I've been having a virbration in my car at highway speeds that has been bugging me of late. Tonight I noticed that my driver's side front tire has started to cup, it has approximatly 10,000 miles. My last tire in the position in the car cupped as well which prompted me to buy the new set.

The car is an 87 GT with 180,000 miles. The inner and outer tie rods, the wheel bearings, lower ball joints, shocks, and sway bar end links (poly) have all been replaced. The car has had a recent allignment as well. Essentially this means only the control arm bushings and upper ball joints have not been replaced.

Does anyone have an idea what causes a tire to cup? The tires wear evenly other than cupping.

tHANKs

How often do you rotate and balance? Good rule of thumb for maximum tire wear is every 5-6 thousand miles.

Well these tires have 10,000 miles on them......so less than every 10,000 miles. I do plan on rotating the front tires now that I identifed the issue.

Rotating wouldn't explain why this only happens on the river side front and why not on the passenger side?

alignment and low air pressure.
and not rotating

Does it pull hard?

If the front has too much toe, the tires can skip, causing the cupping at the wheel with the least grip.

quote Originally posted by Hank is Here: Rotating wouldn't explain why this only happens on the river side front and why not on the passenger side?

odd tire wear in just one corner is the reason you need to rotate them.

http://www.partsamerica.com...anceTireProblem.aspx

"Cupping can be caused by an unbalanced tire condition, faulty wheel bearings, loose parts, fatigued springs or weak shock absorbers. Check the condition of the shock by forcefully bouncing the front end of the car several times and releasing it on the down stroke. Failure of the vehicle to settle after two strokes suggests worn shocks or struts."

More than likely it is your alignment and not rotating. I work at a tire shop and about 70% of the time most customers get new tires is because they neglected to get an alignment at all. I usually recommend getting your alignment checked when you are buying new tires and also about once a year IMO.

Hope it helps,
Tommy

Majority of the time its bad balance or shocks/ struts. It cups (flattens like little divits in the tread) because the tire is bouncing or skipping on the pavement.

cupping is caused by excessive spooning with your car.......
or check for loose front end parts (tie rods, balljoints, bushings) any movement is bad. Worn out dampers (shocks and struts) will cause cupping. Low air pressure will not.
Dave

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1999 Mercedes ML430, 450hp 1987 Fiero GT, 1986 Fiero SE-soon to be 3800, certified master technician
www.njautobahn.com

My vote is for a weak spring. Usually shocks will cause cupping, but a weak spring will also. If you have replaced the shocks, then you have ruled this out. Bad alignment, toe, camber/caster will cause feathering or abnormal wear, but not cupping. The cupping is caused by bouncing, that leaves two possibilities, shock or spring. Did the same wheel cup before you replaced the shock? You could still have a bad shock, wouldn't be the first time I have recieved a bad part ( comebacks suck at the shop, especially when it is not your fault). Just my $0.02....

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carpe diem

quote Originally posted by frankenfiero1: My vote is for a weak spring. Usually shocks will cause cupping, but a weak spring will also. If you have replaced the shocks, then you have ruled this out. Bad alignment, toe, camber/caster will cause feathering or abnormal wear, but not cupping. The cupping is caused by bouncing, that leaves two possibilities, shock or spring. Did the same wheel cup before you replaced the shock? You could still have a bad shock, wouldn't be the first time I have recieved a bad part ( comebacks suck at the shop, especially when it is not your fault). Just my $0.02....

Damn, You would fail an ASE test. Caster doesn't cause tire wear. A weak spring would change ride height, but has nothing to do with the dampening of the suspension. That is the purpose of the shock absorber. Toe being out can cause cupping, but only on the edge of the tire. If the cupping is over the entire tread, I would replace the shocks. If you have any more alignment questions, my wife would be happy to answer them.
Dave

[This message has been edited by bmwguru (edited 08-09-2007).]

as mentioned above - cupping is either something loose & vibrating - or the tire "dribbling" due to weak shock/dampening or unbalanced. the fun of cupping is the fact that the cupping causes even more vibration, and more cupping - its a self feeding problem once it starts.
and, if the upper balljoints are sloppy enough to cup the tire - the guys doing the alignment would have told you so. part of their job. and, that brings in $ for the install. so, that leaves the shocks. might even just be a loose shock - do you hear a rattle up front? either way - if you never have - replace the shocks. they be cheap. they be easy.

My friends cupped due to dropping the clutch at 4k at every stop light.

The tire appears to only be cupping on the very inside edge, the center and outer side are still okay. Sounds like an alligment may be a good idea specifically looking at the toe. I'll remove the shock and see if it is still good shape since it doens't take too long.

blown shocks/struts are a major cause of cupped tires

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Former West Coast Fiero Employee
www.WestCoastFiero.com


Eric Nelson
Internet Sales Manager
Power Ford Valencia
nelsone@autonation.com

quote Originally posted by Hank is Here: The tire appears to only be cupping on the very inside edge, the center and outer side are still okay. Sounds like an alligment may be a good idea specifically looking at the toe. I'll remove the shock and see if it is still good shape since it doens't take too long.

