tomorrow at Laguna Seca. I had a similar experience with Khumos last fall at Laguna Seca in my ACR E. Front left delaminated on the inside. I saw the piece come off in 2.

I'm going to run Hoosier R7's tomorrow. Thanks for the tip to adjust ride height - done.

One thing has me stumped. The Hoosier tire care and safety guidelines for a 3000lb+ car, say recommended pressure hot is 40-42+, cold 30-34 + add more cold if the car has aero. That is in contrast to my experience and most of the pressure levels guys are running on this forum.

https://www.tirerack.com/images/pdf/warranty/HO0914.pdf

Is this a case of manufacturers not knowing how their products are to be used? That seemed odd for a racing tire company!

I would appreciate any advice.

Thanks in advance.

I've gone through a bunch of front Khumos and not once I had issues with delaminated tires. The sides are goners after 2 days (for faster guys, it's more like 1 day) but the inside of the tires still has a lot of meat on.
Not sure what the deal is. I start at 26PSI and keep it to 33 Max. I would think that if the tires are over inflated, a few laps would tends to destroy the inside.
Of course, it could be a defect with the tires, but if both are affected, that'd be the strangest coincidence....

[Arizona Vipers]

Guys - I have a track day tomorrow at Laguna Seca. I had a similar experience with Khumos last fall at Laguna Seca in my ACR E. Front left delaminated on the inside. I saw the piece come off in 2.

I'm going to run Hoosier R7's tomorrow. Thanks for the tip to adjust ride height - done.

One thing has me stumped. The Hoosier tire care and safety guidelines for a 3000lb+ car, say recommended pressure hot is 40-42+, cold 30-34 + add more cold if the car has aero. That is in contrast to my experience and most of the pressure levels guys are running on this forum.

https://www.tirerack.com/images/pdf/warranty/HO0914.pdf

Is this a case of manufacturers not knowing how their products are to be used? That seemed odd for a racing tire company!

I would appreciate any advice.

Thanks in advance.

They are just covering their asses. I and everyone I know that's fast run hoosiers around 30 hot. Sometimes I go even lower, I start as low as 19psi. It's taken me years to figure this out though, be careful. Instead of guessing and wondering just take tire temps. They don't lie!

[dadgoneracing]

Thanks for the help Arizona Vipers...

[dadgoneracing]

38739

I ran similar pressures as Blue Adder - 27 cold 34 max hot, and this is what the fronts looked like after about 3 - 8 Lap sessions.

I wasn't able to make the track day yesterday (son had an emergency root canal), so I didn't get to try the R7's :(

Hopefully soon. Thanks for all the info.

[SRT_BluByU]

Wow.. looks like the inside edge? maybe too much camber?

[dadgoneracing]

Could be. I also made a rookie mistake and didn't add pressure after a lunch break, so they could have been low cold, even though I did an easy warmup lap.

[sharmut]

Was the alignment was recently checked? If I recall several ACR-E owners post their OE lower adjustable camber bolts moved over time. I run -2.4 camber up front and got 4 HPDE days(20 sessions) before the outer edge of R7 cored. They actually started to feel greasy after 15 (20 min) sessions.