Bad wear on front tires

[DaveB]

My son's Comanche is wearing his brand new tires badly on the front. The wear shows up as cupping on the inner edge of the tire. I have checked caster, camber and toe in and they all look good. It has new shocks and a fairly new Rubicon 5.5 inch front lift. Any suggestions on what could cause this ?

 

[Brett]

You're definately more knowledgeable than me, but perhaps ball joints as well?

 

[bobmed]

heres a site about tire wear patterns
http://www.babcox.com/editorial/tr/tr129622.htm

 

[DaveB]

heres a site about tire wear patterns
http://www.babcox.com/editorial/tr/tr129622.htm

I read this and will need to check some of the other things they mention. He replaced all of the ball joints and steering joints when he re-geared the axle a few years ago but he did have one tire out of balance on the front axle that shook it up till he had it re-balanced. Maybe the ball joint got a bit of wear on that side. Both front tires have the same wear pattern but the right side is worse.

 

[NoTrax]

bent axle housing?

 

[tisjeep]

Has it ever been in an accident. Have it checked to see if the SAI is out. This is not adjustable by adjusting the alignment the only way it could be out is if something was bent

 

[DaveB]

Has it ever been in an accident. Have it checked to see if the SAI is out. This is not adjustable by adjusting the alignment the only way it could be out is if something was bent

The axle did come from a wrecked vehicle. What is SAI ? I've checked caster, camber and toe. I found some worn bushings and bolts and replaced them. It is now running better but we will need to keep an eye on the wear.

 

[Rusted]

.... What is SAI ? .....

I had the same question. From this site:

http://www.familycar.com/alignment.htm

I found this:

SAI is the measurement in degrees of the steering pivot line when viewed from the front of the vehicle. This angle, when added to the camber to form the included angle (see below) causes the vehicle to lift slightly when you turn the wheel away from a straight ahead position. This action uses the weight of the vehicle to cause the steering wheel to return to the center when you let go of it after making a turn. Because of this, if the SAI is different from side to side, it will cause a pull at very slow speeds. Most alignment machines have a way to measure SAI; however it is not separately adjustable. The most likely cause for SAI being out is bent parts which must be replaced to correct the condition. SAI is also referred to as KPI (King Pin Inclination) on trucks and old cars with king pins instead of ball joints.

 

[BroncoMama]

Have you checked the tie rod ends?

 

[DaveB]

Have you checked the tie rod ends?

Yes, they are all good.