# Strange tire wear issue - Advice?



## Airy32 (Nov 15, 2007)

I have a MkIV R32 with Pirelli PZero tires on my summer wheels.








I've only run them for about 7k miles. I put them back on my car a month or so ago but took them back off after about a week because of a bad vibration that starts around 60 mph. It feels like they are in need of balancing although they ran perfectly smooth at any speed up until the time I took them off in November. They also have what almost appears to be a blistering of the tread blocks in the center three ribs but is fairly minor and consistent on all four tires. 
The other issue is that the tread is worn about 3-4/32 more on the outer half of all four tires than the inner half. No cupping or feathering or any other weird patterns, just less tread depth. My camber is -1.5 front, -1.0 rear (more than spec in front, less than spec in the rear for better balance due to understeer) 0 toe front and .25 rear. If anything I would expect the inside to wear more than the outside but the opposite is the case. I noticed the wear issue when I took them off for the winter but didn't think much of it since it rode and handled great, and just had a perfect alignment just a couple months prior.
I'm debating getting new tires but hate to dump the Pirellis (over $300 ea) while there is still tread left. I would try getting them rebalanced but don't want to spend the money if they won't last much longer anyway. And don't want to buy new tires if something else is causing premature or irregular wear.
Any expert opinions?


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## [email protected] (Apr 9, 2008)

I'd bet that your alignment is off (caster)......... there's too many things going on at once to blame the tire (or rotation schedule) alone. You'll need new tires regardless.............


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## guerilla_zoe (Apr 15, 2008)

Is caster something you can adjust? I thought that was set via design of the suspension system.


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## Airy32 (Nov 15, 2007)

> [email protected]
> I'd bet that your alignment is off (caster).........


 Would you be able to elaborate on how this would result in the issue? 




> You'll need new tires regardless.............


 Why? As I said, there is still adequate tread across the entire contact patch. It's just notably deeper on the inner half. If it were just an alignment issue and I had it corrected, I should theoretically be able to have the tires/wheels rebalanced and be able to continue driving on them until the usable tread is gone. 



> guerilla_zoe
> Is caster something you can adjust?


 To my knowledge there is no caster adjustment available.


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## [email protected] (Apr 9, 2008)

I thought I read that you had the vibration issue, but if not then you can squeeze some more life out of them ......... 

I was mistaken, I should have stated that it could be an issue with the camber. The specs you mentioned seem reasonable, I'd love it if you could email pics to me to show the engineers ! 

[email protected]


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## Airy32 (Nov 15, 2007)

[email protected] said:


> I thought I read that you had the vibration issue, but if not then you can squeeze some more life out of them .........
> 
> I was mistaken, I should have stated that it could be an issue with the camber. The specs you mentioned seem reasonable, I'd love it if you could email pics to me to show the engineers !
> 
> [email protected]


 I do have a vibration that is definitely speed sensitive which is what made me think re-balancing may get rid of it. Just thought it was odd that they would get out of balance by just sitting over the winter (they are stored on their side, not standing on the tread which might cause flat spotting). Only reason I've put it off is that the nearest place to get a road force balance is over an hour away, and since I only have one day a week free from work it can be pretty full. I'd like, and was ready, to buy new tires but I see these every day with some good tread remaining and just hate to think of dumping them when I consider the high cost per mile that I've put on them so far. And I'd hate to get a new set and discover after a few thousand miles that they are wearing strangely as well because I have another issue that needs addressed. 

I'll try to get some photos that show the tread as well as possible and send them to you/post them on here. I appreciate your offer to try to help with a diagnosis. 

First is a representative pic of the tread "blistering?" 










This is the groove nearest the inner edge 










and nearest the outer edge 



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## animaniac (May 26, 2005)

You may find that adding a slight more negative camber will make the tyre sit better on the road aswell as improving road handling. 

And should cure the wear problem although you will get more wear on the outer of the passanger side tyres due which side of the road your driving on / right hand bends for rhd and left hand bends for lhd vehicles. 

Vibration is a ballancing issue, just having the machine to spin them will tell you if and where they need more or less ballancing weights. 


I noticed that there nearing to the wear limits so it may be worth getting them ballanced and letting them get you through the summer, because the dry weather will wear the tyres quicker, and then you can get some new ones.


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## Airy32 (Nov 15, 2007)

I may try this since it sounds relatively logical. I have nothing against more negative camber since my initial fear of running more than spec (where I am now) would cause the inner half of the tread to wear prematurely. But obviously this is not the case as the outer half is still wearing faster. Just for the record again, spec camber in front is -0.6 and I'm now at -1.5. So maybe I'll go to -2.0, get a new balance, and see what happens.


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## 20AE3600 (Jan 13, 2004)

OK......I will start by admitting I design tires for a living for Goodyear. The blistering is not blistering. It is a different rubber compound that has carbon black in it to conduct electricity to ground the car and keep you from getting shocked from static electricity build up when you get out of your car. The main tread compound likely uses silica for the filler / reinforcement. Silica = Great wet traction....usually faster wear. You can see something similar on many tires, but this is the most noticeable I have ever seen. The wear on the outer edge looks to be more of a fast center line wear issue. The groove you are measuring in for the outer shoulder is actually close to the center of the tire. Very round footprints could do this. Could be high inflation pressures, or just the design of the tire and the footprint that is has.


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## animaniac (May 26, 2005)

20AE3600 said:


> OK......I will start by admitting I design tires for a living for Goodyear.


 Cool, we have a tyre tech guy on the forum. 

I prosume they must pay you quite abit for doing this, do you do the chemistry part of the rubber aswell? 

You may or may not have heard this but, theres a rumor that dunlop back in the 60's developed a tyre which didnt wear, and they put them on a uk london bus and it got ragged around london for ages and on inspection there was no wear on the tyre and it looked like new! 

