2021 Brompton C-Line Explore

[wafter]

Having plenty of far more important things to do today I elected to sort the pedals on the Brompton, having seen some corrosion around the RH item and figuring they'd probably benefit from a clean and refit with anti-seize grease.

For reference the RH pedal axle is 15mm the same as the wheel axle nuts, however with both pedals having a socket in their rear / inside face I elected to use a 3/8" breaker bar and hex bits; straddling the bike and standing on the pedal while I precariously tugged on the bar with the opposite arm.

Perhaps unsurprisingly from the corrosion present on the crank the RH pedal turned out to be loose, while the LH item was somewhat seized; going with a bit of a crack after soaking in paraffin while I dithered with the other one.


RH crank with signs of fretting from the loose pedal:

Cleaned and waxed:

RH pedal as-removed; seems there may have been some scant form of lubrication upon assembly. It cleaned up nicely with some paraffin on a toothbrush, but I forgot to take an "after" shot..

LH crank arm pre and post clean / wax; note the damage from incorrect / hamfisted folding of the pedal; some of which I'm probably responsible for..

LH (folding) pedal, which apparently didn't have any lubrication when assembled. I was impressed to see that the small amount of paraffin half-arsedly bled into the threads from the rear appeared to have made its way through the entire length of the threads in the 10-20 minutes it was left.

Sun Race / Sturmey-Archer branded 6203 cartridge bearing.. looks pretty sturdy which is a good thing since the pedal housing appears peened around it; making it irreplaceable.. which is shoot.

Fixings..

Once cleaned it all went back together with some copper grease; torqued up to 30Nm.

I guess that's one less thing to worry about

 

[wafter]

The tubeless experiment ended earlier this week with a flat resulting from a persistant, partially-sealed leak so it seems pretty conclusive that the Marathon Racers aren't suitable for this (lashed-up) application

Also this week I managed to score some Continental Contact Urbans for a good price (assuming they're not knock-offs), which might fare better in the face of such bodgery, although the earliest I'm likely to try this will be when puncture season is upon us again.

Finally for the second time as many weeks a series of dodgy repairs to the front tube resulted in a slow leak (flat overnight); so I elected to write off the tube in question - this being the last of the originals; killed by a combination of unrelenting punctures and my sub-par-patching.

So, tyre business was afoot today. Both wheels came off and were stripped. After a bit of a clean (especially the rear after having to bang a tube in amongst the still-tacky sealant) they went together with a new Schwalbe innertube on the rear, rear tube swapped to the front and both new Contis fitted.

I figured that since I was stripping the wheels anyway I might as well unfurl the folded Contis, fit them and leave them in the sun to allow them to take a set in a more optimal shape than their contorted as-received state.

Before fitting they weighed in at 221 and 222g; good consistency and close to the published mass of 220g. The Marathon Racers are more like 240-245g; although to be fair they're wired so are going to weigh more.

The tyres went on relatively easily and settled with pretty good seating / alignment... certainly better than others I've tried in the past. Not sure whether this is anything to do with them being folding as I usually run wired since I'm tight.

At 115psi (max in the interest of shape retention) the one tyre I measured came in at 33-8-34.3mm wide - comparable to the Schwalbes and still disappointingly down on the 35mm published value.


While the tyres were being conditioned I turned my attention to the front hub bearings as they felt pretty rough when the wheel was spun.

The DS locknut and inner race came off courtesy of my new bargain Lifeline cone spanners and the standard 15mm ring spanner kept with the bike. The inner race is 1/2" (12.7mm) AF, so since I only had a 13mm spanner I packed it out with a folded piece of ally pop can to prevent any damage..

The hub contains 10-off 3/16" (measured at 4.72mm) balls bearings on each side. These were extricated with a magnet before I realised that the seals just pull out..

All that would fit in the paraffin jar did, the rest was cleaned of the very sticky grease with paraffin on a brush before it was all cleaned up with a rag.


One of the outer races (not sure which; I have become confused) shows some odd repetitive markings inside; these don't look like the result of any issues during use - perhaps from manufacturing when these were pressed in..?

The NDS inner race shows some significant damage; although again I'm unsure how this has happened as it looks mechanical and there's no obvious corrosion in this area.. perhaps contamination during assembly..?

This damage was corroborated by the significant amount of metallic contamination that followed the ball bearings out of the (ostensibly clean) paraffin.

