Forum bmwbike.com

I am installing new front fork sidecar springs in my 1951 plunger. I noticed that the workshop manual specifies the unloaded length of front fork solo spring is 227.5 mm and the diameter is 5.5 mm. The unloaded length of the sidecar spring is 204 mm with a 6.5 mm diameter. Are these numbers correct? I have new 227.5 mm, 6.5 mm diameter springs which I installed. After assembly, the upper and lower metal fork covers do not overlap, and the tolerance between the lower end of the upper fork covers and the lower covers is very small. They rub. Does this sound correct? My concern is that if I unweight the front end when riding the metal covers could bind when they come together. Most of my front end parts like the fork tubes are new and straight. Any thoughts?

hallo Scott,
they do not overlap because you have installed sidecar springs with solo lenght (if I understand you right). this is normal for this case(but not right).
The tolerance of the upper and lower covers is always very,very small but they do not have to rub.
3 ways:
1.: you can can turn the lower cover at 90° steps(or 120° I do not know exactly at the moment) and look if it do not rub at this new position(s).
2.: the lower cover was not fit very strong, so you can move it a little bit by hand until it do not rub and fix it (with glue or little punches(?) with a hammer in the groove)
3.: let it rub and after a few weeks paint again,
now enough material is rubbed away and it is space enough for the paint( I do not know how much it rubs at your fork, if it is too much, forget point 3)
rolf

Rolf,
Thanks for your response.
I understand all your points but I still have a questions about the spring length. You mentioned that sidecar springs with solo length was normal but not right. What would be right? Should I install them at the 227.5 mm solo length or shorten them to the 204 mm sidecar spring height as mentioned in the manual?

Scott

Hallo,
I tried to say that it is normal for a sidecarspring with sololength that the covers do not overlap. It is not right that the sidecarspring is a long as the solospring, they had to be shorter (only 204mm), so that the covers are able to overlap. If you can shorten the springs, do it. Otherwise you will rise your front for 23.5mm (a little chopper).
Greetings
rolf

Thanks Rolf,
That makes sense.
Scott