Does anybody know the seat clamp size for the nimbus II frame? my messuments arn’t acurate enough 
If I remember rightly (which I probably don’t), the seatclamp size you need (assuming you have a 25.4mm seatpost) is 28.6mm. - don’t quote me on it!
Pop into a GOOD local bike shop and they should have a vernier calliper to measure the seat tube for you and maybe they might even be able to sell you the right one.
well I did just that a while ago and the guy said a number in the 20s so I assume your right. I’m sure sombody here will know exactly though.
for the frame, seat post, and seat post clamp you use the same number.
for the nimbus 2 frame it is a 25.4 frame. referring to the ID (inner diameter).
for the seat post it is a 25.4 referring to the OD
and the clamp is also 25.4 referring to the size post it holds.
so you need a 25.4 seat post clamp
no, it needs to fit around the nimbus seat tube, which would have an OD of >25.4, which is it’s inner diameter, 28.6 sounds more accurate, I don’t know how thick the tubing is on the nimbus frames.
its 1mm ish
I’ll try an get better messuments tomorrow
…
the number is not the actuall size of the ID of the seat post clamp.
when you order a custom uni, would you rather say " i want a 25.4 seat post, a 26.8 frame, and a 28.6 seat post clamp." ( and have to remember all those numbers) or say “i want a 25.4 seat post, frame and clamp”. (all you need to remember is 1 number)
the ID of a 25.4 seat post clamp does sound accurate at 28.6, but you go into a bikeshop and say " i want a seatpost clamp with an ID of 28.6" they will most likely give you a funny look.
I understand what you are saying and you have a good point. but I’m buying online so I just need a size number
Despite unicycle.com listing it that way (it does make it easier to buy stuff from their site though) a 25.4 seatpost will not work with a 25.4 clamp as the seat tube is thicker the 0mm as the majority of seatclamp manufactures (let’s ignore UDC here) refer to the external diameter of the seat tube( as in the frame tubing) not the seatpost because not all frame tubing is the same thickness.
if the tube is about 1mm thick and the seatpost is 25.4, it’ll probably be something from 27.4 (accounting both sides of the tube) upwards.
If the bike shop will let you pop down there with your unicycle and get them to measure accurately the external diameter of your frame and then go from there.
Despite unicycle.com listing it that way (it does make it easier to buy stuff from their site though) a 25.4 seatpost will not work with a 25.4 clamp as the seat tube is thicker the 0mm as the majority of seatclamp manufactures (let’s ignore UDC here) refer to the external diameter of the seat tube( as in the frame tubing) not the seatpost because not all frame tubing is the same thickness.
if the tube is about 1mm thick and the seatpost is 25.4, it’ll probably be something from 27.4 (accounting both sides of the tube) upwards.
If the bike shop will let you pop down there with your unicycle and get them to measure accurately the external diameter of your frame and then go from there.
ignoring UDC
everything i have said still applies.
you are right a 25.4 seatpost clamp’s ID is not 25.4
actually most seatpost clamps are 2 layered in the middle (one over the seat post and one over the frame)
so should we call it a 25.4and 27.4 seat post clamp to confuse us more?
it is designed to work with a 25.4 frame and 25.4 seatpost.
which makes total sense.
and if you want to be technicall. a 25.4 ID frame and and a 25.4 OD seatpost would not work. because a minescule layer of metal would have to take up the same space. so should we make the seatpost 25.39999999(repeating)?
and their is nothing wrong with taking the uni into a bike shop.
sorry I forgot to ask because I just remembered occassionally seat clamp manufacturers actually have clamp size etched on the clamp. Have you taken the original clamp off and taken a look all over the clamp to see if it’s size is written on it anywhere?
here is proof supporting what I said, we all know KH’s are 27.2, well, UDC lists the clamp size as 32mm.
here’s the link http://www.unicycle.com/shopping/shopexd.asp?id=1032
NO! UDC says"Aluminum construction in black with Kris Holm logo on the front, 32mm internal diameter, weighs 68g. These clamps will only fit the Aluminium KH frames."
They list the ID as 32.
so what is your point?
delcypher: never bothered. i can tell what it fits by looking at it.
here it is again, but it seems like they variate between both methods, between the OD of the seat tube, or the OD of the seatpost, they use both at different times
Here it is my way http://www.unicycle.com/shopping/shopexd.asp?id=245
and your way http://www.unicycle.com/shopping/shopexd.asp?id=928
- It’s true that most seatclamps have two interal diamters, the larger one is the important one. The smaller int. dia. is the collar which stops the clamp sliding down the frame.
‘So should we call it a 25.4 and 27.4 clamp to confuse us more?’ - I’m affraid we don’t have much choice because that is the way seat clamp manufactures measure it. Personally I think it’s better that way as not all seat tubing is the same thickness which means a 25.4 seatpost will not always go with same clamp.
‘because a minescule layer of metal’ - the frame is not minescule it’s probably about 1mm thick which if you count both sides of the seat tubing(frame) is 2mm so the clamp would need to be about 2mm bigger than the seatpost, making the clamp >27.4mm. That is not a minescule difference.
@thejdw - Personally I think 28.6mm is probably the right size assuming your frame takes a 25.4mm seatpost as when I worked for a bike shop in the past a 28.6mm clamp always went with the bikes that had a 25.4mm seatpost (the seatpost size will written on your seatpost by the way, near the bottom underneath the safety mark.
this thread is not worth argueing. i am right. i know i am right. maybe i am not getting my point across. at this point do i really care you don’t believe i am right? no
@thejdw take it into a bike shop to get the size seat post clamp you need. or just get a 25.4 which is what you need
Is it me or does that come across as slightly arrogant and conceited? Ah well seeing as we’re going nowhere slowly, I suggest as torkerdx has said to go the bike shop, they should be able to sort something out for you.
-@thejdw I still personally thick you’ll be needing a 28.6mm clamp or round about that area. Let us no how it goes so we can settle this argument properly.
Just a quick note in case anyone finds this in the search. The advice above is wrong. Do not follow it if you want to buy something that works on your frame, you’ll end up buying something too small, and being screwed.
A 25.4 frame refers to the ID of the frame, correct. A 25.4 post refers to the OD of the post.
But the clamp sizes are measured in terms of the inner diameter of the clamp.
That is why when you look at this seatpost and these seat clamps, the numbers for the seat clamps are all slightly bigger than the numbers for seatposts.
If this wasn’t the case, frame materials that use different thicknesses, would have to have different clamps, you’d have say a 25.4 aluminium frame clamp, a 25.4 steel frame clamp, a 25.4 really fat steel frame clamp etc etc.
Joe
I’m gona order a 28.6mm, I’ll tell you if it works