Thanks for your valuable info..


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## Airy32 (Nov 15, 2007)

20AE3600 said:


> OK......I will start by admitting I design tires for a living for Goodyear. The blistering is not blistering. It is a different rubber compound that has carbon black in it to conduct electricity to ground the car and keep you from getting shocked from static electricity build up when you get out of your car. The main tread compound likely uses silica for the filler / reinforcement. Silica = Great wet traction....usually faster wear. You can see something similar on many tires, but this is the most noticeable I have ever seen. The wear on the outer edge looks to be more of a fast center line wear issue. The groove you are measuring in for the outer shoulder is actually close to the center of the tire. Very round footprints could do this. Could be high inflation pressures, or just the design of the tire and the footprint that is has.


 That's the kind of expert opinion I was hoping for :thumb:. I was only referring to it as blistering because of not knowing what else to call it other than referring to the appearance. But your explanation certainly makes sense. And you are correct about the groove described as nearest the outside in the photo. It actually is the second groove in nearer the center because the groove nearer the edge is too narrow to slide the penny in and I don't have one of those nifty depth guages. But even that groove on the outer side of the center rib is not as deep as the one on the opposite side of the same rib. And they get progressively deeper the nearer to the inside. 

Would it be reasonable to assume the different compounds have different densities and may cause the balance to change as they wear at different rates? I'm hoping I can eliminate the vibration with a fresh balance. 

Unless you suggest otherwise, my next course of action will be to get them rebalanced, try reducing the pressures a bit, and maybe adding a touch more negative camber to attempt to focus the contact more to the inside than it currently is (was).


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## 20AE3600 (Jan 13, 2004)

Airy32 said:


> That's the kind of expert opinion I was hoping for :thumb:. I was only referring to it as blistering because of not knowing what else to call it other than referring to the appearance. But your explanation certainly makes sense. And you are correct about the groove described as nearest the outside in the photo. It actually is the second groove in nearer the center because the groove nearer the edge is too narrow to slide the penny in and I don't have one of those nifty depth guages. But even that groove on the outer side of the center rib is not as deep as the one on the opposite side of the same rib. And they get progressively deeper the nearer to the inside.
> 
> Would it be reasonable to assume the different compounds have different densities and may cause the balance to change as they wear at different rates? I'm hoping I can eliminate the vibration with a fresh balance.
> 
> Unless you suggest otherwise, my next course of action will be to get them rebalanced, try reducing the pressures a bit, and maybe adding a touch more negative camber to attempt to focus the contact more to the inside than it currently is (was).


 The balance should not have anything to do with the tire itself if all is normal. You may have just thrown a wheel weight or something like that. Also, make sure that they are dynamically balanced. You should have weights both on the rear flange and tape weights behind the spokes. If you also rotated them front to rear front last year to this year, the imbalance could have been there, but it was in the rear and you did not notice it. You will typically feel a dynamic imbalance as a shake it the steering wheel in a certain speed range. I usually have experienced it between 60 and 75 mph. Below that and all is good, and above that, all is good. 

When you take them to be rebalanced, tell them you want them "Dynamically" balanced, not just "Statically" balanced. 

I am running 34 front and 32 rear on my .:R32. I am actually still running the Michelin's that were on when I bought it still. I look at it as competitor testing!  
I would not mess with your camber to try to compensate for a tire issue. 

If you do not need all-season and end up looking for new tires.......Dunlop Direzza Z1 Star Spec is tough to beat for a summer tire.


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## Airy32 (Nov 15, 2007)

Update on this. I just took my wheels/tires to get a new road force balance. I was shocked to see how far off they all were.  Like I mentioned before, I had them balanced by the same guy with the same equipment about 6k miles ago and when he was done they were silky smooth. I drove on them for nearly two summers with no issues and they rode fine when I took them off last November. Then when I put them back on in April the vibrations were horrible. I couldn't imagine the balance would be so far off from just sitting for five months so assumed the tread issue might be contributing to the ride. But obviously something went whacky. Two of them had to be dismounted and rotated on the rim, one about 90 and the other more like 180 degrees, and all four required a significant amount of weights in dramatically different locations than before. I wanted to take pics of all the tape weight residue left behind and where it was in relation to the new weights, but I was just too eager to clean it all off and get them back on the car asap. 

Put them on and took about a 30 minute test ride on a combination of surfaces, and all is right again. Even a quick blast up to XXXmph on the local remote and empty interstate and no issues. They may only last through the summer but at least I don't have to buy new tires right away or drive year round on sloppy all season tires.


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## VMRWheels (Aug 11, 2009)

glad to hear this worked out for you! Roadforce balancers are great, you can pretty diagnose any issues you might have with the wheels/tires assembly


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## waabaah (Jun 24, 2006)

Airy32 said:


> Would you be able to elaborate on how this would result in the issue? (speaking of caster)
> 
> 
> 
> To my knowledge there is no caster adjustment available.


(oops..i didnt read clearly on the tread pattern wear that your getting so this is just to answer this question i guess)

caster cant directly cause tire wear while driving straight BUT once you turn another angle comes into place. "camber roll". camber roll is how much the tire angles during a turn and the camber angle can increase dramatically during turning from the result of high caster. the VW cars have tons of caster compared to other suspensions. this may explain some edge wearing on inside and outside tread blocks.

balancing issue may result in a choppy pattern or a swipe pattern but wouldnt present itself inside/outside edge.

seems like everyone else covered the basics here and the "blistering" is the first time ive seen that. and ive seen tons of worn tread patterns. what i would tell a customer is "really doesnt matter for the tire wear since you need new tires anyhow". best you can do is do a simple check of alignment, rotates, tire pressure and driving habits.


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