Wheel/tire runout specs

[Phrede]

One of my complaints to the dealer (where my car has been for two weeks now) from the beginning is a vibration that starts around 75MPH. Today they tell me that two of the wheels are bent and the tires are old. I am asking for details like how much run out, both radial and lateral, is there and just how old are the tires.

Does anyone know the factory spec on permissible run out?

The car has 30k miles on it and the tires have what appears to be new tread depth. Without knowing for sure I would guess the tread life on these tires to be 15-20k. Is that about right? There is no way these tires are half worn, so I am guessing it is the third set of tires and were put on recently. Unless someone had some very old stock that they put on these tires should not be that old. Otherwise there is a tire problem and should be replaced under warranty (prorated).

The comment was made that the vibration will be there until I buy another set of tires. Just another example of my poor dealer. I am about to go to war with Cadillac.

 

[TED]

The tires will be warrentied by the tire maker. Find a tire dealer that sells those tires and they will be able to help you with that more then the Cadillac dealer. There is a date code on the sidewall that will tell you when it was made. Hope this helps.

 

[Comfortzone]

One of my complaints to the dealer (where my car has been for two weeks now) from the beginning is a vibration that starts around 75MPH.

The comment was made that the vibration will be there until I buy another set of tires. Just another example of my poor dealer. I am about to go to war with Cadillac.

I get a vibration at about the same speed, but I assumed it was due to the oversized low profile tires I have on it.

 

[TED]

I have Michelin 255/35 ZR20 on the front and 285/30 ZR20 on the rear o to 130 plus with no vibrations. Not all tire shops are created equal ! You should have that looked at. Any vibrations are BAD and put undo stress on other components.

 

[Phrede]

The tires will be warrentied by the tire maker. Find a tire dealer that sells those tires and they will be able to help you with that more then the Cadillac dealer. There is a date code on the sidewall that will tell you when it was made. Hope this helps.

I understand that it will require a Pirelli dealer to resolve any tire defects. However, the wheels fall to Cadillac. More specifically, the selling dealer who certified the car. In order to determine where the fault is the dealer will have to break down the tires and measure the wheels. This should have already been done since they have told me they did road force balancing. I tried to explain to them that match mounting was the first step in doing a complete road force balance. In order to do that the run out of the wheel must be measured. Harmonic values are more important than TIR readings.

The dealer told me that the date code on the tire indicated they were made in 2005. I asked how that could be when the car was made 30OCT2007. I really doubt tires hang around the factory for two years as popular as JIT is. The dealer also said that these must be the original tires. I tried to convince him that there was no way these tires had 30,000 miles on them. Obviously, they do not have a clue.

 

[Rockster80]

Lateral and Radial runout should be .762mm / 0.030" or less. Info from XLR Service Manual

 

[Phrede]

Lateral and Radial runout should be .762mm / 0.030" or less. Info from XLR Service Manual

Thanks, that is what I would have guessed. It's better to know the "real" spec.

What kind of life is everyone getting from their tires? I know it depends on a lot of things, but some sort of an idea on life would be good.

I would not want to use Gizmo's tire life. I've followed him before

 

[GizmoQ]

I would not want to use Gizmo's tire life. I've followed him before

Leave me outta this. OBTW, I'm still on my second set of front tires with 56k miles on the car. We won't bother talking about how many sets of rears I've been through.

 

[mtrocket]

Thanks, that is what I would have guessed. It's better to know the "real" spec.

What kind of life is everyone getting from their tires? I know it depends on a lot of things, but some sort of an idea on life would be good.

I would not want to use Gizmo's tire life. I've followed him before

I'm just shy of 30,000 on my first set of run flats... looks like they should last another 15,000 at least. My guess is they are about at their half-life... lot of tread depth left.

 

[XLRJIM]

OEM tires

I replaced the 4 tires with Michelin run flats at 26K..Had NO problems with vibration ever with the car. I did have to replace on tire at about 12 k when I drove over scrap on the freeway and put a huge hole in the tread..Thanks to the run flats I drove to a Michelin tire dealer who got me a replacement over night.

 

[XFireXLR]

Had a similar problem with both of my rear tires (OEM Michelin run flats) both tires where wearing in the center tread area. Both tires were installed at the same time and only had 5800 miles on them when I noticed the problem. My local tire shop (Mom & Pop shop) where they were originally purchased removed them and checked the balancing and the camber on the car and all was correct. We could not figure out why the tire wear out in the same area and so quickly. Put a call into to manufacturer and they where also baffled. Long story short they pro rated the tires and picked up 75% of the replacement cost, my tire shop absorbed the other 25% and the road force balancing in the end I had zero cost. Cadillac insisted that I was doing a lot of "spirited driving" which was not case. I guess some retailers/dealers are willing to go the extra mile and look outside of the box to satisfy and keep a customer happy and coming back.

 

[graytoad]

Can someone explain to me what "Run out" is?

 

[Phrede]

Can someone explain to me what "Run out" is?

It is basically how much out of round the wheel and/or tire is for radial run out. Lateral run out is how much "wobble" there is parallel to the axle but measured at the lip where the tire bead sits.

There are more details. Like how it is measured with TIR (total indicator reading) or harmonic value. Harmonic takes into account the "width" or rotational duration of the high spots.

Imagine having the wheel off the ground and spinning where the center of the wheel is running perfectly. The amount of movement up and down of the tire tread is the radial run out. The amount of movement left and right is lateral run out.

Run out effects more than just wheels. Brake rotors with excessive run out will cause a pulsing in the brakes, to name just one other example.

"Match mounting" is a method used when mounting the tires where the "high spot" on the wheel is matched to the "low spot" on the tire to minimize the total combined run out. Road force balancing measures the radial force variation against a load and takes into account many more variables than a static or spin balance.

Here is a link with more details, if you're interested:
http://www.gsp9700.com/technical/5098t/5098t.htm

HTH

 

[graytoad]

Thanks, it is good to learn something new every day!

 

[graytoad]

Phrede: I really liked your explination, then I went to the link you posted: Wow, too much to worry about, I just want to go fast in the corners without a fight and my XLR does that with flying colours!

 

[Phrede]

Phrede: I really liked your explination, then I went to the link you posted: Wow, too much to worry about, I just want to go fast in the corners without a fight and my XLR does that with flying colours!

It helps that you have one of the fast red ones and not one of the slower black ones.

 

[GizmoQ]

Phrede: I really liked your explination, then I went to the link you posted: Wow, too much to worry about, I just want to go fast in the corners without a fight and my XLR does that with flying colours!

A woman after my own heart!

It helps that you have one of the fast red ones and not one of the slower black ones.

ELWOOD doesn't fit in that generalization.

 

[jackparker06V]

Tires

Hi! I recently replaced all 4 tires with the OEM Pirellis and had them installed at a local tire company that specializes in high performance installations. The tires were speed balanced on the car and run up to 90 mph (at least that is what I asked them to do). Not all shops have this capability. I require it because I have spacers on the front wheels to allow for after market brake calipers. They told me that one of my front wheels was slightly out of round (bent) and that it would show up as a slight vibration at 75 to 80 mph and there was no way to correct for that other than a new wheel. Sure enough, the vibration is there, very slight, but it is there. Point is, you can not get rid of the vibration if your wheel/s are bent.]
Also, as someone else mentioned, my rear tires wear faster in the center. I have now lowered the cold pressure in my rears to 28. I use a gauge that will read in tenths of a pound. I'm hoping this will help in that regard. I think my ride has improved also, but it may be just wishful thinking.
Jack
Jack