Friday, September 23, 2016

Re-shod the Steed

For a while I've wanted to build a new wheelset for my mountain bike. So far I've dabbled in the art of wheel building, and ever since I started playing around with it, I've wanted to scratch build a new wheelset.

For many bike mechanics, knowing how to build wheels is an important checkpoint in skills development, and for me, it's no different. The first time I did it was when I replaced the fork on my first full suspension mountain bike. The new fork had a different axle type, so I had to replace the front hub. I got it back together and it worked well.

The only thing holding me back was the wheels I had were working fine. But then, one day, they weren't. The rear hub bearings were shot and I wasn't able to get replacement parts for the OEM hub.

Pitted Races - No Good.

I went through several iterations of deciding what to do, including simply rebuilding the rear wheel with a new Shimano M525a hub. (That was my second wheel build and I considered it a practice for this build.)

At last I decided on a plan, ordered spokes, and waited for stuff to arrive. During that time I found some great deals on Shimano SLX hubs with centerlock brake rotors (which I prefer to 6-bolt mount). I was lured by the siren song and bought them. It was like  a Shimano Christmas. 

Alas, it was not to be. When they arrived I found I had made an important miscalculation. The hub flange diameter of the SLX hubs were much smaller than the hubs I was originally planning to use. Basically, this meant I would have to reorder spokes, and the spokes I had would not be usable.

So, facing extra expense, and worse, extra waste, I decided to send them back and return to my original plan.

Here's the setup.
Front Hub: Giant OEM (Reused), 15 mm thru, 32 hole, 6-bolt brake mount
Rear Hub: Shimano M525a, 135mm QR, 32 hole, 6-bolt brake mount
Rims: WTB ST i23 TCS, 27.5, 32 hole
Spokes: DT Swiss Competition Double Butted, 2.0/1.8 272 mm, 273 mm, 274 mm
Tires: Continental Trail King 2.2, Chili Compound with Protection sidewalls

Since I decided not to buy the fancier hubs, I had extra money for rubber. For a long time I've been a big fan of Continental Tires for bikes, especially the King series. Just before I sold my Trek, I put Trail Kings on it. My last mountain bike came with Maxxis Ikons, which I didn't care for. After a while I swapped those out for Mountain Kings. Now, my Giant came with Schwalbe Nobby Nics. I thought these worked well, so I wasn't in a big hurry to get new ones, but now I was at the intersection of new wheels and great end-of-season sales. I couldn't resist.

Passing the torch from the Schwalbes to the Continentals.

 And now for some gratuitous images.

I learned a lot by doing the build from the ground up. Spoke lengths have to be calculated very accurately and made to within a millimeter of the right length. I also made careful measurements on the wheels that I took apart and compared those with the spoke calculations to see what they did at the factory. Based on this there are a couple things I'll do different next time.

1. I'll order 14 mm nipples instead of 12 mm.
2. I'll add 1 mm or 2 mm to the calculated spoke length because it would provide a little better thread engagement with the nipple.
Having the extra length on the spokes might make item #1 less important, but we'll see.

I can't wait to get them out on the trail. That will be the true test. Will I have nipple breakage due to over tight spokes? Will I have rim cracks for the same reason? Is my spoke tension even enough? How long will I go without having to retrue? The answers to these questions will determine whether I got a passing grade or not.

The next step is to decide if I'm going to switch to tubeless.

Here's the reading and study list.
Master Wheel Building DVD by Bill Moulds
The Bicycle Wheel by Jobst Brandt
Sheldon Brown
Approximately One gajillion Youtube videos

Spoke Calculators
DT Swiss
Pro Wheel Builder


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