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

Just got in from a lovely 500-mile (804 km) ride. A long day, but well worth it. From about 1100 feet above sea level here in Phoenix, to just above 9000 in the White Mountains near the Arizona/ New Mexico border, and back. The snow is melting up high, lots left, but also lots of rushing melt off streams rushing here there and everywhere. For those that live in the area and haven't already done so, I really recommend Arizona road 191, from Show Low south to about Clifton where incredible natural beauty (the great majority of the ride) gives way to a copper mine of staggering proportion. A study in contrast, for sure.

Anyway, that said, today had a LOT of hairpin turns. I was traveling solo, and respecting the still sometimes snowy and early season conditions, so I was doing a lot of fairly low speed turning. And I have noticed something on my bike (or in my head, or my turn execution, or some combination). It seems to be most prevalent in the speed range around 25-35 miles an hour. I am not sure if I can say for sure that this symptom always occurs when accelerating, but my gut thinks so. And it always (and only) occurs when cornering.

What happens is this... just for a split second, the bike feels like it is "sliding" out from under me. Now, this isn't logical, and is not backed up by the circumstances, as it has happened on clean and dry roads and I have not heard or felt the tire really giving way. (And it has never resulted in a loss of control.) But I get this sensation of lateral movement in the mid to rear of the bike. Enough that my brain wants to trigger the old mountain bike response of putting my foot down to right myself. And I am trying to avoid that response, as I know that doesn't help matters, and will only result in worse injury or loss of control should something really happen, but the reaction is something that is fairly automatic.

Anyway, I feel like I would have a better time deprogramming myself if I more fully understood the issue at hand. I have heard some talk about the bikes feeling like they are "pulling" to one side or the other...is this possibly what I am experiencing? Maybe in conjunction with a less than optimal body positioning or approach angle in the curve? Or could it be a suspension setting that I should maybe think about adjusting? As I said, in my perception, the feeling seems to be primarily to do with the mid/rear of the bike.

I know it is probably hard to offer any insight with my vague description. To put it another way.. I am, in the grand majority of cases and at the grand majority of speeds, very comfortable with the behavior of the machine and my relationship to it. But there is some phenomenon that occurs, and it seems to be at lower speeds (above idle or really slow speed, but below 45 miles and hour and up) where I sometimes get this split second of a feeling like I am "slipping"... almost like a weightlessness(?), which is disconcerting and, as I said, makes my brain want to trigger bad habits.

Anyway, I am sorry to be so full of newbie questions. I guess I am just aware that there is a lot of wisdom around me, and I really want to continue to improve my own understanding and riding skills.

Any insight that you guys and gals might have would be great.

Cheers!

-Kyle

I think you did an excellent job of describing the "shaft effect" of the rotating mass associated with the driveline. You also seem to be really in tune to that feeling (perhaps more so than others).

Try adding a little more preload to your rear shock.

I agree with Jeff about adjusting the rear pre-load. But remember that addresses the symptom without explaining it.

Overall, it seems you are well in tune to your bike and have a good grasp of the dynamics involved.

I'd add the suggestion to check your air pressures (are you getting some type of sidewall flex?) I presume these are radial tires and not bias ply?

Maybe try to pin this down a little tighter - does the sensation occur in highly cambered turns as opposed to simply low speed turns? - is it related to the cold highway surface and cold rubber of the tire? - do you have any throttle responses other than smooth, power-on, fuel delivery?

I'm sure this is a minor thing for you as you seem to already comprehend the effect without problems. I'd keep riding and gaining a feel for it but not worry too much.

It's quite possible that you were getting the bike leant over a little more than usual and thus using the more cambered sections of your tyres, ie right to the edges. This will give that sort of sensation, but what's actually happening is that the bike is turning more acutely because you're right on the outer parts of the tyre. I have it happen to me occasionally, on all sorts of bikes.

55

Does this happen both in left and right-handed turns?

The reason I ask is because our longitudinal crankshafts will lean the bike to the right under acceleration, which could feel like a loss of traction in a right-handed corner. In a left-hander, it might cause you to wander wide off your line. You'll get used to it, and even adapt your riding style to take advantage of it.

Are you sure there wasn't any thing on the roads? I say this because I've had that same sensation, only to find out that DOT puts a grey ash type of compound to help ice/snow melt. You can't see it, but man does it make the bike feel weird.

Just a thought.

ProductUser

Are you just noticing this? Change tires recently? How long have you had your R? How many miles are on it?

I have 27k miles on my Rockster and on the original shocks and I am starting to notice a little bit of wallowing when pressing hard in high speed sweepers. Slower stuff doesn't seem to show any difference though. Maybe you are reaching the point that you are noticing the suspension starting to age on your bike. I also second the notion of checking everyting having to do with the rear shock, swingarm and wheel to make sure nothing is loose. Probably not, but make sure anyway. Also as mentioned, crank the preload up and see if you notice any change.

Honestly, it sounds like you are describing the rear wheel just slightly losing traction due to cold roads, cold tires and the residue that is left behind on the road form salt or ash used to help melt the snow away. I run into this in the winter months when riding too. I normally don't push things too hard when the roads have been recently salted or the temps are below 45F or so. Things can get "interesting" in those conditions.

66

Canyon - I have had similar sensations - and not just at slow speeds. Hasn't happened for quite a while but I felt exactly what you described. It happened about half a dozen times and on different corners and generally in warm conditions. I take the same corners almost daily and am still a bit apprehensive when taking the corners that it has happened on but cannot replicate the feeling/sensation. Happened to me on both right and left bends.
I think as my confidence with the bike has grown I tend to make sure that I am always accelerating through a bend and maybe this has helped?? Just dont know but I sympathise!

For what its worth....

Croc

Wow! Been said many times before, and probably will be again, but this board is awesome!

Had to run out of town for a week or so on business and returned to all these great ideas/ suggestions/ reinforcements regarding my observation.

I sincerely thank you guys...

A few answers to questions asked/ comments made...

Croc- Cheers! Glad I am not alone. I do think some part of this is just gaining time and confidence.

Beemeridian- Good tips! I will check the preload, suspension, swing arm, and lug nuts to make sure it is not something out of spec with these systems.

Cworley- Bought my 05R with about 6K (miles) on it a little under a year ago. I have put a bit more than 8K on it since then, for a total of about 14.5 K. I am hoping that my suspension is still happy, but a good note. And I will be taking the advice of verifying that all is tight with the shock, swingarm, and wheel. Thanks! You may be right about the slip being about the cold and associated road conditions on this trip, although I have felt this on warmer days closer to the valley.

ProductUser- Thanks! May have been... those sneaky DOT guys!

Sunbeemer- Your description is very intriguing as it sounds like it might well match my symptoms. It may well be that this is a natural part of getting to know the tighter turning characteristics of my machine, as I start to ride with more confidence and sensitivity. Hope so!

Riceburner- I think this issue of exploring previously unused parts of the tire, and possibly the "shaft effect", might be combining a bit on this. I know I am a lot less timid now about the lean, so I might just be finding a phenomenon that I hadn't found before.

MikeCam: I am currently riding Metzeler Z6 tires. First thing I did (and have done) is check the tire pressures when this has occured. I have always been in spec for the pressure that has been suggested for these animals. Thanks for the encouragement, and I will try to log the issue more accurately (in my own mind) so I know when to "expect" the possibility.

Biff's R: Preload adjustment first on the list (as soon as work lets me go home and ride!). Thanks!

GTR350cc: Thanks!