What is the cause of this detachment of tread? I had a similar failure on a front tire where a 1" diameter section of tread detached. The pencils point to two sites where it appears similar failure is developing.


Tire is Hankook R-S4 245/40-15 on 8x15" Fuchs rim.Inflation is typically 34 PSIG hot.
Car is '83 911SC PCA D-stock (so maybe 180RWHP). Weight is 2600# wet with driver.
Exclusively used for DEs. Have 8 weekends on them, but I share the vehicle with my son so probably 100 sessions (!). Sometimes we run back-to-back sessions, so total heat cycles may be less than session count.
Obviously, given the number of sessions, we are far from 10/10.


correction: rear toe is -5/32" (i.e. is toe in)


Thanks in advance,
Steve

 

Things that may help diagnosis are:

Suspension settings?

Track clockwise or counterclockwise?

 

100 sessions on that set of tires? They're probably just spent. You got your $$ worth for sure. I wish I could get 100 cycles out of a set of tires...lol.

Maybe take a look at Toe and Camber when you throw the next set on and do a little more aggressive of a track alignment?

IMHO, I think it's just a ton of wear on the tire....

 

I'm not experienced enough to say what causes a tire to fail in that fashion.

That said, I drive a similar car and it is awesome be able to get a full season out of a set of 200tw tires.

 

Suspension settings added to original post. Thanks for the reminder.

Sessions at MSRH (the majority of runs) generally alternated direction, but COTA and ECR are CCW only. Failure is on inside edge of LR.

I agree, we got our money's worth out of that set. I'm just interested in the cause of the failure to know if I need to do anything different (other than the obvious need to drive more to the limit and use up the tires before getting that many heat cycles).

 

Maybe a stoopid question, but could yield an answer:

Do you drive the car to and from the track?

 

Trailered to events, however the car is licensed and I take an occasional check ride for a few miles on the street. Usually just once prior to an event so no significant mileage.

Tires I have used before (mostly Toyo RA1, Bridgestone RE-11) never sloughed off sections of tread, even when worn down to the cords. They were slower, of course, when worn but never gave me concern they could abruptly lose significant sections of tread.

And I agree with the general sentiment that 100 sessions is plenty good.

 

Really recommend you send it to Hankook. They'll want to see it. Do it through a dealer. If not, call the national office.

 

Good. Reason I asked is that I've seen insides of tires wear more than outsides if the car is driven long distances to the track with a track alignment on the car. Glad that's not the case here.

 

That seems like a lot of rear camber for a street tire, and for a setup that can get that many heat cycles. In the rear you would be stressing the inside edge under both straight acceleration and braking. If you are looking for ideas, try running a bit less rear camber?

 

I have an endurance race team and we have used the RS4s exclusively for the past 4yrs, so we have lots of experience with these tires.
I agree about your camber settings being too aggressive. These tires have a very stiff sidewall which means you need far less camber than a race DOT or slick.
Our 944 settings in full race trim are closer to -2.5 front and -2 rear, and we have lovely, even wear after 16hrs of hard racing. Running close to -4 camber will likely overload and prematurely wear the inner tread, not to mention harm your acceleration and braking.

 

So much for "as much camber as you can get". Makes sense that excessive camber on a stiff sidewall would overload the inside tread. I typically watch the outside shoulder carefully to detect rollover resulting from inadequate camber. Am I correct thinking that excessive camber will not roll the inside edge over (because the force applied by the track is coming from the direction of the outside edge), but will instead overload the inside tread? I didn't suspect camber issues because the tread wear seemed pretty even and, of course, I was fixated on the outside shoulder being vigilant for inadequate camber. This is my first set of R-S4s. Great tire, but my setup is probably better suited to the Toyo RA1s I ran previously.

Thanks for sharing your expertise, Gear Rower.

Here are additional photos showing the inside and outside shoulders in the vicinity of the tread failure.


and a better view of the tread

 

A few years ago I ran a set of RS4 on my Spec Boxster for 2 seasons of DE (22 days and at least 100 cycles), camber was 3.2 in front 2.7 in rear, 2,500 lb car with zero toe in front. They wore very evenly and I rotated them a few times but those things would just not die, I finally tossed them as their performance(but not tread) was really falling off and I felt I def got my money's worth.

 

Good one. I see what you did there. Seriously, you're running comparable sessions and heat cycles with no ill effects, just lower performance as the tires aged out. Time to pull out the alignment tools and ease off the camber.

Thanks for the info.

 

Texas heat?