Tire diagnostic help

[///m3]

On the second day of Roebling Road last weekend, I could hear a 'thud-thud-thud' and feel it in the steering wheel in a left hand turn. I'm guessing this is the culprit:

Then about half way through the day, the car was understeering like you wouldn't believe. It was like the front tires were all of a sudden covered in grease. After an inspection following the session, I found this:

All of the tread delamination is on the inside edge of the tire. You can see that there is plenty of 'tread' left on the tire, they've only been used at 7 or 8 events. They're 275/45/17 Avon Tech R on stock rims.

My first thought is a toe problem. But I'll have to find the alignment specs to see what it was aligned to.

Any insight?

 

[gcassidy]

What's your camber?

 

[wheelhopper]

That exact same thing happened to the Tech Rs I was using.* I used them for 5 or 6 events.* I did not have that wave in the first picture, but the tread delamination was there.* I have read elsewhere that this can occure when the ABS kicks on a lot. for the record I was running about -1.6 degrees camber during their use.

 

[Lumpydogs]

Hard to tell from the photos but looks like you might have been a little low on tire pressure. :shrug: Combined with excessive negative camber, the tire pressure issue could have worn the tire that way.

Do you monitor tire temps Inside/Middle/Outside?

 

[ac427cobra]

Patrick:

Is this your right front? Pretty common actually. You need to rotate more. oke:

You're primarily turning right on a road course and that tire is getting scrubbed off on the inside.

If that tire would have spend more time on the left side of the car, the outside of the tire would be scrubbed down as well saving the inside a bit.

FWIW

:thumbsup::coolman::beer:

 

[///m3]

Clarification: The last two pics are the two front tires: LF first and RF second.

I still can't find the alignment specs, but I'm pretty sure they were just the stock settings, with possibly slightly more camber. I have no abnormal tire wear on the street tires. This whole thread may be completely useless without those alignment specs.

I monitored tire pressure to 39-40psi hot through out the day. That was about 31 degrees at cold. I do not have a temp probe for tire temps, but it might be a worthwhile investment to save another set of race tires.

I was actually pretty religious about rotating the tires between each event. :-D LF to RR and RF to LR.

It's hard to see in the last picture, but the outside of the tire was also getting very thin.

We got the Tech Rs for really cheap, but I don't want this to happen to the new tires. Slightly off topic: I'm leaning towards the NT01s. They're $100 cheaper than the R888 and BFG R1. Any objections?

 

[gcassidy]

Did you get the Tech Rs when Tire Rack was selling them at closeout? That was a few years ago. I got some then, and after wearing them thin, have gone through 2 sets of other tires since then.
I wonder if age could play a part? :shrug:
If your street tires look OK, and you put on enough street miles for a camber problem to show up, then it's probably not that.
But then, on the other hand, you say the tires felt greasy, and inspection showed the cording. That must mean most of your traction was coming from that portion of the tire. I know when I corded my last set (on the outer edge of RA1s), I never felt a thing. My buddy in the pits pointed it out to me.

 

[MFE]

Seems likely to me they were overheated on the inside edges

 

[ac427cobra]

Clarification: The last two pics are the two front tires: LF first and RF second.

I still can't find the alignment specs, but I'm pretty sure they were just the stock settings, with possibly slightly more camber. I have no abnormal tire wear on the street tires. This whole thread may be completely useless without those alignment specs.

I monitored tire pressure to 39-40psi hot through out the day. That was about 31 degrees at cold. I do not have a temp probe for tire temps, but it might be a worthwhile investment to save another set of race tires.

I was actually pretty religious about rotating the tires between each event. :-D LF to RR and RF to LR.

It's hard to see in the last picture, but the outside of the tire was also getting very thin.

We got the Tech Rs for really cheap, but I don't want this to happen to the new tires. Slightly off topic: I'm leaning towards the NT01s. They're $100 cheaper than the R888 and BFG R1. Any objections?

With the further explanation, that helps a bit.

IMHO you need to rotate tires more than once per event. More like once per day.

I didn't like the Avon's one bit. But I did find that they worked a LOT better at much lower pressures than what you were running. However, my car may be lighter than your car, I don't know.

You will absolutely love NT-01's after driving on those crappy Avons!!!! :bowdown:

Hard to tell from the photos but looks like you might have been a little low on tire pressure. :shrug: Combined with excessive negative camber, the tire pressure issue could have worn the tire that way.

Do you monitor tire temps Inside/Middle/Outside?

A agree with Jeff here that this could be under-inflation particularily if the worn edges are the left side outers! :idea: But the pressure you were running is quite high so you definitely need to take tire temps to find out the real story!

:thumbsup::coolman::beer:

 

[///m3]

With the further explanation, that helps a bit.

IMHO you need to rotate tires more than once per event. More like once per day.

I didn't like the Avon's one bit. But I did find that they worked a LOT better at much lower pressures than what you were running. However, my car may be lighter than your car, I don't know.

You will absolutely love NT-01's after driving on those crappy Avons!!!! :bowdown:




A agree with Jeff here that this could be under-inflation particularily if the worn edges are the left side outers! :idea: But the pressure you were running is quite high so you definitely need to take tire temps to find out the real story!

:thumbsup::coolman::beer:

Really? It's only about 1.5hr of track time per day, sometimes twice that if the wife and I are running in different groups. I guess that does add up to a lot of track time.

I didn't mess around with the tire pressures a whole lot. It's really her car and we just started sharing it. My only point of reference was the M3 which ran the RA-1s at 39psi and felt great. It's a full interior Cobra: 3770lbs with all 175 lbs of driving fury inside.

