I have a 1998 M3 and am installing Bilstein sport shocks all the way around. How do I tighten the lock nut at the top of the shock? The original equipment shocks are squared off at the very top so a wrench can be used to hold the rod in place while the nut is tightened, but the Bilsteins do not. Seems like an easy problem, but darned if I can figure it out. Dave at david1004@juno.com
Hmmm.... IF the lock nut doesn't offer up too much resistance just threading down the rod, AND there's enough length to the rod, I'd try to thread the nut down the rod (hopefully without having to do anything more than, at most, well-cushioning the rod and holding it no more than necessary with pliers or whatever). If there's enough length to the rod, with the locknut threaded down but not quite to where it should start to be tightened, maybe there would be enough room to thread two nuts on at the top of the rod, and jam them tightly against each other (line them up), and then you can hold the rod in place with a wrench (on both nuts), while tightening down the locknut. You probably need metric nuts of the right thread - either tote the shock to the hardware store, or take the nylock nut, find a bolt/threaded rod that fits (don't thread it into the nylock part), and whatever nut fits the bolt should be what you need. If the top of the shock rod isn't long enough for such an approach, not sure if I have any better suggestion - wrap some leather around it and grip lightly, or if you have some thin leather (I think a solid leather belt would be way too thick), wrap it around the rod and twist it, and it could grip the rod as the twist tightens it. Not sure though if you could get it tight enough to have enough grip to keep the rod from turning as you tighten the top bolt, but might be one thing to try. See what google brings up, likely somebody's come up against the same issue and posed the question on bimmerforums.com, bimmerfest.com, etc. I put some Bilsteins on my truck last year, the shock rods were flattened on only two sides at the top, made that way to get a wrench on 'em. If you were expecting them to be boxed, look again, maybe they have just the two sides and the rounded sides look deceptively circular.
The end of the shaft takes an allen head wrench (5 I think, but don't take my word on it). This will allow you to hold the shaft while you torque down the nut to 16 lb/ft.