# use shim on 34.9 seat tube for lighter seatpost



## dft (Apr 9, 2004)

I have a new frame that comes with 34.9 ST. I noticed for the same post and travel some dropper posts are about 140gramms difference just going to 34.9. seems you could save some decent weight buying a shim and getting 30.9 seat spot. thoughts? should work fine. the new sworks stumpjumper evo comes like that since remote dropper isn't in 34.9.
Thanks


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## Cerberus75 (Oct 20, 2015)

I did it on my wife's Wreckoning. No issues.


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## RobKong (Jun 7, 2010)

I've done it quite a few times, never an issue. In fact since the 34.9 has become more common, I've actually seen some bikes come from the manufacturer with a shim and smaller diameter post.


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## Suns_PSD (Dec 13, 2013)

I shopped pretty carefully for a 34.9mm 200mm dropper for my new Evo, they all weigh a lot. The lightest I found was 710 grams for the OneUp. That's a solid product with a great weight/ adjustability/ low stack/ and low weight for what it is. PNW told me they weighed one for me at 640ish and I ordered it, and it actually weighed over 750 grams so the order was cancelled. after that not sure I'd trust any of their measurements.

In the end, I realized that utilizing the included dropper shim and just reusing my 30.9mm 175mm KS Lev Ci, which weighs exactly 400 grams made a lot more sense.

Now if anyone releases a 34.9 diameter. 200mm travel carbon dropper that weighs less than 600 grams, I'm in. I'd take a weight penalty for the extra drop.

BTW, the included Spesh steel shim weighed 41 grams so consider that. Just ordered a Cane Creek Aluminum shim to replace it. Probably be the cheapest and most reliable 20+ grams I've ever saved.


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## dft (Apr 9, 2004)

Suns_PSD said:


> I shopped pretty carefully for a 34.9mm 200mm dropper for my new Evo, they all weigh a lot. The lightest I found was 710 grams for the OneUp. That's a solid product with a great weight/ adjustability/ low stack/ and low weight for what it is. PNW told me they weighed one for me at 640ish and I ordered it, and it actually weighed over 750 grams so the order was cancelled. after that not sure I'd trust any of their measurements.
> 
> In the end, I realized that utilizing the included dropper shim and just reusing my 30.9mm 175mm KS Lev Ci, which weighs exactly 400 grams made a lot more sense.
> 
> ...


nice, good to know. I'm building up stump evo from frame. I'm just gonna use my 5 year old KS lev that I rebuilt recently and a shim. curious, people that want 200 drop, so 170mm drop isn't actually enough? I'd figure 7 inches even for steeps is plenty


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## KVV (May 22, 2017)

Stumpjumper 2021 S-Works frame is 34.9 and it comes with a shim to 30.9. It's actually a really nice shim included.
Weight of 34.9 posts is certainly a concern. I ordered a shim to 31.6 (since all of my other bikes are), but in the end decided to go with the native size. I could probably fit ~170 post into S3 SJ, but for safety decided to go with 150.

I had a bunch of 9point8 and PNW Loam before. I asked PWN about the weight of 150x34.9 and they said:
31.6/150 - 524g (I have this one, confirmed)
34.9/150 - 638g - oo!!

In comparison 9point8 150x34.9 is 548g on my scale. Their weights come close to spec. Also their 200x34.9 is 638g on specs. This is without the lever / cable.








9point8 | Dropper Seatposts, Clamps, Remotes, and More Bike Components


9point8 provides world-class dropper seatposts, built for users searching for performance and reliability in their bike components.




www.9point8.ca


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## Wheelspeed (Jan 12, 2006)

USE plastic shim should be lighter than aluminum if USE makes one. Never had a problem with shims on all my old standard posts.


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## FJSnoozer (Mar 3, 2015)

We did the same with my wife’s 18 sworks enduro. I wanted to get it as close to 28 pounds as possible. 


Sent from my iPhone using Tapatalk


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## Suns_PSD (Dec 13, 2013)

If anyone can locate a 30.9 to 34.9 Aluminum shim I'd love a link.

I ordered one from Cane Creek that I was told is Al but it's a composite and heavier than the steel one that came with the bike.


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## MattMay (Dec 24, 2013)

Check Worldwide Cyclery.









Problem Solvers 4mm Seatpost Shim, 30.9 Seatpost to 34.9, Black


Shop & Learn About The Problem Solvers Seatpost Shims In The Seatpost Shim Collection - Features & Specs: Thickness: 4, : MPN: 03-000079 UPC: 708752162709, : Problem Solvers Seatpost ShimsLength is 97mm with a 3mm lip totaling 100mmItem SpecificationsThickness4




www.worldwidecyclery.com


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## Suns_PSD (Dec 13, 2013)

Saw that one, but won't order without confirmation it's Al as it looks steel or composite. 

