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Old 11-14-2012, 10:16 PM   #1
Jetblast OP
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Joined: Sep 2012
Oddometer: 2
Wobble

Hi all,

First post here so please be empathic...

After thinking of a sidecar for over 10 years and after 6 months of voyeurism on sidecar forums, 6 weeks ago I got a a new-to-me 1984 R100RS that I got attached to a Bimmer M-103 sidecar by a shop near Montreal. It was delivered to my door. It had a terrible wobble, the frame slapper type (after the tank has been destroyed by the initial tank slapper). I installed a prototype vertical, frame to fork, VW damper that eliminated the wobble enough to get the bike to the shop for safety inspection and take my daughters for their first ride.

Since then I went through the usual manuals and the Design formula thread to learn more about the rigging.

Found out my rig was toeing out and leaning in with almost no lead. I did what someone wrote: puttered with my rig to learn about it.

It's a tandem two seater that looks like a CJ tub. The cargo compartment is modified to add a seat.

I took the lead to a bit over 8", the best I can do with the hardware I got. Considering a wheel base of 58", it's not far from the 15-20% lead (with the conversion rate to Canadian units, it must be for us between 13-18% anyway)

I toed in at 3/4 inch as measured from the back wheel (since it's a BMW). On that, Snowbum, I have 2 questions: why are the wheels offset and how?

The lean-out is minimal.

I took it out and the handling was easier and lighter.

I disconnected the temporary damper (or is it dampener?) and there was no more wobble. I was quite proud of myself. I even put the BMW damper to 0.

Then I went for a longer ride to do errands at city speeds (30-80 kph or 20-45 mph). I was riding loosely and then the tub wheel hit a manhole. The wobble was back. It had been hiding it that manhole waiting for me. I finished the ride with the BMW damper set to 2 and it was ok all the way home. The only pain was from the tension in my you-know-what-muscle-tense-hard-when-you're-scared muscle.

Was the BMW damper sufficient enough or is it because I did not hit other major bumps?

Is that normal to wobble so much?

I need all the help I can get.

Thanks

(I'll try to figure how to post an image of the rig)
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