Wheel alignment

[61770]

Sorry if this is has been addressed before but I am a newbie. I was recently involved in an accident and as I was taking the bike apart, I noticed the rear tire was "off-set" probably about 1 1/2 inches. I had not noticed it prior to the accident, but I did notice it with the rear mud flap taken off. Does anybody have any idea how to align the rear end or is it possible? Thanks for any information.

[Tony_K]

How are you concluding the result of this measurement?

[61770]

First off, thank you for responding. The way that I am concluding is that by standing behind the bike and then looking at the off set of the rear tire by the alignment of the frame. I have looked for any stress points on the frame checking for paint crackling, tweaking, etc. I have not noticed anything out of the ordinary.

[Big_Gray]

The BMW repair manual (1100 RT) describes BMW's recommended method for measurement of wheel offset and suggests a maximum permissible amount of 9 mm. The manual that I have, does not suggest a method of adjustment if the measurement exceeds 9 mm. I assume this implies BMW does not allow for or recommend adjustment but rather suggests replacement of bent, damaged, or otherwise dimensionally inaccurate components to bring the offset back into specification.

 

I would be willing to wager a moderately priced bottle of whiskey that someone more knowledgable than I will offer you more helpful comments shortly but I would hate for you to think the forum isn't responsive.

[Ken H.]

If the rear wheel track is truly 1 1/2 off from the front's, I's say you have a seriously bent rear swing arm or similar. Hard to imagine one would be bent that much without cracking somewhere though, it's cast. Remember on these bikes there is no true "frame." Both the front and the rear are built off the engine block.

 

Or, and this thought just occurred to me, are you just seeing an offset of the rear sub-assembly? That all it really does is hold up the rider, and other parts of the bike.

[61770]

Thanks for the different thoughts. I finally went and took pictures and posted them on the following link. If you don't mind, I would appreciate someone checking them and seeing if I am just losing it? Thanks.

 

http://s291.photobucket.com/albums/ll284/chall61770/R1100RT/

 

[Boffin]

The angles of the pictures make it hard to be sure, but I am going with Ken. The swingarm is a hollow casting that bolts up to the rear of the cast transmission case. That will not bend, it would shatter. The rear subframe is tubular steel, which will bend. To check alignment you need to place a straight edge alongside the rear wheel and chck to the front wheel - do both sides. Compare these measurements to a non-crashed bike, as I believe some offset is normal on these bikes.

 

Andy

 

 

[61770]

Well thanks for the advice. I will check that. I feel a little bit more relieved on the input. Greatly appreciate the assistance of the forum.

 

Curtis

[AndyS]

..... I noticed the rear tire was "off-set" probably about 1 1/2 inches. I had not noticed it prior to the accident, but I did notice it with the rear mud flap taken off. .

 

Have you tried running a couple of straight edges (4 x 2 timber?) along both sides of the rear wheel up to and along side the front wheel?

When you do this, any real offset (or even twisting) will become immediately apparent. Keep in mind there will of course be a gap by the front wheel becuase the wheel is narrower, but the gap should be the same both sides.

Also ensure the front wheel is not turned one way or the other.

 

Andy

 

[61770]

Great idea. Had not thought of something that simple, but makes alot of sense. I will post as soon as I check that. Thanks for the tip.

[Eckhard Grohe]

A 6 inch wide piece cut off from a 4 x 8 sheet of plywood will have a nice straight edge on the factory cut side.

 

You could wrap a long piece, 10 ft of string around the rear arc of the tire and bring it forward and then swing to the bike center line to just touch the front edge of the rear tire. Measure the offset of bothe the front and back edges of the front tire from the string and turn the bars to equalize it. Note the measurement. Measure the other side and you get the offset as the difference of the 2 measurements.

[Jeron]

Can't beat one of these for a good straight edge.

http://www.sears.com/shc/s/p_10153_12605_00948251000P

 

It basically throws up a wall of laser light. Once you get it parallel to the centerline of your bike you stick a tape measure through the beam to get your measurements. I use a pair of these to align my car.