Need to centre the swingarm?

[Kookaburra]

I recently disengaged the swingarm on my dual shock 1985 R65 in order to do spline lube and gearbox seals. I measured and recorded the gap on both left and right sides of the swing arm (they were different but not by much). When I reassembled and retorqued to Snowbum spec I carefully reproduced the original different gaps.
 
Got a nag in the back of the brain that the gaps should be identical on each side. Is the difference OK (even necessary) or should I redo to even up the gaps?


  

[Armen]

Closer is better. Having said that, most of the airheads raced in the 70's ran the s/a offset.

[Bob_Roller]

As long as the u-joint doesn't touch the housing when you turn the rear wheel you're alright .

If I get an equal gap on both sides of my '81 R65, you can just a little 'ticking' when you rotate the rear wheet, so gaps are not equal on both sides when I get done adjusting .

[Kookaburra]

Thanks awesome gurus,

Universal joint is not touching the housing and no ticking on rear wheel rotation so now travelling with confidence. You just never know whether PO (or their mechanic) had set things up correctly. Also now understand the reason for the offset.
BTW  An alternative to trying to measure the gap (for those that are vernier gauge deficient) is to use enough feeler gauges to just drag through the current gaps and bundle them together with rubber bands until it is time to refit and adjust. Just label the bundles left and right.

[Barry]

Not that there is much scope to do this but the only time you would deliberately set unequal gaps is to reduce the offset between front and rear wheel which should be a maximum of 4mm.  There is an optional top hat spacer which is sometimes fitted to increase clearance between the tire and swinging arm on the RH side. This spacer is 10.7mm long instead of the standard 9.2mm so it moves the rear wheel 1.5mm to the left. BMW recommend that if this longer spacer fitted the wheel alignment should be checked and adjusted to ensure it does not exceed 4mm offset and the only way that can be done is by having unequal gaps - wider on the left than the right.

The above could be one of the reasons why you originally had unequal gaps but if that wasn't the case and not withstanding the wheel alignment or clearance issues the gaps should be equal although it's not critical to the nearest couple of thou.

[georgesgiralt]

Hello !
Centre centre centre !
Otherwise the shocks work biased, and the U join will/may/can touch something either at rest or when the swing arm is fully extended or compressed.
As to measure the gap, use Allen wrenches to fit between the frame and the swing arm. Easy to have at hand and quite perfectly calibrated for the job.
Remember to measure again the centre AFTER the nuts had been torqued to spec. Sometimes, when the bearings set it changes.

[montmil]

Hello !
Centre centre centre ! ...As to measure the gap, use Allen wrenches to fit between the frame and the swing arm. Easy to have at hand and quite perfectly calibrated for the job.
Remember to measure again the centre AFTER the nuts had been torqued to spec. Sometimes, when the bearings set it changes.

Drill bit shanks are also a good way to determine gap equality -SAE or Metric- the gap won't know unless you tell 'im.
Finally found a good use for all those metric bits stashed in the tool chest.

And, yes, the gap can and will change as you torque up to spec so take the time to sneak up on the final ft/lbs by working both sides a bit at a time; all the while keeping your finger s crossed.

[montmil]

Hello !
Centre centre centre ! ...As to measure the gap, use Allen wrenches to fit between the frame and the swing arm. Easy to have at hand and quite perfectly calibrated for the job.
Remember to measure again the centre AFTER the nuts had been torqued to spec. Sometimes, when the bearings set it changes.

Drill bit shanks are also a good way to determine gap equality -SAE or Metric- the gap won't know unless you tell 'im.
Finally found a good use for all those metric bits stashed in the tool chest.

And, yes, the gap can and will change as you torque up to spec so take the time to sneak up on the final ft/lbs by working both sides a bit at a time; all the while keeping your finger s crossed.

[Kookaburra]

Thanks gurus particularly for the tip on using allen keys to do the gap measurement. So measurement result is left 4mm and right 3.5mm. I can live with that until next time I do the maintenance when i will try and get it closer to equidistant.

Now on to sorting the issue of slightly clonky forks on big road bumps or potholes. Plenty of discussion and  good information on the forum so I figure most likely to be a damper rebuild.  

[Burt]

A good topic well explained.  As my swingarm is currently removed for access this will be useful info. I have used the drill bit method in other applications but the allen key is probably a tad easier.

Cheers, Burt.