Second Wheelset Woes!

I was determined that the building of the second “budget” set of wheels, consisting of the 32 hole XT disc hubs, Sun CR18 rims and silver DT Swiss Competition spokes, would go exactly to plan and that it would progress at a fair old lick from beginning to end. I wasn’t planning to start the front wheel until I’d finished the rear and would be following the Wheelpro guide to the letter, seeing as I’ve sold Gerd Schraner’s bizarre collection of thoughts to a fellow on the Singletrack Classifieds forum – for a modest profit (assuming that he ever gets around to sending me the cheque that he’s repeatedly promised)!

This was how it was supposed to happen (and may still do so):

1. Lace the wheel: inside right hand side spokes first, then inside left hand spokes, then those of the outside right hand side and finally the outside left hand side ones. This will avoid Schraner’s bird’s nest.
2. Take up most of the slack using the nipple driver.
3. Get the spokes correctly aligned.
4. Take up the remaining slack using the spoke wrench.
5. Make the wheel laterally true (side-to-side).
6. Make the wheel radially true (up-and-down).
7. Equalise the spoke tension on either side.
8. Improve the dish.
9. Final tensioning and finishing touches.
10. Repeat 1-9 for the front wheel!

I got stuck half way through stage two! As I took up the slack on each successive spoke it very quickly became obvious that there was no way I was going to make it all the way round before the spokes became too tight. The reason was pretty obvious - short spokes - but why?

I soldiered on. The Wheelpro guide has a workaround for when you have spokes that are slightly too short and even including this extra work I had the rear wheel laced up in around an hour. I then set about putting the front wheel together to see if it had the same problem, and after correcting a couple of tiredness-related errors (well, it was late evening!) I had this one laced up in a similar amount of time. But there’s no doubt that the spokes were far too tight on both wheel for this stage of the build. Add to this that the ends of the spokes are nowhere near the tops of the nipples and that there’s also at least two turns worth of thread protruding from the nipple on each spoke and it was time to pack up for the night and have a think.

A good night’s sleep and a check on my spoke calculations the following morning identified the cause of the trouble. Like the indolent fool that I am I’d not bothered to physically measure the rims and had relied solely on the measurements in Spocalc.xls, which it turns out are about 3cm too short for the Effective Rim Diameter. The Sun rims really do have a very shallow centre line, so much so that if the ends of the spokes were to protrude from the nipples by any more than a millimetre or so they would foul the rim tape. It occurs to me that I might not actually have Sun CR18 rims but the cheaper, older CR16s which may simply be stickered up as CR18s, as the latter have an ERD 3mm greater than the former.

I have three options:

1. Carry on regardless;
2. Dismantle the wheels, buy the correct length spokes and start again;
3. Dismantle the wheels, buy Mavic XM317 rims and sell the Suns.

Option 1 would be foolish and would defeat the point of the exercise, because if I wanted a botch job then there are plenty of internet retailers ready and willing to oblige. Option 2 is sensible, but Option 3 is tempting because I was never madly keen on the Sun rims from the outset.

The Singletrack Classifieds forum provides the answer – there’s a chap on there selling thousands of spokes for less than even http://www.rose.de/ will do them for and he’s got my size! I have a choice between silver DT Competition spokes, the same as I currently have, or Alpina’s equivalent in black for £15 with brass nipples. So Option 2 it is: I upgrade to 64 black Alpina F1 ACI double butted spokes, which will have the additional benefit of making the wheels look nicer.

With luck I can sell my German DT Comps for something similar to that, as they are a much more commonly required size for MTBs and seem to fit most Shimano hub/Mavic rim combinations, so all I will have lost is the time spent piecing together and then dismantling the wheels. It was good practice, even if ultimately futile!