Wheel offsets

The wheels run centre to the centre line of the bike. Don't know what part of the forks you're referring to but, if you project the steering head down, the wheel centre should lie on that line. Or, if you prefer, the wheel should sit centre on the fork stanchions. This does assume that everything is straight, which is rarely the case on a 50 year-old Commando.

My front rim is on the centre line and it's never been rebuilt and is a Nov 73 build MK2a, it may have a racing lockheed caliper now but I never moved the rim when I fitted it after removing the original caliper. The caliper side spokes are nearly vertical to get the rim centralised and still give room for the caliper, very hard to build correctly and the factory instructions included standing on the rim to move it over before final tightening of nipples.

When building the wheel, the rim does not sit centrally relative to the spoke FLANGES on the hub. In fact , it sits NEARER the disc side, because the hub has a large projection to mount the disc on, so the flanges are offset to the non-caliper side, relative to the fork centreline. So the standard caliper is NOT  the reason for the offset. ( I have just been to the garage to measure/observe it.) In fact, if spokes were more evenly angled relative to flanges, the spokes would have a bigger clearance from caliper.

    The wheel on mine has been relaced to be centred in the forks once all assembled with axle spacers, and wheel pulled to right when axle tightened( caliper on right).

If Gary's front wheel rim is set centrally between the forks, and the rear wheel is in line with it, all is well.

However, if the front rim was previously not central with respect to the forks I suggest that this would have created potentially serious handling problems (with or without the rear being in line with it, although "without" would probably be more problematic still).

Consider that if the rim is set so as not to be central in the forks then it will also be offset with respect to the axis of the steering head — which in turn means that the centre point of the tyre contact patch will be laterally offset with respect to where the steering head axis meets the road.

While I haven't attempted to think through the consequences of this they would seem to involve, at the very least, differential castor action between left and right turns, and possibly an inbuilt tendency to steer to one side.

Think we have to let him get on with it; he's adamant that his front wheel was offset in the forks.

We've all spent enough time staring at our bikes, checking out other bikes in pub car parks, swapping wheels in and out that surely a wheel cocked 5mm off to one side would have attracted attention enough to get a ruler out. Half a century ... someone would have thought it was odd. Can you imagine the fun the Domi crew would have had taking the piss out of our Commandos : they only go round left-handers you know.

Oh, the original, rust-and-all wheel from my '74 Mk2A Interpol is centre to within 1mm (maybe closer but I can't be bothered).

... but taking it from an angle makes it look as though the rim is in fact not central!

Setting the front rim centrally in the forks  and  lining the rear to the front  or equally between the rear suspension units  has always worked well for me. It has also been the case that offsetting the wheels to one side has reduced   handling faults in the case of a badly balanced machine. Before making any changes I would do some hands off tests on a level road as you could make things worse if you move rims away from heavy side.

I seem to be having similar problems regarding where the rear wheel should sit . Early stages of full rebuild and trial fitting the wheels i have had rebuilt to same position as the old rims . The wheelbuilder said that the old wheels had been rebuilt before , with a mixture of incorrrectly bent spokes of differing gauges , wheel is 13mm offset to main centre tube ( ie rim would need moving 6.5mm to center it ) The info i was searching for was whether the wheels should be in center or not . Not got forks or front wheel on yet

That "looks" well off.   How do the sprockets line up ?   If you spin the wheel with the chain on  , the way the chain "finds" a position on the sprockets will be revealing.

Yes sprockets look to be spot on in line althought not tried chain yet . There seems to be quite a space between back of drum and wheel ( picture included ) is this normal ? all felt fine and positive when tightening up . Asking as it was a 2 person job to get wheel on - the new cush rubbers want to squeese the wheel back out so needs holding whilst somone else gets bolt and spacer in . Back to zinc plating today , couple of bits required before i can get front end on and definate conclusions on wheels

New cush rubbers always make fitting the rear wheel an effort, a few miles and they settle in.

It seems logical that the wheels should be in line with the frame and steering geometry, surely?

I’m currently in mid rebuild of a 72 Commando and have had the wheels rebuilt with the aim of getting both rims centrally lined up with the frame. For the rear wheel this means that the rim is off centre in the swinging arm since this is not symmetrical with the frame. I wonder if Lawrence’s has been centred in the swinging arm.

Luckily my wheel builder was patient with me and adjusted the front rim twice for me to get it in the centre of the forks. This is with the standard Lockheed caliper and the proper thicker gauge spokes on the brake side and the clearance between the very upright spokes and the rear of the caliper is acceptable.

Looking great steve , we are at about same stage by look of it . So are we saying wheels should be centered to frame , or offset 5mm or 1/4" to left as bike is heavier on left due to engine offset and clutch n sprockets , my vote would be central to frame and steering .  Anyone got an opinion on my pic of space between brake drum and wheel , would save me a few hours looking for a problem that doesnt exist , thanks

Centered to the frame otherwise the front wheel would not be centered to the yokes.

Why this gets into the ether is odd but BSA Unit Singles get the same stories which are just as wrong. Its a function of the engines starting off at low capacities and growing, then the wheels get bigger and wider, chains get wider and the engineers have to get creative to get it all to fit, engines end up going sideways.

Two rules to guide you, wheels on centre line and sprockets/chain in line.  

What does not help is the disc wheel having the disc side spokes vertical and so the non disc side need to be under tensioned to keep the correct alignment. Even then the rim moves to the non disc side as the vertical spokes have no sideways pull to speak of.

Yes, Laurence, remarkable how close our builds are!

I think wheels must be central to frame. Steering would surely be off if front wheel pivot point was off to one side from steering pivot? Also, both front and rear mudguards are centrally mounted. Hard to believe that wheels would intentionally be offset in mudguards.

I too had a swear inducing job fitting the rear wheel with new rubbers.

My gap looks similar to yours.  I too was initially concerned about this, but I think that as long as all axle components are metal to metal when tightened then all should be well.

Gary,

My Mk3 front end is yet to be reassembled to the bike, but I can put the assembled fork legs in the yokes and then fit an original, not rebuilt front wheel and see what respective slider to rim measurements are.

Andy

Front wheel now trial fitted , seems to be about 2 mm closer to disc side fork leg . Regarding Gary's last post about rim migrating away from disc I don't know if it's worth getting it moved over by 1mm

As long as you make sure the spoke ends inside the rim are not sitting proud of the nipple and smoothed down with no sharp edges/burrs then you can adjust the rim later after a few miles if it has not settled over to the non disc side.

In the mid sixties when the 650SS won the Thruxton 500 2 years in a row it was because of handling. The wheels had been offset to enable equal cornering ability. The other Nortons had the wheels central making it difficult to turn L or R I can't remember which. The scrutineers missed it and the tuner later (much later) admitted how his bike turned better than the others in the race.

If you lace up a rear wheel with the offset copied from the wheel you removed then find that the wheel does not sit centrally in the frame then there is reason for this. if your rebuild of pre-MK3 used the vernier type isolastics then these need to be fitted in the correct orientation. 

Front = adjuster on offside

Rear = adjuster on nearside. 

Sadly I have seen this on finished bikes where they have them incorrect. The bike will ride, but does not look correct from the rear. 

The Hemmings kit for pre-Mk3 models has both vernier adjusters (short one on the front) on the left-hand side of the bike.