Aussie on a Brompton

Tweaking Brompton gearing is quite an art & often with a dollop or two of luck. I think I’ve now maxxed Dan into a 3speed, with the current parts I have available.

When using the classic Brompton pusher-style derailleur, there can be variations that affect what can be achieved. Aside from some slight differences in steel vs Ti rear frames, the derailleur mount can be positioned a smidge out & the tolerances of frame, mount & pusher dogleg can affect the extremes of movement of the derailleur. Once you attempt gearing tweaks, the outcome will also depend on the rear freehub version.

Taking the lightweight NBR-rimmed hub for example, the lockring-style cassette securing method allows an 11T cog but the limitations of the dogleg movement will likely mean that the chain alignment for the 11T cog is unsuitable (or luck is on your side?). My BrommiePlus Hubsmith 2speed wheelset has used the circlip-style for securing the cassette (& therefore limits the smallest cog to 12T). For both these hubs, the largest cog that fits the rear frame is 18T (or maybe 19T if you’re lucky or willing to dremel the frame tubes to give some cog teeth clearance.

I had previously used the BrommiePlus rear wheel with an X5UniBody cassette with 11-25T config but this requires a parallelogram-style derailleur. (The cassette was later mounted onto a BWR hub to create Iggy, a 15speed Brompton.) To provide some flexibility on what I could use the 2speed wheel for, I obtained & installed a BrommiePlus Hubsmith 3/4speed lockring-style freehub. Fitting this 4speed wheel into Dan, the freehub & end cap dimensions meant I still couldn’t use a 11T cog & reliably align with the dogleg derailleur movement, but what the 4speed hub provides is a wider cassette mounting surface & thus the possibility of a larger bottom gear. My gearing for Dan is now 12/16/21T cogs. (I had noted the frame was capable of a 24T cog but the standard Brompton chain tensioner has a max rating of 22T. Unfortunately a 22T cog then clashes with the BrommiePlus pusher I’m using & hence my max becomes 21T.)

So there you have it; Dan running the Hubsmith 4speed hub with 12/16/21T (with a spacer to push the 12T cog inboard to get aligned with the derailleur) instead of the previous 12/18T config. The BrommiePlus wheelset is slightly heavier than the narrow NBR-rimmed wheelset but I’m now back to the same weight as before, by swapping the Schwalbe SV4 tubes to RideNow TPU tubes (ie a reduction in tube weight from 170g (per pair) to 44g.

The Pottering on Dan continues (& possibly the tinkering but nothing planned?)

Mrs Aussie continues to soldier on with her 2 Bromptons, comfortably going anywhere with Ruby, a pretty stock 6speed lightweight (2019 S6L-XD) & Peregrine, a 3speed lightweight (originally obtained in 2013 as an S6E).

Peregrine has been housed on the North Coast for some years & really suits the flattish territory about (or, I should say, that unlike myself, Mrs Aussie has coped with the 3speed external gearing & hasn’t expressed any desire for improved, lower gears?).

My extreme lightweight Bromptons with the lowest gearing I can wrangle, have seen some parts swapping & I figured it was time to put a few of those excess parts to use for Peregrine. (Peregrine may relocate at some time & so having a more useful gearing range could be convenient.) Peregrine now has a similar setup to some of my Bromptons, with a 5speed rear wheel, H&H derailleur & Sram GX shifter.

The standard 2speed wheel has been modded with a BrommiePlus 5speed freehub, dished & re-spoked. The cogs include an 11/14/17T X3UniBody cassette & separate 21T & 25T cogs. With the 44T chainring providing calculated Gear Inches of 66,52,43,35,29, the low range is coincidentally similar to that of Ruby with its stock 44T BWR wheel GIs of 88,72,56,46,36,29. So, Mrs Aussie should be able to go anywhere with either Brompton – & still comfortably leave me in her dust on whatever super-lightweight B I choose to ride?

A goal in my resumption of Blog postings 3months ago, was to provide the current build status of the 5 Bromptons on my side of the family. This posting should achieve that goal, in describing how Iggy has come about (a rather long-winded gestation?).

My recent Genealogy post displays the re-use of Ralph’s mainframe in July 2023, after it lay idle from late 2022 following the setup of BromTi, a full-Ti framed 7speed. Over the next year, the steel mainframe got mated to assorted lightweight bits but then I acquired a used Ti mainframe in September 2024 & moved all the lightweight items to become another full-Ti unit. (This put the steel mainframe back into storage, duly resurrected as Dan in August 2025.)

The used Ti mainframe was established as a 5speed full-Ti unit, which joined Clarence & BromTi as being external geared lightweights. Finally, in July 2025 I decided on some differentiation & to re-use a BWR rear wheel from the parts bin (ex-Clarence in 2020) & setup a 15speed by combining an X5uniBody cassette with the 3speed IGH.

