Rear wheel spacer

[Deaner]

What is the point of the spacer that sits between the rear wheel and the swingarm? When I let go of the handle bars the bike pulls to the right even if I lean pretty hard to the left. Is this the spacer or the crown in the road? It also pulls on one way streets at the top of the crown. Will it harm or help things to remove it?

Thanks,

Dean

[99rtRon]

I removed the spacer and found no difference. I dont buy the "crown of the road" explanation either. None of my other bikes display PTTR traveling on the same roads. Keep searching and Happy Leaning!

[JerryMather]

I believe that the rear wheel spacer puts the rear wheel into alinement with the front one. A few members have removed them and have created a wobble in the forks at high speeds.

Your bike pulls to one side because of the driveshaft, final drive and engine set up. Others around here can better explain the forces that create this to happen.

Welcome to the Beemer Club.

[chrisolson]

On my '99 RT, had it in for about a year and then took it out. These have been the results:

 

PTTR reduced - but not eliminated

No wobble

front tire wear patttern more symetrical

 

It'll stay out as long as I own the bike.

[Joe Frickin' Friday]

It's called "Pull To The Right," or PTTR for short.

 

we got us a FAQ about it.

 

Here's a recent thread about it.

 

The most credible explanation seems to be a right-side weight bias of the gearbox, swingarm, and final drive.

 

On an 1100 bike removing the spacer sometimes (but not always) helps PTTR.

[Deaner]

Thanks...

[ShovelStrokeEd]

For everyone's edification and some food for thought.

 

Simple rear wheel offset - adding removing shims - will not cause the bike to steer in any particular direction. It can create a small weight bias which may or may not cause a pull. Ditto the theory of weight balance caused by the single sided swing arm, tramsmission et al. This stuff weighs so little in proportion to the mass of the entire bike and is at such a small remove from the center of mass that it is unlikely to have any influence whatever on steering. Don't believe me? Fine, but, try my experiment, done with a K bike 20 years ago. Hang the bike at two points, the center of the steering head and the center of the rear sub frame. Any difference in weight will show up in the bike not hanging vertically. It wasn't there. Incidentally, I went over 200 mph on this bike with the rear wheel offset to the left of the front wheel's centerline by 12 mm and no steering correction was needed.

 

Now, what can cause the bike to steer to the right? A rear wheel which is not tracking the front. Picture standing over the bike and looking straight down at the wheels. Assume the front to be centered and aligned with the long axis of the bike. Now, if the rear wheel is pointed slightly to the left, the bike is going to want to describe a long arc to the right (forklift steering). We could and did correct this on the K bikes by varying a shim pack where the motor mountes connected to the frame. I'm pretty sure the same could be done to the R 259 series of bikes. No matter the welding jig or machining fixture, some variation from chassis to chassis is inevitable. Just remember when making the adjustments that things are opposite to the intended effect. You need to move the angle of the rear wheel so that the front points further right to correct PTTR.

 

Betcha a good cup of coffee at my favorite place I'm right.

[Paul Mihalka]

More than likely Ed is right that you can correct PTTR by changeing the angle of the rear wheel in relation to the front, but it would be a major undertaking.

My '99 R1100RT was a bad PTTR bike. Weight shift, like putting heavy stuff in the left bag, helps. Taking out the wheel shim helps. Nobody could tell what that shim does anyways. I ended up moving the swingarm to the right 2mm by putting a 2mm washer under the right swingarm mouting bolt. That cured PTTR completely and stopped left side front tire cupping.

PS Don't remove the wheel shim on R1150 bikes. As the brake disk is mounted on the wheel, alignment to the caliper and ABS sensor would change.

[Haynes]

My view is similar to others; removing the spacer should not affect a significant change.

Another possibility for PTTR is misalignment of the front and rear axis causing camber thrust in opposite directions front and rear making the bike tend to track in a arc. The error in angular misalignment would only need to be relatively small to produce a marked effect.

[eakins]

i removed mine. reduces pttr. 3 sets of tire no wear issues. no wobble. works for me.

i've heard it's there because of the metals, but i don't think that's an issue. of course i coulde be wrong. bmw could have had the cast the rear made that much wider from the begining, so why the spacer? maybe for different models? do any not have a spacer?