26.4mm seat post need a shim to fit this

[martinn]

Hi all,

I am in the process of converting my Thorn voyager Tandem, to allow my 5 year old to ride on the back. Crank shorteners work, have saddle and seat post, and handlebars. the problem is fitting the handlebars to the stoker stem, I cant easily due to the arrangement of the bit that holds onto the bars. It has a single screw point so you have to slide the bars in and out, after removing anything that is on the bars such as grips.
So i am looking to get a new stoker stem, easy. But the problem is that the seatposts are 26.4mm, which seems possibly unusual now, the stoker stem will fit a 27.2mm seatpost. So i need a shim with an internal diameter (ID) of 26.4mm and an external of 27.2 (or 28.6mm) which are the option for the stem. I cant seem to find a shim which has an ID of 26.4mm. Am I making a basic error here or can someone suggest where I could get hold of this.

Many thanks
Martin

[Brucey]

best to think of it in terms of wall thickness;

some options;

1) 0.4mm shim stock

2) 1.1mm shim stock

3) a shim of a different diameter but the correct wall thickness (you may need to file the ends of a 27.2mm ID shim so they don't touch one another)

cheers

[martinn]

Cheers Brucey, I thought filing down a larger one might be an option, so will try that
Martin

[Brucey]

yeah, but file the ends down if you have to, not the diameter, eh...

cheers

[531colin]

Plenty to go at here.....http://problemsolversbike.com/products/seatpost_shims

[martinn]

Thanks Colin,

I had found that site, but it seemed to me that all the problem solvers were for either a 25.4 or 27.2mm seat posts and without modification would not fit on my 26.4mm seat post, (unless I am missing something, which would not be the first time )

Many thanks
Martin

[fatboy]

Why don't you call SJS and see what they've got. Generally helpful, have a good stock of odd bits, and since they made it they might have solved this before.

[531colin]

Thanks Colin,

I had found that site, but it seemed to me that all the problem solvers were for either a 25.4 or 27.2mm seat posts and without modification would not fit on my 26.4mm seat post, (unless I am missing something, which would not be the first time )

Many thanks
Martin

As Brucey says, to go from 26.4 up to 27.2 is 0.8mm. so you need a shim 0.4mm thick, so their ST0508 would be OK. as a starting point.
Its made to fit a 25.4mm post, so you need to open it out a bit, when it might be a bit "gappy" , so I would cut 2 bits to make 2 half shims.....there is plenty of material. Although as fatboy says, a readymade solution is always helpful.......

look here!....http://forum.ctc.org.uk/viewtopic.php?f=5&t=79239&hilit=stem

[martinn]

Thanks for cautionary tale of mind the gap, will be careful where I put it.

martin