Strut mount bearing headache

[snakeye]

I'm trying to assemble my new struts, for which I got some Powerflex poly mounts. Curious if anyone else has run into the problem I'm having: as soon as I tighten the bottom nut, the whole thing just binds and the mount doesn't spin at all. I noticed the plate in the mount if very thick. Here's a pic:



Here's the nut sitting inside of the mount:



It's hard to see, but the bottom of the nut doesn't clear the plate. I suspect this is what's causing my problem. I think the nut is supposed to tighten against the top of the bearing, and loosely hold the mount in place. Instead, it's pulling the whole mount down, essentially joining together the shaft, bearing, and mount. Do I have this right?

 

[P2B]

I think the nut is supposed to tighten against the top of the bearing, and loosely hold the mount in place. Instead, it's pulling the whole mount down, essentially joining together the shaft, bearing, and mount. Do I have this right?

Yes, you have it right. The bottom of the nut is tight to the bearing and the flare at the top of the nut rests against the mount.

It seems your aftermarket mounts are incompatible with the stock nuts.

 

[snakeye]

Ok thanks! I guess I'll just add a washer.

 

[P2B]

BTW installation is a lot easier if you leave the mounts off. Assemble the struts using an outer tie rod jamb nut, install them, then slip the mounts on top. Lower the car so the weight is on the mounts then swap out the nuts.

The extra clearance gained by leaving the mounts off allows the struts to be installed without unbolting any suspension bits.

 

[snakeye]

Ah good tip, but I might already have the clearance, since I'm installing B8 struts. And also a knuckle's gotta come off due to a bad bearing, so I'll be loosening some other bits anyway.

 

[Zak99b5]

Yes the strut nut that goes on after the mount and bearing does not need to hold the mount on; gravity will do that quite nicely when it’s Installed. And top plate with the top nut will keep it all from falling out when you jack it up.

 

[03TDICommuter]

I've used the same mounts on my 03' jetta and 01' beetle with no issue. As far as 'mount doesn't spin at all, it's not supposed to. The mount + shaft are stationary when installed in the car. The whole outer part of the strut + spring + upper spring perch rotate. You can tell that as the upper part of the strut bearing is stationary but the bottom half is allowed to rotate.

 

[snakeye]

I've used the same mounts on my 03' jetta and 01' beetle with no issue. As far as 'mount doesn't spin at all, it's not supposed to. The mount + shaft are stationary when installed in the car. The whole outer part of the strut + spring + upper spring perch rotate. You can tell that as the upper part of the strut bearing is stationary but the bottom half is allowed to rotate.

Funny, I thought I was gonna be done my suspension upgrade by the end of the weekend, but instead I spent the better part of the day staring at my strut components, questioning everything, contemplating my existence on this planet, etc, and so here's a few questions for you:

1) why would it be that way? Why make the shaft spin instead of having the whole unit rotate as freely as possible on the bearing? Essentially the force required to turn the wheel would be dependent on the strut's resistance, and I'm willing to bet a monotube Bilstein would be much harder to turn than an OEM strut, which I highly doubt would be the desired effect.

2) The mount and shaft are stationary if you tighten the Powerflex mount without any modification, but how is this correct, if not achievable with stock components? You can't tighten the stock mount in the same way because a) as P2B mentioned, the nut is tight against the bearing and just holds the mount in place, and b) you can't torque a nut onto rubber, and the stock mount is entirely coated with rubber, even where it meets the nut at the lip.

3) if the nut is not tightened directly against the top of the bearing and instead to the mount, then the bearing is acting as an "intermediary" between the nut and the perch. Now if both these things are moving independently, what's preventing the nut from spinning itself loose?

 

[Zak99b5]

I’ve only installed stock rubber mounts, so no hands on experience with the power flex mount. But the mount cannot twist with the strut because it’s carrying the weight of the car. The bearing allows from the spring hat down to rotate for steering. The upper plate and nyloc nut sit on top of the shouldered strut nut, and prevent that from coming loose.

 

[P2B]

But the mount cannot twist with the strut because it’s carrying the weight of the car.

To be clear, the bearing is just that - it bears the weight of the car. The upper bearing shell is fixed, the balls and everything below them rotate.

 

[03TDICommuter]

1) why would it be that way? Why make the shaft spin instead of having the whole unit rotate as freely as possible on the bearing? Essentially the force required to turn the wheel would be dependent on the strut's resistance, and I'm willing to bet a monotube Bilstein would be much harder to turn than an OEM strut, which I highly doubt would be the desired effect.

That's the way it is. If you look at the bearing, the strut shaft goes up inside and rests on the top of the bearing, not the bottom. The bottom of the bearing is what the top spring perch rests on and the whole strut, spring rotates but the shaft stays put. That aluminum cup on the top of the mount under the hood? That's connected to the strut rod and does not turn.

2) The mount and shaft are stationary if you tighten the Powerflex mount without any modification, but how is this correct, if not achievable with stock components? You can't tighten the stock mount in the same way because a) as P2B mentioned, the nut is tight against the bearing and just holds the mount in place, and b) you can't torque a nut onto rubber, and the stock mount is entirely coated with rubber, even where it meets the nut at the lip.

3) if the nut is not tightened directly against the top of the bearing and instead to the mount, then the bearing is acting as an "intermediary" between the nut and the perch. Now if both these things are moving independently, what's preventing the nut from spinning itself loose?

You want all that as one otherwise you'll get a clunk. And nut torque and the top nut with the aluminum cup to prevent the strut assy from dropping out of the chassis, acts as a jam nut.