About a Brompton: C line Electric Review


I’ve developed an interest in folding bikes as well as small wheeled bicycles over the years.  Lately, I’ve also wanted to explore the growing world of e-bikes.   I combined all of these interests together in purchasing this Brompton C line electric bicycle.

Before delving in to my impressions of the bike, there’s first a lot to unpack about Brompton bicycles in general and the e-bike version specifically.  First and foremost, this is a folding bike with tiny 16 inch wheels.  It folds into a squarish size that can easily fit behind a desk or in even the smallest hatchback.  The folding process is quick, involving only a few steps, and is arguably ingenious as there’s no other (rideable) small wheeled bike that folds up this small and this easily, to my knowledge.  I won’t go into the folding process here, as there are multiple resources on the web to help you learn.

In practice, I have rarely fully folded the bike, but have found this “kick stand mode” very useful, both outdoors and inside.

Of the many quirks and oddities of Brompton bicycles, the most important is the fact that since this is both a folding bike and a “one size fits all” bike, virtually every component is purpose built and cannot be upgraded or swapped without voiding the 7 year warranty (frame only, 3 years for the e-bike components).  Essentially, everything on the Brompton, down to the cables and their housings, is custom made.  I learned this after purchasing the bike with the taller version of the handlebars.  Only one style of handlebar is available with the e-bike version, and it comes in two different heights, achieved by different stem lengths.  Swapping bars is an expensive undertaking and can only be done by the dealer.  Fortunately, having only a few miles on the bike, I was able to swap it out for a different model with the shorter stem.  Even so, I find the medium height bars too tall for ideal comfort.

Likewise, the shape of the bars, necessary for the bike to fold, means that there is no swept-back angle on the grip portion, which instead are perpendicular to the stem.  This rotates your shoulders forward and twists your thumbs and wrists into an uncomfortable position.

I removed the stock grips and wrapped multiple layers of cloth tape to the grip area, opting for a funky two tone look.  This helped to make the grip area less thick, making it less painful for my thumbs to lock under the bar, and I like the feel and moisture absorbency of cloth tape.

Because of the bike’s non-standard design, all of the visual cues that one might use to set up the ergonomics are missing. I needed to get out my angle finder and tape measure to get the bars and saddle set up in the most tolerable position for riding.  One size fits all means some ergonomic compromises.

The utilitarian saddle clamp is made less effective by its single bolt design with the bolt positioned so that one must mount the saddle (I removed the uncomfortable Brompton saddle) on the upper rails of the clamp in order to access the bolt.  If mounted on the lower rails, you can see that the saddle can’t be positioned correctly because the bolt becomes inaccessible from the side. Traditional saddle clamps have the bolt accessible from underneath the saddle.  The clamp itself allows for micro-adjustment, however.

I wanted to use my leather Cardiff saddle with this bike, but ended up swapping it for a well worn WTB Deva which provides a little more cushioning, necessary due to the bouncy ride.  Even though the bottom bracket is offset ahead of the seat tube, I still needed to push the saddle back to account for the forward mounted (and must not be reversed for unknown reasons, per the owner’s manual) no-set-back saddle clamp.  I also angled the handlebars inward toward the saddle to bring my hands into a comfortable position with some elbow bend to provide much needed shock absorption.

Rear suspension block

Short spokes make for a harsh ride

Rear wheel not centered between chainstays

Small wheeled bicycles, with their shorter spokes, are improved by front and rear suspension to help smooth out the ride. I’m amazed, given how harshly this bike rides, that Brompton hasn’t invested in engineering some kind of front suspension.  Alex Moulton figured this out back in 1962 when he designed the first Moulton with full suspension front and rear.  It too featured 16 inch wheels.  The folding stem would admittedly present engineering challenges. Brompton has only managed to engineer a simple rear suspension block, perhaps choosing instead to spend its money on branding every single component of the bike, down to the rear fender flap.

The little 250 watt motor housed in a relatively small flange hub, still eats up a big portion of the front wheel’s diameter, making the spoke length very short. I don’t hear riders of regular Bromptons complaining bitterly about the harsh ride, but maybe that’s because they have three things going for them:  longer spokes on the front wheel, a lighter and more flexible fork, and more (and better) tire options.  Brompton has specified only two tire options for this e-bike:  the Schwalbe Marathon Racer and the Schwalbe Marathon, both harsh riding tires with heavy, stiff sidewalls.

My bike came equipped with the Marathon Racers, which measure 34mm wide on the Brompton rims.  I’ve had to experiment with tire pressure, as there is a trade off between rolling resistance and ride harshness, which I’ve found to be balanced at about 70-75 lbs. front and rear.  You’ll note from the above photo that the rear wheel is not centered between the chain stays.  There is only about 2 mm of tire clearance on the drive side, with about 9 mm on the non drive side.  At first I thought that the rear wheel was out of dish, but upon checking I discovered that while out of dish by about 1 mm, the culprit for the lack of centering is that the drop outs are out of alignment, appearing to be so by design.  Theorizing that the purpose for this had something to do with the bike’s folding characteristics, I contacted both my local LBS and Brompton itself via email, several times, and never had a response.

