Wheel Balance or Alignment Concerns

[uvachief]

I've got an 86 944 na with the original suspension. Yes it is on its last legs (car has about 150k on it). I notice a slight vibration or shimmy in the steering wheel at speeds between 55 and 70. Disappears after 70. I've had the car aligned but not by a true Porsche shop or specialist. I had the wheels balanced with that Hunter Roadforce Touch balance machine. Car drove like a dream for about 2 days and then the vibration slowly returned.

I assume some sort of link or rubber has worn out that can no longer hold the front end in alignment. When I go to replace the suspension, anything I should look for while I am in there?

[djnolan]

Try going over it systematically and look for excessively worn parts:
Ball joints
tie rod ends
sway bar bushings
Strut top bearing/bushing
Strut damper
wheel bearing play
control arm bushings

Most of these should have been checked as part of an alignment. but you can re-check most of this in an easy hour on a lift. However I haven't known the 944 front end to be excessively problematic, so how bad is the vibration?

[flash968]

my bet is that either you threw a weight, or the caster blocks are shot

[Gawernator]

Another thing to check for is a big rock in your tread. Not likely but I actually had the same problem for a day until I knocked the rock out

[uvachief]

The vibration is noticeable is how I would describe it. I've checked the tire tread. No debris lodge in there. I no longer see any of the wheel weights on the outside of the wheels. Before I had the wheels refurbished and painted, I remember seeing them. While most of the suspension parts are passed their prime, I wouldn't say any of them have failed but the car has about 150k on it. I guess I'll find out when replacing the rubbers and upper strut mounts. By the way, can you rebuild the assemblies? I bought some parts off the katalogue schematics but nit sure I have them all. Is there a cheat sheet somewhere? I just want to do Sachs Boge again. These lasted 27 years.

[rhett]

Originally Posted by flash968

my bet is that either you threw a weight

That is what I would check first, it only takes one to come off and then you get symptoms like you have described. Stick-on weights can easily come off due to bad application (not a clean surface), or where the paint layer (+ weight!) actually comes away from the wheel due to poor paint adhesion, etc.

The fact that it drove like a dream kinda discounts quite a lot I feel...

[uvachief]

I can feel something going on with the tires on the drivers side. Slight odd tiny wobble. I replaced the power steering rack 2 years ago and it was a difficult job. It was late and it may have been rushed at the end. Everyone that rides in it cannot feel it. I can. It's driving me insane. I'll have to take to a real tire and alignment shop and have them trouble shoot it.

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[Gawernator]

When's the last time you re-greased and re-tightened the wheel bearings? Next time get your wheel weights on the inside of the wheel, too.

[uvachief]

I did repack all 4 wheel bearings when I redid the brake hardlines but I didn't replace the wheel bearings. I noticed no change at that time. It was early summer. Do I need wheel weights on both the inside and outside of each wheel?

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[andyshoun]

You do not need weights on the inside and outside of your wheels. Weights should be placed on the inside or outside as needed (could be is either or both places). Your tire replacement mechanic should have taken care of this.

You can rotate tires front to back and see if that makes any difference. A front wheel imbalance will have a bigger effect on ride quality. If moving wheel/tire combinations around and you trust you tire change mechanic then you need to look for other hardware issues.

[rhett]

Originally Posted by andyshoun

You can rotate tires front to back and see if that makes any difference.

On a stock vehicle with same size wheels you can do this...not on a 944

[Slam]

Well, many 944 cars have a square setup (951 excepted) so yes you can.

[uvachief]

I've got early offset wheels and tires so I cannot. Would the Porsche dealership be best for this? The tire shop may have put them on the inside but I will be darned if I see them but I have not removed them either.

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[rhett]

Originally Posted by Slam

Well, many 944 cars have a square setup (951 excepted) so yes you can.

Yep..my bad , I forgot about the standard 15 x 7 setup...

[andyshoun]

uvachief, If you are running the same width rims front and rear you can move tires front to rear. Some cars have wider rims in the rear. My '86 NA car runs the same 15" rims at all 4 corners.

[uvachief]

I'm running early offset

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[uvachief]

Weird thing is that when I had to throw on 2 new tires on the rear, the arse was greasy for a few months. Guess the tires burned in or I got the pressure right because it isn't as nearly as slippery on tight curves as it was. Does it take 3,000 miles for tires to break in?

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[Stephen03]

Yes tires take awhile to break in... either that or you forget how sticky your old tires were.

[Tervuren]

First step, lift and check for bearing play, second step inspect bushings, third step take wheels/tires to tire shop/machine and check balance of wheels/tires.

A likely culprit is one or both of your strut inserts is beyond function. If a strut insert is past its prime, any bump or imbalance is gonna throw quite the shimmy in the steering wheel.

I still had an issue after complete replacement of bushings, bearings, dampers(fronts were blown) and springs. Ended up taking my wheels/tires to a small town retired tire shop owner that had his own set of equipment at home. Problem went away completely.

[uvachief]

Okay another dumb question. I tried the old worn shock test. I go to each corner and press down hard and see if it bounces. It doesn't. However, the shock/damper inserts have to passed it - the car has around 150k on it. I think I've bought everything but 200 lbs springs to rebuild the strut assemblies. Lindsey Racing has them quite cheap. Might as well do those.