Since I swapped my 29" tire for a Maxxis Hookworm, I noticed that my wheel is not aligned in the frame. It never occurred to me before as I had a knobby tire, but the Hookworm being so round, I couldn’t help but see it:
It’s not shocking from the center of the tire, but if you look closely, the center mark on the tire (from the mold) is not aligned to the seat post:
Yet, if you compare both sides, it’s pretty clear:
A good 3 or 4mm difference!
Of course, as I’m completely OCD (aren’t all unicyclists?), it had to be the explanation to my problems with going in straight lines. Blaming the equipment is easy, hey…
It became an obsession, so I had to come up with a fix. So I thought: maybe my wheel is not true. I figured that turning the wheel around would tell me if it was the culprit. I could always swap the cranks if it was better. But it didn’t make a difference: the offset was still exactly the same. Well, the frame had to be the culprit then.
And it became obvious when I took out the bracket from one side only, leaving the other side pretty tight:
The wheel was perfectly aligned, with no play. I tried to retighten the side I had just unbolted, the wheel went off right away. More than a bent frame (that can happen, I bought that uni second hand and have no idea what it went through in the past), I thought it was probably a badly made frame, with one leg longer than the other.
For a while, I’ve been looking for an excuse to get a 2015 KH uni. That was the perfect opportunity - CDK has started to offer 2015 KH frames, so I figured I could have a new uni for cheap. Just swap the frame. I have a Zero saddle and a disc brake I could install later (my “bent” frame doesn’t have the disc mounts). Got the new frame, and today I got the tools out to do the swap.
And it’s exactly the same problem…
It doesn’t make any sense, does it? Same offset. I even measured the bearings diameter, in case, and they’re identical.
So I ended up cutting a little insert to put in the bearing bracket. First one I made (.5mm thick) was too thick and the offset went all the way to the other side. Found thinner material (.25mm) and now my wheel is exactly in the middle.
Might get a wheel and build a spare 29". After all, I have all the necessary parts laying around.
Is your wheel perfectly aligned?