Fixed bolt on a Sun

I’ve got a Sun unicycle with one of those “quick release bolt” dealies. While the unicycle is pretty solid, the seat likes to twist around, no matter how tight i make it or how much of the grease I rub off the pole (that’s an innuendo!). Is it feasible to drill a hole through the seat post and put in a fixed bolt? The lady at the bike shop told me not to but didn’t give a reason (p.s. she’s a woman).


The style of clamp on the Sun unicycles doesn’t always clamp tightly. And quick release levers can be worse than bolts.

First thing to try would be to replace the quick release lever with a bolt. sells the bolt, but a bike shop, or possibly even a well stocked hardware store that specializes in fasteners should also be able to get the same type of bolt. Here’s the bolt in the catalog: Seatpost bolt. Note the little tab under the head of the bolt.

Grease the threads of the bolt and then tighten the nut. The grease on the threads will help you get the bolt much tighter than with dry threads.

If that doesn’t work then get a good BMX clamp designed for a 7/8" (22.2 mm) seatpost and a 1" (25.4 mm) outside diameter around the neck of the frame. has some BMX style clamps:
Primo Viking
Your local bike shop may have some other choices.

I’d generally hope the lady at the bike shop is a woman or you got a problem going on there.

Re: Fixed bolt on a Sun

Holy crap! are you this guy by any chance?:


You are very funny mango.(seriously)

P.S. On a Sun unicycle you can do anything you want and not feel the least bit guilty. Drill and bolt it, weld it, epoxy it, whatever it doesn’t matter. (I through-bolted mine and it held up fine.)

The problem I had with tightening a Sun frame is that the seatpost just dented a little bit more each time I tried to clamp down harder. My advice is make the clamp reasonably tight and keep adjusting it. Eventually the seatpost will spin less and less.

By the way, I have the same issue (spinning, not denting) with my new Semcycle XL frame and GB4 seatpost. My hope is this problem will go away just like it did on the Sun.


My old Sem XL used to spin. The design of the clamp meant that as it tightened up it dented the seat post so it wouldn’t slide up and down. It still managed to rotate, though.

I replaced the old clamp with an aluminium one (from a bmx shop) and that holds it a lot tighter without damaging he seat post.

A Sun is a low-end unicycle, nice ride for just getting around.

I already got a bolt put through the seat clamp and it is still twisting. I think I’m just gonna drill a hole through the seat post and move the bolt there. Unless of course this is bad?

iamthewaltrus, if you bring the uni to the Austin Juggling Society meeting tomorrow nite and we can take a look at it. We’ve had several people riding unis there each week for few weeks now. The meeting is every Thursday at 7PM, details here (ignore the old notice posted, the meetinginformation is otherwise up to date).

I wouldn’t drill a hole through the frame and seatpost. It’s just not necessary. You’ll have limited future adjustment. What happens if you grow or change to a different brand of shoes with a thicker or thinner sole. A good BMX seatpost clamp will solve the problem.

The two bolt Primo Viking clamp will definitely solve the twisting problem. The top half of the Primo clamp grips the seatpost and the bottom half grips the frame. It is very secure. I use the two bolt Primo Viking clamp on my stock Coker. With other clamps the seat would twist. With the Primo Viking clamp the seat is rock solid.

One possible problem is that some frames have the cheap stock clamp spot welded to the frame. That makes it hard to remove the cheap clamp so you can replace it with a quality clamp like the Primo Viking. If you can remove the stock clamp then try the Primo Viking. It will solve any twisting problems.

One other possible factor is that on some frames there is weld splatter and/or excess chrome blobs inside the neck of the frame where it clamps to the seatpost. If you carefully sand down the weld splatters and other globs the clamp may clamp better. Just don’t go crazy with the sanding and sand it down too far.

the half owner of the bike shop here in town is a woman, and she can wrench on bikes like none other…

Yes, hopefully being born female does not make one an unreliable source of cycling information.

In general, you just don’t drill through tubing. Especially on a high-end bike frame, but even on a low-end Sun. The problem is, the reason you want to drill it will not be as effective as it will on a Schwinn or Semcycle. Those cycles are made from thick, stamped steel. The Sun frame is thin and light, and will not do well with a bolt stuck through it. You won’t weaken the frame in any important way, but if the seat gets too much twisting force around the holes, the metal will deform and possibly tear.

As someone else mentioned, cheap clamps can poke into the frame and make dents in the post. This kind of helps hold it in place, but makes it impossible to adjust or get out in the future.

The best solution is a higher quality clamp such as the ones John Childs mentioned. They’re pretty cheap, and should do the trick real nice.