Interpreting Caster Alignment Specs

[Harvard]

Thinking outside the box?

Given: 2011 F53 Caster Spec 3.75 +/-1,75 Degrees

This specifies a range of +2.0 to +5.5 Degrees

Logical Interpretation:

+2.00 Degrees for 100% city driving
+3.75 Degrees for 50% city and 50% highway
+5.50 Degrees for 100% highway driving

NOT +3.75 for all !!!

[shlomyo]

i have 1996 ford e350 tioga rv 24 ft that i want to improve the steering that feels loose on highway,

i got the moog bushings +2 deg upgrade to put more positive caster,

this is my aligment report now, it is going to work?

what else can i improve for better steering driving ?

[Harvard]

chris_diane wrote:
Just a clarification of caster settings above 5 degrees is only possible with the F53 axle. Shims are installed between the axle and spring allowing greater adjustments for caster. The cutaway chassis (E450, E350) use bushing in the ball joint which can only go to a little over 5 degrees caster. The aftermarket 2 piece bushing can only adjust to 2.5 degrees caster.

In the beginning I created 2 threads, one for the F53 (Class A Forum) and one for the E350/E450 (Class C Forum).

The moderators must have assumed both to be the same and scratched the E350/E450 in the Class C forum. Then the F53 was mysteriously moved from the Class A Forum to the Class C Forum.

[chris_diane]

Just a clarification of caster settings above 5 degrees is only possible with the F53 axle. Shims are installed between the axle and spring allowing greater adjustments for caster. The cutaway chassis (E450, E350) use bushing in the ball joint which can only go to a little over 5 degrees caster. The aftermarket 2 piece bushing can only adjust to 2.5 degrees caster.

[Waiter21]

I put on 7,500 miles a year, all highway. If I was making an adjustment to my caster (shims) I'd take it out to 7 - 8 degrees.

I have my toe-in set a tiny bit past max.

[theoldwizard1]

phil-t wrote:

RLS7201 wrote:

Caster DOES affect tire wear. When you turn the wheels the tire and wheel assemble will roll over on it side. You will get excessive wear on the both sides of the front tires. If you ever have a chance, watch the front tires of a class A fuel dragster. You can see the effects of extreme, excessive caster. I run about 7° caster on the front of my 95 F53 and you can see the wear.

Richard

Probably so but the advantage in handling is well worth the minimal wear. AND, in the life of an RV tire, it will age out before it wears out; unless there is some other contributing factor.

Concur ! Regular tire rotation will help minimize shoulder wear.

Also motorhomes see very little "urban" driving with a large number of corners.

[phil-t]

RLS7201 wrote:

Caster DOES affect tire wear. When you turn the wheels the tire and wheel assemble will roll over on it side. You will get excessive wear on the both sides of the front tires. If you ever have a chance, watch the front tires of a class A fuel dragster. You can see the effects of extreme, excessive caster. I run about 7° caster on the front of my 95 F53 and you can see the wear.

Richard

Probably so but the advantage in handling is well worth the minimal wear. AND, in the life of an RV tire, it will age out before it wears out; unless there is some other contributing factor.

[RLS7201]

theoldwizard1 wrote:

dodge guy wrote:
If at all possible always go with the higher caster spec. The highway stability will be greatly increased. It may be a bit harder to steer in a gas station, but the highway handling will far out weigh parking lot maneuvering.

phil-t wrote:
I had a shop do my 2010 F53. They do a lot of F53 chassis. Talked them beforehand about the handling. They set the caster - 7-3/4 left and 8-1/4 right. Handles like a dream. Mine is the 22,000 GVWR. All the left/right wandering is gone.

Both are 100% correct. Only "old timers" are willing to go that far beyond the spec, but they know that caster DOES NOT AFFECT TIRE WEAR and it does greatly increase the chassis ability to hold a straight line.

Side to side caster difference is to deal with the "crown" in the road (higher in the center to promote better drainage).

Caster DOES affect tire wear. When you turn the wheels the tire and wheel assemble will roll over on it side. You will get excessive wear on the both sides of the front tires. If you ever have a chance, watch the front tires of a class A fuel dragster. You can see the effects of extreme, excessive caster. I run about 7° caster on the front of my 95 F53 and you can see the wear.

Richard

[theoldwizard1]

dodge guy wrote:
If at all possible always go with the higher caster spec. The highway stability will be greatly increased. It may be a bit harder to steer in a gas station, but the highway handling will far out weigh parking lot maneuvering.

phil-t wrote:
I had a shop do my 2010 F53. They do a lot of F53 chassis. Talked them beforehand about the handling. They set the caster - 7-3/4 left and 8-1/4 right. Handles like a dream. Mine is the 22,000 GVWR. All the left/right wandering is gone.

Both are 100% correct. Only "old timers" are willing to go that far beyond the spec, but they know that caster DOES NOT AFFECT TIRE WEAR and it does greatly increase the chassis ability to hold a straight line.

Side to side caster difference is to deal with the "crown" in the road (higher in the center to promote better drainage).

[dodge_guy]

If at all possible always go with the higher caster spec. The highway stability will be greatly increased. It may be a bit harder to steer in a gas station, but the highway handling will far out weigh parking lot maneuvering.

[Harvard]

phil-t wrote:
I had a shop do my 2010 F53. They do a lot of F53 chassis. Talked them beforehand about the handling. They set the caster - 7-3/4 left and 8-1/4 right. Handles like a dream. Mine is the 22,000 GVWR. All the left/right wandering is gone.

Your post is priceless, I would never have ventured up there (+8.25) without having someone with the personal experience. Thank you.

[phil-t]

I had a shop do my 2010 F53. They do a lot of F53 chassis. Talked them beforehand about the handling. They set the caster - 7-3/4 left and 8-1/4 right. Handles like a dream. Mine is the 22,000 GVWR. All the left/right wandering is gone.

[wolfe10]

I would go for higher end of spec-- period.

So, perhaps 5 degrees left side, 5.5 degrees right side (difference to account for road crown)