front toe problem/mystery
06-30-2018, 07:20 PM
#1
Three Wheelin'
Thread Starter
front toe problem/mystery
front toe can be adjusted and set, tie rod adjustment can be locked in place.
steering wheel held in place with generic holder.
with tie rod adjustment locked, rolling the car 4 to 10 feet results in toe measurement changing by up to 2mm measured using smart strings.
the margin of error, as in using strings, digital caliper, human eyes and so on seems to be .5mm.
as an example, toe measures 0, roll car 5ft back, toe measures 2mm out, roll car 5ft further back toe measures .5mm in.
changes seem to be random and not linear, like a wobble.
rolling the car back to original spot doesn't bring measurement back to original setting.
tested on 4 different sets of wheels/tires. one set of tires is brand new so no klag build up.
haven't found a relationship between right and left toe change.
both sides seem to wobble independently.
the toe wobble had been worse, in the 5mm range, the wobble was reduced by changing parts.
parts changed to new on both sides
-ball joint(caster ball joint)
-tie rod inner and outer heim joint.
-wheel bearings
-control arm monoballs
-steering rack
-spherical bearing in camber plate
steering rack mount shows no cracks. cross and side members show no cracks or bends.
tub mounting points for cross member and side members show no cracks. everything is properly torqued.
steering wheel doesn't shake or vibrate when driving and connection feels solid, quick and responsive.
this is a 1997 993 track only car with no rubber in the suspension.
my smart strings measuring method was tested by measuring rear toe and rolling the car. no change in rear toe.
front camber does not change when rolling the car.
garage floor is smooth and flat, steering wheel holder works well so I don't think this is just the tires moving the steering wheel.
the only steering parts not changed are the steering shaft and universal joint.
can't move or shake the steering shaft by the universal joint and the rubber donut on the shaft seems to be solid.
no clicking or noise from turning steering wheel.
so what am I missing?
what other bearing or bushing is next in line to throw at this problem?
steering wheel held in place with generic holder.
with tie rod adjustment locked, rolling the car 4 to 10 feet results in toe measurement changing by up to 2mm measured using smart strings.
the margin of error, as in using strings, digital caliper, human eyes and so on seems to be .5mm.
as an example, toe measures 0, roll car 5ft back, toe measures 2mm out, roll car 5ft further back toe measures .5mm in.
changes seem to be random and not linear, like a wobble.
rolling the car back to original spot doesn't bring measurement back to original setting.
tested on 4 different sets of wheels/tires. one set of tires is brand new so no klag build up.
haven't found a relationship between right and left toe change.
both sides seem to wobble independently.
the toe wobble had been worse, in the 5mm range, the wobble was reduced by changing parts.
parts changed to new on both sides
-ball joint(caster ball joint)
-tie rod inner and outer heim joint.
-wheel bearings
-control arm monoballs
-steering rack
-spherical bearing in camber plate
steering rack mount shows no cracks. cross and side members show no cracks or bends.
tub mounting points for cross member and side members show no cracks. everything is properly torqued.
steering wheel doesn't shake or vibrate when driving and connection feels solid, quick and responsive.
this is a 1997 993 track only car with no rubber in the suspension.
my smart strings measuring method was tested by measuring rear toe and rolling the car. no change in rear toe.
front camber does not change when rolling the car.
garage floor is smooth and flat, steering wheel holder works well so I don't think this is just the tires moving the steering wheel.
the only steering parts not changed are the steering shaft and universal joint.
can't move or shake the steering shaft by the universal joint and the rubber donut on the shaft seems to be solid.
no clicking or noise from turning steering wheel.
so what am I missing?
what other bearing or bushing is next in line to throw at this problem?
06-30-2018, 11:56 PM
#3
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Two things to check. One is the control arm bushings. As an owner of a (very) variable rear toe on a race car recently, I can attest that it's both scary and dangerous. The reason was... no fender washer on the outside of the bushings and the bushing simply walking in and out of carrier over the bolt's head. The other was more of a loud clunking issue, but, I'm sure, also somewhat variable geometry due to... stretched out threads on the alignment bolts.
both of these things happened on a non-P car, so YMMV. But check anyway. I suspect the bushings for some reason (mine weren't rubber, either).
both of these things happened on a non-P car, so YMMV. But check anyway. I suspect the bushings for some reason (mine weren't rubber, either).
