Guessing I need an alignment...?

[Overdrive]

Sorry if the pictures come out gigantic to where you can see the micro-organisms living on my tires. I just wanted some input from folks on these scallops on my front tires:












I have been running 36psi all the way around for about a year now, and this is the first time I've ever seen my tires do this. The rears are fine, and while I can't say it definitely, I don't recall seeing the tires look like this after autocross a few weeks back. Since then it's just been regular daily driving, and I just saw this 2 hours ago.

It looks like some of the pics rotated and may appear to be upside down or sideways, sorry about that.

I'm running Michelin Pilot Sport A/S Plus tires that have maybe 8 or 9k on them at this point, and the alignment was done maybe about a year ago. Maybe autocross last year ran it out sooner than expected?

[Flavor 987S]

A yearly alignment is not such a bad idea. For sure after new tires. But, from those pictures, to me, it looks normal, from hard cornering (that's why it on the fronts only, and not showing on the rears). Which is what you should be doing.

[mountainman]

I automatically get an alignmet every time I get new tires which works out about yearly. I drive hard on twisty mountain roads about 60 percent of the time and my fronts never get like that. An alignmet may be a good idea.

[Homeboy981]

36psi ALL the way AROUND? Isn't it supposed to be 29 in the fronts? …unless you "squared" your setup on all the same rims and tires.

Again, that is for COLD tires pressure AND regular driving. If you are going on the track or going to drive more aggressively adjust the pressure DOWN - as the tires will heat up alot more more at high speed. Don't know pressures for AX, sorry.

I am getting at least TWICE the mileage out of my fronts and I am in the rear. In fact, I am on my 3rd set for the rear, while the fronts look fine.

[Porsche Chick]

Originally Posted by Homeboy981

36psi ALL the way AROUND? Isn't it supposed to be 29 in the fronts? …unless you "squared" your setup on all the same rims and tires.

Again, that is for COLD tires pressure AND regular driving. If you are going on the track or going to drive more aggressively adjust the pressure DOWN - as the tires will heat up alot more more at high speed. Don't know pressures for AX, sorry.

I am getting at least TWICE the mileage out of my fronts and I am in the rear. In fact, I am on my 3rd set for the rear, while the fronts look fine.

I use about 7 lbs over the regular cold pressure.

In the notes for one of our first AX's it said to go to 40 PSI. That seemed like a big jump from my usual 29/31. I was one of the only Boxsters registered, so that made me suspicious. I looked up 911 pressures and 40 would have put them about 7 lbs over normal. Then I did a little digging (some of those racers' websites are pretty funny) and they were recommending going up 7. Long story short (I know, too late for that now) I'm glad I ignored the notes.

[Porsche Chick]

Overdrive, What, exactly, are we supposed to be looking at in the pictures?

[mountainman]

According to everything I have read when autocrossing or other hard cornering you do need to up the tire pressure somewhat. How much seems to be less clear. According to my wheel guy extra pressure also helps to minimumize wheel damage when we hit the inevitable potholes, etc. As the economy worsens and governments cut back on road maintenance we are getting more road hazards out there. Since I do most of my driving on curvy mountain roads I add about 4 psi to the recommended pressure on both boxsters and my C4 and have found better response and more even tire wear with less wheel damage. Just my experience. Try a few things and do what works for you.

[Flavor 987S]

Originally Posted by Porsche Chick

In the notes for one of our first AX's it said to go to 40 PSI.

Maybe it said 40 hot????

[Porsche Chick]

Originally Posted by Flavor 987S

Maybe it said 40 hot????

No. Cold. I checked, since it sounded like a bit much.

The thing was written for the 911's, which have a much higher pressure. They forgot about the Boxsters.

[thstone]

In autocross, the runs are so short that the tires do not build pressure like they do during a 25 min track session so many people start an autocross run with higher or "hot" tire pressures despite the fact that the tires are relatively "cold". This prevents the relatively "cold" tire from excessive roll-over. Of course, proper selection of tire pressure at the start of an autocross run is an art and there is a lot of variability in recommendations but most will say to increase (over stock pressures) as a starting point.

[thstone]

Originally Posted by Porsche Chick

Overdrive, What, exactly, are we supposed to be looking at in the pictures?

It appears that the photos show what is called scalloping or cupping of the outside edges of the tires.

Unfortunately, this problem can have several causes but the cheapest and easiest fix is to start with an alignment and then go from there, but you should be sure to have the shop do a full inspection of your shocks and suspension just to be sure.

Once the tires are cupped or scalloped, its nearly impossible to "undo" this wear pattern. Some people will have the tires swapped so the cupped outside edge is now on the inside.

