A recently bought a 2004 KH 20, new. I have noticed that the wheel is not centered in the frame. One side of the tire is about 1 cm from the frame and the other side is about 1.5 cm from the frame. This difference is easily noticeable when you take a close look. I am not surprised that it is not center perfectly, but this large of a difference seems out of the ordinary.
Does anyone have a guess as to why this might happen? Is it harmful?
You mention the tire and the wheel. You say the tire is not centered in the frame. Is the wheel also not centered in the frame? Do both the wheel and the tire run true?
The problem you describe can be caused by an irregularity in the shape or mounting of the tire. It could also be caused by an improperly trued wheel where the spoke tension is uniformly greater on one side of the wheel. The frame legs could be bent or the length of the legs on the frame could be slightly different. The hub could be improperly centered in the frame. There are many more possibilities. Take a closer look and see if you can tell us more.
Check the unicycle by removing the wheel and flipping it around (make sure to flip it back after). If it still favors the same side of the frame, its the frame. If it favors the opposite side, it is the wheel. If it is your frame, it isn’t an issue, one of your fork legs is slightly longer than the other. This usually is only a problem if the tire rubs. 2 of my frames (and several others I have seen) have this issue. If it is the wheel try reseating your tire, and if that doesn’t work, you may need to true your wheel.
I had this same issue with my 24" Torker DX when it arrived new from UDC. I had to lean to one side as I rode to keep it going straight, but then I noticed the wheel (and tire) was closer to one side of the forks as you described. I added some shims to one side of the forks at the bearing seat, and this put the wheel/tire dead center after a few attempts. I cut the metal shims out of the side of a coke can, and trimmed these to fit loosely into the bearing seat before bolting the bearing cap on the other side.
what happens is frame “leans” at the leg/crown joints. sabin bent a Yuni frame pretty bad trying to grind. He landed hard on the bearing housing which caused the frame to lean towards the grind side and tire to rub on the non-grind side.
It seems like there is a lot of welding going on in the crown area of a kh frame. All the heat causes expansion if it dosen’t contract equally the frame could be slightly off. but if your tire isn’t rubbing, there is nothing to worry about.
Thanks for all the advise. I finally have some pictures to show the magnitude of the problem. As you can see, the tire is noticably off center but in no danger of rubbing. I tried to take these from an unbiased angle.
The wheel is true. I flipped the wheel the other direction on the frame, as was suggested, and the wheel still favors the same side of the frame. So it must be a frame issue.
Is this off center enough to worry about? I am thinking about trying shims.
I can’t tell if the frame is bent from the photo. You should be able to roughly tell using a carpenter’s square. If you’re going to shim, you want to move the tire by half the difference of the distances from the left side of the tire to the frame and the right side of the tire to the frame. The shim needs to move the right leg up as viewed in the photo so should be placed on top of the right bearing. It should be roughly thick enough so that when multiplied by the ratio of the wheel radius to the center bearing spacing you get a value equal to half the difference of the distances you measured. Then iterate from there.
I have the exact same wheel as you and mine does the same thing…But to the other side…I just dished the wheel so that its centered in the frame…But i dont recomend it. Id say you should try some pop can shims.
my kh4 dosen’t meet the bearings of the kh4 hub evenly , and neither does sabin’s. looks like you might have the same issue. loosen the bearing housings, and re-clamp with the frame in a more centered position.
to answer your question, no, it is not off centered enough to worry about. riding it like that wont do any damage to the uni, it’s just cosmetic.
However, it is not “just cosmetic” if it requires the rider to lean to one side to compensate as I found to be true in my case. Centering the tire fixed the “lean” issue as well. Maybe I’m just more sensitive to this kind of thing. :>