Please help: Fried Tires after Driver's Ed?

[ohecht]

Sorry for the long description, but I am hoping some of the tire experts can help me diagnose this issue.

I had a great time putting on about 140 track miles at VIR on Monday, but something in my tires is definitely out of balance.

I was driving at the limit the entire time, but only locked up the front wheels once during the day, and never the rears.

The symptoms are a vibration whenever the car is turning right at all, and it is worse once the tires warm up. Going dead straight or left is smooth, but anything even slightly right of center (even staying in the same traffic lane) make the vibration appear.

Inside the car, the vibration feels like it is coming from the rear, but it is definitely tied to the steering input (even minor steering that I would not expect to affect the rear of the car) It is also not the drivetrain, as the vibration is the same in neutral with the clutch disengaged.

I have inspected all the wheels and tires for lost weights or broken belts and found nothing.

The fronts, which are fairly old but have some tread left, have a ridge of what looks like melted and dried rubber (probably from my own tires, but maybe it is some of the race compound other cars were leaving on the track) The ridge is on the inside edge of the outer row of tread blocks on both front tires.

The rears, which are new Bridgestone P03 Pole Positions, look fine throughout the tread, but I noticed something suring my inspection. As I rotated the wheel just off of the ground to inspect the tread, I noticed that one part of the wheel would scuff the driveway as I rotated the wheel, while the rest of the wheel would clear the driveway.

Replacing the front tires is an option even though there is tread left, but I want to make sure that is the issue before doing that.

I am worried about the rears, since I would not expect a new tire to go out of round after one day on the track. Could a belt have broken and I don't see it?

Could I just have the wheels and tires rebalanced to see if that helps, or even have the tired switched to the wheels on the other side of the car and then rebalanced?

I also noticed my brake pedal feels softer, even though there seems to be plenty of stopping power. I plan to replace the brake fluid (SuperBlue) and bleed them really well again, since I think I may have cooked the fluid. I was definitely braking late and hard for the turns. Is there anything else a hard day at the track can do to brakes? (the pads are new)

Thanks in advance,

Olivier

PS: VIR was a blast for my first Driver's Ed. I learned a ton, the car did great for driving 150 miles there, 140 miles on the track all out, and then 150 miles back. There was even a Ferrari F40 doing some fast laps, which was great to see.

[jluetjen]

While the vibration problem you are describing could be tire related (such as the pick-up that you described), I kind of doubt it is the cause. My suspicion would be that you might have a bearing going on the left side, or else a tired bushing somewhere on the left.

The pick-up that you described on the front tires sounds sort normal to me, but it would be hard to say for sure without looking at a picture.

As far as the brakes going soft, I would bleed the brakes and see if it improves at all. You might also want to inspect your brake lines to see if there is any distortion or degradation of the lines. If they are old, they might be going soft from the sudden excercise. Check the fluid coming out when you bleed the brakes, is it clear or not? Also check the fluid inside the resevoir prior to bleeding the system. Is it clear or cloudy? If it is cloudy, your master cylinder may be on its last legs.

Regarding the brake pads, did you bed them in per the manufacturers directions?

[makaio]

John beat me to it, but I'll say it anyways:

1. I think you have a front wheel bearing going.

2. you definatley need to bleed the brakes after a hard weekend of driving like that.

[89911]

Street tires on the track could be cupped or chunked, depending on were on the tire it happens. Is VIR primarily a right hand course? Could explain the uneven wear. Possibly youur street tires are getting very hot and wearing uneven, creating a "cupping" of the tread, usually on the outer edges. Welcome to the world of track tires. They are not just for performance, but also to stop ruining $250 street tires. It also why you don't see excessive tread on a track compound tire.

[nhromyak]

Judging by your quote

As I rotated the wheel just off of the ground to inspect the tread, I noticed that one part of the wheel would scuff the driveway as I rotated the wheel, while the rest of the wheel would clear the driveway.

This tells me your old front tires seperated at high speed. I have had this happen to old truck tires that are only rated to 85 mph after I went to 75 mph.

