Yet Another Cycling Forum
General Category => Freewheeling => Folders => Topic started by: LittleWheelsandBig on 19 June, 2020, 11:29:14 am
-
I need to replace the Nylon shims in my Brompton frame and in my telescopic seatpost. The shims are easily available and do not look to be inherently difficult to replace.
The frame shim is listed as both unreamed and reamed in some websites. I understand the shim should be reamed once bonded in place. I guess the reamed price is for a shop-fitted shim.
The seatpost reamer is >£100 and even I am looking sideways at spending that much for a two minute use. How necessary is Brompton frame shim reaming and is there a ghetto way of doing so?
-
I was completely oblivious to this need for reaming the shim when I replaced mine, so I didn't. Couldn't possibly tell you whether doing so would have made any difference!
Bonding it in place is absolutely essential though.
-
Bonding it in place is absolutely essential though.
What did you use - are we talking UHU or epoxy?
-
Superglue with rubber, for use with flexible materials. Brompton’s recommended glue appears to have slow gel and setting times to allow sufficient working time to reposition the sleeve and clamp it down properly. A 20g bottle for £20 is excessive for replacing one sleeve. Loctite do a 3g bottle of suitable adhesive for £3-4, which should do nicely.
I understand that earlier shims might not have needed reaming but that all current shims have an undersized bore and must be reamed. It looks like I might have to get a third expensive, unique tool or break down and go to a shop. For philosophical reasons, I really do not want to do that last option.
-
I did mine without reaming and it's just right. I scraped all the old glue out and Argos blasted the frame before painting. I glued the new shim with Extreme Power Glue https://www.wilko.com/en-uk/unibond-repair-extreme-power-glue-20g/p/0231136 and, after making sure there was no glue on the inside of the shim, left the seatpost clamped up overnight.
I still have a spare shim if you need it. There were two in the pack- one has a locating lug and one doesn't. I can send a photo of the one I didn't use.
-
From Brompton’s instructions:
- On bikes produced after October 2002 a sleeve with an upstanding key (fig. 1) should be used, bikes produced before this date should use a sleeve without the upstanding key, when ordering a sleeve both variants are supplied.
- Two types of sleeve are available, pre-reamed (QSTSLV) and unreamed (QSTSLV-UR).
- A specific reaming tool kit (part QSTSLV-REAMKIT) is needed when fitting the unreamed sleeve.
- The replacement sleeve needs to be fitted with a specific rubberised adhesive (QGLUESS) to secure it in place.
It is difficult to find a retailer with stock of the pre-reamed sleeve (= shim). My bike is a decade old, so needs the sleeve with the key.
-
From https://azshow.info/watch/etHrXIcAz3A/brompton-seatpost-sleeve-full-procedure.html it looks like a fairly standard 32mm reamer.
Can you borrow/hire one from a machine shop? Until a couple of years ago I could probably have borrowed one for you from work but sadly that is no longer the case.
Another option might be to buy a used reamer like https://www.ebay.co.uk/itm/Presto-32-mm-HS-machine-reamer-on-4-MT/164170009434 That has a Morse taper on it but should still be usable. If it isn't long enough to go all the way through you should be able to bodge a drive extension onto it.
-
You are right JB, the Brompton tool is a parallel 32mm hand reamer. Buying a generic one of them from China starts at about half the Brompton tool cost and goes up fairly quickly. Reaming nylon is a little different to steel and I am uncertain whether a standard steel reamer with fewer cutting edges would overcut the nylon shim (anybody here know?). Given the difference in cost (<£60) and likely delay in shipping, getting the proper tool starts looking more bearable.
I am a little pissed that Brompton deliberately swapped from user-serviceable to enforcing dealer replacement for a consumable that their own website suggests needs replacing at least annually for intensively used bikes (seems excessive, given the Folding Society folk I know). I understand that reaming every shim ensures a good fit for a mildly distorted seat tube but even so...
-
RZ, thanks for the offer. I think the second sleeve (with slot) is otherwise identical to the sleeve with a key but I’m not sure. It looks like pre-reamed frame sleeves are now unobtainable, so you may want to hang onto your spare for the next time you need one. Without the key, you just need to be careful that the sleeve slot is correctly aligned.
