# 26.8 Seatpost in 27.2 frame ? Safe ?



## Megaclocker (Sep 28, 2005)

i want to put an old (very light) seat post that came stock on a Rocky Mountain Hammer 1999 on my Race bike (that have a shitty kalloy seatpost).

My local bike shop sell shim to put a 26.8seatpost into a 27.2 frame (i assume thay have one they have a box full of shim)

My bike is used for allmountain riding... Is it safe to put a shim ? How long the shim must be ? Etc

Any recommendation because i am sceptical


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## pimpbot (Dec 31, 2003)

*Shims are safe....*



Megaclocker said:


> i want to put an old (very light) seat post that came stock on a Rocky Mountain Hammer 1999 on my Race bike (that have a shitty kalloy seatpost).
> 
> My local bike shop sell shim to put a 26.8seatpost into a 27.2 frame (i assume thay have one they have a box full of shim)
> 
> ...


as long as you use the correct size. The post has any play in it, don't clamp it down.


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## Megaclocker (Sep 28, 2005)

I was thinking about this ? 27.2 - 26.8 = 0.4mm which is pretty thin are you sure they even make shim of those size ?


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## Hardtails Are Better (May 4, 2005)

Yeah, that souns like a really thin shim to me. If they make it though, shouldn't be a problem.


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## jlang002 (Jan 10, 2005)

Megaclocker said:


> i want to put an old (very light) seat post that came stock on a Rocky Mountain Hammer 1999 on my Race bike (that have a shitty kalloy seatpost).
> 
> My local bike shop sell shim to put a 26.8seatpost into a 27.2 frame (i assume thay have one they have a box full of shim)
> 
> ...


cup up beer cans = cheap shims
-jon


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## theturquoisewarrior (Nov 15, 2005)

*Do it like this*

I've done it on my Yeti 575 so I guess that qualifies as all mountain. It too is a 26.8 (came out of my Yeti ARC) and went into the 575 which is a 27.2.

As previous poster stated, use beer can (any beverage can will do, but you deserve a beer for doing this. In fact you may need two beer cans, so even better).

Can wall thickness is 0.1mm, thus once around the seatpost adds 0.2mm, so you need two shims on top of each other. Don't just wrap can twice round, as where it overlaps it doesn't lay flat and you won't get the post in the frame. Also leave a small gap at the ends of the shims, about 2-5mm is fine. As for length, just make it as long as the minimum insertion as marked on the seatpost, or to at least the bottom of where the top tube meets the seat tube.

If you want to be crafty, leave about 5mm of shim sticking out of the frame. Then slice it the exposed 5mm into lots of vertical slits, fold them outwards over the seat tube and then slide the seatpost clamp over them. This allows you move your seatpost up and down as the clamp holds it in place. You do still need to be careful.

If you do a neat job, no-one will even notice it.


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## Megaclocker (Sep 28, 2005)

theturquoisewarrior said:


> I've done it on my Yeti 575 so I guess that qualifies as all mountain. It too is a 26.8 (came out of my Yeti ARC) and went into the 575 which is a 27.2.
> 
> As previous poster stated, use beer can (any beverage can will do, but you deserve a beer for doing this. In fact you may need two beer cans, so even better).
> 
> ...


Did you bought your shim or made it of beer can ?


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## rkj__ (Feb 29, 2004)

jlang002 said:


> cup up beer cans = cheap shims
> -jon


I can attest to that. I did not want to buy a new post for a .1mm difference, so i used a "Fresca" can.


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## Hardtails Are Better (May 4, 2005)

rkj__ said:


> Fresca


Best soda ever.


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## theturquoisewarrior (Nov 15, 2005)

Megaclocker said:


> Did you bought your shim or made it of beer can ?


Just made it from beer can. Use a craft knife to cut it.


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## Nigel (Jan 13, 2004)

jlang002 said:


> cup up beer cans = cheap shims
> -jon


"cut up beer cans"
Never a good plan. In my experience that is never a sure thing. Thin shims like that are bound to eventually crush and cause possible damage to the post and the frame.

Id avoid using a shim, unless you were certain you had the ideal shim for the job.

The weight savings with this smaller diametre seatpost you have are not worth the hassle and risk of a shim.


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## theturquoisewarrior (Nov 15, 2005)

*Crush?*

Crushed? How? Do you mean the shim (beer can) will eventually be squashed so that it is thinner at the front of the seatpost where the most force on it goes? In my experience and estimation that will never happen.

If you are someone who likes to raise & lower their saddle a lot then I suppose the shim could wear a bit thinner.

The person who started this thread wants to use an old light post that they already have. I would never intentionally buy a post of a smaller size & use a shim to save weight. But like them, I too wanted to use an old, light post that I already had (couldn't afford a new post the correct size that was as light).

I must say though, I wouldn't recommend shimming a post any more than 0.6mm using aluminium cans. Once you get past a few layers of can, you're better off making a proper shim on a lathe.


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## Megaclocker (Sep 28, 2005)

Issue solved i got a Truvativ XR seatpost (not light)for cheap, but it will last... II broke 3 1bolt seatpost last year and i am frustrated now...

The XR i bought is 300g at 350mm (double clamp) :s, it will be cut to 250mm

Hopefully it will be alot stronger then my Kalloy 240mm (280g) and a bit lighter... I hope...


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## MaLóL (Nov 11, 2005)

theturquoisewarrior said:


> I've done it on my Yeti 575 so I guess that qualifies as all mountain. It too is a 26.8 (came out of my Yeti ARC) and went into the 575 which is a 27.2.
> 
> As previous poster stated, use beer can (any beverage can will do, but you deserve a beer for doing this. In fact you may need two beer cans, so even better).
> 
> ...


yeahhh, nice advise. I´ve done exactly this several times and it works great. No 0,4 shims available i think...


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