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:



https://www.youtube.com/watch?v=c6DHRGdlFDk&feature=youtu.be

[Rich_NYS]

Right side rear:


https://www.youtube.com/watch?v=JBDakxHBFHY&feature=youtu.be

[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. :dunno:

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.


https://www.youtube.com/watch?v=ZU_V-MEiivk&feature=youtu.be

[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-outboard-dshaft.aspx

[DMC5180]

As long as you have it up in the air, you should consider removing both wheels and take them to shop that has a Road force balancer. Have them rebalanced and they will also do a runout check on the rims.

[Rich_NYS]

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.





As long as you have it up in the air, you should consider removing both wheels and take them to shop that has a Road force balancer. Have them rebalanced and they will also do a runout check on the rims.

I'll try all of the above this week. The popular vote is to get them road-force tested, I'm going to check on that tomorrow.




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-outboard-dshaft.aspx

This latest video is after I swapped sides.

[DMCMW Dave]

I'll try all of the above this week. The popular vote is to get them road-force tested, I'm going to check on that tomorrow.

This latest video is after I swapped sides.

Ask what that costs first. Might be half the price of a new tire anyway depending on who you go to.

[DMC5180]

Rich,

Here is the Hunter Road force Locator Link. Just put in your info and click Locate

http://www.gsp9700.com/search/findgsp9700.cfm

My local GM dealer had one which made it very convenient for me.

[DMCMW Dave]

My local GM dealer had one which made very convenient me.

What did they charge for that, i.e. road force balance on carry-in wheels?

[Rich_NYS]

Rich,

Here is the Hunter Road force Locator Link. Just put in your info and click Locate

http://www.gsp9700.com/search/findgsp9700.cfm

My local GM dealer had one which made very convenient me.


Dennis, yertheman....it shows a place in my town on my way to work.



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.

I forgot to mention that there is a bit of a gouge in the edge of the rim in question....sonofa!

[DMC5180]

Ask what that costs first. Might be half the price of a new tire anyway depending on who you go to.

My local shop charges $16 per tire. Mount and RF Balance. That's me bringing in the rims/tires off the car. A re-balance might be even cheaper. Not as much labor involved. It certainly could be more if your in a high rent district.

I've never done just a re-balance. It was always in conjunction with new tires. Those were also carry-ins. I do know some places will charge a higher Mount/balance rate if you don't get the tires from them.

[Rich_NYS]

I made the videos Rich suggested and I removed the rears to try & have them tested tomorrow.

I'll upload the new videos tomorrow, but when I was looking from different angles I think I might've see a problem with the rim.

[Rich_NYS]

No time to upload the videos yet, but here's the update:


I dropped the rears off at the shop where I got them; I'm well-acquainted with the owner, he wants to try & figure out the issue and warranty as needed. He doesn't have a road-force machine, but thinks he'll be able to figure things out with the equipment he has. If that doesn't work out, there's a place with a road-force machine nearby (thanks Dennis.)

I mentioned I might be too gun-shy about the Cobras to get this set warranteed, what's the consensous on that...should I avoid a replacement set of Cobras or give it a try? (BTW, I have CS4's on the front.)

He said they haven't seen any issues with the Cooper brand, but I mentioned it might be the DeLorean is more sensitive to the imperfections. I also proposed the possibility of upgrading to a different tire. I've seen Toyo mentioned multiple times....should I just put those on the rear with CS4's on the front? I'd like to get Vredestein's, but I think it'll take longer than I want to wait (hoping to get this resolved B4 Friday.)

I'm going back in a few hours to see what he found and let him know what I want to do.

Thanks for all the advice!

[NightFlyer]

No time to upload the videos yet, but here's the update:


I dropped the rears off at the shop where I got them; I'm well-acquainted with the owner, he wants to try & figure out the issue and warranty as needed. He doesn't have a road-force machine, but thinks he'll be able to figure things out with the equipment he has. If that doesn't work out, there's a place with a road-force machine nearby (thanks Dennis.)

I mentioned I might be too gun-shy about the Cobras to get this set warranteed, what's the consensous on that...should I avoid a replacement set of Cobras or give it a try? (BTW, I have CS4's on the front.)