Once dry it all went back together with lashings of moly - it still feels rough but noticeably better than before.. since it's only the inner race that's currently damaged I'm tempted to leave it, although ideally I'd prefer to replace it. Brompton don't seem to list this as a separate part but I suspect it might be a pretty standardised item across many different bikes.

Contis will remain on the wheels in the sun for as long as possible, then I'll fit the worst two Marathon Racers in my possession in an effort to finish off the most worn and reduce what I have kicking about.

In other news the Brompton is now well past 3000 miles and has saved me about £500 in fuel so far

 

[wafter]

A bit more for the sake of completeness... Sunday saw the original tyres refitted with two new tubes after fun trying to find a leak on one of the existing ones.

The original rear tyre has had a hard life anyway (as rear tyres usually do) however it's interesting to note how much more cracked and pale it is compared to that from the front - the latter having only covered around 2k miles compared to the rear's 3k miles. While obviously tyres wear out, it's a bit disappointing that they should be subject to such obvious UV damage over a year of normal use..

While bothering the wheels the near-dead front brake pads were re-aligned and the rear wheel attacked with a spoke key as it'd developed a bit of a kink.. while it's not perfect when spun next to to a strategically-placed finger nail, it looks true and I reckon there's only maybe half a mil runout axially and radially.

And so concludes another scintillating update

 

[wafter]

A depressing update.

*EDITED* as I got the pin orientation wrong initially..

As per this thread, recently I noticed a fair amount of play in the main frame's hinge, which I don't recall being present when I bought the bike.

This morning I've wasted however many hours investigating this issue further in an attempt to better understand why it's happened, how it can be resolved and how best I can fortify myself against the manufacturer's likely rejections if I try to get it sorted under warranty.

To clarify before we start, yes - I know these "wear" and that replacement pins are available.. however I'm not convinced that this particular situation is the result of legitimate wear (i.e. abrasion between the rotating parts of the hinge due to repeated folding operations) while the way in which it's failed seems counter to what one would expect from the design..

The hinge setup consists of two 11mm deep outer / upper & lower sections attached to the front part of the frame, located above and below the 35mm deep centre section which is attached to the rear part of the frame:

The two sections of the frame pivot relative to each other about a 6mm nominal diameter pin, which (from the videos and images I've found online) is fitted from above and retained by a spline on its top end that's driven into the upper section of the front's outer hinge. Below is an image of the pin from the net; showing the splined section at one end that would sit at the top of the hinge when fitted:

From the presence and location of the spline it appears that the pin is intended to remain static relative to the front / outer portions of the hinge, while the central / rear section of the hinge rotates relative to the pin during folding. This makes sense as the middle section has the longest bearing area and appears to be best shielded from dirt and contamination that might accelerate wear.


Concerningly my hinge behaves nothing like this ideal. When the hinge clamp is slackened off and the front and rear parts of the frame moved relative to each other (most easily with the bike upright, lifting and lowering the rear portion causing the whole assembly to "hog"), the top of the hinge pin visible from above shows significant radial movement relative to the upper section of the front / outer portion of the hinge.

When repeating the process with the bike inverted, the bottom of the pin can be seen moving axially (in and out along its length) relative to the lower section of the front / outer portion of the hinge. I've measured this float at around 0.25mm.

Perhaps most concerningly, while from the presence of the spline one expects the pin to remain static in relation to the front / outer section of the pin during the fold, it actually remains stationarly relative to the middle / rear section - suggesting that the spline has torn its way out of the upper portion of the front hinge and seized inside the middle section of the rear

Finally, looking at the pin from above again there's a counterbore into which a tool has evidently been driven during fitting to expand the end of the pin into the upper section of the hinge; causing the pin to crack in two places:

The pin from underneath...

I'm keen to learn more and stand to be corrected, however currently it seems to me that through nothing other than normal use (riding) the cracked / "expanded" upper end of the pin has been slowly beaten into submission, unsurprisingly collapsing in on itself as the cracks resulting from its original expansion during manufacture close up. This has reduced its effective diameter and caused the slop in the joint.

Further, it appears that perhaps this play / loading through ongoing use has caused the splined end to move / wear inside the grooves its cut into the upper / outer section of the hinge, eventually causing them to fail and allow these two parts that should be locked together to rotate relative to each other.

I don't understand why the pin would rather remain static inside the middle section of the hinge, while I'd have thought I'd have noticed an event as significant as the splined end ripping itself out of the upper portion of the frame during folding, but I've had no issues that suggest this has happend during use.

