Bad tires?

[Rich_NYS]

These are Cooper Cobras on the rear; I put them on just before DCS, they have about 1800 miles on them. I'm sure I felt something when I first got them, but didn't expect it to be the tires. Does this look like it could be anything but the tires?

If I get to where I think I can really tell the difference one side to the other, I'll swap them and see if the humptity-hump pattern follows the tire.


Left side Rear:

[Rich_NYS]

Right side rear:

[Dangermouse]

LSR definitely looks odd. I'd swap them L to R and do it again and see if the bump moves.

[DMCMW Dave]

Look like typical Coopers to me. They don't seem to get the fact that tires are supposed to be round.

Just for fun set the air pressure really low and see how they drive.

To prove to yourself that it's nothing else, eyeball the edge of the rim, inside and outside, as the tires spin like that. They will be very true.

[Rich_NYS]

I'd swap them L to R and do it again and see if the bump moves.

Just for fun set the air pressure really low and see how they drive.

To prove to yourself that it's nothing else, eyeball the edge of the rim, inside and outside, as the tires spin like that. They will be very true.

I'll try all all the above tomorrow...thanks!

[Rich_NYS]

Dammit....I forgot to look at the inside of the rim, but I made a video of the outside. I'm getting it loaded and will post it soon.

I swapped the rears and lowered the air pressure to 25 PSI.....it rides better.

Stay tuned for the video.

[alexwolf1216]

I had a brand new set of coopers, less than 100 miles on them. They were all out of round. treaddepot.com, which is where i bought them, didnt believe me until I sent them back. Got a set of Toyos, the difference is amazing.

[Rich_NYS]

Here's the video I made after switching the rears, same air pressure as yesterday. Not sure if I see the rim is true or not; If I "block out" the view of the tire and only look at the rim, I think it looks OK.

[Rich]

Here's the video I made after switching the rears, same air pressure as yesterday. Not sure if I see the rim is true or not; If I "block out" the view of the tire and only look at the rim, I think it looks OK.

The rim shown in the latest video looks like it is bent/deformed.

Send up another video of it for confirmation. Use a tripod and get at least 10sec. of each of two conditions particular to the wheel, not the tire:
1. Facing the wheel parallel shooting parallel to axle (to see radial runout)
2. Looking almost straight ahead from rear with at least the front of the rim visible past the outer rear of tire (to see lateral runout), the way your last video started.
3. And try repeating #2 looking along the inner face of the rim.

Or take it to a decent tire shop. Any wheel can have both of those problems. A few minutes of spinning with a dial indicator on the wheel in various positions will tell the story. Remember, the outer face is the one that is mechanically best-supported from the hub and more of a problem may exist at the inner face.

And none of this means the tire is necessarily good. It could be bad because it wasn't made right to begin with or it could be bad because it has gone too many miles on a bad rim or with bad balance/alignment/shocks.

PS, from the original two videos it looks like both tires/wheels are not running true. One is about 2X worse than the other. Neither of them look like they should.

[hmcelraft]

Move the wheel to the other side and check it to be sure it is the wheel. I have seen a wheel get bent but there is usually some curb damage or some sign. Although, once upon a time, I actually had a bent outboard drive shaft - (I don't how it got bent). http://store.delorean.com/p-8712-rr-...rd-dshaft.aspx