free play in 930 front struts

fredmeister · fredmeister's Garage

Guys,
I have been attributing rocking or free play in my front wheels to loose wheel bearings on my 79 930 turbo, but after checking the bearings and found them ok, the free play is still there.

The front struts actually seem to be worn allowing the wheel to rock slightly. I have not been able to put a dial indicator on the hub to quantify the amount of motion side to side, but I am guessing 10 thousandths or so at the hub. It is pretty evident and I have failed tech inspection for a DE the last time out because of it, telling me to tighten the wheel bearings up.

I know there is a guide bearing inside the strut housing that the strut insert slips into and there has to be some amount of clearance there, but how much is acceptable? Kind of like a valve guide, how much clearance is allowed between the stem and guide OD?

Can these bearings be refurbished and how do a skilled mechanic like me remove and replace them?

Thanks,
Fred

fredmeister · fredmeister's Garage

Bump. Can anyone offer some tech advice for this one?

Thanks,
Fred

Cory M · 06-01-2015, 12:59 PM

If you are talking about the seal that fits in the top of the strut tube you can buy them from Tarett Engineering and Rebel Racing. They sell an aftermarket low profile version of it. You can probably get the original ones from Bilstein too. I think they just press or thread on. There shouldn't be any clearance there, it should be contacting all around the circumference.

gamtart · gamtart's Garage

Do you have the green strut housings with Bilstein inserts? Can you feel the play where the insert enters the housing? I had this problem on my 81 SC and had to replace the bushings that are inside the housing. I got them from Elephant Racing. There are two of them, one near the top and the other about midway down. Getting them out required me to make a "puller" with a threaded rod and some plumbing flanges. I can send you a pic of what I made if you like.

Chuck Moreland · 06-02-2015, 09:37 PM

Bilstein struts have a pair of linear bearings inside. This is what the insert slides against as the suspension compresses and rebounds.

The bearings wear over time. When the bearings get loose, the strut can rock on the insert. symptom looks like loose wheel bearings, but on closer inspection you see the movement at the strut.

The seal at the top of the strut that Cory mentions sometimes fails. Failed seals allow contaminate to enter the strut and accelerate wear on the linear bearings.

We have both the linear bearing and the seals. Yes, the bearings are difficult to replace.

Clearance between the linear bearing and the insert should be on the order of .005 inches. Measure with a dial indicator.

Cory M · 06-03-2015, 07:16 AM

Good info, thanks Chuck!

Walt Fricke · 06-03-2015, 07:59 PM

Assumes you have Bilsteins. Identify either by the thickness of the silver rod up top (Bilsteins are very thick, almost as wide as the strut), or by the roll pin Bilsteins have down by the spindle which holds the bottom of that insert in place (other types don't have a pin or hole for one down there).

If Boge or Koni, you can tighten the cap nut which clamps the tapered top of the insert in place.