For reference, here is an example photo of what extreme cupping or scalloping looks like. Of course, I chose the most extreme example that I could find to make it easy to see in a photo. In more typical situations, cupping is usually more subtle, so it is best found by running your hand over the tire and feeling the up and down wear pattern than seeing them.

[woodsman]

Overdrive: new tires, massively stressed look just like that or, tires grossly underinflated and overstressed--slow leak? Either way they don't seem to be rolling over too much and the trailing lip on the edge of the tread blocks is indicative of tread deformation caused by severe loading (hard cornering)...autocross

[Overdrive]

Hey folks. Sorry, was away for a bit, but thank you for the discussion and responses. I will be bringing the car in for an alignment soon and having the shop check things out to see if there are any serious issues throughout the rest of the suspension...hopefully not, but if so then maybe I'll have to accelerate my M030 plans...?

The tires are at least a few years old at this point, though they've yet to accumulate 10,000 miles yet (I know, I know, I'm driving it a lot more now than I used to, gosh...). I'm sure autocross is just destroying their lifespan, but this is really the first time I've ever seen them look like this, and I only noticed it going on a few weeks after the event while using it to commute for work the week I posted those pictures up.

Also, to one person's question above, I've run 36 all the way around for some time, and no, I'm not squared up. I still have the 7inch fronts and 8.5 inch rears. The car used to plow with the placard-recommended 29 up front compared to how it drives with 36 all the way around.

I know these are pretty benign scallops compared to what they could be, but since I'd never seen it before I was concerned that something may be up. I'm pretty sure there are no leaks, but will check anyway. These tires have been solid since I got them, so I expect that I'll see the same 36psi I put in them a few weeks ago 10 minutes before I took off for autocross.

Thanks again, and I'll throw an update up here if there are any discoveries or changes.

[Flavor 987S]

If those tires are more than 5 years old, they are ready to become a swing.

Why are you autocrossing old tires, and old tires that are all season tires?

[Perfectlap]

^ sounds like he doesn't want to get summer tires let alone an autocross set of wheels/tires.

Probably not a good idea to start autocrossing (assuming the OP is new at it) on expensive summer tires though. Worse to go out and buy ax tires before you've learned the ropes. Better to tear up what you already have first and get all the mistakes out of your system. Coming to think of it, in these parts that's probably what all season tires are best for... tearing up. They suck in snow deeper than an inch and they are big compromise in summer for such an excellent car.

[BYprodriver]

[QUOTE=Homeboy981;340926]36psi ALL the way AROUND? Isn't it supposed to be 29 in the fronts? …unless you "squared" your setup on all the same rims and tires.

Again, that is for COLD tires pressure AND regular driving. If you are going on the track or going to drive more aggressively adjust the pressure DOWN - as the tires will heat up alot more more at high speed. Don't know pressures for AX, sorry.


Porsche specs lower psi in the front tires because there is less weight on the front tires.
If you install larger tires on the front you should reduce psi because the larger tire has a larger volume of air, thus same psi in a larger tire = more air than you had before supporting the same amount of weight. Temporary spare is a good example, smaller tire needs 60psi to properly support the vehicle.

In all situations too much psi is a minor problem, normally only ride comfort is "impacted". Too little psi is always a problem, as every Ford Explorer driver should know!

[Topless]

I agree with this from another website. Scalloped tires usually mean worn or bent suspension or possibly out of balance tires.

"Tire is scalloped:
when the tire is scalloped or cupped across the tread it is usually caused by bad shocks or struts. This can also be caused by out of balance tires. Jounce the front end to see if it oscillates and test drive the vehicle to see if it floats and leans excessively around corners. Bad struts are the number one cause of cupped tires."

[Overdrive]

Interesting. Though they're talking about the scalloping being "across the tread". Am I correct in assuming that means that they mean "across" as the full width of the tread? If so, the only area I'm seeing this happen is the outer shoulder of the tread that I've shown in the pictures. The rest of the tire appears to be fine (of course now I'm going to go double check now that the seed of doubt has been planted).

The suspension is all original as far as I know, but it doesn't feel like it's hurting or doing anything strange. I don't float on bumps or get extra bounces that I can notice while driving.

Either way I'm going to have the tires rebalanced and the alignment done because it's likely needed anyway, and I'll have the suspension checked while they're there. Hopefully I won't get bad news.

[Flavor 987S]

Originally Posted by Overdrive

Either way I'm going to have the tires rebalanced

Don't waste your money if the tires are near 4-5 years old. Buy new. What are your DOT code dates?

[Overdrive]

The tires are around 2 years old as far as how long they've been on the vehicle, and were made only a few weeks before I had them mounted on the car, so they're between 2 and 2.5 years old, no rot or cracks in them at all.