The wobbles

I'm curious about the wobbles, or rapid weave since I viewed a British chap in the Seventies at a track showing all bikes ridden in the film go into wobbles, and then how to stop them, on YouTube. Including an R90s in what appeared to be standard trim.

Have owned a few bikes, one of the things always done at some point was to hold'em WFO to see if they'll pull high RPM in high gear, just for fun and to see how fast they go.

Maybe I was lucky, but at any speed never a one started wobbling. Not at 30, 45, 65 and on up. Even wiggled the bars to see what would happen. Always snapped back to straight. So when I saw the BMW S type wobbling down the track my eyeballs fell out. Never saw that before. Very strange and likely to scare bejeebers out of non motorcyclists. It was the wobble-ee-est film I've ever seen. Don't remember the tag, but fun in the dead of winter.

Sorry if this was on a thread here, but it's still in the curiosity bank.

In most cases, "wobbles" are a result of a defective or incorrectly tightened steering head.

The /5's were notorious for high speed "tank slappers". Once one experienced that one truly did hesitate to try full throttle roll ons again. That is after one cleaned out one's shorts.........For me, it was just cruising along at 70 mph with heavy duty expansion stips in the concrete pavement.
Duane Asherman talks in depth about this situation on his web sight and it is also why the platform was lengthened by a couple of inches in the late /5's. The factory KNEW they had real problems and for sure that lengthening pretty much fixed it. Now, as pointed out above by Mike, other models of BMW's showing this tendency are attributed to bearings, tires, alignments, and on and on.......God bless.......Dennis

Rode an 90S for a few months in the late 70's that had a very disconcerting "head shake" at about 62 mph. Never developed into a tank slapper, but it had me worried the first couple times it happened. I eventually decided the best thing to do was to go faster and it settled down. I blamed it on the Luftmeister fairing.

Actually, All my wobbles were caused by the rear.

Not saying there aren't more reasons. I have been able to trace every front end complaint I have ever encountered on a two wheeler to something from the rear.

A speed wobble does make your bottom sphincter work harder.

EMSimon said:

In most cases, "wobbles" are a result of a defective or incorrectly tightened steering head.

Click to expand...

+1. I've had two bikes with the wobble. The worst was a '91 R100 (dealer converted to a R100RS)....quite the handlebar oscillation...way too loose steering head bearing.

I had a few tank slappers on my R100RS; one was so bad I nearly went down. The problem was the steering head bearings and a bent front wheel.

Having extra weight up high and out behind the rear axle, as in a fully-loaded touring rig with an over-stuffed top box and camping gear strapped on top, can contribute to the wobbles by levering the front wheel up. Getting more weight on the front end helps with stability.

The Honda ST1300 has a reputation for a high speed "weave", usually showing itself at 100mph-plus speeds. Top boxes may contribute to it. Reportedly some police departments gave up their ST13s for this reason. I never experienced it with my ST13 but never went much over 100 anyway. No manufacturing "fix" was ever reported. Some bikes just seem to have it.

pete

steering oscillation

Steering occupation (castor oscillation) is inhering in any wheeled vehicle with steering and rake and trail. The contact patch of the tire is behind the centerline of the seeing axis, this causes the wheel to self center. There is a small amount of oversteering during this process. If there is not sufficient friction in the steering assembly,or if things are loose, steering head bearings, wheel bearings, swingarm pivot bearings, or a bent wheel, then the oscillation can increase.

If an oscillation is occuring, tapping the front brake firmly will most of the time stop it. This is not the best time or way to deal with it. Better to keep the machine tuned up. Even with a well tuned machine, high speed, surface irregularities, and acceleration can cause a wobble. Seen world class, top shelf machines wobble at Louden Speedway coming up onto the final straight, 100+ mph, woo hoo! These iron testicled and steel overied riders accelerate through it (only recommend for big power to weight ratio).

Bent wheels, especially the front, are often overlooked. Also a damaged tire can be the culprit.

Hope this helps.