jimmyb

I have a 2008 convertible with 2000 miles on it. I traded a 2005 with 18,000 miles on it. My 2005 had to have new tires on the front as they were down to cord on the inside, the rears looked to have another 5,000 miles left on them (I replaced all 4 tires with Firestones anyway as it was not much more to do 4 Firestones than just 2 Goodyears. My 2005 was base suspension). Clearly I don't sling the car through corners hard enough! I would like to get more than 18,000 miles out of my 2008's front tires! What would be an acceptable settings for front end alignment to get more front tire mileage, without sacrificing ALL the handling, knowing that my car is not driven particularly hard.

Thanks,
Jimmy

Modshack

You're correct to be concerned about factory alignments. i figure they have 3 minutes to dial in 10 adjustments. Not to confidence inspiring, and proven when I took mine to an independent for an alignment.

The spec ranges are so broad that it can vary from precise to sloppy but still technically be in spec. I wanted mine as close to centered as possible but I drive the car fairly hard so figure my wear will be pretty even. If you're just a cruiser and don't put any premium on handling, then reduce the camber front and rear. Some Zero this out. It will reduce potential cornering ability though.

Top chart is my '08 at 6000 miles with nothing hit...Pretty much as it came from the factory. Note the items in red which are outside even the broad factory specs.

Bottom chart is after. the car feels much better BTW..

jimmyb

Steve,
If you set the alignment to cut down this inside tire wear, how is the tracking and the car's sensitivity to "tramlining" as opposed to the alignment settings from the factory.

Thanks to a fellow Tarheel (not the university, the state!)

Jimmy

Modshack

No Problem! In my experience, tramlining is more a function of incorrect Toe settings (plus road condidtions and tire width)

eboggs_jkvl

If you want to keep the car for Xcross, then the specs shown are fine. If you want to set the alignment for maximum tire mileage get that camber DOWN. Put the camber on ALL 4 down to -0.1. The caster shown is fine. Set the rear toe to 0 and the front to to -0.01. You will not be able to feel any difference while you drive. If you X-cross, then you will lose a few tenths. If you X-cross, set the camber back to -0.45 up to -1.0 for racing applications.

The stock settings will wear the inside off of the tire.


http://forums.corvetteforum.com/show....php?t=1795091

Elmer

jimmyb

Elmer,
Thanks to you and Steve for the info. I am going to research alignment shops here in Charlotte on Monday (unless someone here in the Queen City has a suggestion!). As I said in my earlier post, my 2005 was down to CORD on the inside of the front tires with probably 4 - 5/32nds on the outside (this with 18,000 miles) Both of my C5's performed similar tire munching capability.

Jimmy

jimmyb

Steve or Elmer or both,
Can you explain to me (clearly alignment knowledge challenged) what each term (camber, caster, toe, thrust and the numbers) mean in terms of how the tire is sitting. I remember old independent rear suspension cars like late 1980's 280ZX's where the top of the rear tire would be noticably canted towards the center of the car. Is that "toe in". Thanks for your help and knowledge on this, I want to be able to communicate properly to the alignment shop what I want done (and accomplished).

Jimmy

SimonStern

It's always a good idea to make sure your alignment is set correctly.

That said, the nature of a sports car is that it makes use of negative camber. This means the tires lean "in" at the top. In corners, the outside tires will be pushed out flattening the contact patch (as seen from the front or back.) giving you more cornering ability. If the tires were straight up and down at rest, then in a turn the inside of the tire would lift and reduce you ability to handle around turns.

Negative camber, does have the "negative" of causing more wear on the inside of the tire.

Also keep in mind that the GY tires are soft, sticky performance tires. 18,000mi is actually considered pretty good wear for them.

SimonStern

What you are describing is negative camber.

If you stand with your feet pointing parallel to each other they would represent the tires. If you point your toes towared each other, so your feet are not exactly parallel anymore, that would represent tow-in, turn your toes out a little, and that is toe-out.

Here is a pretty good article, with pics:
http://www.ozebiz.com.au/racetech/theory/align.html

Modshack

Here's a good visual on the various adjustments...

eboggs_jkvl

That's absolutely great. It shows the terms and a picture of the tire in relation to the terms. The tire killer is camber. + camber would tilt the tire out at the top and in essence lift the inside bottom edge and wear the tire more on the outside edge. Negative camber pulls the tire in at the top and puts the pressure on the inside of the tire and tends to "lift" the outside edge. Thus our negative camber wears out the inside of the tire. Getting the camber down to a small number is the goal but NOT to a "0". You need a touch of camber thus the -0.1 that I suggest. The negative camber of -0.45 to -1.0 on the Vette makes the foot print of the tire flat while you are doing turns thus giving you all the traction you can get from the tires to take the turns quicker.

Elmer

MYVetteBy25

Besides camber, what would cause the OUTSIDE of the tires to wear faster than the inside? Toe out or toe in? When I got an alignment recently, the camber was approx -0.6, which is within spec. However, my tires were wearing much faster on the outside. My car is 100% street driven. No autox or HDPE. I don't take it easy in the corners, so that may be it. But I'm still curious whether toe in or out would cause wear on the outsides?

07MontRedcp

Errors in toe alignment will cause the tire to wear faster than errors in camber and castor. Basically, think of it as the tire being drug sideways as it rolls down the road. Depending on the degree of error, a tire can be toast in a few hundred miles or less. The error is further amplified in turns.

BJK

eboggs_jkvl

Too much toe in. (negative number)

Modshack

Yup, that's correct...My post was incorrect (deleted)...

SkyKing421

I have seen a Cadillac dealer's expensive "Laser Alignment" machine be quite a bit off, due to bad calibration.
Our CTS had an obviously excessive positive camber on the rear, verified with a simple level. The tires were wearing badly on the inside. We had 1" difference between the bottom and top of the rear tires on level ground. The "Laser" machine said that the left rear was at "0" camber. Oh Boy, now what do you do? The manager said he would get it calibrated.

My point is, that sometimes you can't trust these "infallible" machines.

I did my own alignment in the garage. Worked out great. (If you do your own, be sure to roll the car a foot or two, after coming off a jack.)

If you can't double check it yourself, get second reading somewhere else.

SkyKing421

Oops!
The above should have read "Our CTS had an obvious NEGATIVE camber....

autoxnut

Actually inside tire wear means the inside of the tire is in contact with the pavement more than the outside of the tire. Since the Vette is a sports car, it comes with some negative camber on the tires (meaning the inside edge is more in contact with the pavement than the outside) for handling reasons. When the car is cornered hard and the body leans, the tire will then be flat on the pavement and give the most cornering power. Therfore you may not be in need of a realignment, you may simply need to spend more time cornering hard to get even wear!

zero5see6

Exactly! When I had my 05 aligned, the tech mentioned that toe had more to do with wear than camber. He aligned to factory specs and made sure toe was 0.00. It's been a few thousand miles since the alignment and I have no inside tire wear whatsoever.

fnsblum

Too much toe in either direction will feather the tire all the way across the tread. You can run you hand in across the tire and back out. You will easily feel it. Similar to feel to the scales on a fish or a snake. The factory specs take into account what the load on the suspension will be down the road. The Vette is very stiff and not going to push the readings more negative in a straight line. Other vehicles need more positive camber to ensure good wear. Later! Frank