I'm using one of these https://www.chainreactioncycles.com/dmr-hinged-clamp/rp-prod745 to stop the seatpost slipping on one bike. Its a 27.4 seatpost, but the 28.6 clamp nips up enough to stop slipping. As said before, just clamp it round the seatpost above the top of the frame clamp. They are fairly unobtrusive.
If it were mine, I'd fit the new post, ride it and if it slipped make a shim and forget about it.
I personally also feel that shimming is acceptable. But how would you do it? The shim required is only .1 mm thick (AIUI). What did you have in mind?
I make it 0.05 mm thick and would also like to hear how to make a suitable shim that thin.
Besides the coke cans mentioned, one can purchase shim strips from tooling supply companies. They can be purchased in assortment packs, or rolls of a single size. Somewhat depending upon the desired material (the most variety is available in carbon steel), they come in increments of 0.01 mm, starting at 0.02 mm thick.
“In some ways, it is easier to be a dissident, for then one is without responsibility.” ― Nelson Mandela, Long Walk to Freedom
Shims are a worthwhile idea if in future I am unable to find 27.4mm seatposts to get machined to fit, as are seatpost collars, but none of this would be necessary if Spa had had the frames manufactured properly in the first place!
In future I think I will only be purchasing small items from Spa....
I don't understand why this problem appears to be particular to Spa. It's a standard Reynolds 725 seat tube, and I presume that the frame is made by a large contract manufacturer in the Far East which produce frames for other brands, and that Spa only accounts for a small fraction of their output.
slowster wrote:I don't understand why this problem appears to be particular to Spa. It's a standard Reynolds 725 seat tube, and I presume that the frame is made by a large contract manufacturer in the Far East which produce frames for other brands, and that Spa only accounts for a small fraction of their output.
Indeed. As an aside (and doesn't help the OP), my Spa Tourer from 4 years ago doesn't have the issue. I suspect it's most likely the tubing has been made out of spec (though one wonders how), as I can't imagine the seat tube has been reamed out oversize. Certainly a Quality control problem somewhere, but I suspect very difficult for Spa to have any control over.
fastpedaller wrote:..... Certainly a Quality control problem somewhere, but I suspect very difficult for Spa to have any control over.
Why? Spa can do the same as anybody else and return faulty goods. It is Spa's quality control at fault and they should simply replace the frame. Packing it with coke cans etc is fine for a cheapo 2nd hand frame but not for something brand new from a shop with any reputation to maintain.
fastpedaller wrote:..... Certainly a Quality control problem somewhere, but I suspect very difficult for Spa to have any control over.
Why? Spa can do the same as anybody else and return faulty goods. It is Spa's quality control at fault and they should simply replace the frame. Packing it with coke cans etc is fine for a cheapo 2nd hand frame but not for something brand new from a shop with any reputation to maintain.
I absolutely agree - but sending frames back to Taiwan isn't as easy as around the corner!
fastpedaller wrote:..... Certainly a Quality control problem somewhere, but I suspect very difficult for Spa to have any control over.
Why? Spa can do the same as anybody else and return faulty goods. It is Spa's quality control at fault and they should simply replace the frame. Packing it with coke cans etc is fine for a cheapo 2nd hand frame but not for something brand new from a shop with any reputation to maintain.
in which case by that definition any bike-selling emporium that sells any frame/bike that is made in Taiwan (to the usual standards) has 'no reputation to maintain' and should immediately return most of the bikes on their shop floor; similar problems commonly exist in most such frames, alu or steel. Accurately reamed seat tubes are more the province of handbuilt frames these days and unsurprisingly these do cost more.
Note that the OP initially had a problem with a seat pin that was definitely undersized and (IIRC about typical 'pro' branded seat pins) might have been relatively short so would (for any given diameter tolerance) wobble more for that reason as well. If a longer seat post of the correct diameter had been used from the start it would probably have stayed put and not been noticed either. It could easily have had about 1/4 as much wobble to it, or (if the bottom is very slightly squished out of round), effectively none.
If you demand perfection then you can either ream the seat tube and/or get a seat pin machined to fit. Several times I have done the latter because that was definitely easier than trying to persuade someone profoundly ignorant/obstinate that their frame wasn't going to break if you removed 50um of metal from the inside of the seat tube.
If you demand perfection then you can either ream the seat tube and/or get a seat pin machined to fit. Several times I have done the latter because that was definitely easier than trying to persuade someone profoundly ignorant/obstinate that their frame wasn't going to break if you removed 50um of metal from the inside of the seat tube.
cheers
It's not about "perfection" it's about normal practical tolerances and quality control. If a piece of coke can is the best solution then Spa should have fitted it before supplying the frame - and explained that this was normal and to be expected! TBH it's nonsense - the frame was substandard - the bike shop should replace it.
fastpedaller wrote:..... Certainly a Quality control problem somewhere, but I suspect very difficult for Spa to have any control over.
Why? Spa can do the same as anybody else and return faulty goods. It is Spa's quality control at fault and they should simply replace the frame. Packing it with coke cans etc is fine for a cheapo 2nd hand frame but not for something brand new from a shop with any reputation to maintain.
I absolutely agree - but sending frames back to Taiwan isn't as easy as around the corner!
Spa's problem, not the unlucky purchaser. They can't just pass it off "sorry mate can't do anything it's these Taiwanese chaps you just can't rely on them".
The fact that these frames (all?) have externally butted seat tubes does make me wonder if that is a factor. I'm still puzzled by how external butting works in a seat tube. In his post above 531Colin stated that Reynolds don't provide the internal diameters, they only provide the wall thicknesses, and he surmised that these particular Reynolds tubes are a uniform (nominal?) 27.4mm throughout their length. Even if a tube is described as externally butted, I would have thought that it would make more sense if Reynolds manufactured these seat tubes with a small degree of internal butting as well, so that:
a) the internal diameter of the butt at the top of the tube was 27.2mm or slightly less, to ensure that it would take a 27.2mm seat post or could be reamed to do so after the frame was built, and
b) the internal diameter of the middle of tube was larger than 27.2mm by enough to avoid the process of reaming reducing the thickness of the thinnest part of the tube (given that modern seat posts can be very long and inserted well down into the tube).
Given that these particular tubes are 1.2mm thick at the butts, and only 0.6mm in the middle, I would have imagined they would be amenable to being butted both externally and internally.
wearwell wrote: It's not about "perfection" it's about normal practical tolerances and quality control....
yes, and you are assuming that those tolerances are not 'normal' whereas IME they are. It will (or should be) on an engineering drawing somewhere; blithely saying 'oooh you ought to reject frames like that' is all very well but if there is not a clear breach of the agreed dwg and tolerances (according to some agreed standard and method of measurement) then there will just be a pointless argument followed by a deeply soured business relationship, not to mention a little problem of 'no frames to sell' in the meantime.
The acid test is whether your seat pin moves in normal service or not. Plenty of seat pins in all kinds of bicycles do move too easily (see t'interweb for details) but most don't. If you have seen your seat pin move or you want to be as close to 100% sure as you can be that the seat pin won't move in the future then you need to worry about this stuff. Otherwise you don't.
slowster wrote:I don't understand why this problem appears to be particular to Spa.
It isn't, throughout the thread you'll see several people have had similar issues and the ways they've resolved them, did you think they were all referring to Spa bikes?