A third possibility is that the middle / rear section of the hinge has always been tight and the spline was knackered the first time it was folded at the factory and pushed out of the door regardless.


Sadly having taken the time to look at this properly I'm pretty disgusted by the implementation of this hinge - the cheap, irreversible, single-use nature of the splined pin; the method used to expand the top end of the pin into the upper part of the hinge (and subsequent damage / invitation for it to collapse as it apparently has here) plus the apparant failure mode encountered in this case.

When I initially read about the replacement process for a "worn" hinge (remove original, ream holes oversize, fit oversize replacement) I assumed this was something that would happen after many thousands of miles and folds, as a result of bearing surfaces on the pin and hinge literally wearing out through natural, unavoidable abrasion from the fold.

Conversely in this instance the failure appears to be the result purely of the failings of "questionable" (to put it extremely charitably) design decisions. Further, it concerns me that this might be the standard failure mode for these parts which Brompton might euphamistically refer to as "wear", and if so having failed so obviously after only 3k miles / a year of use, suggests that the bike will be scrap after 12k miles / four years of use.

I fully expect Brompton to try and fob me off when I raise this with them; likely suggesting that I pay one of their agents to "fix" this with an oversize pin.

The idea of slowly destroying my frame by perpetuating this lash-up is clearly unpalatable so I've been considering other options. The obvious alternative would be to ream all holes in the hinge to the same size and fit a ground, plain-shanked shoulder bolt with a head on one end and thread on the other for a retaining nut - which would be an immeasurably superior approach - easily removable, reversible, far more resileant.. you could even add easily-replaceable top-hat plain bearings to mitigate any wear to the frame and make it essentially last forever.

While searching for images of the hinge pin for this thread I came across one for a T-Line and quelle surprise - it seems that the setup on this bike uses exactly this approach:

So, it looks like spending the fat end of two-thousand quid isn't enough to get a sub-par hinge design that doesn't eat itself in short order / ultimately result in the destruction of the frame, and that Brompton want to you spend five grand to get something that's actually competently designed and fit for purpose

I'm going to drop Brompton an email now; I suspect I won't be happy with their response.

 

[Kell]

Hopefully you'll be surprised.

Good job you're thorough though.

Imagine if that had collapsed under you?

I'd keep stressing that point above.

A friend of mine at work had the weld fail on his new Brompton a few years back and they immediately offered to replace it with a (then new and current) 6-speed Superlight bike. He dithered though as he didn't like the colours and then they stopped making them.

In the end, he got a brand new 4-speed.

I'm fairly sure it's a T-line, although he says not. But when I lifted it once, it felt like half the weight of mine.

 

[rogerzilla]

I have had a few really quite old and well-used Bromptons (one green L3 model only had about 3/4 of its paint left after the original owner had slung it on the luggage rack of a Surrey commuter train for 9 years) but these two frame/stem hinges were fine, although the rear pivot had got sloppy.

This early failure is not normal, unless Brompton have cheaped out on materials or assembly processes.

 

[wafter]

Thanks both - really appreciate the positivity and support as I've literally spent all day trying to address various facets of my life collapsing around me..

Hopefully you'll be surprised.

Good job you're thorough though.

Imagine if that had collapsed under you?

I'd keep stressing that point above.

A friend of mine at work had the weld fail on his new Brompton a few years back and they immediately offered to replace it with a (then new and current) 6-speed Superlight bike. He dithered though as he didn't like the colours and then they stopped making them.

In the end, he got a brand new 4-speed.

I'm fairly sure it's a T-line, although he says not. But when I lifted it once, it felt like half the weight of mine.

Hopefully I will, but I'm not holding my breath.

I'll certainly labour the safety element, however don't want to dwell on it too much as I need to use it for work next week!

Despite the float the hinge pin seems reasonably secure axially, while I think at least with the clamp done up everything is pulled up tight and shouldn't move to the extent that it's a genuine safety issue.

That's reassuring about your friend's experience. I think given their target demographic Brompton attempt to cultivate an image of generous customer service; however on the few occasions I've dealt with them I've never really managed a positive outcome (issue with chain wear to the back of the frame resulted in me essentially being TTFO, for example).

That said, obviously a weld failing is a pretty obvious, safety-critical failure. This hinge on the other hand could, either through ignorance or design be argued at "wear and tear".

