Rear Tire Alignment

[Air4Life]

Possibly my rear fender is off, or the rear wheel is, or maybe both.  Viewed from the rear, the center-line of the tire is about 3/8 off from the center of the fender.

I think its that it appears to the right...

[tvrla]

Most likely it's the fender or the subframe.

First check to make sure the fender has the proper rubber washers betwen it and the frame, and they're squished evenly.

If that's all good and it's still off, then it's probably the subframe. Often they're bent and need to be tweaked one way or the other.

The swingarm can be off center in the frame so you can check for that too by ensuring that swingarm/frame gap is the same on both sides.

[Bob_Roller]

Most likely it's your rear fender, it sits on two pins at the front, not too uncommon to have the holes elongate after years of use .

[Barry]

3/8" is not grossly excessive.  You should be able to get it better but may not get it perfect due to a number of variables already mentioned. I doubt many are perfectly aligned.

[clonmore1]

I have the same issue, but I have been told it's the subframe. Now, where did I put that rather large piece of wood?

[Air4Life]

Well, I took a quick look at the points mentioned by you all.  I suppose I could loosen and persuade the fender to line up with the tire, that is, if it bothered me enough.  

*** Wirespokes:  I'm interested to learn more about the swing arm alignment (then again, maybe not), because there is slightly more room on the left side.  I dropped my ignition key between the spaces and it fits comfortably in the right side, whereas the left side has a bit more room.

[montmil]

... I'm interested to learn more about the swing arm alignment (then again, maybe not), because there is slightly more room on the left side.  I dropped my ignition key between the spaces and it fits comfortably in the right side, whereas the left side has a bit more room.

Centering the swing arm to the frame is not a difficult chore. Visit the Snowbum's site and read article #43.

http://bmwmotorcycletech.info/technical-articles-list.htm

[nhmaf]

It may be that the tire is properly aligned with the swingarm not quite exactly centered.   One also has to be aware of the drive shaft running through the swingarm tube and not push things such that it can hit on the inside.   If your bike's pivot pin area gap on each side are within 1mm of each other I wouldn't worry about it if the bike is handling well.   Take measurements/pics and post em up and we can tell ya if they look skewed or normal..

[Barry]

I'm interested to learn more about the swing arm aliegnment (then again, maybe not), because there is slightly more room on the left side.I dropped my ignition key between the spaces and it fits comfortably in the right side, whereas the left side has a bit more room.
 

Yes the swinging arm should be centred with equal gaps either side but this is not critical to the nearest thou as there is some offset built into the wheel alignment in any case. An easy test is if you can get a 3mm rod or drill bit in both sides then on my bike at least you are within 5 thou of dead centre.

[Air4Life]

Cent 1.55 mm Nickel 1.95 mm Dime 1.35 mm Quarter 1.75 mm
1/2 dollar 2.15 mm Presidential 2.00mm

April 22, 2012  

Swing Arm Gaps

Two dimes (2x 1.35 mm) Right Side = 2.70mm
and One quarter plus one Nickel (1.75mm + 1.95mm) on Left side = 3.70mm

Difference favoring 1 mm rechte Seite

Based on the picture of the rear tire I would expect the offset to be the other way.  Unless of course the fender is grossly positioned off the other way.

[tvrla]

Yeah, that's pretty far off. You'll need the special swingarm socket to loosen up the 27mm lock nuts. I used to use the calipers to measure the distance but found that fitting an allen wrench in each side and comparing 'wiggle' worked good enough. But yours is WAAAY off! I'd fix that.

There is a little bit of tech to this job, and like a lot of tasks on these bikes, is made over-complicated. The simplicity of it is (like wheel bearings - except the LS and monolever fronts) these are tapered roller bearings and need a little preload. The correct procedure calls for preloading them to 12 pounds, backing off, then 8 foot pounds and locking them with a torque of something like fifty or sixty foot pounds. You don't want those suckers coming loose!

But if you don't have a torque wrench to follow that procedure, then just tighten one side (no need to do this to both sides since tightening one will tighten the other as well) a little bit to preload the bearings some. Tapered roller bearings need just a little preload - you don't want them sloppy as then they'll wear quickly. Harley runs the same bearings and they specify zero preload, zero play and they don't have problems. In my old cars (all ran tapered rollers) I used to adjust front wheel bearings and there was never this complicated procedure - just a slight bit of tension was called for and that was good enough!