This latest creation name became Iggy – an “IG-thing BrompNot”, full-Ti 9kg 15speed unit. Another Brompton Meccano exercise.

I decided to resurrect a Brompton 2speed lightweight wheelset, acquired used about 5years ago, for Dan, my all-steel minimalist 2speed. The plus point for the wheels is the weight, just 836g for the set. This compares with 960g for the BrommiePlus wheelset removed & 1268g for a stock lightweight wheelset (& 1373g for a standard 2speed wheelset).

The negative point for the wheelset is that it uses Kinlin NBR rims, very narrow & inappropriate for any tyre wider than the Schwalbe Kojak 32-349 size. I recently noted the availability of Goodyear Eagle F1R 30-349 tyres, weighing a claimed 120g. Seems ideal for my wheelset?

The tyre parcel arrived & I was immediately alarmed of what was included. It seemed from the dimensions of the boxes, I’d been sent tubes rather than tyres? No, all well; just small boxes containing tightly wrapped folding tyres.

The tyre weights didn’t stack up to the 120g claimed weight, being 133g for one & 135g for the other. Still, the replaced Kojaks were 185g & 203g so I’d made a saving, now just gotta hope the Goodyears do the job.

The final tweaks for Dan are probably now done. Weighed at 8.2kg & again ready for pottering service about local streets.

Acquired in 2014 as a Claret S6L, Clarence became my main Brompton with little more tweaking for many years than “better comfort items, etc”.

Once my Chpt3 v2 came along, with the realization that lightness & fast tyres were a godsend for me, tweaking turned to Rudolph (but minimal variation away from the Chpt3 look).

In wondering what a 2speed Clarence would feel like (& a solid chunk of Covid lockdown), I started with a 2speed wheel from the parts bin (squirreled away from the Cheeky Transport closing sales) & before long some Ti bits started arriving. The Meccano experience came alive & tinkering spread into other Bromptons.

Clarence finessed (eventually) into a 5speed lightweight, with lots of experience gained into what mods were possible (& problematical?). Clarence now weighs 8.7kg for a S5E-X format. (Other Bromptons have since been created that benefited from the early learning, with lighter & better gearing configurations.)

In my previous Blog posting, I attempted to explain how specifically my 3 Bromptons have become 5. Actually, much of the action revolves around how 2011 Ralph transitioned to 2025 Dan.

Back in 2021 the Alfine 11speed gear was shed & here’s the BB named creation, still wearing the 2011 mainframe (& stem) but with a lightweight 3speed setup of 8.3kg.

Tinkering happens & by 2025 the 2011 mainframe & stem combined with other steel rear frame & fork parts to become Dan, a minimalist 2speed local pottering B – funnily enough weighing 8.3kg.

How did 3 Bromptons purchased become 5?

Read on…

12/2012 Ralph S11E

• #1 – a used 2011 Alfine 11spd

11/2014 Clarence S6L

• #2 – a new Claret 6spd

5/2019 Rudolph S6E-X

• #3 – a new Chpt3 v2 6spd

1/2020 Clarence S6R converted to S2E

5/2020 Clarence modded to S2E-X

• with progressive tweaks to become S5E-X

8/2021 Ralph S11E converted & renamed to BB as S3E-X

2/2022 Rudolph modded to S9E-X

11/2022 BB morphed to BromTi (full Ti & 7spd)

• #4 – Full Ti, 7spd

7/2023 BB mainframe (ex-Ralph) resurrected as S5E-X

• #1 re-lifed

9/2024 BB morphed to BMBN (full Ti & 5spd)

• #5 – Full Ti, 5spd

7/2025 BMBN modded & renamed to Iggy (15spd BWR)

8/2025 BB mainframe (ex-Ralph) resurrected to S2E as Dan

• #1 re-lifed (again)

11/2025 Rudolph modded to S15E-X

My Chpt3 (v2) has now got the lowest gearing I can wrangle. Aside from various bits to lower the weight, I’ve tried to retain the Chpt3 look but keeping the gearing as low as possible. My 9speed setup of 38T chainring & 13/15/18T cogs a few years ago was very effective but with the lowest gear being only a smidgin below my 7speed lightweight, the porky Chpt3 needed some tweaking.

In theory, an X4UniBody cassette in the BWR wheel should be a simple 12speed upgrade, with BrommiePlus providing a 4speed pusher & shifter conversion. However the big 21T cog didn’t mate well with the pusher capability & the result wasn’t ideal; workable but not so livable?

Upgrading to 15speed now provides the ultimate gearing combo to help my weakened climbing capability, via an X5UniBody cassette (11/13/17/21/25T) & with H&H derailleur & sequential shifter. The component weight comparisons balance out on aggregate & the Chpt3 weight remains at 9.8kg with the GI range now 90-16.