R65 mono swingarm problem... any suggestions?

[YuhoR]

i was stripping out my r65 and i found out that the rear wheel isnt in the center of the frame... i eyeballed the thing for an hour but couldnt find anything that could be bent or broken...
any suggestions where i should start looking for the problem?
swingarm bearings or...?
weird that i didnt feel that when i was driving it last summer...
from the front the tire is quite close to the center but in the rear its roughly 2cm off... (almost an inch)

[Bob_Roller]

Not many members here have a monoshock R65, so it's hard to get much of a perspective as to whether this is the way the it is built, or if there is a problem with yours .

[Tony Smith]

Firstly I'd be more inclined from the photos you provided to suspect a bent rear sub-frame than a bent swing-arm. You could check to see how close to even the gaps between the frame swing-arm mounts and swing-arm are.
 
If it rides OK I'd stop worrying. The only way to be 100% sure would be to get a mechanical surveyor to laser graph the frame centre line and then check alignment of the rear  (and front) suspension components.
 
With the greatest of respect your photo is not taken square on and the superimposed line does not pass through the centre of the bolt hole in the sub-frame, that alone accounts for a substantial amount of the apparent misalignment .
 
On the very great assumption that the sub-frame is straight and the holes in the sub-frame and the main-frame are in fact at true centre, it is entirely possible that there is no misalignment. Or, if there is, it is within production tolerance.
 
Anyone who has ever owned or ridden a Norton Commando will affirm that quite marked misalignment has no discernible effect on handling.

[Luca]

My brother had his nighthawk hit by his drunk neighbor.  Trued the headstock back up with a piece of pipe and me on a footpeg and put another 20k on it.

But to the point... after that his bike always would break left if he locked the back wheel up.  You could see if yours consistently breaks away to one side in a skid.


How do they handle the wheel on the monos?  Is there a spacer between the wheel and the final drive?

[nhmaf]

Many airheads appear to have the rear wheel out of alignment with the rear subframe /fender, but usually it is do to a tweaked subframe and/or fender.   My 82 LS actually is a little bit like this with respect to the fender, but it is due to some of the mounting holes in the fender being a bit egged out.

I seem to recall that on my 88 R100RT that the rear wheel was actually a little bit out of line with the front wheel centerline, but I think it is intentionally that way - unfortunately I don't have any good pics available to show this.   So, your issue might be a combination of photo angle/perspective, rear fender mounting hole tweaking, possibly tweaked rear subframe, and/or designed in offset - I *think*.

[YuhoR]

thanks for the reply you all!
ill be checking out the rear subframe next, maybe remove it completely, measure it and the mounting holes and compare the rear wheel to the actual frame.
my bike is in a garage 150km away so i have to think these things before i head out there... thanks for the tips!
i know the pictures arent straight but no matter how i looked at it in the garage, the rear wheel wasnt close to center....
but now looking at the vague angle photos i started to think, maybe the rear sub frame has twisted... that would explain why its mostly straight and the wheel off center.
looks on the pic like the sub frame is a bit lower on the left side...

[Barry]

BMW's spec for the twin shock airheads is a maximum of 4mm offset taken from a service bulletin issued in 1984 so before the mono's.

That said they all seem to have some offset without problems. Regardless of offset I would have a real concern if something really is bent and the wheels are not straight with respect to each other i.e. the usual concern for alignment on chain driven bikes and I would check alignment the same way using lines or straight edges. It's hard to see how frame damage would result in more offset but still keep the wheels in straight alignment so any damage should show up in a proper alignment check.

I agree with others that the sub frame is not the best guide to judge alignment.

[Luca]

Another thing to check is tire wear, both front and rear.

Examine the cross section of both tires and see if they are worn off center.  Also, see if the "chicken strips" are significantly different in width.

[MR.E]

I'm not sure i'd be worried.
But to be sure can you not get a long straight bar and place it against the wheels to see if they're in line.

I took the enduro bike in for an MOT and they tested it that way.

Thanks

[YuhoR]

im working alone so i dont think i can use a long bar because of the centerstand but i think i could use a string on either side of the tire to see roughly if its in spec...
we'll see. im sure ill come up with something when i have time to visit the garage again...
thanks for the tips!

[georgesgiralt]

Well you can put the long bar clear of the centerstand an d measure the distance at two points on the front tire to the bar and repeat at the rear. If 4 measures are identical, wheels are aligned, if not, you'll can check if the bar is parallel to the wheels and then see if the wheels are aligned or not.

[Matt Chapter]

It's hard to tell for sure but a glance at your picture doesn't show anything different than mine.  I do know that the single sidedness can visually make it appear as if there is a spacing problem, especially if you're comparing against the muffler positions.