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I know lots of threads out there on this, but thought I'd share my journey to get rid of the dreaded highway shimmy.
I purchased the car with Cup 1 Italian imitation 17" wheels. The highway vibration at ~70MPH was awful. I actually started to hate driving the car. Started by changing out shocks for Koni's, no real difference. I got new tires, helped a little as I figured out I had a flat spot on one of the tires, maybe 15%. I balanced the wheels, that helped a little, maybe 10%. Swapped the imitation Cup wheels for Fikse FM5 17" wheels, that made a big difference, got me to about 80% there. But I still had the shimmy/vibration at 70MPH, just not as bad.
And then I finally purchased Elephant Racing 968 style caster blocks. And wow, what a difference. Zero vibration/shimmy on the highway at any speed.
I will note, the rubber OEM blocks I replaced felt solid, not tears or cracks that I could see or feel.
Do yourself a favor and buy new 968 castor blocks. They take 2 hours tops to do the complete swap. My car was already on stands so took me 30 min.
Per Porsche TSB Group 4, Number 9303, 968 type caster blocks are required when running 17" wheels. The TSB also says to use new eccentrics and nuts. I'm not sure if the eccentrics are required or not, but I did update mine when I installed the 968 type caster blocks years ago. It's possible that new eccentrics are required to obtain the recommended caster specification of 3 deg, 15-45 min.
Per Porsche TSB Group 4, Number 9303, 968 type caster blocks are required when running 17" wheels. The TSB also says to use new eccentrics and nuts. I'm not sure if the eccentrics are required or not, but I did update mine when I installed the 968 type caster blocks years ago. It's possible that new eccentrics are required to obtain the recommended caster specification of 3 deg, 15-45 min.
yup, I had read that too. But being a stubborn cheap bastard, I waited to purchase the caster blocks last LOL
Chroma Cycle Works does a rebuild on worn out 968 blocks where he sleeves in an Igus bushing for a low price (focused on spec944 guys). I have a set but haven't run them to compare yet. Anyone who has old, worn out 968 blocks, send them to him so they get another life!
The new eccentrics are recommended because the flat face that clamps the control arm is knurled on the new revision. The original ones back in the 951 days were flat faces. The knurled ones have a hole through the metal 'flap' that protrudes from the eccentric, for easy identification.
The new eccentrics are recommended because the flat face that clamps the control arm is knurled on the new revision. The original ones back in the 951 days were flat faces. The knurled ones have a hole through the metal 'flap' that protrudes from the eccentric, for easy identification.
Thanks for the image of the eccentric adjuster. The latest parts are 951 341 431 03. I installed the 02 version back in 1998 when I updated my caster blocks and I don't recall the knurling, so will have to check if they have the little hole, which I don't think they do. They've been fine all these years but when I update the suspension on the 951, I'll install the newer versions, along with Racer's Edge caster mounts.
08-10-2022, 01:05 AM
Highway Shimmy Solved
