Sunday, February 14, 2021

Upper Control Arm bearings

The movement of the Upper Control Arms relative to the frame is to a large extent a function of the amount of torque you put on the Wishbone Pivot Bolt (#43) and Nut (#29). It's a shame considering the fine engineering modifications many of us have done to our suspension, only to have the movement hog-tied by the thru-bolts' arbitrary clamping force. Also, there seems to some confusion within the Delorean community as to what washers, and how many, go where.  

I started researching how to decouple the bolt torque from the UCA movement and found what appeared to be a very good solution from my favorite supplier McMaster-Carr:
Up to this point, this is how my UCAs were arranged:
Bolt head - Large Washer - CONTROL ARM - Two snub washers - FRAME - Two snub washers - CONTROL ARM - Large Washer - Nut

So, replacing the two snub washers with one thrust bearing and two thrust bearing washers on both sides would result in the following: 
Bolt head - Large Washer - CONTROL ARM - One thrust bearing washer - One thrust bearing - One thrust bearing washer - FRAME - One thrust bearing washer - One thrust bearing - One thrust bearing washer - CONTROL ARM - Large Washer - Nut

One thrust bearing and two thrust washers

The thickness of a thrust bearing and two washers is about 0.2 millimeters more than the combined thickness of the two snub washers so the fit is pretty tight and can be a little tricky to get in there, but once it's in there it is as if it was "engineered in".

Some pictures with the thrust bearings/thrust bearing washers in place:
Thrust bearing washer/thrust bearing/thrust bearing washer. Right front wheel; left of UCA. 

Thrust bearing washer/thrust bearing/thrust bearing washer. Right front wheel; right of UCA.

Is it worth it? Hard to quantify but from my personal point of view this modification is definitely working: If you grab the bolt head with one wrench and the nut with another wrench, the Wishbone Pivot Bolt/Nut spin freely about its axis even after they have been fully torqued down. I'd say that it's a testament to its effectiveness!

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