A tire probe is definitely on the to-buy list before the SVTOA event at Sebring in May.

Thanks guys.

 

[wheelhopper]

FWIW, I ran the Avons at 36psi front and 34 psi rear, cold. I had the best feel on the track at these pressures. I also thought the Avons hooked better than the Hoosiers I am using now. Though the price for the used Hoosiers is going to keep me using them for a while.

Also found out from several different resources, in the know, this past weekend that the Hoosiers like to be run around 30psi hot. I set the cold pressure at 26 front and 24 rear cold. I did not check hot pressure, so I may have been running them a little high. But, they felt real good. My next event I will drop the pressure a couple psi and see how they feel.

And if the Nitto NT01s feel way better than the "crappy Avons", I need to get some NT01s, cause I liked the Avons.:shrug:

 

[David Hester]

Wheel
Did you talk to Hoosier folks?
I've been racing on Hoosiers since the late 80's. Slicks, DOTs, Rains.
Yes the "new" R-6's like less pressure, but more in the 40 psi range hot.
I ask the tire guys every time I buy a new set what they are suggesting.
Appalachian Tire
Rodney Perry
Mike Haworth
1919 Airbase Rd
Louisville, TN 37777
ph. 865-681-6622
fax 865-681-0775
e-mail: [email protected]
Rodney has never steered....me wrong. :nonono:
Hoosier Tire
^ tire tips. Note 3/4 down about IRS cars, still looking like 37-38 cold for 3700+lb car.

You spend alot of time in corners at Roebling. Over aggressive driving, Too much or too little toe, ( I don't think you can get too much chamber there), and you wear fronts.
Something else to consider, chamber is for corners. Really is crappy in a straight line. Too much braking in a straight line will wear the insides quickly, especially if you are using ABS... without it you just get flat spots.
Another FWIW, I have corded tires at Roebling, too, but always the outside even with 2+- degrees of chamber.

 

[brkntrxn]

Patrick,

How often were you inducing ABS at T1? I am really curious about your alignment settings...



David,

Not to hijack this thread, but I believe Doug has the same "used Koni Hoosiers" as myself and a few others. I tried to go by the suggested air temps for the R6/A6s and they were just too high.... I used to start them at 33-36 cold. After taking the advice of a couple of racers I trust, I dropped the cold pressure two weeks ago on VIR South to 22psi cold and the tires felt much, much better. Then again, they may have had a lot of heat cycles in them by that time and the lower pressure could have just been off-setting the greasiness of the age.

 

[David Hester]

Could be. The Koni Series tires are not DOT.
Hoosier racing slicks, we used 10-11 psi.
That being said, all the racing DOT "treaded tires" react pretty much the same- Hoosier, Yokohama, Goodyear, BFG. I talked to tire engineers from all 4 over the years. Not sure Avon DOTs would be any different.
And yes, those pictured are blistered tires, not jut wear, but popped blisters. Those tires got hot in a small area.

 

[brkntrxn]

And yes, those pictured are blistered tires, not jut wear, but popped blisters. Those tires got hot in a small area.

So would that go back to the ABS induced braking question/comment? Did Patrick hit threshold braking too often and that is what killed his tires?

 

[wheelhopper]

Dave, Bruce Griggs was one of the guys that enlightened me to low pressure in the Hoosiers. He gave a seminar at the VIR NASA event. A couple instructors prior to the seminar said the same thing. One of them mentioned to a friend of mine to start with 20psi cold in the front and 18psi rear. That sounded like drag racing pressure to me, so the lowest I went was 26 front and 24 rear. My friend was running a couple psi lower. Neither one of us had any complaints about the way the tires were hooking.

As far as the issue with the tires in the pics. I happened to read an article in MMFF when they were building their CMC car. The article had a picture which looked exactly like those tires above and like mine. MMFF had listed pics of tires with various issues and said that this problem was seen in cars that enacted their ABS a lot on track. I know that I have done that at times. Though the edges of the Avons were blue.

 

[gcassidy]

I also remember in the past Roebling Road was paved with a mixture of asphalt with ground sea shells mixed in. It had great traction, but was hell on tires. Is it still like that? If so, that would accelerate any tire wear issues.

 

[David Hester]

Remember ABS engaged when the sensor picks up a change in relative wheel speed with the other wheels-point of lockup.
I'm guessing if you just stomped the brakes at the end of every straightaway, you could really generate some real heat. Maybe try a more steady increasing pressure on the brakes. Blue tinge to tires happens from time to time from heat, but from what I've heard, doesn't hurt them- just the oils escaping. They will work fine next time out.

Yes, Roebling did resurface a few years back and they do use crushed sea shells.. don't know where they would get them.
Pretty abrasive stuff, but that being said, I've run the same set of tires there all weekend and still had something left. 15 practice, 20 qualify, 35-40 race.
The race I got got down to cord I was chasing a Porsche. I pass him, he'd pass me, I pass him, he'd pass me.....and stayed there. Steel cords just wouldn't grip the shells.

 

[///m3]

I know I never got into ABS and probably only near threshold less than half a dozen times over two days. It's only my 3rd day driving the car and I hadn't built up the confidence in the brakes yet. It's a full interior street car with stock brake calipers/rotors. I do have cooling ducts from Mid-Continent and Carbotech XP10 in front, XP8 in the rear.

 

[David Hester]

How about tire squeal? What about push? Something heated up the tires.
3 and 5 are the left handers, but you aren't in either as long as you are in 1,2,4,6,7 and 9. :shrug: