Groove of Death

Gwen Habenicht · **Posted:** Mon Nov 02, 2009 3:30 pm

Friday when we were packing to head down to Sanford we noticed this groove, just inboard of the outside "tread" of my Kumho V710s. These tires are basicly new. I used them for NCAC and 1 other event for a total of 20 runs. At the time I thought it was wierd, but didn't look too closely, so didn't see the cording until Saturday morning on site. I took these pics today with my phone to email to Tire Rack when I was talking to them. If anyone has seen this before could you tell me more about it?

This shows the size of the patches that are starting to cord.

This shows the indentation just inside of the tire's tread line.

The groove that goes all the way around both of the tires (both with the same lot code) looks like the outside rubber is a skin and what's under it has separated.
I've been using Kumho V710s for 4 years now, and usually get well over 100 runs on them before they get designated to rear use only.

I'm waiting to hear back from the tech guys now at Kumho. I sure hope they'll be willing to do something for me. Just shy of $700 for 20 runs is steep. I have only used 2 of the 4 that I bought, but still, how much different will they be-same lot and all?

Aaron Buckley · **Posted:** Mon Nov 02, 2009 4:47 pm

That looks like the "Groove of Death" of Hoosiers. Is that the inside of the tire or outside? - AB

Gwen Habenicht · **Posted:** Mon Nov 02, 2009 5:08 pm

It's on the outside.

Aaron Buckley · **Posted:** Mon Nov 02, 2009 5:19 pm

Who mounted the tires for you? IIRC, the grooves are supposed to be to the inside of the wheel.

That wear you see is due to lack of camber and under-inflation. The sidewall is rolling over and putting most of the "effort" on that groove. While Kumho has said for a long time that their tires are designed to be non-directional, the highest concentration of tread is on the non-grooved side and the belt layering is setup as such.

Hopefully Kumho will help you out, but I have seen this with Kumhos when flipped. - AB

Karl Shultz · **Posted:** Mon Nov 02, 2009 5:31 pm

Gwen, are they holding pressure properly? Earlier this year, I had to get a Hoosier plugged. It was a slow leaker after that. As I continued to use it, it never came apart or delaminated, but it certainly did wear strangely.

Gwen Habenicht · **Posted:** Mon Nov 02, 2009 7:07 pm

Aaron, good eye. You are correct. As a matter of fact, they were mounted backwards. While we always flip our Kuhmos-which is probably why we didn't notice- I've never mounted new ones that way. I haven't gone home yet, but I'll check the 2 I haven't used, and if they're mounted wrong I'll get them changed. If the problem continues, we'll have an answer in that regard.

Karl, as far as pressures are concerned, I run 35-36# on the front and have for some time-like 2-3 years. I'm pretty anal about pressures and check before and after every run. So, since it's never happened before, I'd guess that low pressure is probably not the culprit in this case.

I haven't heard back from the tech guy yet, but I guess we'll know something soon. He's got the pics so he'll see they're mounted backwards. Now we'll find out if they really say it doesn't matter.

Scott Johnson · **Posted:** Mon Nov 02, 2009 7:48 pm

Gwen Baake wrote:

Karl, as far as pressures are concerned, I run 35-36# on the front and have for some time-like 2-3 years. I'm pretty anal about pressures and check before and after every run. So, since it's never happened before, I'd guess that low pressure is probably not the culprit in this case.

Pressure gauges sometimes get way out of calibration...

Gwen Habenicht · **Posted:** Mon Nov 02, 2009 8:26 pm

scottjohnson wrote:

Gwen Baake wrote:

Karl, as far as pressures are concerned, I run 35-36# on the front and have for some time-like 2-3 years. I'm pretty anal about pressures and check before and after every run. So, since it's never happened before, I'd guess that low pressure is probably not the culprit in this case.

Pressure gauges sometimes get way out of calibration...

Scott,
Did you overlook the word "anal'? :wink:

We have 4 gauges, not including the one on on the compressor in the shop that we use when we check the tires before we leave home. I'm pretty sure the pressures I run are pretty close.

(Side bar: did you just move to Durham? I thought you guys lived down east.)

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

I vote for more air pressure. I first saw this on the old BFG R1 224/226/230 series tires, which had the "hinged" belt construction, but I've seen it on Victoracers too. The belts bunch up under side loads and bulge outward, forcing the tread at that spot to press harder into the pavement. As to why you're seeing it now:

a) It's possible that having the tread groove near the outside weakens the carcass.

b) With the fixed roof, your new car's chassis is stiffer and probably lets you corner harder.

c) You're driving faster.

More air will help, but you should get those tires flipped ASAP.

Carl Fisher · **Posted:** Tue Nov 03, 2009 12:32 am

We've had the "groove of doom" before, though not on V710s. We were told by the Tire Rack folks that it was from running pressures too low. I don't know if the mounting direction could be the cause, as I've also heard you can flip V710s, but for sure I would at least start out with them mounted the right way so the big shoulder takes the majority of the wear (assuming that well over 50% of the life is gone before they're flipped).

Gwen Habenicht · **Posted:** Tue Nov 03, 2009 3:44 pm

Well, I haven’t heard the final answer on the tires yet, but here’s what I suspect. My bad for not noticing that the tires were mounted flipped. While we routinely flip tires, when we do so they usually get limited use on the front and then get moved to the “I’m just here to keep the tail from dragging” position. We’ll take these 4 back to the garage and have them mounted properly. Well, 3 anyway, since the 4th one is corded. I think Bernie hit the nail on the head. The guy who took the old tires off the rims (old=flipped) simply mounted the new ones the same way since I’m pretty sure that he doesn’t read English and wouldn't have seen the note on the wall of each tire. Lesson learned; check tires each time they are mounted to be certain they are mounted correctly.

They did also ask what pressures I run on the front, so we’ll get a definitive answer on that as well.

Chuck Frank · **Posted:** Sun Nov 08, 2009 12:22 am

I'm pretty anal about tires as well, we even keep a log of how many runs each tire has had and in which position on the car. IIRC when Donna was driving Mark and Jeff's Minis on Kumhos that was pretty typical of the wear pattern of the front tires due to the camber challenged nature of the Minis. They were pretty pleased if they got 24-30 runs, including with flipping, out of a set before the edge of the belt started showing like that. Of course they all drove them pretty hard. That year with 3 sometimes 4 drivers driving the two cars they went thru 16 sets of tires! We bought a new set for Donna and I to use on the H/S car at a weekend invitational test and tune at Peru that year and we completely corded them by mid day Sun. (had them flipped Sat eve and rotated them every 8 runs). I'd also suggest going up a couple # on the front tires, they may not feel as good, but your times should improve as well.
Until the tires start to cord in the centers, upping the pressure increases the grip. I know some will disagree, but I have been personally told that by both the Khumo and Hoosier engineers, so I tend to believe them over the seat of the pants evaluations.
I also put a chalk X on the outside sidewall before taking tires to be mounted or flipped, stand there while the work is being done and recheck them while loading them before leaving.

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