07-01-2018, 10:08 AM
#5
Three Wheelin'
Thread Starter
Two things to check. One is the control arm bushings. As an owner of a (very) variable rear toe on a race car recently, I can attest that it's both scary and dangerous. The reason was... no fender washer on the outside of the bushings and the bushing simply walking in and out of carrier over the bolt's head. The other was more of a loud clunking issue, but, I'm sure, also somewhat variable geometry due to... stretched out threads on the alignment bolts.
both of these things happened on a non-P car, so YMMV. But check anyway. I suspect the bushings for some reason (mine weren't rubber, either).
both of these things happened on a non-P car, so YMMV. But check anyway. I suspect the bushings for some reason (mine weren't rubber, either).
but I can't start changing out brand new just replaced items.
07-01-2018, 11:12 AM
#6
Three Wheelin'
Were the wheels hard to balance? Maybe you are measuring variations in the tires?
Check ride height, and tie rod level, at each measurement. Maybe you are measuring some minor suspension articulation.
That’s all I can think of.
Check ride height, and tie rod level, at each measurement. Maybe you are measuring some minor suspension articulation.
That’s all I can think of.
07-01-2018, 07:15 PM
#7
Have you locked the steering rack? There is a threaded hole in the rack. When the steering wheel is centered there is a “divot” in the movable part of the rack. You can take a bolt with the proper thread and grind it to a point. You then screw it into this hole and it locks the rack so it can’t be moved. Do this a see if the toe still changes. I’m betting your steering wheel is moving ever so slightly.
Pete
ps. There should be a rubber plug in the hole that you need to remove first.
Pete
ps. There should be a rubber plug in the hole that you need to remove first.
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07-01-2018, 08:46 PM
#8
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07-01-2018, 08:48 PM
#9
Three Wheelin'
Thread Starter
I've read basal skull's thread on the centering pin, and its a great idea to isolate the problem.
but it worries me because the rack centering hole is cone shaped, so if there is pressure coming from whatever is the source of the toe deflection the steering shaft centering hole could ride up the m10 bolt damaging the shaft seals. but I've never taken apart a rack so really don't know.
my current plan is to somehow lock the universal joint in place. if that can be done the issue will be isolated to either the suspension or the steering shaft.
but it worries me because the rack centering hole is cone shaped, so if there is pressure coming from whatever is the source of the toe deflection the steering shaft centering hole could ride up the m10 bolt damaging the shaft seals. but I've never taken apart a rack so really don't know.
my current plan is to somehow lock the universal joint in place. if that can be done the issue will be isolated to either the suspension or the steering shaft.
07-01-2018, 08:50 PM
#10
Three Wheelin'
Thread Starter
07-01-2018, 09:19 PM
#11
Locking the rack with a bolt is the procedure that is in the factory shop manual. Of course they use a special tool, which is a bolt with a cone on the end. I made my own using a bench grinder.
Trying to lock the steering at the u-joint won’t work any better than trying to lock it at the steering wheel. You won’t do any damage doing it the factory way
pete
Trying to lock the steering at the u-joint won’t work any better than trying to lock it at the steering wheel. You won’t do any damage doing it the factory way
pete
07-02-2018, 12:06 PM
#13
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07-03-2018, 09:11 AM
#14
Burning Brakes
The only thing that comes to mind is the mating surface of the hub, debris or rust keeping the wheel from mating flat. There are two things against that though. Your multiple removal / reinstall of wheels should have caught that by now, and the no vibration when driving.
Sounds like all of the usual suspects on the front suspension / steering have been verified good.
A question for those more knowledgeable than me:
Ii there anything in the rear that would affect front geometry? I think not.
When following along that line, what happens when the vehicle is moved? A person gets inside and grabs the steering wheel while someone pushes.
Your ride height changes with weight. Doesn't ride height affect alignment? ( I am aware it is usually minimal, and maybe not the toe, but I am thinking out of the box)
Are you sure the other things that affect alignment are staying stable when moving the car?
just a few wag, not a professional opinion.
Sounds like all of the usual suspects on the front suspension / steering have been verified good.
A question for those more knowledgeable than me:
Ii there anything in the rear that would affect front geometry? I think not.
When following along that line, what happens when the vehicle is moved? A person gets inside and grabs the steering wheel while someone pushes.
Your ride height changes with weight. Doesn't ride height affect alignment? ( I am aware it is usually minimal, and maybe not the toe, but I am thinking out of the box)
Are you sure the other things that affect alignment are staying stable when moving the car?
just a few wag, not a professional opinion.
07-03-2018, 11:44 AM
#15
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since new wheel bearings, double check front hub bolts are still tight. Cannot think of anything else going on there based upon what you have already checked.