At any rate, the lack of clearance means that it is impossible to install wider tires on this bike.

The drivetrain consists of a wide ratio Sturmey Archer 3 speed hub with two cogs, 16T and 13T, mated to a 50T chainring up front.  This gives a gear inch range of 33 to 100, which is a good spread for just about any kind of riding.  There’s an oddball “chain pusher” clamped to the chain stay that shoves the pulleys, which are plastic, from one side to the other of the the also plastic chain tensioner.  The (plastic again) shifters have the cog shifter on the left side and the internal hub shifter on the right side.  I found the half step gear shifting pattern to be non-intuitive until I made the above gear shifting chart.  Now, it’s easy to remember that any time I am shifting the rear hub, I’ll need to do a double shift to maintain cadence.  The whole system is noisy as can be, with something always whirring and clicking. Combined with the thunking and rattling noises caused by the harsh ride, it’s taken a while to get used to, and has at times caused me to think that something is seriously wrong with the bike.

There’s also a lot of friction in the drive train, which you can note by trying to spin the crankset backwards.  It simply doesn’t.  Normally, there would be about a 5-9% loss in power due to the internal gear hub as compared to a derailleur geared bicycle, but this drive train feels more sluggish when “unplugged” than my vintage 3 speed bikes.  I suspect this is caused by the pulley placement on the chain tensioner:  there is almost no clearance between each pulley, barely enough room for the chain to fit through.  Add to that the drag from the front motor, and this becomes a bike that’s not fun to ride with battery turned off.

But, many faults and flaws can be overcome with the addition of a little battery power and a motor. The bike comes standard with a soft case to hold the battery, which clips into a specially designed front bracket.  The case is very small, but can hold a U-lock, cell phone, and wallet.  I opted to purchase the larger commuter bag and have found it very useful, and big enough for a change of clothes or a day’s shopping.

The bike comes with some thick owner’s manuals and the learning curve for this bike is  steep, especially if you haven’t owned a Brompton or an e-bike previously.  But, I’ve learned a few tips that I can now share.  First of all, when you insert the battery onto the bike, make sure it is fully clamped in by giving it an extra shove, otherwise the battery can pop out/turn off unexpectedly while hitting a bump.  Secondly, the battery, sensors, and motor are re-calibrated each time the battery is installed, so do not turn the cranks or move the bike for the first few seconds.  Wait until all the lights come on, and even a few seconds after that.

There are three power modes.  Don’t waste your time on power mode 1, as it is too wimpy to overcome the bike’s drive train flaws.  I’ve found that using mode 2 consistently, with the lights always on, gives me about a 30 mile range before re-charging.  Mode 3 is great for steep hills, hot days, and miserable rain, but will use the battery more quickly.  According to the owner’s manual, the battery likes to be recharged early and often.

As per British e-bike standards, the power cuts out at 15 mph, for which I am thankful.  This little bike with its tiny wheels can be scary on descents, especially if encountering a bump or pothole, which can turn the fork and even swallow the front wheel.  For me, it’s also nice to not overtake super-fit riders.  I’m not riding to get there as fast as I can.

There are many other quirks and “Bromptonisms” that need to be learned.  I’ve found the videos by Brilliant Bikes especially helpful and humorous.

Poorly designed rollers

Roller on fender which doesn’t actually roll

One locking solution for quick stops.

I did consider selling the bike until just recently, as I’ve come to think of it more as a commuting appliance, rather than a bicycle.  There have been so many notable flaws, including the fact that this bike isn’t suited for multi-modal transportation (except via car).  It is too heavy (about 39 lbs. with battery) to comfortably carry up steps, and the poorly designed “rollers” to be used when the bike is partially folded, simply do not work on this bike.  Perhaps because it is heavier than regular Bromptons are, but the bike doesn’t roll when folded on anything but the smoothest polished surfaces.  There are aftermarket rollers available, but it is disappointing that Brompton would not properly engineer these rollers to work with the e-bike.  Because of the weight and inability to roll when partially folded, you can’t take this bike with you into the grocery store, as you can with regular Bromptons.  That means you have to figure out a way to lock it.  I’ve come up with one solution, shown above, that locks the battery as well.  So far, so good.

Likewise, failing to provide for a bottle cage mount is another disappointment.  Fortunately, I found a suitable solution with this clamp made by “Monkii”, but it is puzzling that such an important feature is left for the consumer to problem solve, especially on a bike in this price range.

To end on a positive note, I’ll say that one redeeming feature is this adorable pump, engineered to fit perfectly on the left side seat stay.  It works fine, too.

