Building a Mk.3 front wheel

I wouldn't know where to start building a wheel from scratch but I can recommend Central Wheel https://central-wheel.co.uk/ in Birmingham who will supply you with a correctly drilled rim and matching spokes for you to build the wheel yourself. And, if you ask nicely, they'll give you the offset distance and spoke tensions.

Also, consider going a little wider than original; 2.15 or 2.50 front, 2.50 or 2.75 rear. And 18" for the rear.

I have an original Mk3 front lying around that I can measure if you let me know what reference points to use.

The stainless rims and spokes for my Mk3 were supplied by Devon Rim Co. and my wheel builder didn't have any issues with the parts.  He builds and races sidecars and is very experienced at building his own wheels.
You're right about one set of spokes on the front wheel being almost vertical which means the tension is high to get the rim in the correct place.  So much so, that one spoke broke after lacing and the free end hit his garage ceiling!  Devon Rim supplied a new spoke free of charge.
This was done in 2013 and the rims are still excellent.

I am a complete amateur in wheel building but have just rebuilt my mk3 front wheel using the original rim rechromed.

The steps I took was to:

1. Note which side the rim was facing and location of valve to hub position.

2. Photographed the spoke lacing positions and also drew them on a cardboard template noting where every spoke went inside and outside.

3. For the offset I had a flat square board.with holes in the middle to mount on the hub with the disc removed, then simply measured the distance all round from the rim edge to the board surface.

Rebuilding was just using the notes above especially note 3.

Once the offset was done I then put the wheel in a jig to true it up.

As you already know how rebuild wheels it all depends if you have the confidence in yourself to do it. ?

Graham
 

Graham,
How did you find your rims after rechroming?

I had my Mk3 Dunlop rims rechromed by a well established classic car and bike plater, but now that I have finally got to the rebuilding stage, I am concerned that the nipples seem looser in their piercing ones than previously, being a somewhat  rattly fit, which they weren't when removed.  I am suspicious that the polishing process has taken too much material from the top edge off the cones, increasing the hole diameter (and potentially the cone wall thickness).  I guess this is one of the risks with rechroming rims, and I may have learned an expensive lesson.

Go for it Peter!

I recently rebuilt the front wheel of my Velocette, my first ever, and it was very satisfying to do. I'm looking forward to replacing my own MK3 rims in due course, and have done a little research.

An important point is to take your time - don't rush it.

Norman White describes the process in detail in his Commando Restoration book, and I recommend you get hold/borrow a copy.   There's lots of photo's too.

He also includes factory offset figures which is handy, and I would recommend you borrow an OE front wheel to confirm this for yourself, as well as for copying the spoke pattern when you do it.  It does seem that other spoke patterns are possible, but are not advised?
 
What you want is the distance from the outside of the OE WM2 Dunlop/Jones rim to the disk mounting face on the hub.  Should you decide to fit a wider rim then the new offset figure will be the OE offset figure plus half the difference in the additional external width of your new rim.  Avon list the appropriate rim sizes for their different tyre sizes - it's a bit of an eye-opener.

Clearly, the rim drilling is handed, and I will be demanding that any supplier indicates which way round the rim goes.

I'm not sure that it is realistic to expect either CWC or Devon to accurately bend the spokes other than at 90' degrees, and if so, do wonder if making a small jig for making minor adjustments might be worthwhile??  Another thought might be to have a word with Doug Richardson, who originally set up Devon and now works as an independent wheel-builder nearby?  Or some other wheel-builder?  Then there's the question of spoke gauges along with rim drilling.  Please let us know?

What I did find difficult was trimming the spokes neatly after everything was built-up and trued - what do others do?

Hi Andrew.

My rechromed rim was OK as there was only slight rust to polish out, if a rim is too badly corroded it might not be worth doing as too much polishing can remove the original numbers which defeats the object of putting the original rim back on.

As mentioned above I took pictures before dismantling as there are 4 different spokes in fixed uniform pattern around the rim.

I also made sure the rim went back on in the same position and direction as it was removed. ?

As mentioned above when the rim was finished I smoothed the spoke ends using my dremel and a spot of silver paint to protect them.

You might wish to ask Devon as to which way round the rim needs to be in consideration of the disc side. They will tell you it is the side of the rim where the stampings are and which stamping relates to the disc side orientation.
I can't remember in my case as it was a number of years ago now but could take a look at the wheel to confirm if required.

Some things to note on the MK3 front wheel. Using stainless spokes will have no relation to the original spokes as stainless spokes usually tend to be a thicker gauge. 
Tension - yes, the tension differs massively between the near vertical and the spokes controlling the offset, that does not mean that one set has very high tension, if it does you have not offset the wheel correctly prior to pulling it over to get the correct offset - check the tension on an original MK3 wheel, it might surprise you how little tension there is in the spokes. getting that initial offset is a real pain but worthwhile getting that stage correct. 
The rim must be pierced to the correct Norton 40 hole pattern for disc wheel. Also, look on an original MK3 wheel you'll notice any lettering on the rim is on different side to that on a pre MK3 rim. The drawings and much online says the lettering should be on certain side, and even the drawings have this wrong - how can it be, as the spokes are not only different from one side to the other they are also laced in a different direction due to braking. If the manufacturer of the rim suggests that the lettering should be on one side then make sure they are fully aware that the rim is going to be used on a MK3, many just assume that the rim will be used as a 'Norton disc brake' not an issue but the piercings and the lettering may not follow convention as the rim needs to be spun 180 for MK3 lacing. You'll soon know when this is wrong as the spokes will be bend either in relation to the nipple or over a and adjacent spoke as they are tensioned up. 
I have a pile of photos of original MK3 front wheels and even laced my own, if anyone wants photos then they are welcome.  
Always buy the rim, spokes and nipples from the same supplier, do not mix and match.