Seat post shim?

[snapper_37]

Probably a thicko question. Have recently got a cracking MTB from fleabay but want to upgrade a few bits and bobs, starting with the post. The seat post is 26.8 which seems to be quite an obscure size and have found my options are limited for swapping How do I/what do I get shim wise in order to get something a bit more easy to find,

Thanks.

 

[mickle]

26.8mm is (was) a popular size - far from obscure. Though it's not so common now due to the popularity of non-ferrous frame materials. Keep searching, you'll find a nice one.

Coz actually you'd only shim it down to an even more obscure size.



It's all about standards. There are only three sizes of front mech. They are described in metric: 28.6mm, 31.8mm and 34.9. The first two - the oldest - reveal their origin when converted into Good Olde Imperial: One and an eighth - and one and a quarter

28.6 millimetres = 1.125 inches
31.8 millimetres = 1.25 inches
34.9 millimetres = 1.37 inches

Your frame is steel, and the quality of the steel used determines the wall thickness - the better/stronger the tubing the thinner the wall section. Which has a knock-on effect on the diameter of the seatpost - the thinner the wall thickness the larger the seatpost.

531 (steel alloyed with Manganese and Molybdenum) tubing has an internal diameter of 27.2mm. High grade Chromoly (Chromium and Molybdenum) an internal diameter of 26.8mm. And so on.

 

[snapper_37]

Oooh ta Mickle. A wealth of knowledge and advice as usual. Have found a couple so will just keep on looking as you say.

 

[mickle]

Oooh ta Mickle. A wealth of knowledge and advice as usual. Have found a couple so will just keep on looking as you say.

 

[fossyant]

Decathlon do posts that can be used from the Peugeot standard of 25.x to 27.2 - with shims.

My Diamond Back MTB is 27.0 and could do with finding a spare post so can leave the tag-a-long bracket on a post and saddle, to speed up swaps.

 

[HLaB]

I could be wrong but 28.6mm was the size of my old bike post, when I replaced it I used the size smaller and a coke can shim.