If it is only on one tire on the inside edge, I would take a closer look at the tightness of the front end. A bushing, balljoint, or something that will cause the tire to wobble down the road. A shock would leave the tire cupped across the whole tread unless your camber is pushed way in. With the age of the car, I would look closely at the arm bushings, but check everything.
Dave

Yes GURU, caster will not affect wear, I was combining factors. If you read the post however, the shocks HAVE been replaced. I have had to replace two springs (variable rate) in my shop because all of the ASE mechanics he had gone to before had replaced the shock (4 mindless garbage in garbage out ASE mechanics). I think OUTSIDE the box, not what I am told to think. It is principles, not some test made by college idiots. GURU, you must be a young pup, because you spout off book smarts when you should be spouting "years of experience". Also proclaiming yourself as ANY type of "GURU" proclaims a severe air of arrogance or even inferiority. The spring can still be weak and not assist the shock enough, thus the cupping. Due to the geometry of the front shock however, it might also be the lower front rear control arm bushing. This however should be picked up by alignment (centering the steering wheel). Yes I have done well over 150 alignments, so I know when problems cause a flag. And BTW, I scored well on alignment for the ASE, even though they based most of their questions on the Corsair. Yea, you see that outdated crap everyday...

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carpe diem

quote Originally posted by frankenfiero1: Yes GURU, caster will not affect wear, I was combining factors. If you read the post however, the shocks HAVE been replaced. I have had to replace two springs (variable rate) in my shop because all of the ASE mechanics he had gone to before had replaced the shock (4 mindless garbage in garbage out ASE mechanics). I think OUTSIDE the box, not what I am told to think. It is principles, not some test made by college idiots. GURU, you must be a young pup, because you spout off book smarts when you should be spouting "years of experience". Also proclaiming yourself as ANY type of "GURU" proclaims a severe air of arrogance or even inferiority. The spring can still be weak and not assist the shock enough, thus the cupping. Due to the geometry of the front shock however, it might also be the lower front rear control arm bushing. This however should be picked up by alignment (centering the steering wheel). Yes I have done well over 150 alignments, so I know when problems cause a flag. And BTW, I scored well on alignment for the ASE, even though they based most of their questions on the Corsair. Yea, you see that outdated crap everyday...

Sorry, I didn't mean to insult you, but if you were a tech in my shop and you came to that conclusion, you would be packing up your tools right now. A spring does not assist the shock to prevent tire wear. A weak spring will change ride height, but that will throw the alignment out, but a spring does not dampen. Yes, I am a young pup (almost 33), but I have 15 years experience working in shops and I opened my business (auto repair) back in 2002 and have been very successful with it. And yes, I do concider myself to be somewhat of a guru being that when the local new car dealerships can't seem to diagnose a car, it winds up at my shop. When a 1959 Mercedes needs repair, I'm the guy they come see. I am constantly approached by companies to teach seminars to help inexperienced techs like yourself. I am an ASE Master tech as well as L1 advanced certified, state certified and have the best rep within three counties for german car repair. As for you doing well on the three questions for alignment on the ASE test (steering & suspension is the whole test), I am proud of you. That should be worth $8.00 an hour at Firestone. And, speaking of which, when I was a young pup, I saw alignments get done with ball joints falling out, worn bushings, but as long as the tie rods are tight, they'll align it. The ways they are teaching the new techs puts our business to shame, but it helps me keep my prices high....I get paid for what I am worth.
Sorry, to throw the thread off topic with this penis measuring contest. If you still need assistance, pm me.
Dave

[This message has been edited by bmwguru (edited 08-10-2007).]

I finally had the time this evening to jack the car up, it appears that there is some motion when holding the rim at the 12 and 6 o'clock position. It also appears that the little movement that there is comes from the wheel bearing.

Would a loose/bad wheel bearing cause cupping only on the inside of the tire?

I'll have the time Saturday to look into it further.

I am sorry for throwing this thread off topic also. BMW, sorry for the rant, I had a bad day and it caught me wrong, but I did correct those two vehicles with a spring change (one ford one chevy). Hatchet buried? Anyway back to the wheel bearings, how excessive is the play?

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carpe diem

quote Originally posted by frankenfiero1: I am sorry for throwing this thread off topic also. BMW, sorry for the rant, I had a bad day and it caught me wrong, but I did correct those two vehicles with a spring change (one ford one chevy). Hatchet buried? Anyway back to the wheel bearings, how excessive is the play?

Nothing personal and I don't hold grudges, so we're cool.
As for the bearings....my opinion is that the up and down play could cause a cupping if it is excessive. I'd still take a prybar to the lower control arm bushings to see how much they flex or if they are torn. Also, is it only on one tire????? If both front are inside cupped, I'd check the toe measurement, but one tire check for loose suspension on that wheel.
Dave