I did briefly consider a T-line since this seems to get the benefit of actual competent design in areas where it's lacking on the lower models, but quite frankly five thousand pounds is an utterly ridiculous sum - especially for me. And besides, it has a plastic fork which instantly turns me off.

I have had a few really quite old and well-used Bromptons (one green L3 model only had about 3/4 of its paint left after the original owner had slung it on the luggage rack of a Surrey commuter train for 9 years) but these two frame/stem hinges were fine, although the rear pivot had got sloppy.

This early failure is not normal, unless Brompton have cheaped out on materials or assembly processes.

Thanks - I appreciate the reassurance.

I understand and accept that things wear, but this seems to be the result of a clearly flawed design.



I've sent Brompton a video of the slop as well as a description; we'll see what they come back with. Ultimately even if it costs me nothing to get it "fixed", realistically they're only going to carry out the usual pin replacement so the grossly sub-par design will still be sat festering at the back of my mind.

Maybe when the frame warranty's up and the last of my prissyness gone, I can set about it with my proper engineering hat on and actually do a competent job of resolving this grotty little mess.

 

[a.twiddler]

I spent some time fretting about how I'd go about fitting a rear hinge pin on my 12 year old Brompton, but in the end, a local Brompton dealer fixed it easily and relatively cheaply, without me having to get involved in buying expensive tools, etc. It's quite possible that your front hinge problem is a known issue, even if rare, and there's hopefully a relatively easy (and preferably free) fix for it. Sometimes it's all too easy to overthink things and let the clouds of doom and gloom spoil the enjoyment of unrelated things. Been there, done that, got the T shirt!

 

[wafter]

I spent some time fretting about how I'd go about fitting a rear hinge pin on my 12 year old Brompton, but in the end, a local Brompton dealer fixed it easily and relatively cheaply, without me having to get involved in buying expensive tools, etc. It's quite possible that your front hinge problem is a known issue, even if rare, and there's hopefully a relatively easy (and preferably free) fix for it. Sometimes it's all too easy to overthink things and let the clouds of doom and gloom spoil the enjoyment of unrelated things. Been there, done that, got the T shirt!

Thanks - fully appreciate your perspective and can totally identify with your position.

All that said my pessimism about others working on my gear is the result of largely of experience; I can count the times I've been 100% happy with someone else's service on my possessions on one finger.

On top of that having looked at the design it's clearly shite, and will remain so whether it's "resolved" FOC or otherwise.

Typical Brompton tbh - innovative and great in so many ways; however undermined in many ways by piss-poor implementation.

 

[wafter]

More largely sub-optimal goings-on..

It seems that Brompton have little desire to accommodate my protestations about the frame hinge pin situation so I've resorted to pestering a dealer in the hope of a more positive outcome.

Yesterday I dropped into Warlands in Oxford. Having spoken to one of their staff members earlier in the week (who was great) I was hoping for an inspection with a view to gaining some evidence from a trustworthy source that I could use as evidence to persuade Brompton that the problem wasn't just "normal wear".

It was somewhat relieving that both staff members I spoke to agreed that this failure mode was unusual; to the extent that neither had seen this happen in collectively decades of experience. Faced with a stout dose of my my morning's rampant anxiety (sorry!) yesterday's chap was very helpful, accommodating and supportive - suggesting that they'd replace the pin under warranty and send a fault report to Brompton.

So far I'm very impressed with the service - I told them I was happy to pay for it since the bike didn't come from them but they were happy to do it FOC (I hope / assume they charge Brompton for warranty repairs).

Assuming the job's done to a decent standard realistically I guess this is the best outcome - while I'm potentially still stuck with a prematurely worn frame Brompton are highly unlikely to replace it currently if there's life left in it, while I hope the fault report will at least get the issue on record; which may be of use should it become problematic again in future. I'll feel better if they don't have to fit an oversize pin.. although my gut suggests they probably will due to the slop in the outer part of the hinge.. time will tell I suppose.



On to the next problem; the slipping seatpost tube. The clamp is currently done up to the maximum (3mm bolt protrusion from the top of the nyloc nut) and it still slowly slips down over the course of a typical ride.

