What contributes to caster adjustment?

[username182]

I am fighting with a suspension issue and I need some help.

First off the basics: Car is a 95 Mustang GT, auto, 100k miles. 1 owner, no accidents, all original suspension components. It had been a daily driver, then garaged for 2-3 years, and now I'm back using it as a daily. Car has never been in an accident, not even a minor fender bender.

Now, on to the problem.

I am getting a pretty nasty shake/vibration in the steering wheel between 50-65mph.

First thought was tires (they were pretty old and worn), so I threw on new wheels and new tires, still had the issue.

Then I brought it in to Les Schwab for an alignment. Basically, the guy told me that the Caster is off and that is what is causing the vibration. He said that there is no way to adjust the caster on these cars. His only suggestion was to install a camber kit which might help get it where it needs to be.

What would cause the caster to be off?

The right front specified range is 2.9 - 4.4 degrees, I am right at 2.9. I am also right on the line for the Left front camber, specified is -1.4 - 0.2 degrees and I am right at -1.3 degrees.

Is my only option to install a camber kit and hope that gets me the necessary adjustments? Any other suggestions?

 

[CC'S95GT]

caster being off sounds like B.S. to me. any time i've had a vib like that ended up being tie rod ends. try taking it to a different shop to see what they say, or lift one tire off the ground grasp it at 3 and 9 o'clock and move back and forth looking for play, next to ck the ball jounts -hands at 6 and 12 o'clock and move up and down looking for play there too. now repeat for the other side. there should be little to no play.

 

[username182]

Thanks for the info, I will definately check that out. That could very well be the culprit considering all the suspension components are oem and have never been replaced.

 

[2slo95fiveoh]

caster would not necessairly cause a vibration.. too much positive caster would make the steering wheel harder to turn in low
speed situations, but have good high speed stability, where as too little caster would be the opposite. Did they give you an alignment
printout by chance? If so post the printout on here, specifically with the front end specs. But usually only severe instances with
your cars toe are the usual culprits if it was only an alignment problem.

 

[GDawg]

Caster is a "front/Rear" extention of the front wheels. Has nothing to do with your camber. Maximum/Motorsports has Caster/Camber plates but you can do this adjustment without them if you aren't afraid of drilling your strut towers.

I would take your car somewhere else. They are trying to rip you off.

 

[username182]

I'd like to avoid any modifications if possible. I guess I just don't understand how a completely stock suspension that has never been touched can be tweaked to the point that the alignment guy can't get it back to spec....

I don't have a scanner, but here's what the printout from the alignment says...

Front:Left Front:Right
Actual Before Specified Range Actual Before Specified Range
-1.3 -1.3 -1.4 0.2 Camber -0.8 -0.8 -1.4 0.2
3.3 3.3 2.9 4.4 Caster 2.9 2.9 2.9 4.4
0.14 0.21 0.00 0.25 Toe 0.12 0.21 0.00 0.25

Is that just the best I'm gonna get with this car without adding the caster/camber plates?

I am going to get the tires re-balanced this weekend, that way I can completely eliminate that as causing the vibration. I lifted the car up checked out the tie rods and ball joints, everything looks fine to me with no abnormal play. I might just go ahead and replace the ball joints, just because.

Yea, I'm definately not letting them do any type of work on the car, I do all my own work :thumbsup:

 

[vermilion]

bent tie rods, need new struts, or wheel bearings, wheel out of true.

 

[2slo95fiveoh]

bent tie rods, need new struts, or wheel bearings, wheel out of true.

Caster is the measurment foward or rearward of the strut angle in comparison to true straight up and down. All of those listed would most
likely not affect caster, tie rods would affect toe, and unless your struts are HELLA bent, a defective strut wouldn't affect caster either.
A bent spindle or shifted cradle are going to severly affect caster, but since your caster is in spec, why are you worried about it? Minor bumps
such as potholes are going to ever so slightly move alignment angles around, that's why manuf. recommend checking alignment a couple times
a year. Your vibration could very well be your brakes... have you checked them lately?

 

[username182]

Caster is the measurment foward or rearward of the strut angle in comparison to true straight up and down. All of those listed would most
likely not affect caster, tie rods would affect toe, and unless your struts are HELLA bent, a defective strut wouldn't affect caster either.
A bent spindle or shifted cradle are going to severly affect caster, but since your caster is in spec, why are you worried about it? Minor bumps
such as potholes are going to ever so slightly move alignment angles around, that's why manuf. recommend checking alignment a couple times
a year. Your vibration could very well be your brakes... have you checked them lately?

I guess I was just hoping that my alignment barely being in spec had something to do with the vibration...

Haven't checked the brakes, its one of the several things on my list...

 

[2slo95fiveoh]

well, in my experience in the automotive field, a highway speed vibration is (most of the time) either wheel imbalance, or warped rotors.
I would take it out on the highway, try and get up to around 70mph, (where you should notice a significant vibration) then press on the brake
pedal with MILD pressure (don't need to be locking the wheels up on the highway.. haha). If your vibration gets worse/more intense, then you
have some warped rotors, regardless of brake pad life. Now if the vibration begins to disipate as your speed slowly decreases, then i would begin
to lean more towards a wheel/tire problem. You mentioned you put new wheels/tires on, when you had them balanced, did you buy them as a
package deal (already mounted and balanced) or did you have a shop mount them?