However, you should be feeling this bump/vibration no matter when turning the tires. Unless this bulge is on the inside of the front right tire. I am not sure about this still...

Good luck.

[Superman]

I respectfully disagree about the wheel bearing thing. This is a wheel or tire problem, probably tire. Perhaps a tire is flat-spotted (you reported locking up the fronts). Poor alignment can cause tire cupping. The fact that the vibration comes up through the steering column proves it is a front tire (which you already know). At 120 mph, tires have to be ROUND. Not sort of round. REALLY round.

[69911e]

I would check all wheel bearings, because a bad wheel bearing will 'kick' the brakes in making them appear to need bleeding.
ED

69 911E
71 Volvo 1800E
71 142E ITB Volvo from hell

[ohecht]

I repacked the right wheel bearing, but I will check them more carefully and I still have to do the left side.

NHromyak: The rear tire seems to be out of round, but it is new <1000 miles, and the tread surface looks great. Could a belt or something be broken and not be obvious? There are no bulges or chunks at all.

VIR is a road course with all kinds of turns, though the hardest (Oak Tree) turn is a tight right-hander.

On the fronts, I do not think the "extra" rubber is pickup from the pattern it formed. It is an almost unbroken ridge around the curcumference of the tire, just on the inside of the outermost tread blocks (i.e. just to the outside of the first tread "void") I don't know what the technical term is, but it seems that some dynamic of the car's motion stressed this part of the tire. The alignment was set recently by a competent shop and the car was corner balanced.

I definitely learned the value of track tires for protecting my street tires!

[Botman]

It sounds to me like your front tires were over-inflated at the track and the tire's "edge" was too far inboard. This would explain the "pickup" on the fronts; nothing more than your own tire rubber.

As to the rear out of round tire, are you sure it's not your wheel?
The symptoms you describe could fit the bent wheel scenario.

Lastly, the vibration on the right front is probably the wheel bearing, but could be a worn tie rod end or ball joint.

Have you tried jacking up the front right and maneuvering the tire around to try to duplicate the slop?

[nhromyak]

OOPs: I thought that was the front tire.

Easies thing would be to find another set of tires, and "trade" them with another P-car for a short drive. See if the problem goes away.

Good luck.

[ErVikingo]

What scares me (as an instructor) is that you say you were at the limit all the time and this is your first DE.

[Superman]

I'm hoping to learn something here. Enough people have suggested wheel bearing problems that I'm paying attention. My experience would not support this conclusion. Respectfully, I woudl otherwise be calling this a no-brainer. A tire is simply not round. With an out-of-round tire, are we still thinking that vibration is a wheel bearing matter? I have never known wheel bearings to make a vibration problem. Noise problem, yes. Definitely yes. Wheel bearings can sound like a Douglas dive bomber. They can compete with the best of sound systems. But vibrations are nearly always tire-related, or at least wheel-related. And we know that at least one wheel is not round. Are there any rocket scientists out there to help us make this connection?

[jphillips-998]

Juan,
Being at the limit as a first time DE'er and a 20th time DE'er is a LONG way apart. I thought that I was at the limit for my first DEs as well. Checking lap times and videos I was no where close. I am guessing that the "edge" is a moving target that comes with experience, smoothness and speed.

[ErVikingo]

Amen Jeff; very well put.

[spinner]

I had a somewhat similar problem a few weeks ago. I have a 87 911 with Yoko 032R tires which are very noisy tires. I started noticing a sound coming from the wheels/tires and thought the cause was a wheel bearing going bad. So, I replaced them since they were (probably) the factory originals. To make a long story short, the bearings were not the cause. The cause were sticky pistons. One piston on each caliper were sticking. Once I rebuilt them, everything is back to normal. To check, try removing the pads. If a pad feels "frozen" and you need to attack it to remove it, the piston is sticking and you need to rebuild the caliper.

