Monthly Archives: November 2021


My conversions of some of my Bromptons into external gear 3speed & 4speed lightweight bikes is a personal thing, creating Bs that suit me & my limited power generation capabilities. I think that “power hides things” & I was bogged down by/with 3 factors; slow tyres, IGH hub drag, excess bike weight

Rudolph (Chpt3 v2 S6E-X) was “illuminating”, with fast tyres & a lot less weight than Clarence was running (S6R with Marathons, Brooks saddle, etc, etc). At first I couldn’t put my finger on what was holding back Clarence but once my experimenting with a 2speed rear wheel (acquired some time before, for “the parts bin”) & swapping accessories & tyres, here was a B that was lively & effortless (in comparison). With Covid lockdown (#1) & noticing lightweight parts available, the journey began!

Becoming aware/awake to component weight differences, I’ve tried to limit extras & only replace parts with lighter items. My extras are lights, bidon cage & essentially, a roller wheel extender to primarily protect the Ti rear frame “ears” (having seen a lot of pics of broken Ti frames with savaged roller wheel mounts, I’m hoping the extender is “insurance”?). Probably my first weight-saving consideration was the seatpost area. With a steel seatpost, Pentaclip & Brooks saddle weighing about 1kg, my replacements provide a saving of 500g – hence my following of the Brompton proverb, “Look after the grams & the kilos will look after themselves”. Nowadays there’s very little steel bits left on Clarence & BB, just the mainframe & stem?

Tinkering to improve/tweak performance has come from countless people before me, their tales littering the Internet. Lockdown learning skills & capabilities has shown that the tolerances to modify parts is tiny & often I’ve had to marvel at the original Brompton parts & design. I’d have to say that many of my Brompton tweaks require a “mechanical sympathy” & aren’t going to suit everyone – eg the SunRace shifter is great; I just need to feel when to feather the lever a touch! The whole derailleur system needs precise setup & variations between components & frame tolerances can make for some frustrating/baffling times – eg BB’s 3speed vs Clarence’s 4speed, where exactly the same derailleur & shifting components are used – but with different wheelsets!

So, to now see Brompton’s new P Line Urban models released is partly justification & reflective: I’m content with my creations but now I get to see how Brompton would do their redesign. In brief, I’m impressed/awed/appreciative – & already frustrated to see the “social media knockers”. I’m suspecting the first bike reviews to make many eat their words (hopefully not me?).

Perusing Brompton’s website (& apologies for pinching all the pics below) reveals countless touches – many unexpected. The P Line Urban seems truly a 2speed redesign, where the factory have noted flaws & taken their chances.

My main observations:

• The rear frame ears

• The external mudguard stays

• The 2-position seatpost locking

• The Pentaclip redesign (with oval saddle rail suitability)

• The derailleur design

• The rear hub design (& tweak possibilities?)

• The new 20spoke front wheel

• The roller wheel frame

• The website Support section videos

• The engineering efforts throughout

An earlier video? Due for replacement?

Now let me see, what weight savings could there be? Hmmm… golly, Clarence & BB are under threat!?


Lockdown learnings

Lots of Brompton fettling during our Sydney Covid lockdowns, mainly 3 older IGH bikes transitioned to Ti lightweights. Plenty of time to await parts, learn skills & tinker? New things for me were Ti fork & rear frame changes, lightweight headsets, Ti BBs & even wheel rebuildings. It’s all just Brompton Meccano really!

In preparation for finally being able to revisit our MidCoast beach unit (woopee, we got there last week!), I also resurrected some pre-Brompton steeds from storage, deciding that the coastal strip would be a good home for them.

The 20year old Giant MTB got by with a wash & lube & seems almost as new. I also had thoughts that the Trek TT bike would suit conversion to a single-speed beach cruiser, however plans got adjusted. The bike wash revealed an “exploded front hub” (something I discovered that era Bontrager aero wheel type was renowned for, but I could hardly claim warranty after 12years in storage!).

