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99 Chevy Tahoe Alignment Question


trinitro's Avatar
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Join Date: Jan 2002
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07-23-04, 06:52 AM   #1  
99 Chevy Tahoe Alignment Question

I took my truck in yesterday for an alignment and tire balancing (truck was pulling to the right slightly and had a wheel shimmy above 65 mph). I went to my trusty Sears Auto store (there was nothing else available at that hour). Anyway, now the truck is no longer pulling to the right, but to the left. I guess I have to go back for another 3 hours to rectify that. The question I have is about the alignment specs. The fron cross caster is supposed to be within -0.5 to +0.5 degrees. However, it is -1.2 degrees, and the mechanic says that it's not adjustable. Why would they have a value for something that's not adjustable? What does the "cross caster" do? Can it be brought back within spec?

The rears are different from eachother, but I guess there is no rear allignment to be done on this car as there are no specified values. Other then the cross caster the total toe for the front was off, and so was the toe for botht the left and right tires. Everthing else was within spec.

The funny thing is that the caster for the front are almost at the extremes of the spec. The left is 2.3 while the right is 3.5, with the range being 2.0 to 4.0. What does the caster do anyway?

 
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Johnc280's Avatar
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07-23-04, 10:43 AM   #2  
Johnc280
From experience I would say most cars have a pull because of the tires and not the alignment. Look at your tires and you will probably see that they are worn unevenly and the tread close to the sidewall will be worn a lot more than in the middle. There are a few things that can cause this: low tire pressure, toe or camber out of adjustment, worn steering linkages etc.

I am thinking when the technician balanced your tires he probably rotated them and maybe went side to side. I bet if you rotate the tires back left to right then your pull will change directions also.

Johnny

 
Desi501's Avatar
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07-23-04, 02:08 PM   #3  
That caster split is definately causing your left pull. It can be adjusted, they just don't know how. Caster is a pulling angle only and that is what gives you a problem, when you have a split that large from left to right. Ideal is 1/2 deg less positive on the left to overcome the road crown. Camber can also pull if the split is too severe. It will pull to the side more positive for camber or the side more negative for caster.
Chevrolet gives you adjusting cams but the problem is they don't elongate the holes so it can move. What needs to be done is remove the upper control arm, there is a tool made to punch out the stampings to give it travel and it will be adjustable from that point on. There will be an extra charge for doing this, usually an hour per side. I just did one today.

 
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