Tire wear information
01-28-2014, 12:03 PM
#1
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Tire wear information
Preface
Keep in mind this is assuming good balance (changes with wear) and tight ball joints and good shocks. Those will compound any problems dramatically if they are not right.
So… here is what I know so far:
First; camber doesn’t cause wear, it only concentrates it on one side. Toe in (or out) causes wear.
Second; there is no such thing as a perfect alignment, it is a compromise. There is so much flex in our suspension that specs call for lots of tow. It flexes back to straight at 180mph, but you are scuffing your tires off at 55 mph. The trick is to eliminate some flex, then pick your compromise on the toe. (I’m speaking of the front end. I’ll get to the rear later) Eliminating camber spreads whatever wear you have over the whole tread, making it less noticeable. The first thing to look at is the lower front thrust arms. They are the aluminum ones and the ball joint is not replaceable. From the factory they come with a big squishy hollow rubber bushing oem replacement has solid rubber and is much better. See early post “Front tire wear solved” Kmac bushings will eliminate both rubber mounting points and give you camber/caster adjustment as well. The more flex you eliminate, the less toe you need to compensate for it. I don’t have time to explain castor, except that it will pull your car one way or the other if it’s not even, and sometimes it’s set uneven to compensate for road slope.
Rear suspension: the forces are different here. Specs call for even more toe in, and it flexes strait under acceleration loads. All this flex gives you more traction (front and rear). If you set the rear tow at Zero the tires will stop wearing on the highway, but when you punch it they tow way out, and it feels like someone is steering the back from one side to the other. (depending on where the weight and traction is) It’s a bit unsettling but you can compromise and get used to a little bit of it and double your tire life, or save it for a fun way to wear it off. Kmac bushings should reduce the flex and allow for a compromise tow setting closer to zero. But as you lose flex you lose traction. Might get some back by reducing the camber, but you’ll lose some cornering grip. Tires are the same way, softer compound =more grip and faster wear.
The factory setup put a nearly 2 ton sedan in the same neighborhood as a Ferrari on the track, but you will go through tires like they were paper towels on the highway.
So to sum it up flex = grip, but the more flex you have the more toe-in you need to compensate.
Toe-in = wear.
Negative Camber = cornering grip but concentrates the wear on the inside edge of the tire.
Low UTQG tire rating (200) = grip
High UTQG tire rating (540) = long life
I just got 26K miles out of a set of continental DWS. I built a wooden jig to do my own alignments and found a good high mileage compromise. The front ones still have more than half their tread except for the inside edge so I will be installing Kmac when I get the car out this spring. The back ones… well, you know what happens to the back ones I’m happy with 26k.
Now maybe I can start spending my money on upgrades instead of tires.
Last edited by StarvingArtist; 01-28-2014 at 06:50 PM.