Paul

[6 Shooter]

Whenever I've seen a bad wheel bearing (broken cage/bad pitting-beat up races), I've heard a bad wheel bearing. The bad wheel bearings/worn races/broken roller cage can make a low, gravelly sound. But then, I'm not a rocket scientist... just my 2 cents....

[stormcrow]

Oliver,

First thing I would do is return the out of round tire for a new one that will definitely cause a vibration.

As far as the front vibration, with your tires worn on the inside, that would definitely cause the vibration because as you turn, the load is on the inner part of the tire where the cups are. You should think about replacing them. The cupping would cause a vibration when you turn especially if it is uneven - there could be a high spot there. Were the weels turned when you locked them up?

If you had a bad bearing, you would definitely know it - it would be noisy. Since they were inspected and there is no excessive play I would rule out them as being the problem.

Steve

[ohecht]

Juan,

I definitely meant at my limit during the DE.

The tires were straight when I locked the fronts, and it was only for a split second.

The only play in the front end was a slight side-to-side that I expected, as I had taken it easy on the outside bearing preload during the last inspection. The cadence of the vibration is very rythmic with the wheel revolutions and definitely sounds more tire/wheel related than like a bearing.

I would love to trade tires with someone just to confirm my suspicions. They are unidirectional, but I wonder if swapping sides for a short drive would help me pinpoint the problem. THey wheels are aluminum alloy (C2 cup?), which I would be suprised to see bent with no major trauma.

I should check the calipers and pistons. I have rebuilt them once before, and they were in pretty rough shape then. One of the pistons was seized then, and I could definitely tell. I could hear the pad rubbing the rotor and it would groan as I left a stop.

The ridge of rubber was on the outside of the front tires. I'm not sure if that makes a difference regarding what may have caused this or if that is the problem.

I think it is time for new front tires anyway, so I will probably put P03s there and then keep looking at the rears and the brakes if that does not get rid of the vibration. I need to hurry before I get used to it. I had become accustomed to a similar vibration last year, and it turned out to be a severly broken belt in the rear tire with steel through the rubber (hidden on the inside during all of my inspections). I didged a bullet on that one, as it was only discovered as I replaced the tires anyway due to wear and because an autocross was coming up.

Olivier

[ErVikingo]

Olivier,

I didn't mean to sound mean or anything. Just a concerned instructor here. Ain't it fun to drive the car the way it was supposed to (and in a controlled environment)?

My recommendation is to get a second set of wheels with tires for the track only as street tires don't take the heat cycles as well. I have seen tires that look perfect on the outside yet have had "delamination" due to the heat and heavy braking forces put into them.

I recently saw a tire which apparently got out of round after putting it through a grueling session (1.5 hours) at Homestead and then after one cool down lap parking the car for several hours. I spoke to the owner and the tire never recovered trueness.

There is apost which mentions the AO32's from Yoko. I have a set of those on one of my cars which I use for the road and DE events. They are very noisy (sounds like a busted bearing) but offer a great compromise for what you are doing.

The R1's are another option but (from personal experience) I wouldn't drive them around a lot since they are so sticky that they pick up a lot of rocks and can "sandblast" your wheel openings or at least the edges of them. Since you are doing DE, I would not get them shaved.

The Kumho's have a very good reputation also but I have not used them. Another thing to consider is the cost of this whole thing, SO3's are very expensive and you could go through a set in one day.........................

On the brakes, always bleed before every event, cool brakes help a lot and do not change aesthetics of the car. Super Blue is excellent and reasonably priced. I will not comment on pads here as I'm afraid I'd start a very long thread.

On the bearings, I cannot comment just based on your post but, when in doubt, have them gone over (cheap insurance!) also have the CV's checked. CV boots not used to hard work at tracks tend to give up due to the high temperatures generated.

Now, go back and enjoy the car.

Juan

[dickster]

i'm with super on the bearing. it would be making a hell of a noise.

sounds to me the fronts are out of balance, which makes sense if you just tore half the rubber off.....and you say they need replacing anyway.

i'd start with new front rubber/balance.

how fast before vibration sets in???