Seatpost Shims

[Drewson]

Hi all,

Just bought a McMahon Ti seatpost for my McMahon Ti frame. It was listed as 27.2, but on measuring (& trying to fit it) it seems to be about 25mm or something (25.4mm?).

The welds on McMahon frames had a bit of a poor reputation, and i'm concerned i may risk destroying my frame by using a shim to fit my seatpost. :cry: , especially as i've heard seatstays have apparently come away on McMahon frames.... could be only the suspension McMahon frames (mines a hardtail) this happened to, but not sure...

Any advice on whether i should avoid the shim idea? :?

McMahon Ti posts don't come along everyday unfortunately, and i'd like to keep the bike as original as possible....

Cheers,

Drew

 

[tintin40]

If in doubt then I wouldn't do it. Better safe than sorry. Aren't USE post 25 with out shim?? Then maybe no shim

 

[Harryburgundy]

I'm certainly no expert on the subject, but would a good deep shim like one of these
http://www.chainreactioncycles.com/Cate ... goryID=215
solve your problem :?:
HB

 

[Drewson]

Thanks TinTin & Harry....
Very tempted to give it a go, as i may be worrying about nothing.
Drew

 

[stevet1]

I think I'd be tempted to contact the original seller if it was advertised at 27.2? unless your happy that you would have paid the same knowing it was 25. something.

OTOH Most Ti frames have an internal shim already in place so the decision about using a shim is already made for you.
As mentioned though USE shims work from 25mm, if your post is 25.4 (1") then you're going to struggle to find a correct size shim. Although you could feasibly use a 25 > 26.8 which should be the same as 25.4 > 27.2.
As long as you can have enough seatpost to make contact with the shim all the way down its probably going to be okay…

 

[Drewson]

Yeah, still deliberating on whether to contact the seller....Wasn't cheap either.

No shim in place at the mo', but i have a feeling that the post is probably 25.4mm. It's so damn difficult to say if thy're is 0.4mm difference :? Anyhoo, tempted to try a nice long 25.4mm-27.2mm shim.

If i can make it work it'd be good, esp as it may be a while before i find another McMahon Ti post...

Drew

 

[Elev12k]

I would simply try several. I would see to it that it is properly filled. Personally I use a 29.8 outer dia shim in a 29.4 frame for example. Fits tighter. Paid 2.50 euro per shim.

Shims are normally 8cm long. Only USE adds 2cm.