Checking Caster

[nvrenuf]

So I put my angle finder on the driveway at the base of the tire, angle is -1°

I set the angle finder on top of the D60 king pin cap, angle is +10°

My GM service manual says the spec is +8° "nominal".

I think this means I need a 3° shim but that doesn't sound like enough. To eyeball my axle, the spring perches appear to be tilted rearward (approx +5°) when I thought they should be level.

Am I doing something wrong?

 

[4X4HIGH]

Don't worry about where the perches are, caster angle is caster angle. If the ground is -1* and the knuckle is +10* then you are right at +9* caster and i'd leave that alone.

 

[Hogback Fabrication]

Stock caster is 4-8 depending on variances and specific axles. The bigger the tire the more caster it will take to keep the thing driving straight, as Scott mentioned I'd probably keep the 9*.

 

[folkenheath]

If the ground is down -1, and the caster is +10, then they are opposite angles and you would have 11 degrees of caster. Unless you flipped the protractor around?

Still, unless you are having issues with front pinion angle, I would leave it alone. A little too much won't hurt, may even help, but too little will be very bad. But if you are having front pinion issues then you could easily shim it 3 degrees or 5 degrees and probably be OK.

And I agree, perches are irrelavent, caster and pinion angle are what matters, and caster is most important for the front.

 

[nvrenuf]

Ok, I'll double check it again just for good measure but I may leave it alone then. I'm chasing death wobble and was hoping I had found a contributing factor.

 

[folkenheath]

Ok, I'll double check it again just for good measure but I may leave it alone then. I'm chasing death wobble and was hoping I had found a contributing factor.

Nope, extra positive caster won't hurt death wobble, may even help. As long as it is + caster, and the upper kingpin is behind (closer to the back of the vehicle) the lower pivot bearing. If it's the other way around, then you probably did find your problem...

 

[Hogback Fabrication]

And I agree, perches are irrelavent, caster and pinion angle are what matters, and caster is most important for the front.

There is no caster in the rear, unless it's a steering axle.

 

[4X4HIGH]

Quote:
Originally Posted by folkenheath
And I agree, perches are irrelavent, caster and pinion angle are what matters, and caster is most important for the front.

There is no caster in the rear, unless it's a steering axle.

I think what he means is that out of spring perches, pinion angle, and caster angle, caster angle is the most important.

 

[folkenheath]

There is no caster in the rear, unless it's a steering axle.

I think what he means is that out of spring perches, pinion angle, and caster angle, caster angle is the most important.

I agree with both of you, and you both confirmed the points I was trying to make, thank you.

I added "for the front" at the end of the sentence because I thought someone would say, "no the pinion angle is more important in the back".