He said they haven't seen any issues with the Cooper brand, but I mentioned it might be the DeLorean is more sensitive to the imperfections. I also proposed the possibility of upgrading to a different tire. I've seen Toyo mentioned multiple times....should I just put those on the rear with CS4's on the front? I'd like to get Vredestein's, but I think it'll take longer than I want to wait (hoping to get this resolved B4 Friday.)

I'm going back in a few hours to see what he found and let him know what I want to do.

Thanks for all the advice!

Tough call, and I'm afraid that I don't have a good answer for you.

If you can get a refund on the Cobras, then I'd probably just get the Toyo's. If not, and only replacement tires are offered under a warranty claim, then I'd try the replacement set of Cobras. Or, if you could get anything bearing the Cooper name under a warranty claim, then you may want to consider dropping down to a 225 in the rear and trying one of Cooper's other models.

Best luck :thumbup:

[Rich_NYS]

Tough call, and I'm afraid that I don't have a good answer for you.

If you can get a refund on the Cobras, then I'd probably just get the Toyo's. If not, and only replacement tires are offered under a warranty claim, then I'd try the replacement set of Cobras. Or, if you could get anything bearing the Cooper name under a warranty claim, then you may want to consider dropping down to a 225 in the rear and trying one of Cooper's other models.

Best luck :thumbup:


Thanks man....I'll go for the Toyo's if that becomes an option unless I hear that Cobra's are more prone to issues than the CS4's I have on the front.

[DMCMW Dave]

The DeLorean is VERY susceptible to imperfections especially in the front tires. This is due to a couple of things:

--it's light up there. That's why the factory pressure spec is so low, and if you run the tires slightly hard it has a much bigger impact than on a front-engine car.

--very direct steering. There is no shock-absorbing joint in the steering. The only isolation at all is the fact that the rack is mounted to the frame in rubber joints. Most cars have the rack solid mounted and then add some sort of flexible coupling.

--relatively hard bushings. Even the stock ones. Really hard on urethane bushings.

--manual steering. No damping as commonly provided by a power steering system.

One other oddity:

--alignment change - When you load up the trunk of the car, the toe in changes dramatically. This is not a problem on cars with the trunk in the rear. This itself doesn't make it more susceptible to vibration, but it is something to think about. If you have a non-lowered car, and have it aligned without weighting the front end, loading the trunk can actually move the front wheels to a toe-out position. Which is why a stock car with a fully loaded trunk handles pretty strangely on the highway. This is not a problem on a lowered DeLorean as the toe goes in on bumps when aligned correctly.


------------
I think one thing that leads to issues on the Coopers is age. Check the date code on the tire sidewall. Last for digits is week/year, i.e. 3212 would be week 32 of 2012. They have not made the Cobras for a couple of years, so it's likely the ones you got may have been in a warehouse for a long time and could even have been customer-returns for the same problem.

Tires also need some break-in heat cycling to stabilize. The worst thing you can do to tires is mount them on a car and then park the car for a long period of time before it's ever driven. I've seen brand new 5-year-old tires that were egg shaped from this.

[Rich_NYS]

Thanks Dave,

I'll check the date code and likely avoid the Cobras with whatever option I have. I have CS4's up front, so if I need to stick w/Coopers I'll likely get those for the rear but if possible, I'll switch to Toyo.

Uploading videos I made last night, here's the first of four I'll post from this side:


https://www.youtube.com/watch?v=VAbuvy5pOes&feature=youtu.be

[Rich_NYS]

https://www.youtube.com/watch?v=lt0wPnncgoQ&feature=youtu.be

[Rich_NYS]

https://www.youtube.com/watch?v=YuFFdpZUJgA&feature=youtu.be

[Rich_NYS]

https://www.youtube.com/watch?v=HQbNF1NQFQg&feature=youtu.be

[NightFlyer]

Just wanted to update this thread with some valuable info:

Rich's Cobra's were made in Mexico.

I'm not sure of exactly when the transition was made, but Cooper appears to have fully transitioned the Cobra (and equivalent Hercules and Mastercraft models) over to Mexican and Chinese production facilities.

When the Cobras were made in the USA, they were a decent average tire, however, quality appears to have suffered significantly since the relocation.

I know that Dave S (DMCMW) has always said that the Cobras were difficult to balance, regardless of where they were made, but from what I've observed, the Mexican/Chinese made variants are definitely worse than the USA made variants.