After retrieving another wheelset, I pushed on & stripped the TT bars & removed the large chainring. Instead of a single-speed setup, I used the rear wheel bar-end shifter & mounted it to the bullhorn bars (trying to make use of components wherever possible). With a single chainring & a 9speed rear hub, I cut back the cassette cogs to 7 to ease the chain line & dispense with the highest gears. Adjusting the derailleur limits for the 7cogs was perfect & it all seems to function well. (The setup has a 39T chainring & 13-23T gearing, pretty suited to my beach side cruising needs? – & now with a bike weight of 8.5kg)

Playing around with all this older technology made me aware of the likely difficulties of replacing parts in future, so decided to retain the Bontrager wheelset if possible. Finding a low spoke count front hub took time & when I dismantled the hub I discovered the rim used “hidden nipples” & that I couldn’t re-use the bladed spokes in the new hub! Very fast service from a WA spoke supplier & another wheel finished in quick time, if I may say so myself?

Only a couple of rides so far & I’ll need time to reacquaint with the twitchy TT handling – & I hope the locals aren’t upset about the rear hub buzz? (very loud; who needs a bell?)

BB genealogy

Aside from a new name, this little Brompton has undergone lots of changes during its life

• Built September 2011, probably as a S1E

• B11E UK modded with Bullhorn bars & Alfine 11speed IGH & sold to Aussie traveler

• S11E Sydney mods to replace Bullhorn bars, sold to me in December 2012 (name: Ralph)

• S11L mudguards added, various traveling (incl 2013 BWC & 2014 BAC)

• S11R-e GrinTech motor kit added, September 2016 (name: Ralph-e)

• S11E “naturally aspirated” during Sydney lockdown, June 2020

• S4E-X converted during Sydney lockdown #2, August 2021 (name: BB)

• S3E-X wheelset change, September 2021

Some drastic changes but maybe not as insane as they seem?

GrinTech mode was setup after giving up on waiting for Brompton’s e-version release. Very successful mod, although folded weight (23kg with battery) was sometimes awkward. Also, torque-sensing power delivery didn’t mate well with my health issues (“fatigue on big hills meant reduced pedaling effort, resulting in reduced power”; config best set to provide power at low human watts input; later GrinTech motors similar to Brompton version weight)

After my Chpt3 purchase (Rudolph) & finding that I could ride comfortably with an easy-rolling light bike, I removed the GrinTech kit during Covid-time & tried to get Ralph as light as possible & to compare with Rudolph & Clarence (now S4E-X modded). The project almost got to Rudolph’s weight but my conclusion was that the Alfine hub drag was too much for me. (The Alfine IGH was a good range of gears but suffers from increasing hub drag as you change to higher gears. Ralph may cope better with hills but elsewhere Clarence rolls so much more effortlessly.)

Lots of thought on whether I was likely to use (& enjoy) the new Ralph but it seemed inevitable that I ought to let Ralph go to a new home? Another lockdown & I decided to make Ralph enjoyable for me – by doing a Clarence act. So, now I have Clarence & BB (ie Black Brompton, Bitza Brompton, or whatever feels right as a name?) in similar but different configs. Clarence’s spec as a S4E-X now stands at 9kg, with mini rack & standard Brompton lightweight wheelset – sorry Brompton, your newly released P Line doesn’t interest me; too heavy, lower range of gears & “Clarence is already here” – in my favorite colour!

BB’s spec is a S3E-X & has various lighter components to weigh in at 8.3kg. Once again, lighter & a better range of gears (11/14/19T) than a new P Line version – although I’m sure Brompton’s new 4speed shifting is better integrated. (I’d like to say that I’ve given up trying to run BB as a 4speed; lots of tinkering but various factors involved (tensioner distortion, shift cable tension, derailleur clearances, wheelset hub dimensions, etc) but BB’s 3speed runs so well that I’m content – & resisting looking for any expensive bits/kits that may help?)

I suppose I’ll never decide which of my Bromptons is best. They all suit different situations & it’s always a difficult choice for a ride. Clarence & BB are so light & lively that porky Rudolph often gets overlooked?