The shim will work great, but I'm not sure if you can find a shim for 30.9 to 31.6 though.

 

Not sure that you even read his post. He has "a shim specifically for this application" and is concerned whether or not he can use it with a carbon frame.

 

Maybe contact the frame manufacturer and ask them?

 

My bad. Still, a shim will work perfectly. Ive been using a shim, 31.6-27.2 on my Cannondale road bike for a couple of years and used shims in other applications over the years with zero problems.

 

So, were any of those frames carbon? That's the crux of the questions he was asking.

 

Potential problem:
Frame breaks, manufacturer won't warranty because of shim.

 

I wouldn't do it. I wouldn't use a seatpost at the minimum insertion depth on carbon fiber in principle, plus risking voiding a frame warranty.

Lengthy discussion about shims voiding warranty. I think it's BS on the frame manufacturer part if the shim is a decent quality one, but not all shims are created equal. I think the shim used here was not a proper length high quality one.
http://forums.mtbr.com/fat-bikes/bikesdirect-frame-warranty-1004487.html

 

The "minimum insertion depth" is to keep the seatpost from breaking, not the frame.

Sell your dropper and get THE CORRECT SIZE.

 

You will die. And, every time someone uses a seat post shim, god kills a kitten.

 

God sure kills a lot of kittens. But still not enough.

 

I've had a shim in my Scott Scale since day one. Zero issues.

 

Yes, a few were( are) carbon, never an issue. The frame doesn't know that it is a shim, a wooden dowel or a solid piece of titanium billet, it just knows that it is the proper diameter. I also think that the use of a shim is more secure because it spreads the load of the clamp along its length of the shim, as opposed as just at the clamp...my opinion.

If there was ever to be a warranty issue caused by using a shim, which I have never heard of, would you tell the manufacturer that you were using a shim?

I used to make my own seat posts and at that time, we only made the popular sizes of 26.8, 27.2 and 31.6 seat post diameters. At that time, mid 90's-early 2000's, there were several unusual seat post diameters going around, 28.6, 29.8, etc, 30.9 was just starting. We sold shims to customers that had those sizes which we didn't have a post size for. I never had anyone complain about a failed frame or post, at least, they never let me know if they did.

I believe in the use of a shim, if necessary, don't really want to get in a disagreement with you in regards.

 

Yes, a few were( are) carbon, never an issue. The frame doesn't know that it is a shim, a wooden dowel or a solid piece of titanium billet, it just knows that it is the proper diameter. I also think that the use of a shim is more secure because it spreads the load of the clamp along its length of the shim, as opposed as just at the clamp...my opinion.

No, it doesn't. There isn't some mechanism to exert clamping force along the entire length of the shim...just at the clamp, just like not using a shim.

If there was ever to be a warranty issue caused by using a shim, which I have never heard of, would you tell the manufacturer that you were using a shim?

You need to look at the thread linked to above. Manufacturers spec a seatpost size for a reason, that is the size you're supposed to use.

Seems a bit dumb to try to save a few bucks when you're talking about a carbon frame, which is more than a few bucks...in the same way that OP in the thread linked to above was dumb to not buy an inexpensive seatpost of the correct size.

It's like buying cheap tires for your Porsche 911.

 

i did what you are describing with an aluminum shim into a carbon frame. The aluminum I believe has corroded and now the dropper post is welded into the frame.

This is possibly similar to the issue that people had with alum nipples in carbon fiber rims.

At some point hopefully the shim will dissolve and I can get the seatpost out.

Or maybe it is just stuck. I did not have tube clamps to try to get the post out.

 

Like I said, not trying to get into a arguement or disagreement with you or FP....but your wrong in regards to the clamping of the shim. Shims, usually are about 3"-4" long and have a cut from top to bottom, when tightened it clamps the whole length( easy to see for yourself, take a shim and squeeze it at the top, see what happens), yes the clamping force lessens the further away from where the initial clamping force is applied, but over the length, it still has a larger clamping area

Of course manufacturers spec a size for theirs seatpost size, you cannot have several sizes in one frame, besides, the current clamping method works fine.

The reason some people have to use a shim is that there are frame made where a there is a post that doesn't fit their frame. For instance, when dropper post first came out, there were plenty to fit the popular 30.9 size, but not the 31.6, so you used a shim.

 

The reason some people have to use a shim is that there are frame made where a there is a post that doesn't fit their frame. For instance, when dropper post first came out, there were plenty to fit the popular 30.9 size, but not the 31.6, so you used a shim.

That's not the case here. You can easily pick up the proper sized post for a minimal (in relative terms) cost by selling a functional, but incorrect sized, post and purchasing the correct size. You could probably come out almost even if you pick up a used one to replace your used post. People spend more than that on a set of tires.

Nothing will probably happen, but if something does, something that doesn't even involve a shim-related failure, you're left ass out with a broken $1500-3000 frame. Not worth the risk.

 

I run a Problem Solvers 31.6 to 30.9 shim on my carbon hardtail. As it happens, I'm running it about an inch farther in than the minimum insertion depth, which keeps the shim coverage rather complete. I err on the side of lower end of tension (4.5 N-m), so if I'm lazy through a rock garden I can deflect the seat off to the side, but aside from that I've had zero issues with it.

Because it's a rather minimal shim, and I live in a place with minimal corrosion (also, carbon paste helps a ton), I'll probably run this setup into the ground because I'm extremely happy with how it's working.

In all fairness this is a budget carbon frame (random chinese carbon with Diamondback decalwork - but this bike has withstood a remarkable amount of all-mountain riding with 250lb of stupid riding it) - so I won't be all that broken up if I end up destroying it or needing to repair it..

 

I have a KS LEV Integra carbon dropper seatpost that I have taken off my Canyon Lux...but it is 30,9mm diameter

Would you guys think it is safe to use an aluminum shim [30,9 - 31,6] like in the link below in order to use this seatpost in my new Scalpel Si?

30.9MM I/D SHIMS | Ultimate USE

 

I've now put 18 months of use on a KS Lev DX - shimmed from 30.9 to 31.6 using the ProblemSolvers shim, without any issue.