t34418l31

what is the size of the lower rear shock bolt? the threads look to have gotten messed up in mine so im looking to get a helicoil kit for it. thanks!

krystar

? if threads got screwed, just get another bolt and nut? what u helicoiling?

it was a 17mm hex head....i'm guessing M10x1.5

Van

I think it's an M14 bolt... but don't helicoil that one. It's currently a hardened steel insert in an aluminum arm. First try to clean it up with a tap. If that doesn't work, replace the arm.

krystar

we must be thinking of diff bolts. or the late rear susp that much different that early

xschop

The rear lower shock bolts are M14 x 1.5
I used cutting fluid and an M14 x 1.5 tap to clean out the insert and then cleaned the factory bolt with an M14 x 1.5 die, then re-used the bolt after coating the bolt with high temp anti-seize, so the bolt does not galvanize itself into the steel insert next time.....

alpinewhite951

I had the same problem, and Porsche does not carry the bolt any longer. The size is m14x1.5x85mm, and BMW uses it on some of there previous models, and they are still available. The part number is 07-11-9-914-829. The Porsche part is an 8.8 grade bolt and the BMW is 10.9.

pontifex4

Just bumping this thread for the quoted information above. I've ordered a pair of the BMW bolts for use on my 968's Escort Cup coil overs. I'm hoping that 10.9 is adequate for my 500lb springs.

Van

The bolt will be adequate... are there spherical bearings on the shocks, or just rubber bushings.

pontifex4

Thanks, Van. They're rubber bushings.

Van

This is what happens to the rubber bushings...

Van

I'm not trying to "scare people away" - I'm merely pointing out that when Porsche designed the torsion bar suspension, they did not intent for the shocks to be a load bearing part of the system. When the torsion bars are deleted and coil overs are used, the shocks become load bearing. Over time, if the load bearing shocks have rubber bushings, those bushings will deform. It's neither "good" or "bad" - it just is.

Like any of the other rubber bushings on the car, as they get old, performance goes down because the components move around more. For the shocks, like in my picture, rear ride height will be reduced.

All things in life are a compromise, and we decide what's best for us based on our unique factors. For me, for a race car, I had Bilstein Motorsports weld spherical bearings onto the shocks when I had them rebuilt. But, it was an expense I was prepared to make for the performance rewards.

pontifex4

Van, I appreciate your perspective. I have another, more immediate problem though, which is that the 500lb rear springs won't actually clear the trailing arm, and the arm isn't even yet at full droop. The collars won't even clear below the halfway point of adjustment. They are touching in the attached photo, with the arm at about 4" above full droop.

Do you traditionally install a couple of washers BETWEEN the shock and the trailing arm for the Escort Cup coilovers? (Note that the shock is installed properly at the top and bottom -- I did check).

Van

Charlie, are the perches for 2.25" or 2.5" springs? I had 2.25" ones, and they cleared without touching.

For the record, my new car has torsion bars, and the shocks (without helpers) have rubber bushings.

pontifex4

2.25". They're on now, and the perches happen to need to be right at the top of the adjustment range to have the car at the right height, so I think it should be okay, clearance-wise.

Anyway, sorry to derail the thread.

Oddjob

Charlie,

Do not put washers between the shock and arm. Something looks wrong there. Check that the offset mounts are indexed correctly both top and bottom (bottom does look correct from the pic). Also check the OD of that perch. Even if it is for a 2.25" Spring, is the OD excessively large? That does not look like a Bilstein perch or jam nut.

It gets tight, but I was always able to run the perch and jam nuts down to nearly the bottom of the thread engagement on the bilstein shock bodies. If anything was going to hit the trailing arm, it was actually the springs (which depending on rate, were sometimes slight larger OD than the perch, maybe a 1/16" or so).

As far as the rubber bushings - yes they do deform under load. Over time it will be a permanent deformation/creep. Bilstein rubber bushings are somewhat softer than koni and the steel insert/sleeve is smaller diameter (so more rubber) so the destortion is much more noticeable. I was never a fan of it, but drove them like that for many years w/o problem. And yes, you have to use the washer (or a toe eye plate) on the bottom bolt. Impossible not to, as the shock body will slip right off the bushing if you dont.