-
This one looks to be pre-reamed. It has helical reaming marks inside. Let me know if you want it - I do so few Brompton miles that I'll never wear mine out .
It also has the key. I probably used the wrong one for my 2009 bike, not that it matters if you locate it correctly.
-
Thanks for the offer RZ. PM sent.
-
A ready-reamed seatpost sleeve bonded into place and ... the seatpost slips when ridden. Yes, I have degreased the seatpost and the sleeve. The bolt is tightened as far as I dare and the seatpost doesn’t slide under its own weight when the QR is opened, which suggests it is a little too tight. There were reaming marks visible in the sleeve and I can even see the sleeve has a gap at the front of the seatpost from a reaming mark with QR closed.
Right, time to replace the sleeve with an unreamed sleeve and buy a reamer to do this properly. This bloody bike is going to be fixed, whether it likes it or not!
-
That's unlucky.
One factor might be that I have the Brompton titanium post, which is a bit less slippery than chrome.
-
Such is life, in the words of that great Aussie philosopher.
It does give me an excuse to buy another silly expensive tool, which is nice.
-
Some more Brompton heavy metal has arrived.
(https://pbs.twimg.com/media/EgWqWr8X0AAitJd.jpg)
After picking up a couple of unreamed sleeves from Stows Cycles, everything should be sorted soon with a sleeve to spare.
-
Bonkers design, isn't it? The tolerances must be crap if they can't make a shim that fits straight in.
-
It took a couple of passes with the reamer to get the right tolerance for the seatpost to drop with the QR open but to be secure when tightened. At least it all works now.
There is little clearance between the chainring and reamer handle which made it difficult to grip the reamer tight enough to turn it. Next time I might ream the sleeve without the RH crank installed.
-
Hi.
I would like to continue the topic.
I found some reamers on marketplace, it is not exactly like Brompton's original, but instead it is very cheap, like 15€. Total length: 26,5cm, "reamer" part is 13,5cm. What do you think, it might work? I think I just need to extend it (probably weld it and center it on a lathe?), or the length 26,5cm would be OK?
(https://i.imgur.com/qalvmcq.jpg)
Someone on FB told be that this Acceofix (https://www.aliexpress.com/item/4000506424809.html) shim is pre-reamed and it works fine in Brompton.
-
The factory tool has a threaded hole in the end with a single Allen bolt securing a multi-lobe handle. You might be able to do something similar. All the reaming is done from the underside of the Brompton with a plastic split guide keeping the reamer aligned in the bottom of the seat tube. That guide can be the old removed sleeve.
The Brompton seat tube is 24 cm long and the sleeve is pretty short, so it might just work with its current length, depending on how much taper there is on the end of the reamer. I had to run my reamer twice, going further the second time, because the first pass with the reamer only protruding a centimetre or so didn’t remove enough plastic.
You will also need a tube or suchlike to press against the inner wall of the unreamed sleeve while the rubberised superglue is curing (pick something with a slow set time), otherwise it won’t bond properly. The seatpost won’t fit until the factory sleeve is reamed.
If you select a sleeve that doesn’t need reaming, why worry about a reamer? Of course, the seatpost itself would work to bond the sleeve in place.
-
"The factory tool has a threaded hole in the end with a single Allen bolt securing a multi-lobe handle."
Very good idea and it is easy to do on a lathe.
"You will also need a tube or suchlike to press against the inner wall of the unreamed sleeve while the rubberised superglue is curing (pick something with a slow set time),"
This is the small tool beside the reamer on your pic, right? If you have a little time, can you measure it for me? I might 3D print one or I do one on lathe.
"If you select a sleeve that doesn’t need reaming, why worry about a reamer? Of course, the seatpost itself would work to bond the sleeve in place."
Very good question. I don't know the main reason why Brompton stopped to sell reamed sleeves. Just to make extra work for official stores? Somebody wrote on FB that "The sleeve needs to be reamed because it is purposely made too big so that it can account for frame irregularities.". I don't know how true this is. Now I don't know If I should go with the out-of-the-box solution from China or go with the official way. What do you think about this?
