Loose seatpost - Spa Aubisque frameset

[bgnukem]

I'm currently building a Spa Cycles Aubisque frameset and on inserting my 27.2mm 'Pro'-branded seatpost found it to be a very loose fit, the seatpost can be rocked inside the seat tube and the (separate) seat tube clamp had to be significantly tightened to grip the seat post. AFAIK the recommended seat pin diameter for that frame is 27.2mm.

Measuring with vernier calipers I found the seat post to be around 27.15 - 27.2mm in diameter and the seat tube to be around 27.3 - 27.31mm at the open end. I was amazed that such a small diametric clearance (0.1 - 0.15mm) could result in such a loose fit. tried another 27.2mm 'post from my commuter bike but it's also a loose fit.

Currently in contact with the shop regarding possible courses of action but it seems just buying another seatpin will not be an option as a 27.4mm pin (hard to find) won't fit and no-one makes a 27.3mm diameter.

Is there any chance of finding a 0.05mm shim (seems unlikely) to make the post fit, or some other option to make the seatpin fit? I'm rather loath to dismantle the whole bike in order to send back the frameset!!

Ben

[rjb]

A coke can is 0.04mm thick if i remember correctly.
And a pair of scissors is all you need.

[Brucey]

I have machined seatpins to fit frames when the frames have been 'between sizes' and can't be reamed. This can cure loose/moving seat pins completely. However this would need to start out 27.4mm nominal for this frame.

In your case a couple of suggestions;

1) fit a (coke can) shim with a lip that is trapped beneath the seat binder collar

2) squish the bottom of the seat pin into a slight oval shape so that the seat pin can't wobble fore to aft.

cheers

[pwa]

I have machined seatpins to fit frames when the frames have been 'between sizes' and can't be reamed. This can cure loose/moving seat pins completely. However this would need to start out 27.4mm nominal for this frame.

In your case a couple of suggestions;

1) fit a (coke can) shim with a lip that is trapped beneath the seat binder collar

2) squish the bottom of the seat pin into a slight oval shape so that the seat pin can't wobble fore to aft.

cheers

Do you think just rotating a 27.4 pin in a wrap of emery paper would achieve an acceptable result, or would that be too haphazard?

It does seem like a problem Spa should be asked to solve.

[slowster]

I would be interested to know what Spa say. I think the seat tube on the Aubisque is Reynolds 725. I would have expected it to be relatively rare for a seat tube which is well out of specification to slip through the quality control of a company like Reynolds.

[Brucey]

Do you think just rotating a 27.4 pin in a wrap of emery paper would achieve an acceptable result, or would that be too haphazard?

it might work OK but it is liable to be slow work. It takes quite a while to take off 0.05mm using an abrasive. FWIW working by hand, I'd favour abrading lengthwise.

It does seem like a problem Spa should be asked to solve.

yes, if they either have specified that a particular seat pin will fit or have supplied said pin to fit.

FWIW it isn't unusual to find that seat pins are slightly under the nominal size, but unless a seat pin that is 27.2mm (exact) actually slips in use, Spa are quite likely to say there isn't a problem, if they say a 27.2mm pin is the right size.


The ideal is if there is no appreciable wobble with a dry seat pin/frame but the acid test of course is if the thing slips in use; if it does then you have a real problem and if it doesn't you don't. If the seat pin is inserted with grease on, you mightn't notice a little wobble unless/until it causes a problem.

cheers

[bgnukem]

Spoke to Spa today and will take bike back to shop next time I'm in the area (June) for them to take a look.

measured seat tube at 27.31mm diameter, one nominal '27.2' seatpost was between 27.02 - 27.08mm and the other around 27.14 - 27.18mm. So it seems the seatpot I bought for the bike is a little undersized and the seat tube is oversized. Amazing that a diametric clearance of just 0.2mm can produce such a pronounced rocking fit of the seat post in the tube!

In the meantime I might look into getting a 27.4 post and abrading it to fit. Not many to choose from though....

[slowster]

The standard Spa build for the Aubisque uses a FSA SL280 seatpost. If Spa have not experienced problems with that seatpost's fit in their own builds, I would be tempted to buy and try the FSA SL280. If its diameter also proved too narrow in your frame, presumably you could return it when you see them in June.

