Author: admin

A reasonably common question I get asked about my Brompton frame parts is what standards are they built for (and why)?

All my forks are 100 x 9mm QR, rear triangles are 135mm x 10mm, and disc mounts are IS (International Standard), intended for 160mm rotors.

Some people do ask about through axles, flat mount, and other standards – so why do I stick with these older standards? There’s a bunch of reasons:

• Compatibility: a few hub gears can be made to work with through axles, but everything works with 135x10mm, and it can also work with derailleurs and pretty much anything else. At the front, 100x9mm works with disc hubs, dynamo hubs, and it works nicely with the fork hook. For disc mounts, IS allows a wide choice of brakes.
• Ease of manufacturing: Not a trivial concern when I make several hundred of these every year! Flat plate dropouts and disc mounts are much quicker to manufacture than through axle or different disc mounts.
• Cost: A connected reason (because time is money) but different standards would either need more expensive parts, or would need custom parts made via more expensive processes (CNC machined vs laser cut).
• Being ornery: New standards come and go, sometimes the new standards actually make something better, sometimes they’re just a marketing thing, sometimes they’re a good idea but not for little folding bikes. Bromptons don’t need the stiffness of through axles or the aerodynamics of flat mount brakes.

Brompton’s naming conventions are a bit confusing, and have changed several times, so I thought I’d put together a simple table to show you what upgrades are possible on the different models:

A and C Line All Older Models apart from X	All conversions are possible, by replacing the rear triangle and/or forks
P and T Line Older X Superlight Models	Hub gear and belt drive are possible by modifying the titanium rear triangle All conversions are possible, by replacing the rear triangle and/or forks
G Line	Hub gear and belt drive are possible
Electric	Hub gear, rear disc brake and belt drive are possible Wheel size change is possible with a front V-brake instead of disc

With the launch of the new Brompton 20″ G-Line, I’ve put together a table comparing the G-Line to the MTBrompton. I’ve also added a comparison with an 18″ Brompton, because I think that is actually more like what the G-Line is like.

	Brompton G-Line	Kinetics MTBrompton	Kinetics 18″ Brompton
Folded Size?	730 x 690 x 402 mm (0.2 m3)	750 x 680 x 320 mm (0.16 m3)	650 x 630 x 310 mm (0.13 m3)
Weight?	13.9kg (no rack or mudguards) 14.85kg to 15.25kg (with rack and mudguards)	14.1kg (no rack or mudguards) 14.75kg (integral rack and mudguards)	12.9kg (no rack or mudguards) 13.5kg (integral rack and mudguards)
Disc Brakes?	Tektro hydraulic	TRP Spyre Magura MT4, MT5 etc Hope XCR	TRP Spyre Magura MT4, MT5 etc Hope XCR
Hub Gear?	Alfine 8-speed	Alfine 8-speed or 11-speed Rohloff 14-speed Enviolo	Alfine 8-speed or 11-speed Rohloff 14-speed Enviolo
Derailleur Gear?	4-speed on Electric models	Up to 12-speed	Up to 12-speed
Drive?	Chain drive	Chain or Belt drive	Chain or Belt drive
Wheel Size?	20″ up to 2.1″ wide	20″ up to 2.4″ wide	18″ up to 2″ wide 20″ up to 1.35″ wide
Electric Assist?	Yes, rear hub motor with 4-speed derailleur	Yes – any front hub motor system, or Pendix mid drive	Yes – any front hub motor system, or Pendix mid drive
Lighting?	Optional battery lights	Optional battery lights or hub dynamo	Optional battery lights or hub dynamo
Rack?	Optional rear load platform for top bags	Optional integrated rack for panniers	Optional standard Brompton rack Optional integrated rack
Colours?	Adventure Orange, Traildust White, Forest Green	Any standard Brompton colour Custom colours at extra cost	Any standard Brompton colour Custom colours at extra cost
Luggage?	Brompton-specific front bags, small rack-top bag at back.	Brompton-specific bags, or full-size panniers front and back	Brompton-specific bags, or full-size panniers front, and rack top bag
Material?	Steel mainframe and rear triangle, aluminium fork and stem	Steel mainframe, stainless rear triangle, Columbus steel fork	Steel mainframe, stainless rear triangle, Columbus steel fork
Geometry?	Bottom bracket height 290mm Wheelbase 1115mm	Standard geometry: BB height 350mm Handlebar height (S) 1030mm Head angle 70 deg Seat angle 72 deg Dropped geometry: BB height 300mm Head angle 66 deg Seat angle 68 deg Wheelbase 1118mm	Bottom bracket height 300mm
Upgrade?	All new bike, existing bikes cannot be upgraded	Existing Bromptons can be upgraded from £1435	Existing Bromptons can be upgraded from £1275
Made?	Made in the UK and other countries	Handmade in Scotland	Handmade in Scotland
Cost?	From £2499 (with rack and mudguards)	From £2635	From £2660 (with mudguards)