Perhaps someone skewed the swingarm to bring the wheel over so the fender didn't look so out of alignment? Best to just figure out what the real problem is and fix that! I've heard the subframes quite often are tweaked, and it's not that difficult to adjust, just requires two big guys and a long lever. Then it's easy.  

[Bob_Roller]

When you are done adjusting the gap on the swing arm, rotate the rear wheel and make sure the universal joint doesn't contact the swing arm housing .

If it is, you will hear a light clicking sound .

This happens on some bikes and not others !!!!!

Can't tell from the picture, but are there large area washers covering the swing arm bearings ?

[Air4Life]

nhmaf: You originally offered a value of 1 mm and it would seem that this is right where this bike is at.  Do you still agree that this is permissible?

Wirespokes:  Yes, it does seem a bit techy, but after reading your explanation along with snowbums last night, I believe I now appreciate the preload/load to put on these.  Thanks.  And Yes, I finally received my torque wrench.  I'll have to see about the 27mm socket thought.  Maybe I'll get lucky and it will fit (at least that was a possibility I read somewhere).  

You see, I'm not exactly setup here for grinding or just about any bench work.  ...got it stored in a cargo trailer with basic hand tools.  But this job should be within my grasp of my abilities and the aforementioned shop setup.

Bob_Roller:  Thanks for the input on the "clicking sound".  I believe I read that as well last night.  If this proves to be the case, could this explain why it was secured offset to begin with?  Maybe it will interfere with any centering...

I'll have to go check on those washers you asked about, later.

Barry:  I welcome your input. In light of my swing arm measurements I would like to learn what you think?

Aegis_Chris:  Would you remember off hand how far out your swing arm is/was?

Montmill: Yep, I'm learning to be patient when I venture to his site.  His kind of reading makes me miss the good old days of real books.  Computers are great for reading snippets, but anything of length gets awfully frustrating.  I'm the kind of reader that needs to go back to check on previously read sections of the material in order to get a better image of what is being described.  On print that means I highlight or underline.  

I've already begun compiling a printed version of other operations he has dedicated to his site.  Thanks.
 

[Barry]

I would want to improve on 1mm difference and you should easily be able to get it better than that. 3mm drill bits or Allen keys are good ready made gauges for this job that many people have to hand.

Any 27mm socket can be made to work but it will need at least 1 modification and possibly 2. Normal sockets always have a short tapered lead in so the face of the socket will need turning or grinding down so that you get maximum purchase on the thin lock nuts. The next problem is there isn't much clearance between the lock nuts and the recess that the socket has to fit in. Some thin wall sockets will fit in without modification but you may need to reduce the outside diameter of some sockets slightly by turning or grinding. I had to do both mods on the 27mm socket that I already had in my socket set.

After having set the pre-load of the pivot pins you have to lock them in that position with the lock nut. As you tighten the lock nut you won't be able to see if the pivot pin has rotated at the same time adding even more pre-load which would be undesirable. It's worth marking the position of the pivot pins so you can check they haven't moved. This also tends to move the gaps around a bit so don't expect to get the gaps perfect at the first attempt. It usually takes a couple of adjustments to get them right.

[nhmaf]

I'd say that it is OK to try to get the two sides closer to equal in gap, but it can be over-analyzed - it is more important that the drive shaft/u-joint doesn't contact the inside of the swingarm as it turns and the rear suspension pivots through its travel.   This means having the drive shaft centered in the swingarm - but one cannot see it while it is mounted ont he bike and doing this adjustment - so take things slowly and methodically..

You want the pivot pins to be tightened to a specific torque, and have the 27mm locknuts to be torqued to keep things properly pre-loaded, but, the pins can rotate when you are tightening the locknuts - I put a dab of paint or use a sharpie marker pen to make a line on the end of the pin by the allen key hole so I can tell if it has rotated while I torque the 27mm nuts up.   I'd recommend that you loosen the lock nuts on both sides, loosen the pivot pin on the narrow gap side and then loosen&tighten up the pin on the opposite side until you notice clearance change.   Might also want to loosen the nuts on the shock absorber mounts to make things easier to move and, if your subframe is tweaked, that you aren't trying to fight the subframe's tension to nudge the swingarm over.

All said, my rear fenders on both my airheads do not line up perfectly with the rear tire.  Partly due to fender&hole misalignment and elongation, and I don't worry about it as long as there aren't any clearance problems.   There are plenty of other asymmetrical things on these bikes (and their riders)!