So, why do I still have this bike?  In addition to commuting on hot days, cycling on unpleasant errands, and riding through rain storms, I’ve also taken this bike on some almost fun jaunts out of town.  I’ve expanded my normal routes to include previously unconquerable hills.  While not my favorite bike by any means, I have found it helpful to have an e-bike on hand when I want to ride even though conditions are bad. Its folding capabilities mean that I can take it with me on out of town trips even when I am bringing another bike, because I can squeeze it in just about anywhere.  But, I cannot recommend this bike as one’s only bike, except maybe in an environment with very smooth roads. Wired Magazine declared this bike un-rideable in its recent review.  Let’s hope that as competition in the e-bike market increases, Brompton will be required to address some of this bike’s glaring shortcomings.

Sturmey Archer AW Hub Overhaul: Curiouser and Curiouser

Rainy, dark winters are the perfect time to hunker down and disassemble something.  Since I’ve been wanting to know more about servicing SA 3 speed hubs, last winter I decided to take the plunge, having two potential candidates in my parts bins:  a 1974 model and one from 1978.

I knew I needed to do more than just endlessly stare at this parts schematic.  Fortunately, Glenn’s Complete Bicycle Manual dedicates 16 pages to the overhaul process.  And, I found especially helpful the online repair guides from Sutherland’s (courtesy of the Sheldon Brown site) and from Sturmey Archer (courtesy of Tony Hadland’s site).  The Sheldon Brown site also has detailed instructions as well as some helpful illustrations.

Before going down this rabbit hole, I also consulted several video guides and read a lot of interesting commentary regarding the “right” way to service these hubs.  RJ the Bike Guy’s video turned out to be the most practical and helpful.

First up was selecting which hub I wanted to overhaul.  I ended up choosing the earlier model due to its differently shaped slot on the “ball ring” which is a threaded part that connects the innards to the hub shell.  To loosen the ring you use a drift punch and hammer, then tap away counter-clockwise until the ball ring gives.  Unfortunately, newer models of the AW hub have ball ring slots which are more rounded and designed to take a proprietary spanner tool (which appears to no longer exist except perhaps in Wonderland).  After whacking away at the newer 1978 hub, I gave up and switched to the older 1974 model and had the ball ring loosened right away.  It’s also much easier to loosen the ball ring if you have a hub which is attached to a wheel.

But, before doing that you need to remove the outer nuts and washers and the cog which is held in place with a clip, as shown above.  Immediately after that you remove the left hand side locknut, washer, and cone, but leave the right hand assembly in place.  It’s important to keep all the parts in proper order as you remove them – I used zip-ties for this purpose.  It’s also important to note the orientation of all washers, and to make sure that the cog is re-installed correctly with its spacers and dished side as originally configured.

Once you unscrew the ball ring, the whole hub assembly comes out of the hub shell, intact.  Inside the hub shell you can see the ratchets at the bottom along with the left hand side set of bearings, held in a clip.   From there, you can remove the bearings from the left hand side of the hub shell (first you remove the “upside down dust cap”) and then set the hub shell aside.  Why are the dust caps upside down?  One site I consulted suggested that the troughs are meant to be filled with water proof grease, to further seal the hub from the elements.

After the driver is removed on the right hand side, which is done by removing the cone, the hub internals come apart in stages. The above photos document the series of steps to remove the clutch spring, gear ring, clutch assembly, and planet cage assembly.  You’ll note both the gear ring and the planet cage assembly have pawls.  The final photo above depicts the sun gear, which is permanently affixed to the axle.

For cleaning and reassembly, I found it easiest to tackle each sub-assembly separately.  The above photo shows, from top left to bottom right:  the planet cage, the clutch assembly, the driver, gear ring, and the ball ring.

The ball ring is aptly named – its a ring of ball bearings.  Studying the instructions gave me a lot of pause though, with confusing references to the ball ring having a “two thread start” and therefore meaning that in reassembly you might start the threading on a different thread than as it was originally threaded which could cause the wheel to be out of dish.  After doing a lot of reading about this, I came to the conclusion that this is of no importance to me, since my hub has no rim attached.

Unfortunately, at this point in my life I became very busy at work and didn’t get back to this project for many months!  When it came time for re-assembly, after having cleaned all the parts with a citrus cleaner, alcohol, and brass brush (I do not use toxic cleaners that can’t be safely disposed of), my brain needed a refresher course.  And, as I looked at the little planet gears I realized that I didn’t really properly understand how these hubs work, so I did some further research.

I found some answers by watching this interesting video, which depicts how the gears are engaged in this 3 speed hub. This is really different from how I thought these hubs worked.  I had imagined that each planetary gear circulating around the sun gear was of a different size (an idea I developed in childhood), and that’s what created the different gear ratios, much like a derailleur shifting through different sized cogs.  How wrong can you be!  Learning the importance of the clutch position has made me much more careful about shifting when I’m riding bikes equipped with internal hubs, remembering to lighten up on the pedals for each shift.