-
I tried a factory pre-reamed sleeve and the seatpost slipped, hence why I bought the reamer. Everybody else I know who has fitted a pre-reamed sleeve had no problems. You pays your money and you takes your chances.
Welcome to the forum, what brought you here?
-
Well, thanks for the answer. :thumbsup: If you don't forget and if it's not a big ask, please post the size of that small tool later.
-
LWaB, did you check the actual size of your seatpost? Just in case this is an unfortunate clash of tolerances, with the post being slightly undersized?
The glue is probably the unknown in the equation. Brompton should be perfectly capable of making a seat tube to an accurate ID, since everyone else can (the "frame variation" excuse is BS from them). However, if you're going to stick a shim in with glue, it all becomes a bit random, especially if you are cleaning old glue out and putting new glue on top.
A glueless insert, secured by a lug at its lower end to stop it popping out with the seatpost, would seem to be a sensible way forward. But Brompton don't move forward - no need to, when they can sell them faster than they can make them.
-
The frame sleeve is about 67mm long and the Brompton bonding mandrill is 31.0mm diameter and thick-walled steel.
The SH extended post is a tiny bit larger diameter than my telescopic post. My telescopic post could just be twisted by both hands without a saddle on it.
Normal frames get reamed after fabrication to get a snug fit for the seatpost. Normal 28.6mm Reynolds 531 seat tubes theoretically need a 27.4mm seatpost for a snug fit but heat-induced distortion means that a 27.2mm seatpost is the correct fit. Very rarely, a silver brazed frame will need a 27.4mm seatpost instead. I have only seen that once.
-
Tony Oliver frame?
-
I have never pulled the seatpost of an Oliver frame (only seen one of them in the flesh). It was a Frezoni frame. It takes minimal heat, even with silver brazing, to not shrink the seat cluster down to 27.2mm. Too low a heat risks not getting full braze penetration. Too much heat means a metal puddle on the floor. Brass has a wide temperature range between too hot and too cold; silver has a much narrower and lower range.
-
Tony Oliver silver brazed all his frames, and all the 531 frames take a 27.4 pillar (he expounds upon tnis in his book*). AIUI he jacked it in because the fumes were getting to him. I don't know how many he built in total but I imagine it was only in the hundreds.
*which contains quite a lot of opinion and some inaccuracies; the description of steering geometry is completely arse-about-face and I wouldn't like to ride his radial drive side, narrow-barrel hubbed, rear wheel! That trick is ok with a big fat hub designed to cope with the torsion...
-
How many 531 frames out there use a 27.4mm seatpost? Vanishingly small numbers in my experience.
Most bicycle frame tubes have a subtle curve and applying heat to the top tube, seat tube and seat stay junction is not usually done in a single heat cycle. More heat cycles and higher temperatures mean more distortion.
There is a reason virtually every brazed or welded frame needs its seat tube reamed, usually with a fixed 27.2mm reamer. You could always ream out to 27.4mm but that means less wall thickness and there isn’t a huge amount of steel to start with. A perfectly reamed seat tube that matches a specific post (there are manufacturing tolerances in seatpost diameter) is lovely though. I worked on a friend’s Team Fat Chance that had a sealed seat tube at the BB. Grease on the seatpost would bubble out because of the trapped air being compressed as you lowered the seat.
Frezoni, like early ICE trikes, likes to use eutectic silver brazing for lugless frames. That takes pretty good torch control to avoid puddles of silver on the floor. The capillary action of nicely matched lugs and tubing makes silver brazing a bit easier.
-
Oliver didn't ream the seat tube, or so he claimed.
A sealed seat tube suggests Chris Chance was building for the California market (despite being an east coast business), or didn't understand how water usually gets into a frame. Such a frame runs a big risk of rotting out in a wetter climate.
-
Fat City Cycles sealed most of their frame tubes at both ends. Even the bidon bosses were blind fittings. You are right that a sealed seat tube is asking for water to accumulate and rot it out at the BB.
https://raleigh-sb4059.com/2017/02/01/reynolds-tubing-wall-thickness-tube-gauge-and-seat-pin-size/ is an interesting read. I knew there were some dimensional quirks but not quite this many. To avoid reaming the seat tube entirely is tough though requiring minimal reaming is reasonable.
