Michelin Sport Cup Concern

[GR8_ASP]

Luke,

I was looking at my new Sport Cups after about 800 miles. All but the left rear looked fine. The left rear has a crack or cut across most of the tread that looks like a problem. Note the crack/cut extends beyond into the radius on the outside edge indicating a mechanical cut is unlikely. Take a look and let me know what you think.

Full width:


Then 3 blow-ups

[GR8_ASP]

Any comment Luke?

[DavidSB]

I think he's off work for a while with a new baby.

[GR8_ASP]

At the recent MCVO spring tech day I showed it to the engineer that was responsible for tires and suspension from the original Viper team. He thought it was a splice or overlap location from when they place the raw rubber product on the drum. He did think it was unusual that the region was not fully vulcanized and fairly deep.

I am not sure I am comfortable driving at high speed with these anymore. Who can I contact from Michelin that can assist me (I purchased them from JonB and indirectly from Tirerack)?

[Luke@tirerack]

it definitely is a tread splice .... and since the sport cup uses a butt splice I doubt it will go away like other tires will with a change of rotation. I am going to contact Michelin on your behalf but I do have a couple of questions.

1.) how long have you had them
2.) what is their use (i.e. street, track days, drag racing etc.)
3.) if primarily used for track events how many?

and any other info you care to add

[GR8_ASP]

Luke here are the answers.

1.) how long have you had them
I purchased them in mid April (with a set of SSR's through Partsrack). They have about 1000 miles to date.

2.) what is their use (i.e. street, track days, drag racing etc.)
So far primarily street. I had them a Gingerman for about 30 laps total, with about half easy laps due to a braking issue (loss of ABS).

3.) if primarily used for track events how many?
Answered above. In general I go to 1 to 2 track events a year and would consider myself moderate for how hard I am on tires (1 road and 1 autocross). I got 14,000 miles out of the stock Pilot Sports with the same overall driving (though only the rear were worn to the limit - all 4 tires were over heat aged and lost traction). No drag racing to date on the Sport Cups and only once on the Pilot Sports in 4 years.

[Luke@tirerack]

ok, Michelin will cover it under warranty ... give me a call for specifics

[GR8_ASP]

Thanks Luke. I will give you a call tomorrow.

[Vipera Russelli]

Interesting. Thanks for sharing those pictures, Ron.

By the way, it looks from one of the pictures that you might be wearing the outer edge a bit more than the rest of the tire. Have you added any negative camber? I had to, but not before burning through a set of Cups too soon by wearing out the outer edges.

[GR8_ASP]

I noticed the wear on the outside as well. The other thing is the tire pictured wore at about twice the rate of the right side tire (Luke how does this impact the warranty?). Not sure if it is related to the splice issue or what but it was very noticeable when we had our tech day last week (mine was on the hoist). The fronts wore even right to left side.

I did not change the alignment settings - they are stock.

[JonB - PartsRack]

I noticed the wear on the outside as well. The other thing is the tire pictured wore at about twice the rate of the right side tire (Luke how does this impact the warranty?). Not sure if it is related to the splice issue or what but it was very noticeable when we had our tech day last week (mine was on the hoist). The fronts wore even right to left side.

I did not change the alignment settings - they are stock.

The LEFT REAR shows more wear, in part, due to your weight on the left, and making more right-hand turns. Normal, esp if you are a heavy guy like me!

HOWEVER: Placing a NEW REAR on the left creates a slight STAGGER. It will make the car turn Right, and push Right, toward the 'low' side. I would measure the tread on the used tire, and ask Luke to SHAVE the new tire (and heat cycle it) to match, IF THE DIFFRENCE is more than 3 or 4 32nds........ The stagger matters on a stiff-framed Viper, but not an Oldsmobile..

[JonB - PartsRack]

........By the way, it looks from one of the pictures that you might be wearing the outer edge a bit more than the rest of the tire. Have you added any negative camber? ..

Outside Shoulder wear is the result of OE-stock ALIGNMENT, esp w/track events.
If he had dialed in some negative camber, the INNER would wear more, becuase the tire becomes 'flat-footed' during hard cornering. With stock alignment, you use more outer shoulder.

Thanks to Luke and Michelin for jumping in to fix this tread anomaly

[GR8_ASP]

[The LEFT REAR shows more wear, in part, due to your weight on the left, and making more right-hand turns. Normal, esp if you are a heavy guy like me!

Now now Jon

The higher number of right hand turns could be the cause for the higher wear. I had a passenger for about 25% of the laps, though they were laps after I had the ABS issue so they were not as aggressive. had to divert the attention away from my weight

Note Michelin recommends an adjustment in alignment with the Sport Cups. I did not as I was/am planning on lowering the rear a little and doing that afterwards.

If the right to left stagger is an issue I will just have to go to the track and correct it.

[GR8_ASP]

ok, Michelin will cover it under warranty ... give me a call for specifics

More to come on this saga. I will post later with more info and pictures.

[Luke@tirerack]

More to come on this saga. I will post later tonight with more info and pictures. I expect that it will not paint a pretty picture of Tirerack, Michelin and indirectly Partsrack.

actually, your beef would be with Michelin not The Tire Rack or Parts Rack. We are working with Michelin on your behalf though.