Meanwhile, back to the torture of the reassembly process:  things went fine until I tried to reassemble the pawls and pawl springs in the planet cage.  I dutifully lubricated the pins with Phil’s Tenacious Oil (as recommended by various mechanics), but when it came time to put the pawls and their tiny springs back in I had trouble getting them assembled correctly.  The pawl springs are so small that I actually “lost” them a few times only to realize that they were still right there on my work table, just basically invisible.  It’s also important to orient the pawls correctly, taking note of the slight beveling on one side.  I proceeded on with re-assembly, following carefully the instructions from Sutherland’s and from RJ the Bike Guy’s video.

After proceeding through the re-assembly of each of the subassembly, finally the hub is back together.  I was initially unhappy with the cone adjustment, which was a relatively easy fix.  The Sheldon Brown site has a good discussion of this process.  There should be a tiny bit of free-play in the hub if it is properly adjusted, and generally speaking, the adjustment should be made from the left hand side.  Once the cone adjustment was right, I also checked to see that the indicator spindle moved freely, so that the 3 gears can be engaged.  The true test will be to build the hub into a wheel and install it into a bike, but I’ll save that project for another rainy winter day.  And, now I will feel more confident overhauling the SA hubs on the two bikes I own which feature these hubs:  a 1950 Raleigh Sports Tourist, and a 1966 Sears/Puch.  I’ve gained a lot of useful knowledge and look forward to expanding on that.


1973 Jack Taylor Revisited

While I’ve been working on other projects, my 1973 Jack Taylor Tourist bike has been languishing in my storage area, along with far too many other bikes.  I thought it was time to bring it back out again for the coming spring weather, and that meant assessing why I wasn’t riding it so much anymore.

When getting the bike up into the shop stand I realized that I still hadn’t solved the ergonomic issues resulting from its large frame (for me).  Back in 2015 I had replaced the moustache bars with a more upright style, and a short reach, tall stem. But the bar shape didn’t really work for me, and I ended up setting the bike aside a few years back.

I needed some bars with a more swept back profile and with more rise, so I tried out these Sunlite Northroad bars, a set I haven’t tried before.  I cut them down about 2 cm, which turned out to be just right for this bike.  If I were using these bars on a smaller bike I probably would have cut more, but on this bike these bars look well balanced.  As part of the bar swap it was necessary to install new brake housing, which needed to be a little longer due to the swept back shape of the bars.

I made a few other changes as well.  The original Soubitez front lamp was held together with electrical tape and needed to be replaced.  I was able to find an exact match on eBay, shown above.  In the same purchase I acquired a NOS Soubitez dynamo from the same era. This one works more reliably that its predecessor and seems to have a little less drag.  I also replaced the pedals with a vintage Phillips French threaded set.  The pedals are very grippy, more so than the Lyotards previously installed.

When I threw my leg over for a test ride, I was reminded just how tall this bike is.  The bottom bracket height is a whopping 11.5 inches (29.2 cm).  That’s mountain bike territory, and definitely different than many of my other bikes.

This bike features 27 inch wheels rather than 700c. The rear wheel is laced to a Sachs Orbit 2 speed hub which takes the place of a front derailleur.  The big wheels roll smoothly and absorb road shock very well. They have never gone out of true since I acquired the bike 15 years ago.  I have found this to be the norm for any well built wheel, including wheels I have built myself.

The Sachs Orbit hub offers about a 25% drop from the direct drive gear.  As originally equipped, the bike had a 34 tooth chain ring on the front.  That was a bit low for me, so I replaced that with a 36 tooth version.  Gear inch range with this hybrid set up and the 14-28 cog set is 25-70.  Still pretty low, but with the bike’s front and rear racks, the low gearing makes it easy to feel comfortable hauling stuff and climbing hills at the same time!

I had previously changed out the original saddle for this vintage Ideale Model 75.  The leather was very stiff and unforgiving, which made for an uncomfortable ride.  After applying some Brooks saddle treatment and using a hair dryer to heat it up and work it into the leather, the saddle is now more supple.  With the newly installed upright Northroad style bars, this saddle style is perfect.  The springs do a great job at absorbing shock without being bouncy.

So, will I ride this bike more often?  I do think so.  Now that the ergonomics are right for me, the smooth ride quality and easy gearing will make it appealing.  It can handle any kind of weather, and even though I dislike sidewall dynamo lighting, getting caught in the dark will not be an issue for this bike.  This is a bike that can handle a lot of different riding requirements. The Reynolds 531 fillet brazed frame makes it responsive and light weight.  It’s also a beautiful bike and gets a lot of complements wherever it goes.