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

Besides the obvious of the jugs / pegs ultimately being in the way...what makes sport bikes (and K1200 S/R series) able to lean further, and easier in to curves than RRs?

G. The riders

I had aYamaha YZF600R, I switched to the BMW R1150R. To my mind, the weight difference is the difference. 530# for the BMW, 405# for the Yammie. Both have sport bike tires as delivered. Some of the difference is the width of the Boxer, to be sure, rotating over in corners that mass stuck out there is different than a four thats about half as wide.

Some thoughts from a half-fast racer.

There is a lot of hardware in the way on the R. When it comes to lean angles, I think that is the only limiting factor for this bike - ground clearance.

Cornering speed? Turning radius? Traction, weight, wheelbase and suspension set-up are all important.

Side-to-side transitions is where mass centralization really pays off. The R has wide bars for leverage, but the sportbikes are like a skater spinning with arms tucked tightly to the body, they just rotate more quickly.

Don't forget the race machines of the 1980's, which by today's sportbike standards were somewhat lacking. The right rider can make the machine fast in the corners, so long as it is set up properly.

The R can lean over pretty darn far, but it does have a bunch of junk hanging off it to drag on the ground. The big old handlebars on the R put your hands out wide and make countersteering a bit of a chore. If you want to hang off the Beakster and drag your knee on the ground, the bike will not limit you from doing so - but at the end of the day the frame and suspension are set up for the road, not the track.

It's all down to the geometry. Short wheel base, sharp front forkes angle, very litle trail on the head stock. All these things make a bike less stable and the less stable it is the more inclined it is to turn. Center of gravity has a much less effect on turing and for that the higher the better, Although the best place is bang smack in the middle because the further awayit is from the turning point it is the longer the pendulum is the slower it will react.

+1

All this is explained very well in books by Hough ([more] profecient m/c), Parks (total control) and Code (twist of the wrist (1 and 2).

Shorter wheel base means you have to lean lesser for a given turn at a given speed. Conversely, shorter wheel base will let you go faster for equal lean angles for a given turn.

leno wrote:It's all down to the geometry. Short wheel base, sharp front forkes angle, very litle trail on the head stock. All these things make a bike less stable and the less stable it is the more inclined it is to turn. Center of gravity has a much less effect on turing and for that the higher the better, Although the best place is bang smack in the middle because the further awayit is from the turning point it is the longer the pendulum is the slower it will react.

I'm pretty sure that for a given turn at a given speed, the lean angle is independent of the wheelbase. Otherwise, a unicycle wouldn't have to lean. (And it does.)

pretty much what Leno said - it's the geometry.


Also it's the riding attitude, experience, skill - faster riders who will corner faster are naturaly drawn towards the Sportier bikes.



Like with most things in life there is no simple answer - and for every person you ask, the situation is different.

NoRRmad wrote:I'm pretty sure that for a given turn at a given speed, the lean angle is independent of the wheelbase. Otherwise, a unicycle wouldn't have to lean. (And it does.)

Very true but it does effect the speed that it will tip into a corner.

Very simply, to lean further only requires two things, well only one thing really, and that is more ground clearence when leaned. For all practical purposes, wheel base has no effect on lean angle, it has an effect on lean rates and other things but not lean angle in the purest sence. Sticky tires and a grippy road surface would perhaps help in not either low, most likely, or hi siding.