Sanding a carbon seatpost down to 27.0 from 27.2… stupid idea?

Yes, I know Thomson make a 27.0mm seatpost, but I want a carbon post in my old steel road frame. This seems easier than reaming out the seattube.

Will I die?

I work with f**kwits every day, are you one of my users by any chance?

You could do it and win an award[/url]?

0.1mm off of the wall thickness will probably just remove the lacquer. Will it weaken it? No idea but I would be surprised.

0.2mm, so only 0.1mm all round, depends how thick the varnish is, do bike parts even have a varnish layer to protect against UV? My gut feeling would be it’s fine as long as you don’t sand down to the fibres, but then I’d be woried about the effects of UV on the epoxy.

Will it weaken it? No idea

In use, seatposts are located close to genitalia and important arteries 😯

What exactly is the reason you must fit that particular carbon post ? I’m intrigued….

Try it – none of the above have, 0.1mm is not much to remove, keeping it round and even may be the tricky bit.

Have you tried fitting it with QR / seatclamp removed? If it fits / almost fits then you should be ok.
You’ll find it hard to get it sanded evenly though….

I machined a 27.2 USE post down to 27, used it for years, never impaled myself. That was alu, would I do it with carbon? I think not.

I’d go for the reaming method…Had this done to one of my old steel frames; didn’t cost much, done by Bikeplus in South Croydon iirc

‘d go for the reaming method…Had this done

so will he if it snaps 😀

I’ve hammered/gouged/ripped a 27.2 post into a 27.0 frame , if its rusty oldsteel frame likewaht mine is just get it started and the riving/ratching process should remove sufficient lacquer to get it in. Either that or your seat post’ll be ****. Nothing ventured etc.

Could you not just carefully scrape the outside of it off with some sort of implement. A spoon, maybe? Spoons are good for carbon fibre.

I once turned a alu 27.2 post down to 27.0 and it was fine. Went across Tibet without a squeak.

http://www.ebay.com/itm/New-Uno-MTB-Road-City-Folding-Bicycle-Bike-Carbon-Fiber-Seat-Post-27-0-x-350mm-/360823000887?pt=US_Seatposts&hash=item5402ba0f37

IT WAS NOT A SPOON

😡

Why don’t you want to ream the seattube out??

18 bikes do seatpost reaming and i’m sure plenty others do.

I’d rather lose 0.2mm of metal than carbon.

IT WAS NOT A SPOON

Spork then?

Ha, I’m loving the responses, thanks everyone!

I hadn’t seen those YoKaiser, but I’m tempted to try sanding mine anyway just so I can bring this thread* to a satisfactory conclusion 😆

*and my ability to relieve myself without a colostomy bag?

whack it in a lathe, what could possibly go wrong
Think I’ve got a 27.2 reamer if you want to take the easy route

Spork then?

Brilliant! 😀

I don’t think you could sand and maintain the roundness of the post. You’d have high and low spots all over the place and the contact area inside the seat tube would be compromised. If you put it in a lathe then you might do it, just be cannae when doing up the chuck and use a centre and a dust mask.

Carbon fibre dust is possibly as dangerous as asbestos dust if inhaled, wear a mask when sanding or cutting it please.

measure the wall thickness of the seat tube. If it’s anything over 1.2mm then I would definitely just ream the frame out to 27.2mm. Where are you? I have a reamer.

You didn’t mention the wall thickness, but I think that this is probably possible. However….

You would need to do this with something mildly abrasive and uniformly to avoid having some areas thicker than others. A lathe with a feed and an attachment to hold some emery cloth for example, I would also lubricate with water.

The average UD cured ply thickness is about0.2 so you are not losing a great deal of material. Also as someone mentioned a proportion of this would be lacquer. I don’t worry about UV deterioration as most epoxies are resistant these days.

I would advise against the use of normal turning tools as they can promote delamination and lifting of fibres. This is not the same type of removal that we are after here.

As someone mentioned, reaming out the seat tube is also an option and possibly easier depending on what tool you have available.

Good luck!

Thanks for the detailed advice Spazzolino. I’ll get the verniers out for the frame and the seatpost and have a go at one or the other. And thanks very much for the kind offer of the reamer Sam – I’m in St Albans…

Jesus wept. Buy a post that is the correct size and do NOT ream a frame out if it’s fine as it is.

I’ll even put £10 towards the new post.

Edit: No,go ahead. (Just read ‘old steel road frame’) :O)

Double Edit: ::puts wallet back in pocket:: :O)

I snapped my 27.2 Ritchey carbon seatpost not long ago. Surprisingly thick walled too i thought but i did run it quite long out of the frame.
Probably be alright on a roadie tbh but you’ll curse lots if it goes ‘balls up’ (in a high pitched voice).

rayyoung – Member
Carbon fibre dust is possibly as dangerous as asbestos dust if inhaled, wear a mask when sanding or cutting it please

Any evidence?

Carbon fibre dust is possibly as dangerous as asbestos dust if inhaled, wear a mask when sanding or cutting it please.

Carbon dust is certainly not as dangerous as asbestos. There have been many studies carried out on this and dust/fragments from carbon fibres certainly do not have the same effects in living tissue.

However, as with all materials I would still recommend a dust mask. If you are using water to lubricate, it stops the dust getting airborne, so you could afford to be a little less vigilant.

we all like to do sports here, so we should all protect ourselves to maximize our “potential”

😆

Cheers