BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

Today, I felt a weird wig-wag type whole bike wobble at 80+ mph. I was part-throttle accelerating up a slight incline in 6th (so not a LOT of acceleration forces, but some). I DID pass over an overpass that had a diagonal transition from the regular fwy to the overpass portion. Just a strange and scary feeling at that speed, especially since the R1200R has been so rock-stable over the past 4000 miles.

Does just mild acceleration at high speed + slight incline allow the front end to unload enough to misbehave like that when passing over that diagonal transition? - I don't really want to repeat the feeling, so I am trying to understand what happened here. Seems that the bike self-stabilized afterward though - I just let it do its thing (not much time to do anything else).

I've done plenty of high speed accelerating in different conditions on this bike and never had that happen. Sounds scary. You're tires and steering damper are in good condition? I've heard of worn tires doing some strange things.

tobes wrote:I've done plenty of high speed accelerating in different conditions on this bike and never had that happen. Sounds scary. You're tires and steering damper are in good condition? I've heard of worn tires doing some strange things.

Interesting, what sorts of strange things? I AM beginning to think its the rear tire - it has 3900 miles on it and is a Metzeler Z6. Here is a photo of it, its a bit cupped and the center is flat. I have a tight turn before my house and when I lean the bike down, it seems a bit squirmy now (but only during that turn which is the sharpest one I take during my ride). The front has a tiny flat spot in the center, but nothing like the back.

Damper has the same resistance as it had a few months ago when moving the fork back and forth quickly on the center stand when its on the rear tire (feels ok - resists quick movements)

I think I will replace the rear for piece of mind.

You should have gotten MUCH more mileage out of that rear tire. Do you run it with the highest recommended pressure? I doubt if you do burn outs, but I have to ask. lol. Hank

blue (dunno real name..)

Windshield on the bike, or anything else adding weight to the front end?

I'd also check the steering damper condition with the rear mount unscrewed from the telelever wishbone (use LocTite blue - medium strength - when replacing it.) It should move fairly easy at low speeds, but if you try to move it quickly, you should feel resistance.

And no experience running with Metzler's on the R12R - so can't say if it might be tire related.

hankth wrote:You should have gotten MUCH more mileage out of that rear tire. Do you run it with the highest recommended pressure? I doubt if you do burn outs, but I have to ask. lol. Hank

I did run it at the highest (42 psi) for the first 3500 miles, then 38 psi for the last 400 miles. (nope, no burn-outs..)

I have just the Wudo Windshield which is much lighter than the previous CB 20".

I did try to move the fork quickly while on the centerstand and during quick movements you can feel the resistance and hear the damper working.

The Metzler Z6 seems to have a tire life as low as 4000 miles, together with running the max 42 psi for the first 3500 miles, and not a lot of aggressive cornering, it seems that I ended up with a flat spot in the center. But it also has some cupping.

deilenberger wrote:blue (dunno real name..)

Windshield on the bike, or anything else adding weight to the front end?

I'd also check the steering damper condition with the rear mount unscrewed from the telelever wishbone (use LocTite blue - medium strength - when replacing it.) It should move fairly easy at low speeds, but if you try to move it quickly, you should feel resistance.

And no experience running with Metzler's on the R12R - so can't say if it might be tire related.

I have found that road conditions can make me think all sorts of bad things have happened to the bike. i cant remember how many times the TMP clarified that i do NOT have a flat tire, despite my own insistence.

Ride that piece of road again and see if it happens again. There could be other inconsistencies in the roadway that you can't see at speed.

If you feel anything like that again--it is surely not normal--I'd get it checked out (maybe start with another wheel balance) and be sure there're no flaws in the tire.

All I can say is that I have a Z6 on the rear with a similar wear pattern. I feel it in left handers, i.e. I feel the non-smoothness of the tire through the suspension. However, I have never had any wobble at sustained Interstate rides of 75-85mph, with or without wind.

Here is the diagonal ridge - you can see the darkened area from years of cars/trucks compressing their suspensions in this area and releasing any oil about to drip ahead of it. I was in the center of the lane. Now that I see the area, hitting that dark spot at 80+ mph cannot be a good thing....

Don't know, this is what happened to me about a month ago.
Commuting home on I 95 southbound , two lanes and i'm on the fast lane, 65 to 75 mph.
My exit was approaching and i was switching lane moving to the right when all the cars around me started to act crazy, breaking and swerving.
At this point i'm slightly leaning to the right and i panic brake, there were two big empty garbage cans on the hi-way on the right lane.
Whether someone just lost them or not, i couldn't tell but as i pulled the front brake i felt the whole motorcycle oscillating.
I think that if i had been on the previous ride, a Bonneville, things would had been much worse.

Has the steering damper saved my butt?

Now that I see the area, hitting that dark spot at 80+ mph cannot be a good thing....

Looks like that bump will unsettle the bike for sure. Is that surface of I-5 rain-grooved?

Remember that some high(er) speed wobble is part of the naked bike riding experience, even with a windshield augmenting bike aerodynamics. Depending on how much PLUS you were riding at 80+, some speed instability is likely present, even if imperceptible under normal road conditions. Add in that diagonal bump and you suddenly get perceptible wobble.

I am reminded of the naked bike inherant instability when I ride my Buell XB during trackdays. Despite track-tuned suspension, adjusted steering damper, and the best racing crouch I can muster, I always get speed wobbles above 100 MPH down the straights. It's due to the unfaired bike's "messy" front (rider's arms, wide handlebar, headlight, instruments, turn signals, etc.) causing major havoc with airflow, and the resulting unstable turbulent eddy. I'd heard about the phenomenon, but didn't believe it until riding a smooth track at speed, on otherwise track-ready motorcycle. Never noticed it prior when riding a faired sports bike on the track.

At this point i'm slightly leaning to the right and i panic brake, there were two big empty garbage cans on the hi-way on the right lane.
Whether someone just lost them or not, i couldn't tell but as i pulled the front brake i felt the whole motorcycle oscillating.

As for Paul's experience - do you have ABS? I get that same squirrely rear when hammering the (front) brake at end of my local track's back straight, this on a short-wheelbase bike... just an indication that there's (almost) no weight remaining on the rear tire contact patch. That's not good timing for a direction change. For my Rockster, it takes LOTS of front brake to get into (or out of) the same shape, due to the porky bike's weight and long wheelbase.

Perhaps we should point this thread out to the .. gentlemen.. who took their steering dampners off because it hurt their arms when walking the bike through cones in a parking lot.

sweatmark wrote:

Now that I see the area, hitting that dark spot at 80+ mph cannot be a good thing....

As for Paul's experience - do you have ABS? I get that same squirrely rear when hammering the (front) brake at end of my local track's back straight, this on a short-wheelbase bike... just an indication that there's (almost) no weight remaining on the rear tire contact patch. That's not good timing for a direction change. For my Rockster, it takes LOTS of front brake to get into (or out of) the same shape, due to the porky bike's weight and long wheelbase.

Yes, ABS on the R12

Hiya and 1st post (my lady Linda, picks up her 06 R1150R today).

Did you have a top box fitted or anything on a rack, especially anything heavy.

I've had a combination of regular undulations and a heavy bag on a rack set the bike into a full blown tank slapper - not a Beemer though.

Peter

When I have been touring with a very heavy load on the pillion seat and rack, I have sometimes had a really annoying shake at 70mph and above which I think is buffeting from flow over and around the windscreen (I have the BMW tall sheild). It is too irregular for me to call it a wobble.