Summit Measurement Help

OK, I know that my measuring calipers are really old and my eyes are not nearly as keen as they used to be but I do admit that I need a little help here. I recently stripped a pin from the seat clamp of my Summit trials uni. I measured the O.D. of the seat tube at 31.2. I contacted Uni.Com and Bedford looking for a replacement. However, both said that they cannot find a replacement from any of their distributors. I contacted Kris Holms - looking for the manufacturer in Asia – but Kris said that these are off-the-rack- bicycle components and any bicycle distributor should be able to hook me up, I did a Google search of clamps only to find a few 31.0mm and even fewer 32.0mm and certainly no 31.2mm.

Can somebody who has access to a Summit, a good set of measurement calipers and the eyes to read it get me a measurement of the O.D. of the seat tube at the clamp?

Any help would be greatly appreciated.


Re: Summit Measurement Help

Tommy, regrets that I can’t help in the caliper department, but I can confirm the off-the-rack aspect. I wanted to swap the two-allen-bolt OEM clamp on my Summit for a quick release, and was able to pick up one–a Salsa I believe–at my LBS. Maybe just drag your Summit in with you and you can test what they have right there?

yeah, like my main man Tom says. the summit seat tube is a standard size…just bring it to a shop and im sure they will have a clamp that fits. if you go with a single bolt clamp make sure it is a big bolt with a 6mm hex key at least. dont go with anything that has less than a 5mm hex key bolt. the ones with the 4mm hex bolts are easily stripped.

isn’t that measured inner diameter? so possibly a 31mm? as others have said, go to bike shop, say “I need a new clamp for my unicycle.” someone should be able to help you out.

not a seat no…

or sould i say " no not a seat tube, no"

Thanks, guys.

Knowing that one of the Salsa clamps will fit gives me hope. That Salsa clamp comes in 31mm and 32mm. I have tried the “Hi guys, I need a seat clamp” routine - with no success. That is why I wanted the measurement so that I could expand my search without actually having to be there in the shop with my uni .

The quest continues.


If I remember correctly, the inside diameter is 29.2mm and the outside is 30.7mm. I’m actually not sure on the inside, because with the above figures, that leaves a frame thickness of .75mm. But then I never measured the frame thickness, and three quarters of a mm sounds really small. I have a KH post (27.2) and a shim, so maybe those numbers are correct. I am pretty sure on the 30.7mm because that’s what Darren told me and that’s also what the bike shop told me they couldn’t get. I was lucky enough to have the previous owner send me the clamp.

Good luck.

It feels like it is time for me to call Steve Howard. I may need start with a block-o-aluminum and just make one. With all the time that I’ve lost looking for a clamp I could have made one. At least it is winter and not cutting into my riding time as much as it would have in September.



I finally found a seat clamp that will fit my beloved Summit. Though it is only a single bolt clamp it is holding firm. FYI: The seat clamp size that fits was marked as 31.8mm.