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Home Forums Sidecars Sidecar setup Reducing Trail – Leading legs Reply To: Reducing Trail – Leading legs

#24816

Ken Moncrieff
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  • Rank: 50cc Rider

Mine has a smaller alloy sidecar wheel so there is no problem there.

The sidecar is a copy of an English Squire sp2 or sp3 made under licence I believe, in South Africa in 1975. I bought it from an older guy who brought it with him here as a new BMW R75/5 outfit many years ago.. I don’t know how he ever steered it tho’.

As for the trail, I’m not sure what it is for a standard R75/7 but it must be a lot, so what’s left I have no idea. I’ve found that even with this 83mm trail reduction, it handles and tracks so well. I can drive easily “hands off” at 110 k/hr with no wobbles and steering damper off. It just tracks true and corners both ways very well. It has only 15mm toe-in on the sidecar wheel and about 310mm lead ahead of the back axle. (I do carry 30 litres of water as ballast when I don’t have a passenger in the sidecar)

Yes. for the 52 mm set I made which were certified by our local transport department. He has yet to certify this increased trail reduction set at 83mm. That should happen next week if possible.

This bike has a set of 1981/82 forks fitted to it by the previous owner in Victoria. That’s why the brakes are twin Brembos on these model forks from a CS model I believe. It really does drive so well, it’s like having power steering now compared to the first set I hand-made. This set is also made from T6, 12.9mm structural alloy and cut by water-jet cutters from a template made for the job.

I could not find any firm anywhere in the World which makes leading legs for this model group of BMW front forks to buy outright, so it became a do it yourself project,and it’s taken me over a year to perfect these now after making many model templates out of 10mm craftwood to get it just right before going to the steel or alloy cutting system to make them. To fit them to the forks properly, it’s necessary to shave 1mm off the inside of the bulge on the bottom of the tellies to clear the brake disc on both sides in its new position. Several other factors are also involved with the leg plates and axle/hub spacers to get it just right for minimum clearance of the hub and discs and anchoring the calipers in their new position. That was no easy task. New and longer steel brake lines had to be made as well.

Also, I’ve braced the rear sub-frame of my bike between the rear shockies under the seat and under the bike between the pillion foot-rest mounts for extra rigidity and strength for connecting the sidecar to the bike.