Horribly uneven tire wear * UPDATED*

[Masher]

I've put about 4000 miles on my truck since the SFA 1-ton swap and the passenger side front tire is almost wore out. It is only wearing on the outside half of the tire, the inside half looks almost new. The driver side tire looks fine though. I pulled the tires off last night and checked the toe by measuring from brake rotor to rotor and it is toed in about 1/8". I got the front end on jack stands and the axle tube sits pretty close to level so I put an angle finder on the rotor and its sitting pretty much straight up and down, 90º. What else should I be checking?? The truck drove fairly straight and didn't pull to either side. The D60 was totally rebuilt before I put it in with new upper and lower kingpins/bearings, although I didn't actually do them. It does have crossover steering with a 3" block under the arm and a WTO ram mounted on the passenger side. My truck weighs about 5800lbs and I ran the 39.5 TSl at about 20 psi. Any advice or ideas are appreciated, 39.5's are too expensive to burn up in 4000 miles!

 

[Grim-Reaper]

Re: Horribly uneven tire wear

I always set my alignment 1/8 at the tread as closeto the horizontal centerline on the axle as possible. If your running a big tire what's 1/8 at the rotor at 7 inches from center of axle is going to be around 1/2 inch at 18 inches from the centerline on 36's.

Why it only wore the one side is the crown on the road is going to cause the vehicle to want toturn right to begin with. You turn a little left to compinsate. Well with that much tow your pushing that tire sideways down the street.

Caster and camber can play into this as well. If you had to shim to fix a pinion angle issue then your caster angle is going ot be on the excessive side. Think about a shopping cart with a bent caster and how it wobbles....the wheels can do the same thing with too much caster. Ths will also make bump steer worse.

One of the best things I did with my truck was move the axle foward 1 inch and took the shim out. It got rid of the bump steer I had and 1 inch did help my pinion angle. THe other major thing that took a bunch of bump steer our was the ORD sway disconnects/ correction. The suspension was binding on the sway.

 

[Masher]

Re: Horribly uneven tire wear

I found it hard to measure the toe with the tires on, that's why I used the rotor it gave a clean edge to measure to. Should I try it again with the tires on?? Do you measure outside tread to outside tread? I do have shims under the springs, they are 3º on 10" Superlift springs. Is there a way to check the actual caster? I do plan on moving the axle forward an inch this winter, should I try removing the shims from the spring pack?

 

[Masher]

Re: Horribly uneven tire wear

I did some more checking last night and found a couple things. I put the angle finder on top of the Kingpin spring cap, drivers side, and get an angle of about 6º-7º and then i put it on the steering arm, passenger side, and get just about 10º. Shouldn't both knuckles be tipped in the same?? I also took the steering block off and measured how deep the hole was where the Kingpin spring sits, it was about 1 1/2" deep. I then measured the stock steering arm I had laying around and it measured about 1 5/8" deep. So it seems the block I put on would put more pressure on the spring which I didn't think was a bad thing. Could that be throwing the angle of the knuckle off?? Anybody have any idea what is going on, burning up a tire in about 4000 miles just don't seem right to me.
Thanks

 

[tRustyK5]

Re: Horribly uneven tire wear

I also think you're running too much toe. I run the same 39.5" TSL's on a Chev D60 front. The tires have roughly the same mileage yours do and are wearing evenly with what appears to be 80% or better left.

I set my toe in to 3/16" at the tread face. It's hard to find good places to measure from on TSL's, but on the sidewall there's a flat raised surface that's consistant all the way around the tire. I had a helper hold my tape against that part while I checked the other side...

The tread should be feathered a bit if it really is toed in too much.

Rene

 

[Masher]

Re: Horribly uneven tire wear

Thanks for the advice. The only reason I didn't think it was toe because the drivers side tire looks fine. When I get it put back together I will try setting the toe as you described. Thanks