-
It used to be common practice to wedge a greasy rag down the seat tube to keep any water creeping down the seatpin out of the BB bearings. Decades later, if the frame is still being ridden, it rots from the inside out where the rag has retained all the moisture. If water can get in, so can oxygen.
-
Some more Brompton heavy metal has arrived.
(https://pbs.twimg.com/media/EgWqWr8X0AAitJd.jpg)
After picking up a couple of unreamed sleeves from Stows Cycles, everything should be sorted soon with a sleeve to spare.
Hi there,
I was told that the original Brompton reaming tool set was only sold to commercial sellers. Where did you get yours?
Regards
Jan
-
Your understanding is correct, so that is not a question I can answer.
Try searching for Brompton’s part number for the tool. https://www.vlerickfietsen.be/download-asset/158a1670-1731-11ea-9eb5-005056985c04 might be helpful to you.
-
I bought an unused kit from a private owner. The Brompton tools are sold to the public in other countries, normally on the understanding that they won't ship to the UK. Brompton are not my favourite company. They also engage in something very close to retail price maintenance, and have done so since the early days. The replacement value of an M3L with lighting on the hire scheme is only just over half RRP, which makes you think.
-
I bought an unused kit from a private owner. The Brompton tools are sold to the public in other countries, normally on the understanding that they won't ship to the UK. Brompton are not my favourite company. They also engage in something very close to retail price maintenance, and have done so since the early days. The replacement value of an M3L with lighting on the hire scheme is only just over half RRP, which makes you think.
Well someone has to pay for BWC! lol
-
I notice that Cyclus make a 31.8mm reamer (https://www.bikester.co.uk/cyclus-tools-handle-for-seat-tube-reamers-o316mm-M989307.html). Would .2mm matter? Would that with its holder (https://www.bike-components.de/en/Cyclus-Tools/Reamer-Holder-for-Seat-Tube-p4517/) be usable? I think I've read somewhere about clever tricks to insert something in the bottom of the seat tube to get good alignment for the reamer.
Or adjustable reamers (https://www.tredz.co.uk/.Cyclo-Adjustable-Reamer_206045.htm)?
-
Loctite do a 3g bottle of suitable adhesive for £3-4, which should do nicely.
Could I ask which Loctite you used?
-
Loctite Super Glue Power Gel, from memory. A rubberised cyanoacrylate.
-
:thumbsup: :thumbsup: That looks good.
-
I recently successfully replaced and reamed with a generic 32mm reamer (a big 4MT taper one). I used Loctite Power Flex (I had the 'mini trio gel' set where one tube seemed about the right amount for a shim).
The only problem I had was that it grabs very quickly, whereas I think the Brompton one gives you more time to align everything, so it's worth seeing if you can find something that gives a bit more handling time. I found that I couldn't get the alignment tab to click into place before it was impossible to twist the shim, so ended up knocking it out and using the second one that is supplied in the kit without the tab.
I ended up just using the remains of the previous shim as a guide to keep the reamer straight, and used a simple toolmaker's clamp on the tang of the reamer to turn it. I was a bit worried in advance about the alignment, but it seemed to work well.
If anyone wants to borrow an old 4MT 32mm reamer, and a piece of brass machined to 31mm to clamp onto while the glue sets, let me know!
-
Well I finished it off last night, and today had the not insignificant pleasure of riding on a seat that stayed where I put it :thumbsup: :thumbsup:
I used Loctite Super Glue Power Gel as recommended by LWaB. I think I didn't use enough glue first time, and maybe also didn't wait long enough - the reamer pushed the insert out. So second time I used more glue and waited overnight. For good measure, I left the mandrel partly in place, so that the insert couldn't really go anywhere, until the reamer was half way along it.
Of course, no job is ever finished. In the process, I found that my saddle height insert was breaking up and my O ring was failing, so I've been back to Condor's today to get replacements for those.
Thanks to all who have contributed here.