Alignment pro: please give me free diagnostic of tire worn problem

[rnln]

Looking at my front tires, pics below, one will say I have too much positive camber right? Well, looking at the car, it's doesn't seem like that. Is there any other factors which makes this happen? Too much toe in/out? Shock worn? Torsion bar defective/degrade?? The car is very lowed.

I don't corner that fast all the time. My friend used to tase me that I drive like an old lady. oh.. the rear tires look good. They all have almost 2 years of age but the rear tires still have a lot of meat while the front worn much faster and uneven.

[911pcars]

If it's worn that way around the entire circumference, it's either camber or toe wear. The difference is that toe wear will also show some feathering of the tread on the outside.

Is the outer shoulder of the tire also worn (part of the sidewall)? If so, could be due to cornering wear.

Take it to an alignment shop to check and confirm.

Sherwood

[rnln]

Thanks Sherwood, it's you who response me again.
Yes, it is like that all around the tire, some tread has a tiny more than the other. There is no feathering, the edge is very clean. So more like (+) camber? I fill so.
Somehow, I feel the driver side is lower than the pasenger side, and happen that the problem is more pronouced on the driver side... Maybe the (+) camber made the lower side worse than the taller side.
Well, time for an alignment. Why it's never stop

[rnln]

After some search, I have several questions.

Caster:
Someone posted an instruction on playing with the suspension. One thing I read was "remove the 3 nuts on top of the strut tower and push it all the way to the rear if you want competition".
Why does it have to be "competition"? Don't we all want more caster? Is there a down side of max caster?

Camber:
On my case, does anyone know how much I should push the strut top in (toward the mid of the car)? By mm or by couple mm?

Note: the handling on my car feel somewhat well. Only once in a while the steering "feel" a little loose at high speed and windy. I am not sure if this is true or it just my expectation.

Thanks.

[911Mac]

I could be wrong, but the tread pattern on your tires looks like they're unidirectional. If that's true one of them is mounted backwards. The tires should have an arrow on the sidewall that indicates the direction they should rotate in.

[911Mac]

Oops, just looked at the inner outer labels, you took the picture of one tire from the front and the other from the back. Never mind!

[rnln]

no, they are correct. THe top one is the driver side and I took pic sitting toward the front. The second pic was the passenger side and I was sitting facing toward the rear.
They both worn more on the outter edge.
Thanks.

[dentist90]

Have you actually measued the tread depth across the tire? It looks to me like you've got assymetrical ( and directional) tires. If you are concerned that you don't see the extra siping on the tread blocks on the outside of the tire, this is very common in tread design. The outside blocks are made more robust to deal with the cornering forces that build up more on the outside and also reduce tire 'squirm'.
Worn outside edges either mean excessive positive camber or a lot of hard cornering.
I notice that your driver side tire has extra sipes on the inside tread blocks, but the passenger tire doesn't (see photo below). Did you buy these tires at the same time?



I'd measure the tread depth at the outside and the inside just to confirm you actually have a problem.

[dentist90]

Also note the dimples in the tread are still present on the outer blocks... this looks like even wear in an assymetrical tread.

[rnln]

Actually, the outer side wear more than the inner side. The middle doesn't get worn. And the driver side wear more than the passenger side. Yes, the tires were all good and at the same time.

[DanielDudley]

Both edges wearing , no wear in middle and outer wearing more than inner sounds like spirited driving on underinflated tires

[rnln]

I will check air tomorrow, for sure.
Thanks.

[rnln]

I just checked tires, air pressure look ok.
I also check camber using the old home traddition method, but good enough to know that I have (-) camber on both sides.
Anyone know what make front tires wear more on outter edge beside (+) camber and/or low tires pressure?

I assume this is not toeing problem because if I have toeing problem, my tires will wear faster, but evenly, not outter edge wear more than inner edge. Am I correct?

[Tyson Schmidt]

Originally posted by rnln
I just checked tires, air pressure look ok.
I also check camber using the old home traddition method, but good enough to know that I have (-) camber on both sides.
Anyone know what make front tires wear more on outter edge beside (+) camber and/or low tires pressure?

