SF1 wheel lacing

A

Adam K

New member
Location
QLD
Hi all, After noticing the front wheel was closer to the right slider by about 6mm I thought it was a spacer problem.  Turns out the wheel had been laced that way. I took the wheel down to Ash's wheels and asked him to centre it.First question he asked was what is the offset measurement. Not knowing any measurements I went home ,put the forks together and assembled the front end complete and went back to Ash,s. He took measurements from sliders to edge of rim and said no worries will move rim to left 3mm problem fixed. That got me thinking if the same bloke who laced the front wheel also did the back wheel. Put rear wheel on bench,drum brake up,put straightedge across drum and it was level with the edge of the rim. Did the same with the front and this time it was 2-3mm higher than rim edge. So that seem,s to be why the front was out. So because front and rear hubs and brakes are the same would I be correct to say that they should be set the same to the edge of the rim. Does anyone have any information about how to set the hubs properly.  cheers Adam
 
I have no proper info but I would expect the concept of centering the disc front hub would be simpler to do. The drum hubs less so, finding where the drum hub is measured from would be what defines this. Does it include the brake backing plate for front and rear and  the couch and sprocket on the rear. I expect aligning the rear drive chain would also impact on this as well. Gets complicated very fast.I have read its important to measure this before pulling a wheel apart but that doesn't help to confirm what correct at the start. Be good to get as you have asked for the right dimension.
 
I asked the wrong question,because the hubs are locked in position between forks and swing arm (with right spacers) I should ask how I do I get the rims in the right position
 
G'day Adam

At the risk of stating the obvious, the tyres (and therefore the wheel rims) should be on the centreline of the bike.

Front wheel is pretty straight forward. It needs to be centred between the forks as you've just had done. 

Back wheel is not quite so easy to check because swing arms are not usually symmetrical. That's because the drive side and brake side have to accommodate different bits of apparatus. Unless someone can come up with some reliable measurements for your bike between the edge of the rim and the swing arm on each side, you'll have to go back to first principles which basically involves setting up a centreline reference and checking the rear wheel against it.

Set the bike up on the centre stand and shim the stand feet with some thin bits of material to get the bike perfectly vertical. A spirit level against the rear wheel will tell you when it's vertical. It doesn't matter if the wheel offset is wrong, as long as the rear wheel runs true (and the swing-arm isn't bent) you can use the wheel as a vertical reference. If you suspect the swing-arm is bent, that's another issue.

Actually, the swing-arm pivot is a better reference point, but Laverda swing arm shafts are solid so you can't put an alignment rod through it.

You'll have to remove the seat and rear mudguard to perform the following measurements.

As far as I've been able to work out, the top rails of laverda rear sub-frames are equidistant from the centreline, so you can use them as a reference. Clamp or gaffer tape a bit of wood across the top frame rails above a spot where you can see vertically down to the rear wheel, measure and mark the centre between the frame rails.  A plumb line or spirit level dropped from the centre mark on your bit of wood should align with the centre of the rear tyre (or rim if no tyre is fitted). If it doesn't, your wheel offset is incorrect. That could be due to incorrect axial wheel spacers or incorrect rim offset (ie. spoke setup).

If the chain alignment is good, then the spacers are OK and any rim offset is due to wheel lacing. You can get little magnetic laser things to check chain alignment - or you can do it the old fashioned way with a straight edge.

Cheers,
Cam


 
One other thing is the lace pattern is different between front disc and rear twin leader drum. I dont know if the lace pattern is he same on front and rear drum wheels.
There is some resent posts on this subject so worth a seach
 
Thanks Cam for your advice , At the moment I have the bike in a 1000 pieces so I can't do those checks yet.I had the frame straightened by Dave Kellot and he checked the sprocket alignment and swing arm.He was the one told me about the front wheel being laced wrong.I thought being identical rims, brakes and hubs on the left hand side, wouldn't you think If you put a straightedge across the hub to the rim what ever that measurement is should be the same if the bike is straight.When they made the wheels in the factory I wonder how they set them up. Thanks Vince , I read the posts about the different lace patterns .
 
Hi Adam its probably best to start again with your wheel lacing.
Provided the spokes installed into your wheel are the same length right and left hand side its a simple process to ensure the rim is symetrical about the hub or drum. Laverda did not make different length spokes from the right or left side so if the rim is offset you would find spokes on one side would be barely engaged in the nipples and the spokes on the opposite side would be threaded through the nipples and would be pushing into the rim tape! causing punctures!!
 
Adam K said:
Thanks Cam for your advice , At the moment I have the bike in a 1000 pieces so I can't do those checks yet.I had the frame straightened by Dave Kellot and he checked the sprocket alignment and swing arm.He was the one told me about the front wheel being laced wrong.I thought being identical rims, brakes and hubs on the left hand side, wouldn't you think If you put a straightedge across the hub to the rim what ever that measurement is should be the same if the bike is straight.When they made the wheels in the factory I wonder how they set them up. Thanks Vince , I read the posts about the different lace patterns .
Click to expand...

Simple jigs keep everything in position while lacing.  It's not rocket surgery... ::) :D

piet
 
Adam K said:
wouldn't you think If you put a straightedge across the hub to the rim what ever that measurement is should be the same if the bike is straight.
Click to expand...

Unless you know what the hub/rim offset should be, a straight edge across the wheel won't tell you much about the alignment of the wheel in the frame. I suppose that would be a handy figure to include in the workshop manual for anyone rebuilding wheels. I don't think I've ever seen such a specification though. If you can find a bike that you know is set up property, and measure its wheels, you could transfer the offset measurements to your own wheels.
 
Cam, every thing you said makes sense to me. I could get the front wheel done and when the bike is back together do those checks you recommended but was trying to save a bit of time and work. The wheel builder was hopping for some measurements for his file as well. Would it be to rude to ask the next owners of SF 1,s  with good wheels with late laverda drums when they have their wheels off to check to see what that offset is front and back.  Cheer's Adam.
 
Like I said,specifying where on the drum compared to the edge of the rim.The drum only or the drum plus the cush drive, or the drum cush drive and the sprocket.
Been here,I had my wheel wright offset the rim a couple of mill to get the rear centred to the front as they were parallel but not centred. Years later I found I was missing the thin left rear wheel spacer, there are 2 spacers on the left side of the wheel one thin washer and a big cylindrical one ,added it and moved the rim back. But all this was only found by carefully measuring the bike.
 
I have an original rear drum brake wheel from a 750. Putting a straight edge across the face of the cush drive it measures 25mm to the outside lip of the rim.
 
Hi Adam,

73/750,  Checked offset on my bike as per Rob and BlackJota but i have 22mm ! wheel reasonably true.

Brake hub side front and rear measure 10mm from outer edge of wheel to outer face of shoe hub.  ;)

Hooksey.
 
Looks like you're pretty right then. 1 mm is negligible in this context. I've had tyres with more offset than that.

I have a bike with the rear wheel offset by 10 mm so the wider than standard tyre will clear the shaft drive tube. Can't notice any detriment to the handling. Mind you, it has a sidecar hanging off it so steering is a bit lopsided anyway  :D
 
Reckon this is sorted, but you can reference the virtual centre from any Breganze Laverda (assuming RGS is the same as 3C?) by simply measuring the distance from the sprocket face of the cush drive or sprocket outer (as long as you include the width of the sprocket (for 530, 630, 520 etc), as all Lavs have the same gearbox output shaft chainline.

For eg, measure to the outside edge of the rim (doesn't matter how wide it is) and add to that figure half the width of the rim ... that's the centreline relative to the sprocket or sprocket carrier..
 
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