Castor found to be under spec ?

[bmw330cic]

I recently had my dealer perform an alignment on my 01 330cic w/42K miles. The technician wrote that the "right side of the castor was found to be under spec, castor is non-adjustable, vehicle may drift right."

I asked the service advisor for an explanation, but so far they haven't given me a response. How and why does a castor become under spec and how is it corrected?

For what it's worth, the car just doesn't track like it did for the last 10K miles before this.

-Keith

 

[jrt67ss350]

Caster is not adjustable in most vehicles, and BMWs are no exception. In your car, the caster angle was set when your body was welded together at the factory - it is produced by the angles of the strut mounting points and the lower control arm mounting points. Caster can get thrown off as a result of a couple of reasons. You could have a bent strut at the right front wheel, or the geometry of the frame/strut tower on that side of the car is out of spec.

The caster angle setting is not critically important in and of itself for an everyday road car, but the caster angles need to be the same on both sides of the car to keep the car from pulling to one side when tracking down the road.

I hope that helps out a little.

 

[Big Daddy]

Excellent explaination Justin, well written and right on!

 

[epj3]

I recently had my dealer perform an alignment on my 01 330cic w/42K miles. The technician wrote that the "right side of the castor was found to be under spec, castor is non-adjustable, vehicle may drift right."

I asked the service advisor for an explanation, but so far they haven't given me a response. How and why does a castor become under spec and how is it corrected?

For what it's worth, the car just doesn't track like it did for the last 10K miles before this.

-Keith

I wouldn't be too concerned, The car will drift to one side or the other anyways depending on the road surface. I agree, justin did a great job explaining it.

 

[bmw330cic]

Thanks everyone, especially Justin for the response. -Keith

 

[Kirby]

it can be corrected by installing castor/camber plates. They install at the top of the strut and have slotted bolt holes to allow the adjustment that the factory doesn't provide. They will only be sold in pairs for $200 - $300 or so.

Your out of spec castor could cause faster tire wear.

 

[kayer]

I had the same problem with my 2001cic. The dealer advised me not to spend money on the repair, but I had the strut replaced and it was then alligned to spec--$600.

 

[bmw330cic]

Interesting stuff, I appreciate it. Thanks Kirby and Kayer.

-Keith