The joy of bike building

Building your own bike is highly rewarding. Not only do you get a bike where every part has your own individual stamp on it, but you get the personal satisfaction of knowing you made it work.

However, you will run into some truly idiotic situations if you mix parts. Of course mixing parts is the whole point of building a custom bike.

So here’s the most recent bit of ridiculousness that I’ve had to deal with;

Giant XTC

I’m building a bike for a friend right now, a Giant XTC. I believe it was the second best hardtail that Giant made in 2005. It’s very light, and it was certainly state of the art in it’s day. It just looks like a serious bike, doesn’t it?

He brought me a frame with a box of parts, and said “Make it go!” This is my dream scenario of course, but it has required a lot of background work, like finding the right disk brake adapters, and the handlebar clamp for the brakes (which was so silly in fact, that it deserves it own post, coming soon).

I was setting up the brakes yesterday, which are Avid XX World Cup units, with the Shimano XT wheels and Ice Tech rotors, and when I put the rear wheel in the bike, it was locked in position. I’ve had this happen before with adapter bolts that are too long, but that wasn’t the case here.

Shimano Ice Tech rotor

This time, it was the weird Shimano Ice Tech rotor design. It’s a two-piece deal, with the rotor riveted to a five-arm “spider.” Others have six-arms, and some have four, but these have five.  I don’t believe there is any ice involved in the construction of the rotor.

You can see the splines in the hole in the center of the rotor in the picture above. These match up with splines on the hub, and then a lockring holds it in place. The very same lockring used to hold the cassette on the rear  hub – which is really cool, because everybody should already have these parts, and the tools to work them, kicking around.

A “regular” rotor, ie EVERY OTHER rotor made in the world, is a flat piece of metal with six bolt holes that you attach to the hub. It’s much much thinner than an Ice Tech rotor. So, if you look where I’ve put an arrow in this image, the five-arm spider on the rotor is running into the brake caliper.

Welcome to your custom mountain bike…

It’s OK though because we’re professional mechanics and we can make this work. I have identified five different ways to fix this problem, and here they are, presented in increasin levels of difficulty/stupidity/sketchiness;

  1. Different brakes. I’ve got a set of Maguras that I’m not using, so I can just slap them on here and see how that goes. In fact, I can just  look at the caliper and get a pretty good idea of whether or not they’ll fit right away.
  2. Different wheels. I have a set of Shimano hubs of Alex rims with regular rotors that should easily fit. Except that the front rotor is a 180mm, and I’d need a different adapter on the front for that to work.
  3. Washers. I can tuck a couple more washers under the caliper, pushing it up a little bit. I don’t need a lot more clearance here – I may only need one washer on the back bolt. However, I have to make sure that the bolt is in the adapter far enough for it to be safe.
  4. Centerlock adapter. You can buy an adapter to run a regular rotor on a centerlock hub. In fact, I’m pretty sure I have one, because I tried one on my Blizzard when I wanted to run XTR wheels and Formula disks – it didn’t work. The adapter pushed the rotor too far outboard, and there was no way for the caliper to move out to compensate. So, not too confident in this option.
  5. File it down. I can force the wheel to turn without a lot of effort, so maybe I don’t need to file the caliper that much to make it work. I would worry about getting aluminium filings in the brake itself. And it was designed the way it was designed for a reason I’m sure. Modifying it this way may not be so safe.

I think I’ll start with #3. There are some other issues with these brakes, so swapping them might still happen, but if I can just fire a washer in there – that’s easy. #5 is pretty tempting too.

The washer would go right where the yellow arrow points, and in making that yellow arrow, it occurs to me I can fix this issue really easily. Notice there are a pair of washers above and below the caliper. They’re made to work together – one has a concave face, the other is convex.

These washers allow you to angle the caliper relative to the adapter (the black part here). These are the same washers used in mounting pads on V-brakes. And in the two sets of washers, there’s always a fat one and a thin one – this allows you to adjust the V-brake relative to the rim, as it should be straight up and down when it contacts the rim.

I hope this is all making sense…

Anyway, looking at this picture, it sure looks like the fat concave washer is on the top, so if I move it to the bottom, that should give it the clearance we need to make this work.

Maybe it’s not as bad as I thought. I’ll keep you updated.

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