[bohrsatom]

I had a similar issue with my Spa steel tourer. The seat tube was a little too large and the seatpost a bit too narrow and so my saddle would slip down over the course of a few miles. I rooted around my spares box and found a different seatpost which must have been larger as it fit just fine. Coke can shim did the job well, too.

I didn't particularly like the FSA SL-280: it only has one bolt for adjustment so was almost impossible to get my saddle position just right.

[fastpedaller]

No problem with my Spa Tourer (bought 2014) using an on-one seatpin. I never thought to measure the seatpin ('cos I had no problem), but when I get a chance I'll put the verniers to it and see what it is. Maybe Spa use a number of different manufacturers or have changed manufacturer over time?

[wearwell]

Spoke to Spa today and will take bike back to shop next time I'm in the area (June) for them to take a look.

measured seat tube at 27.31mm diameter, one nominal '27.2' seatpost was between 27.02 - 27.08mm and the other around 27.14 - 27.18mm. So it seems the seatpot I bought for the bike is a little undersized and the seat tube is oversized. Amazing that a diametric clearance of just 0.2mm can produce such a pronounced rocking fit of the seat post in the tube!

In the meantime I might look into getting a 27.4 post and abrading it to fit. Not many to choose from though....

I'd get them either to replace frame or supply correct fitting seat tube. If the latter I'd also check the rest of the bike thoroughly - it may be another "Friday nighter" like mine, with other faults overlooked.

[bgnukem]

Rest of the frame looks OK but I've not checked alignment or dimensions TBH. So far efforts to sand down a 27.4 'post to fit haven't been particularly successful. I'll be taking the bike back to the shop in June.

What other issues did you find with your frame?

[wearwell]

Rest of the frame looks OK but I've not checked alignment or dimensions TBH. So far efforts to sand down a 27.4 'post to fit haven't been particularly successful. I'll be taking the bike back to the shop in June.

What other issues did you find with your frame?

My frame seemed perfect* until I had a near death experience with the steering getting stiff and nearly seizing up. This was whilst going fast down the windy hill past Robin Hoods Stride in Derbyshire. It turned out that they hadn't cleaned out the sand blasting sand from inside the tubes, which had gradually drifted down into the bottom head set bearing.
Basically failure of quality control. There were other issues over-looked too.
Don't give them the benefit of the doubt - insist on having it dealt with, new frame if necessary. Doing us all a favour; they will improve their game if people object enough.
P.S. * except for peeling off lettering - should have been a warning sign!

[Brucey]

FWIW a lot of welded frames have a seat tube which is externally flared and butted near the top. Ideally the internal profile is nominally parallel sided but in practice (on a frame that hasn't been reamed) there are likely to be three internal diameters;

a) the diameter at the seat clamp and in the main part of the external butt.
b) the diameter at the seat cluster welds (which ought to be the same as a) but less an amount because of weld distortion)
c) the diameter lower down where the OD reduces to the standard 1-1/8" size.

So the top section ought to start at about 27.3mm if the frame is not to be reamed, to allow for b) to pull in slightly. But c) could potentially be a bit smaller.
Obviously the seat clamp is tightened until it clamps the seat pin. However whether a true 27.2mm seat pin wobbles in the frame is dependant on how far it goes into the frame and what the internal diameter of the frame is at that point. I happen to have a steel Spa touring frame to hand just now and the transition in the OD is set about 11cm down. A nominal 27.2mm seat pin (actual size TBC) is a slightly wobbly fit but the amount of wobble seems to me to reduce somewhat abruptly when more than 11cm of seat pin is in the frame.

[edit: the seat pin I used measures a lot closer to 27.1mm than 27.2mm; this is not at all unusual.]

In a lugged and brazed frame I'd consider the amount of wobble I have seen to be potentially excessive, and I'd want to ream and fit a larger seat pin. However in a welded frame I'd consider it 'fairly normal' and (if the seat pin slipped in service) aim to ream to the next size up or machine/adapt a seat pin to fit accordingly.

cheers

[JohnW]

Many, many moons ago (on the basis of a moon every 28 days, it works out at about 530 moons!) I had the same problem for a different reason. My LBS had stocked a 27.0mm Campag Record seatpin by mistake - he couldn't sell it but he offered to sell it to me for 33.3% off. I wrapped some Chinese takeaway tray around it, and it was still operating in the same frame three years ago - all those years (about 37) on. The frame was been resprayed than.