1988 R100RT Front End Oscillation

[economou]

Does anyone know what caused the front end of my bike to suddently get in to an oscilation and within less than a second to cause the bike to instantly fall over going at 40MPH? Needless to say it threw me over and I was lucky enough to get away with a fructured wrist. I owned this bike for two years and never had any indication that it was that dangerous to ride. Any advise would be greatly appreciated. Thank you. Peter

[Ray from Indiana]

A tank slapper eh?

Have you done any work or mods on the bike recently?

Some possible causes ( I'm no expert ):
- bad or loose steering head bearings
- bad front tire or wheel
- bad front wheel bearings
- forks out of alignment
- hitting a rock that makes the front tire airborne
- accelerating on a bumpy road surface in a turn
- overloaded with touring gear?

I hit a good size hole on I-80 in Illinois while riding my Guzzi. The Guzzi EV shook its head pretty good but damped out by itself. I think there is still a munch mark left on the seat. Glad you didn't suffer a worse injury although wrist injuries are not welcomed either.

[khittner1]

For not being an expert, Ray certainly hit the obvious culprits. Any of those would be aggravated by a worn-out rear tire, rear swingarm bearings in need of service/adjustment, and sacked rear suspension bits. Sounds like the ol' RT is in need of some knowledgeable service attention (which may or may not be available at your closest roundel-clad unit movers); that isn't the way well-maintained airheads behave, even on lousy road surfaces.

Konrad

[Duane Ausherman]

That is what is called a low speed wobble. I suggest always starting with a Google search. As search terms, try "bmw motorcycle speed wobble" and see what you get. My article on speed wobbles should come up on the first page, or it used to anyway.

Those are predictable and preventable. I suggest that you spend some time reading first and then examining the bike. If you can find an expert, get help. It probably won't be at your BMW dealer.

This is a subject full of a lot of old wives tales and ignorance. Many seem to think that it is in the realm of lightning striking you, it just happens. Not so.

My information is related to older bikes, so I would expect that some factors might be out of date and new ones important.
You are invited to keep us informed.

[ME 109]

Duane, Peter did a google search and here he is. This forum is supposed to be one of the best sources of information.
I don't have problems with people finding Boxerworks and asking questions.

Peter, did you have your hands off the bars when the wobble started?

[dwerbil]

I had a nasty wobble on the /7 a few years ago between 25 to 30 mph for a day. It'd clear up above that speed. Ended up being the moderately worn front tire had a very slight bulge on the outer surface. A new tire retired the problem.

[Major Softie]

Be happy you weren't going 70.

[chasbmw]

If the OP does a google search he will come up with lots of stuff about wheel alignment.

However he is riding a 1988 bike and by that time BMW had pretty well sorted the front forks with a very well engineered triple tree built to proper tolerances.

Unless the bike has been subject to considerable abuse, the forks were most likely to be in alignment Before the accident. Alignment should be checked after the crash however.

What caused the wobble, could be a worn wheel, swing arm or headstock bearings, or worn tyres, but likely to be combination of the above. If I was a betting man, I would look at the headstock bearings first.

[moosehead]

Check tire pressures, both front and rear. If front has been running under inflated and is "cupping" then you will experience the wobble...just my $.02. Plus check ou t all the other things too.

Don't know about the rest of you guys, but I am lackadaisical about checking tire pressures on a regular basis and sure enough I get the low speed wobble noticed mostly on slow speed deceleration and/or a low speed e.g. Under 60kmh turn. Soon as I get back I check the tire pressures and sure enough they're usually on the low side.

Just experienced yesterday on my RS...front tire was down to 24 psi...put back up to 36 psi and all is good. Now I have a sticky on the tank bag....Tire pressure.... it's due for new rubber at end of season so going to put in new tube as I think there is a slow leak somewhere.

[Duane Ausherman]

Duane, Peter did a google search and here he is. This forum is supposed to be one of the best sources of information.
I don't have problems with people finding Boxerworks and asking questions.

Peter, did you have your hands off the bars when the wobble started?

I see no evidence of his mentioning a Google search. No, this is one place to start if one has a lot of time and ability to figure out which posters know the subject and which just are able to type.