Yesterday the seatpost came out, everything was degreased with isopropanol and inspected before being reassembled dry. It seems the plastic shim is retained axially in the frame by a circumferential lip at its top that engages the top 1/4" or so of the seatpost tube. Mine has evidently started to split here; beginning on either side of the slit down the length of the shim at the rear of the bike:

In addition to this we can see that the shim has worn at the upper-rear face of its bore; as evidenced by its relatively flat, uniform finish in contrast to the circumferental marks further down / towards the front remaining presumably from reaming at the factory.

It's (arguably) interesting to note the state of the seatpost itself in these areas; which is now a lot more highly polished than the coarsely-scratched finish it displayed last time it came out. I assume this is because the front mudflap extension is doing a pretty good job of keeping crap out of the seatpost tube; meaning the only abrasives left were those embedded in the shim which have been slowly broken down to finer particles by the relative movement between parts as the bikes' been ridden.

I measured the diameter of the seatpost at around 31.66-31.80mm; the worn areas shown no descernible reduction in diameter so I suspect this variation is down the manufacturing tolerances.


Frustratingly it seems the shim requires replacement; something else I'm not keen on as unless I want to spend however much on the tools to do it this will mean entrusting someone else not to f*ck it up on my behalf. This is compounded by the liklihood that this was mostly preventable since it would no doubt have hardly worn at all; were it not for the presence of road grit finding its way into the frame thanks to the inadiquate mudflap and design shortcomings of the frame itself.

I'll hold my hands up as probably being responsible for the shim starting to crack however, since I run the seat nearly as far back as it'll go (with the clamp reversed) which will put more load on the shim.

Not sure what to do yet; the obvious route is to replace the shim.. more accessible options might be to scuff up the seatpost at the bottom with some coarse paper to increase friction, or maybe try and fit a captive ally shim between the existing plastic one and seatpost itself depending on the clearances involved.. although neither of these are ideal.


Finally, yesteday's ride was decidely lumpy at the back. When I got home I found the rear tyre to have a significant bulge radially / axially towards the drive side; suggesting that the ply has failed on the NDS in this area. I'm not sure if this is connected to the faily significant area of glass damage in the vicinity, or just the result of the tyre having had a very hard life - being run under-pressure for a short time at the beginning, while having been pushed flat a number of times when it wasn't time efficient to stop and fix a flat.

There's still tread remaining and it's disappointing that I couldn't wring the full wear out of it; however it's been on borrowed time for a while due to a gradually growing cut from a bit of flint while it's covered in tiny cracks I think due to UV degradation (again, disappointingly) so it's fit for the bin on many levels; having made it to around 3350 miles.

The lower-mileage front tyre is now on the back, a part-worn Marathon Racer that was previously fitted for a while when playing with tubeless now on the front. The one on the rear isn't without its issues either so we'll see how long that lasts...

I have one new Marathon Racer left, however when the bike needs another tyre I think I'll fit one of the Contis I picked up a while ago for a good price (assuming they're legit) as I'm tempted to see if these accommodate council tubeless any better, while generally they seem to be better-regarded than the Racers - about which I have mixed feelings myself..

 

[EckyH]

Not sure what to do yet; the obvious route is to replace the shim.. more accessible options might be to scuff up the seatpost at the bottom with some coarse paper to increase friction, or maybe try and fit a captive ally shim between the existing plastic one and seatpost itself depending on the clearances involved.. although neither of these are ideal.

The shim is designed to be a wearing part, therefore replacing it from time to time is normal.

Roughing up the seatpost means faster wearing of the shim. Nevertheless I decided to go that way and the first approach with the rough side of a kitchen sponge was already successful: no slipping anymore and the thread of the bolt protrudes roughly 2.5mm, so it's not that tight.
Perhaps that is helpful for you.

E.

 

[Gunk]

Get Warlands to pop a new inset in, had mine done a few years ago (my old Mk2) the process involves reaming the seat tube and gluing in a new insert.

 

[Fastpedaller]

Not being pedantic but should that be ' glueing in a new insert and reaming it"

 

[rogerzilla]

I have the reaming tool and a supply of seatpost bushes. The hard part is breaking out the old bush.

Those left-hand pedal bearings don't last long as it's a single-row bearing loaded off-axis. You can file away the lip, knock out the bearing and fit the best 6203-2RS bearing you can buy. It is a tight interference fit and you can add high strength bearing retainer. Or pay £55 for a new pedal.

 

[Fastpedaller]

I have the reaming tool and a supply of seatpost bushes. The hard part is breaking out the old bush.

Is there any solvent which will help by dissolving the 'glue', at least to some extent?