I assume this is not toeing problem because if I have toeing problem, my tires will wear faster, but evenly, not outter edge wear more than inner edge. Am I correct?

Not true.

Excessive toe-in will cause your symptoms.

Used to be that you'd get feathering from toe problems, but with modern radials, the carcass flexes in such a manner that it can be difficult to diagnose whether it's camber or toe related. With old bias-plies it was much more obvious.

[rallyracer]

it's a toe problem. you would have to have like 2.5 deg + camber to get wear that far out on the outer edge. in other words, very obvious + camber, which you say it has not. so, put her on the rack and get readings.

i'm with Tyson, most likely too much toe-in. maybe the rack, sensor, whatever was off for the last alignment and gave it 1/8" toe-in each side or more by mistake.

to your caster question, more caster generally gives more stable high speed stability (shopping cart effect). this needs to be balanced with steering effort. 911's get around 6deg caster max, which isn't that high, so max even caster on these cars is good. also, caster problems won't cause tire wear.
David

edit: on second look, those look like Kumho 712 tires, so if you leave the alignment, you can get rid of those rocks a lot faster!

[rnln]

If not 1/8", what should be the toe for each side? 1/16"?

This might sound silly but when we are talking 1/8 or 1/16, is it the different of the distants between front point and rear point of the wheels? If so, 1/6 or even 1/8 is very small.
Thanks rallyracer, tyson.

[jluetjen]

RNLN, small differences can make a significant difference in a car's handling. But everything is a compromise. For street use set-up's are usually compromised for wet and dry stability both when cornering and braking, and overall tire wear. A slight change in toe such as 1/16"* (especially as you get close to 0 toe) can make a noticeable difference in a car's handling.

Personally I think that the "signal to noise" ratio is pretty low here based on the problem description and the pictures. Looking at the tires, I'm not seeing anything that would suggest there are any significant alignment issues, nor set-up issues. If the alignment was done by a reliable shop, and there are no handling issues (which there don't seem to be), I'd say just get in and drive the thing. Quit obsessing!!! Most cars do not wear their tires perfectly evenly, especially if they have wide tires.

* PS: Yes this measurement is generally done by drawing a chaulk line around the circumfrance of the tire (or using and existing line), and then measuring the distance between these lines an equal distance to the front and back of of the bottom of the tire

[rnln]

John,
Thanks for more info.
For that small of the diff., I don't think I can play with it. I used to play with alignment on other car but the worn on the tires would give me the lead. Also, front engine car would give me the room to do some measurement from tire to tire. On our car, the gas tank is on the way for measurement between front tires. I guess it's time to visit the alignment shop.
note: I still want to know my car's status before stoping by the shop. Also, would like to know if their diagnostic is correct. Oh well...
Again, thank guys.

[jluetjen]

Originally posted by rnln
On our car, the gas tank is on the way for measurement between front tires. I guess it's time to visit the alignment shop.

True. I had blanked on that. When I've aligned my 911 I used a string set-up and measured the distance at the rim, at the height of the hub. If you're not familiar with string method, do a quick search on "alignment string" and you'll find lots of data. In my case it cost me less then $40 in materials and now I can do it any time I want, and set the alignment to whatever I want, as opposed to what the shop choses to set it to.

[rnln]

Exactly as rallyracer said, I got more than even 1/8 toe in the front wheels. For 2 days seting the string up and some measurement (many times to get it right), I found that my front wheels get more than 1/4" toe-in (both sides together).
I tried to adjust it to closed to zero but maybe I did it wrong, it drove it even worse. Set it up again after around 60 miles and found that the outer edge of tires is flat at razor cut and thick feathers on each tread. This time, I adjust it, measured it again and again. Went out for a short drive. Come back set it up and measure again and again. I think I got it to even a little less than 1/16" total for both sides. Very happy now but.. I need new tires soon :lol:
What an experience.

I think I agree with John now, stop looking at the tires/suspension and drive.

Thanks all.