Sent from my SM-G892A using Tapatalk


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## Cerberus75 (Oct 20, 2015)

I forgot which one I ordered, probably Problem Solver but found an aluminum shim on ebay. Had to search but the material and weight were listed.


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## Suns_PSD (Dec 13, 2013)

Cerberus75 said:


> I forgot which one I ordered, probably Problem Solver but found an aluminum shim on ebay. Had to search but the material and weight were listed.


Link please?

Sent from my SM-G892A using Tapatalk


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## Cerberus75 (Oct 20, 2015)

Suns_PSD said:


> Link please?
> 
> Sent from my SM-G892A using Tapatalk


I looked through my purchase history and cannot find it. Over 1.5 years ago. But I did just take it out of the bike and it's the one in the world wide link above. Addonized aluminum 80gr.


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## MattMay (Dec 24, 2013)

Yeh Worldwide Cyclery actively sells on eBay...how they got started actually.


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## Cerberus75 (Oct 20, 2015)

You probably could trim and drillium some more lightness to it as well.


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## Suns_PSD (Dec 13, 2013)

Cerberus75 said:


> I looked through my purchase history and cannot find it. Over 1.5 years ago. But I did just take it out of the bike and it's the one in the world wide link above. Addonized aluminum 80gr.


That's not Aluminum, that's a heavy composite. The steel one that is included from Spesh weighs 41 grams.

Al of the same size weighs right at half what steel weighs, so an Al shim should weigh about 20 grams. That's something I'm willing to pay $10-15 for.

I suspect that due to the thickness of a shim like this, that Al isn't the best choice, and that's why they are all heavy.

2 droppers on the shelf over here, both KS Ci 175mm travels. the one I'm using now is the 30.9 but I also have a 31.6 and the 31.6 only weighs 8 grams more.

I'm going to look for an Aluminum shim for 31.6 > 34.9. Thought I saw those out there. That will likely result in a lower net weight. However this might be getting too weight weenie even for me!


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## phlegm (Jul 13, 2006)

Suns_PSD said:


> Aluminum shim for 31.6 > 34.9


Looks like Cane Creek has one...









Cane Creek Seatpost Shim (31.6mm)


This is a Cane Creek 31.6mm to 34.9mm Seatpost Shims. Features: Solution for fitting 31.6mm seatposts to 34.9mm seat tube size 3-7/8" tall machined... AAE0008-P




www.nashbar.com


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## Wheelspeed (Jan 12, 2006)

I don't know why you guys are liking aluminum. Here's a note in my Excel spreadsheet from like 9 years ago:


Shim for seatpost, aluminum, 27.2->30.941g(USE shim would've been 22g!)


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## Suns_PSD (Dec 13, 2013)

I have a 30.9 > 31.6 Al shim in my garage that weighs 4 grams.


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## Suns_PSD (Dec 13, 2013)

Well that didn't work. Ordered an Al 31.6 > 34.9 shim on e-bay all of the way from France. 
It is nicely built for certain, but weighs 50 grams.
Actuality just ordered the most un-WW thing ever: a 210mm 34.9mm dropper. 
In the end, as heavy as the dropper is, it's only 50 grams heavier than a smaller diameter dropper at the same length with a shim and I gain complete contact between the dropper and the frame internals. 
We'll see if this works. 

Sent from my SM-G715A using Tapatalk


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## Wheelspeed (Jan 12, 2006)

Cerberus75 said:


> You probably could trim and drillium some more lightness to it as well.


I would think you're right. Actually I'd think you could really hog out the sides so there's just a skeleton there, and just leave most of the front and back portions. Probably could cut out 10g from the person's 40-gram example.


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## FishMan473 (Jan 2, 2003)

I'm as big a WW as anyone, but I don't think this is a good way to save weight. 

First, you're not saving as much as you think, as others have stated the weight of the shim easts into the savings.

Second, dropper posts get put through a lot of abuse, and a larger diameter one is going to be stronger, and stiffer, which means it will work better for longer. Nothing more annoying than a dropper that isn't working right.

Third, once you introduce seat post shims you add a couple dimensions of problems to seat tube-seatpost interface. You add another variable for this precision fit, so you might get slipping, noise and accelerated wear. 

I can tell from the experience of years of running suspension seat posts, the shims are a giant PIA and almost make it not worth it. The performance gain from a good dropper is worth the weight.


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