saddlebag on carbon seatpost

[webber]

ive just picked up a bike with a carbon seatpost that I would like to fit my bridge street saddle bag https://road.cc/content/review/123753-b ... bag-medium but is it safe to clamp to a carbon seatpost???

[Paulatic]

The seat post is clamped at the top of the seat tube. Why not clamp it further up too?

[webber]

The seat post is clamped at the top of the seat tube. Why not clamp it further up too?

im sure i was told that you shouldnt camp anything to a carbon post but i make you right

[Paulatic]

I’ve read all sorts of nay sayers reports on carbon fibre. When I bought a bike with a carbon seat post I asked the shop if I could clamp my carradice sqr to it. They couldn’t see there would be a problem. I was wary but I have done it with care of course.

[pwa]

I’ve read all sorts of nay sayers reports on carbon fibre. When I bought a bike with a carbon seat post I asked the shop if I could clamp my carradice sqr to it. They couldn’t see there would be a problem. I was wary but I have done it with care of course.

On the other hand I would be cautious about attaching anything to seatposts, of any material, that are particularly light. I've broken a lightweight alloy post when using an SQR Carradice bag, and a ten mile journey over several hills to get back to my car, with no saddle, didn't half have my thighs burning.

[foxyrider]

I certainly wouldn't clamp anything around a CF seatpost, especially anything where there will be a load at the interface. The potential for crush damage is perhaps not so great but cantilever weight may well cause premature and catastrophic failure.

Personally I don't trust CF for seatpost or stems - if I want light I use Ti (which I am quite happy to clamp stuff to).

[webber]

thanks for the replys so I can but shouldn't then

[Mick F]

I had a carbon seat post on my Moulton.
I sold the carbon one and bought an alu one and made a profit on the deal.

Not only a profit, but all the issues with carbon have gone, and the alu post was a whole 19g heavier!

[Paulatic]

thanks for the replys so I can but shouldn't then

You are now armed with information you can make your own mind up. I should add I only had my sqr on for a few weeks and had the post sleeved with an old inner tube.
I’ve just took a look at your bag linked..... viewtopic.php?f=1&t=125530&p=1280904&hilit=Bridge+street#p1280904 You’ll be lucky

[webber]

thanks for the replys so I can but shouldn't then

You are now armed with information you can make your own mind up. I should add I only had my sqr on for a few weeks and had the post sleeved with an old inner tube.
I’ve just took a look at your bag linked..... viewtopic.php?f=1&t=125530&p=1280904&hilit=Bridge+street#p1280904 You’ll be lucky

i might just get an alloy post but don't know ive got a carradice super c saddlepack which will do most of the time might even get a super c audax and bagman but have heard of them snapping seat rails

[Brucey]

believe it or not, not all CF is the same. Quite a lot of 'CF seat pins' are made by wrapping CF around an aluminium post. They are not especially light and much of the strength may come from the aluminium not the CF. Others are all CF, but the CF is of poor quality. Such seat pins may break anyway and a saddlebag may just give them the final nudge...

Seat pins only don't slip because they are a snug fit over a length, and the binder is nipped up. If the seat pin is inserted only a short way into a frame, it doesn't matter how tight the clamp is or what the seat pin is made of; it'll move, and it'll move more easily with some seat pins than others. Same goes for anything clamped round a seat post too.

Clamping to seat pins to support a saddlebag is inviting trouble if the seat pin is light-built and/or the saddlebag is heavy and/or the clamp is tight.

cheers

[webber]

believe it or not, not all CF is the same. Quite a lot of 'CF seat pins' are made by wrapping CF around an aluminium post. They are not especially light and much of the strength may come from the aluminium not the CF. Others are all CF, but the CF is of poor quality. Such seat pins may break anyway and a saddlebag may just give them the final nudge...

Seat pins only don't slip because they are a snug fit over a length, and the binder is nipped up. If the seat pin is inserted only a short way into a frame, it doesn't matter how tight the clamp is or what the seat pin is made of; it'll move, and it'll move more easily with some seat pins than others. Same goes for anything clamped round a seat post too.

Clamping to seat pins to support a saddlebag is inviting trouble if the seat pin is light-built and/or the saddlebag is heavy and/or the clamp is tight.

cheers

so saddlebag and bagman is best the??

[Chris Jeggo]

In one image you link to

the seat pillar appears to be a saddle cradle insert fixed in a plain tube. In this case, if the insert is a good fit and goes further down the tube (by a distance of several tube wall thicknesses) than the whole of the bag support clamp, then it is probably all OK.
Or, to put it another way, if using the bag support loads the seat pillar in much the same way as fixing the saddlebag direct to the back of the saddle then the situation is fairly easy to evaluate.
Otherwise, think about it very carefully.

[pwa]

thanks for the replys so I can but shouldn't then

You are now armed with information you can make your own mind up. I should add I only had my sqr on for a few weeks and had the post sleeved with an old inner tube.
I’ve just took a look at your bag linked..... viewtopic.php?f=1&t=125530&p=1280904&hilit=Bridge+street#p1280904 You’ll be lucky

Yes, if you do it you are very naughty, but do protect the surface of the post with a wrap of something to avoid scratching.

[althebike]

When I was looking for a bag, for my carbon SP I was met with a sharp intake of breath with any metal clamping, and so I brought an alpkit that uses velcro, I have been told this is fine, the proof is in the pudding of course, if a prev.poster broke an alloy post, maybe it is not the material that is the key issue.