About rear wheel/hub/rim offset.

I read on the manual book that the rear hub/drum brake of 750 commando should have an off set of rim compared to 3/16 hub to the right side speedodrive.

I wanted to know if the rear wheel of the 850 ES has an offset or is in perfect center  between hub and rim.

Ciao.

Piero

The axle drum sprocket to chain alignment is the only thing that matters back there and that is fixed by the spacers in that assembly. The 750 rear rim is commonly seen off set 3-16" to 3/8" to LH but can be relaced to center to spine for better looks from behind to center tire with fender and loop. Some say theirs came centered so you call to diddle it or not as non issue on tire wear to handling.

Piero, It's very difficult to say as the Mk3 doesn't have a flange on the disc side, the spokes being fed into the hub itself. I have a spare loose wheel but I wouldn't know where to measure from. It has a 2.50" rim so measurement on one side wouldn't be relevant.

All I can say is that if the spokes are the correct size, they should lie flat along the drive side flange and not be bent or curved in any way.

Piero , try lacing then truing etc. with the bike on the centerstand and periodically spinning wheel to find the perfect placement of the brakedisc to home into the center of the caliper. That's the goal . It's an ancient Italian Art .

Thanks for your comments.
I would like to submit this question: the 750 (drum hub) has the pokes all of the same lenght and so the rim should perfectly be the center of the hub and with standard spacers the off set should be automatically respected, or not???
For the 850ES is different, the spokes in and out are of different lenght and there is a flange for the rear disc: the off set should be between 89/91 (2.28 cm.) to LH.
What i would mean with my reasoning?.
I have rebuilt the conical rear disc hub of 850 ES with a new rim with the spokes, in and out, perfectly the same lenght to those standards and therefore the camber centering should be the standard one (but for me the brakedisc positioning perfectly in the center of the caliper not depends from offset but only from the correct use of the spacer!)
That is fine, but why the mounted wheel seems to be more left of the center (swing arm) and not central to the fender?
Maybe i cannot explain me: on the font disc hub you can have the disc/caliper goal but the rim is not in the center of the forks/sliders.
Ciao
Piero

That is fine, but why the mounted wheel seems to be more left of the center (swing arm) and not central to the fender?
Maybe i cannot explain me: on the font disc hub you can have the disc/caliper goal but the rim is not in the center of the forks/sliders.

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Who knows why Norton issued them with rear rim off set to the LH but Norton sure did issue many of them that way - if not most of them, as all the 750's I've checked that someone has not bettered the factory offset.

The front rim should always come centered in the forks so if not that is some error outside of factory issued kit.

Piero,

The drum rear wheel has the rim pretty much centred between the flanges of the hub - I measured my '72 Combat wheel before I stripped it and the datum I used was the machined surface of the hub where the brake drum locates.
the WM2 rim was flush with the machined face of the hub on the drive side.
The front wheel is very different! - on the same bike I used the face of the hub where the disc is bolted to, and the WM2 rim was 11.75 mm inboard.
I get my spokes from Hagon, and the front wheel spokes are all different depending on location, so there are 4 types spokes to lace up.

Oh yes - your Fastback is very pretty! - in some ways more British that us Brits could manage :wink:
Best Italian styling this side of an Imola Ducati, if I may be so bold 8)

I just completed my rear wheel and the offset was 21 M/M from the hub.I use a straight edge against the hub to set the rim.You know that the rim has a direction the Dunlop is to the left side.

I have understood that the off set wheel is one thing and the cambrr/centering from hub and rim is another thing!.
Are two different threads.
Ciao
Piero

pierodn said:

I have understood that the off set wheel is one thing and the cambrr/centering from hub and rim is another thing!.

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Yes Piero. This thread from the NOC has the final word on offset. Skip to the chase, the last post by Vern Fueston. The dimensions of the 850 and 750 rear wheel are the same. The MkIII is a different matter. But the end result is the same, the rim is centered in the frame. And the swingarm is centered in the frame, at the axle pads, not the front of the swingarm. Swingarms aren't symetrical. True the rear rim centered on the axle pads. The 750, 850, and MKIII rear wheels are all the same in this regard. (The shock upper pickup points are centered in the frame, the frame is symmetrical. The lower pickup points, the axle pads on the swingarm, have to be centered too or the shocks would be tilted in the frame).

http://www.nortonownersclub.org/support ... el-offsets

By the way, when Vern says the offset is 1/8", that is the actual offset, not the apparent difference between the right and left side dimensions. The easiest way to see this is the difference between the 750/850 front engine mount and the MkIII. The MkIII is centered in the mount. It looks like the pre-MkIII's are offset 1/4" because that's how much the tubes are hanging off to the right and it's how much you need to cut off to center the pre-MkIII mounts. The offset is actually 1/8" because that's how much the plates were shifted before they're welded up. The right side picks up 1/8". At the same time the left side loses 1/8". 1/4" is the total difference, but the offset is 1/8".

rpatton said:

pierodn said:

I have understood that the off set wheel is one thing and the cambrr/centering from hub and rim is another thing!.

Click to expand...

The easiest way to see this is the difference between the 750/850 front engine mount and the MkIII. The MkIII is centered in the mount. It looks like the pre-MkIII's are offset 1/4" because that's how much the tubes are hanging off to the right and it's how much you need to cut off to center the pre-MkIII mounts. The offset is actually 1/8" because that's how much the plates were shifted before they're welded up. The right side picks up 1/8". At the same time the left side loses 1/8". 1/4" is the total difference, but the offset is 1/8".

Click to expand...

Well,
I understood but, now, borbs another question.
I have fit on 750 frame the rear 850 ES cradle and swing arm.
I mount transnission (750) and engine (750) but with 750 front mount, not the 850ES front mount.
Do you think i could have problems with the engine off set?.
I can see problem now but may be was better to mount the 850ES front mount?
Ciao.
Piero

hobot said:

Who knows why Norton issued them with rear rim off set to the LH but Norton sure did issue many of them that way - if not most of them, as all the 750's I've checked that someone has not bettered the factory offset.

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It should be no surprise that the rear rim is not central in the frame,but offset slightly toward the primary side.The primary side is always the heavy side of the bike.

Forget all the measurements from edges parts that may or may not be made accurately to the edge of a rim that may not be perfectly standard width.You only need to know how far the gearbox sprcket centreline is from the frame centreline.

If you use the same distance from the rear sprocket centreline to rim centreline,you can have the sprockets aligned and the rim will be central in the frame (which is not exactly where you want it).Shorten that distance a mm or 2mm,and have the rim slightly toward the primary side.