Monday, 13 July 2015

New wheel

As regular followers will know, I ride a B'Twin Triban 500 road bike. B'Twin is the house brand of French chain Decathlon and while it's a cheap bike, overall I'm very happy with it. Besides, it seems to climb hills better than a few hideously expensive carbon-framed bikes I've encountered out on the road. Nudge, nudge, wink, wink. Say no more.

Now while I rate B'Twin bikes (I also own a Triban 3 road bike, though that's in need of some serious TLC) at least on their road bikes the stock B'Twin wheels are rubbish. In fact, the bikes are probably only fitted with B'Twin wheels to stop the chainrings digging into the showroom floor. Seriously, the B'Twin wheels *are* that bad!

With both the Triban 3 and the Triban 500 I ran into exactly the same issue - after around 1000 miles, the rear wheel bearings pack up and the wheel needs to be replaced. The front wheels tend to last longer, perhaps 3000 miles, but it is still only a matter of time before they too fail, again with the bearings packing up.
I've had a deal on Mavic Aksium rims and while the Aksiums are nice wheels, with super-smooth, sealed bearings, the Mavic rims are soft as butter. To me, that simply means the rim will wear out completely in 6 to 9 months. By contrast, the rear rim on my old hybrid has given many years of faithful service, often over offroad terrain, while carrying laden panniers. Now to be fair, my hybrid has wider, heavier rims, but what I'm referring to here is the brake surface on the rims. That's where the Aksium rims wear through in a hurry.

Some time ago I bought a new Shimano Claris rear hub and rebuilt the rear wheel around that, re-using the B'Twin rim and spokes. That was the 1st proper wheel I'd built. I didn't have any wheel-building tools - other than a spoke tool - and made a crude wooden wheel-trueing stand. I chose a Claris hub because Claris is Shimano's entry-level road bike range and it was cheap. The idea was that if I messed the wheel up badly then it wouldn't have been a very expensive lesson. Since then I've done around 2000 miles on that wheel and it's still true.

I've mostly been riding on the Mavic wheels, but recently I had the rear rim failed on me. Usually I'd expect the front rim to go first, though close examination showed it wasn't far from failing either.

As a result, I ditched the Aksium wheels. On the rear I fit the rebuilt Claris-hub wheel, while a stock B'Twin wheel went on the front. The bearings on that wasn't good, but I still managed to finish the Dartmoor Classic on it, and gain a silver medal in the Grande. During the Dartmoor Classic the bearings started making a fair bit of noise though!

Confident that I can build a front wheel (rear wheels are harder, as they are "dished") I ordered a new rim and hub. The rim is an aluminium deep-section (3cm) semi-aero Rigida rim and the hub is a Shimano Tiagra. Though the rim is far from the lightest on the market, they have a well-established reputation for being strong and besides, I felt the semi-aero design will offset a marginal weight gain. Both rim and hub are 32-hole.

Now I'm no wheelbuilding world expert. I don't claim any secret knowledge and I openly acknowledge that I have lots to learn. When ordering the hub and rim, I deliberately didn't order any spokes, figuring I'd simply re-use the B'Twin spokes and nipples. Except there was a problem...

As the Rigida rim is far deeper than the B'Twin rim, the space between it and the hub is smaller, meaning shorter spokes are needed. I started lacing the wheel, using the traditional 3-cross pattern and had done one side of the wheel before I realised I'd never be able to tension the spokes enough. They were simply too long! A schoolboy error, really, but there you go.

The next course of action seemed obvious: buy new spokes of the right, shorter length. While looking online for spokes (I didn't have a clue at this stage what length spokes I'd need) I found a number of wheel-building sites and some of them had photos of non-standard ways of lacing wheels. This reminded me of something I'd once seen on the absolute best web site in the world, ever, Instructables.com - a wheel laced so the spokes made a flower pattern. Some Google-fu later and I was looking at the relevant 'Ible and decided that I wanted a wheel laced like that. Even better, when deliberately setting out to build a wheel like that, you will need longer spokes! Clearly the fact that I only had longer spokes was a sign. This was destiny knocking on the door loud and clearly, and who am I to go against destiny?

The process of lacing a flower wheel starts off by 1st lacing it as a 3-cross. Once both sides of the wheel are done, the fun* starts. From the hub flange, follow 2 spokes that cross each other - one with the spoke head on the inside of the flange and the other with the spoke head on the outside. Unscrew the nipples holding them to the rim, then swap holes, twisting the spokes around each other as you fit them. When done, move on to the next pair, until you've done both sides.
*Fun = slow going with many muttered curses.

Once done with that step, you will need to start crossing over one spoke from a pair of crossed spokes with the nearest spoke from the next pair of crossed spokes, and keep doing so until you've worked your way around both sides of the wheel. When done, your wheel should resemble this:

Of course, all you've done so far is get each spoke wrapped around other spokes in the right way, and secured it with a nipple in the correct rim hole. You still have to true the rim and ensure that the wheel isn't egg-shaped. This is where my crude, wooden trueing stand comes into play. With the wheel secured in the stand, able to spin freely, I started the task of trueing the wheel and adjusting each nipple so the hub was at the absolute centre of the rim.

Trueing a wheel is relatively straight-forward, usually, but this lacing pattern adds some *interest* to the whole process, making it far more tricky. Once the wheel is true, the spokes still need to be properly tensioned, so a fair old bit of work remains. I had to be careful, making small adjustments as I went along, so the wheel remained true while I was increasing spoke tension. As the spoke tension started increasing, the curvature of the spokes started easing out. When you increase the tension on one spoke, it automatically increases the tension on the spoke it's twisted with, several rim holes over. Finally after some time, the wheel ended up looking like this:

From what I've read (no, I've never built a wheel laced like this before) I knew it was very likely to go out of true during the first few miles and that I may have to tweak it 2 or perhaps even 3 times.

This is due to the spokes settling down. I was also prepared for some noise from the wheel, as the spokes initially twanged and shifted against each other.

As I'd moved the tyre and inner tube over from my old front wheel, I didn't have a spare wheel to ride on. This simply meant the new wheel was tested in anger, so to speak, during my shorter-route 12-mile commute to work. At the start of the first hill the noises started, especially when I was climbing out of the saddle, but as the miles went by the wheel became more silent. After around 6 miles, it started rubbing against the brakes, so I knew it had warped somewhat. I stopped and inspected everything and was happy to proceed, after having adjusted the brakes a smidgeon, just so they don't rub against the rim anymore, then set off again.

The rest of my commute was fine, with only a very occasional noise from the front wheel.

What I had noticed was that my free-wheeling speeds were higher. Down Chittleburn hill on the previous front wheel I'd usually go up to around 28mph, but coming down the hill I went up to 32mph. This rather large difference I put down to the old wheel's bearings being shot. I'll have to test the long-term stability of the wheel, of course, but I expect my commute alone will be a good enough test. I typically take the shorter 12-mile route to work and the slightly longer 15-mile route home. Both routes include some iffy road surfaces and a fair amount of climbing.

I'll update this post over time and report on the wheel's stability.

Update:
I have so far done 420 miles on the new front wheel, and had to true it 5 times. Currently it's holding steady and I don't expect it to warp from here on. I've also built a matching rear wheel, which is on the bike now. I'll do a separate post for that.