Who here has the Sun 28” uni?

Who here has the Sun 28” uni?

I need someone who owns this uni to measure the outside diameter of its seat tube for me, so that after I shorten the seat tube, I can already have the proper size of replacement seatpost clamp on hand.

And one more question, if you happen to know: What is the interior width of the rim that comes with this uni? Once I know that, I’ll be able to determine what tires are compatible with it. I’m considering switching the stock tire out for one that’s 700c x 32c.


Do you mean you’re shortening the seat POST or the seat TUBE?

Usually, shortening the post is enough, in which case the clamp you already have will fit.

Or haven’y you got the uni yet?

28 inch is a nice size of uni. You should be able to fit quite a wide range of tyres on it - it will be a fairly standard rim width, and fairly versatile.

Thanks for the response. I’m talking about the seat tube - the part of the frame that accepts the seatpost. The seat tube on the Sun 28” is really tall, so in order for me to reach the pedals I will have to shorten it (and the seatpost as well, but that’s a mere amputation). No, I don’t have this unicycle yet, I’m just going by what I’ve learned about it so far. Once I shorten the seat tube, the integrated seatpost-clamp will be gone, so I’ll need to have an aftermarket clamp available. That’s what I’m inquiring about here - the size of the aftermarket seatpost-clamp that I’ll need. I’m hoping that an owner of the Sun 28” will determine this for me, by measuring the outside diameter of the seat tube.

Yeah, I’m looking forward to having a big uni so that I can try components of various sizes with it.

Oops, I think I missed what you meant here. Are you saying that I should be able to replace the 700c x 45c tire that came with it, with the 700c x 32c tire that I’d like to use? The number difference seems big to me, and I don’t really know how to interpret it. I have heard that using a tire that’s considerably too narrow for the rim leads to problems.

Hello Saul,
The outside diameter of the frame neck (that the seat post slips into) is 1.0 inches. You may be able to use the old clamp after shortening, I was able to.

I submitted a tutorial on shortening a frame which may be helpful.


Feel free to add to it based on your experience.

Excellenté! Thanks, Ken. Both of your posts have been very helpful. I will certainly add to the tutorial if I think of anything else that might be good to know for shortening the frame neck. BTW, I originally called this part of the frame the “seat tube” because that’s common terminology for the part of a bike frame that accepts the seatpost.

I’m still pondering whether or not the 700c x 32c tire (Avocet Fasgrip Duro Plus - a wide slick tire meant for touring bicycles) will work in place of the tire that comes stock on the Sun 28 (700c x 45c aka 28 x 1.75). Darn these cryptic figures that companies use for tires.

Hello Saul, ‘seat tube’, ‘frame neck’ I don’t know which is more correct.

Good luck.

Yeah, they’re both good enough terms. Didn’t mean to sound like I was trying to correct you.

Thanks again for the help. I will try to update this thread after I’ve made the modifications.

um, how tall are you? I’m 4’ 10" and can easily ride one of these. I can ride a 36" too.

you might not have to shorten it.

I wouldn’t expect it to be a problem to downsize the tyre by a few mm like that.

However, why?

Most people seem to prefer the fattest tyre they can get, rather than the thinnest. It makes sense for a number of reasons.

Personally, and it’s only me, my 700c unicycles have a 23 mm tyre and a 28 mm tyre respectively. The 23mm in particular has to be ridden at high pressure - around 120 - 130 psi which I think is about 8 or 9 bar.

Fat soft tyres make for more manageable, faster, more versatile unis.

I’ll find out if I need to shorten it when the time comes. If I don’t have to shorten the frame, that’s great. But if I do have to, I’ll be glad that I won’t then need to track down a seatpost clamp of the proper size. The promo info for this uni on unicycle.com say that the rider needs to have at least a 32” inseam (it also says that people who are 5’3” can ride it, which I’d say contradicts their inseam statement, enormously). I’ve read various accounts of people needing to shorten their Sun 28 frame, so I won’t be surprized if I’ll end up having to do it too. Doesna seem like a big deal for me, fortunately. I’m looking forward to a cheap, versitile ride.

The trouble is that the tire which comes stock on the Sun 28, judging from the promotional photo at least, is that it’s a holdover from a knobby dirtbike, or something. I won’t be riding this wheel off of the pavement, so I want the slickest tire that fits the rim. Hopefully I will be able to find a wider slick tire, but the 32c is the widest size that I’ve seen so far.

i know a lot of 29er riders like the schwalbe big apple, its not entirely slick, but you should consider it.


I think I’m going to go with the Continental City Contact. It has a nice, slick section up the middle and comes in sizes up to 700x54/28x2.21.

Too bad I can’t buy real slicks in this width. There are even true slick BMX tires available in this width.

Hello Saul, No problem. I have noticed that ‘seat tube’ is the better term to use. Thank you.