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Category: Technical Info

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On Standards

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.
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Brompton Upgrades By Model

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 LineHub gear and belt drive are possible
ElectricHub gear, rear disc brake and belt drive are possible

Wheel size change is possible with a front V-brake instead of disc
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G-Line vs MTBrompton vs 18″ Brompton

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 MTBromptonKinetics
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 hydraulicTRP Spyre
Magura MT4, MT5 etc
Hope XCR		TRP Spyre
Magura MT4, MT5 etc
Hope XCR
Hub Gear?Alfine 8-speedAlfine 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 modelsUp to 12-speedUp to 12-speed
Drive?Chain driveChain or Belt driveChain or Belt drive
Wheel Size?20″ up to 2.1″ wide20″ up to 2.4″ wide18″ up to 2″ wide
20″ up to 1.35″ wide
Electric Assist?Yes, rear hub motor with 4-speed derailleurYes – any front hub motor system, or Pendix mid driveYes – any front hub motor system, or Pendix mid drive
Lighting?Optional battery lightsOptional battery lights or hub dynamoOptional battery lights or hub dynamo
Rack?Optional rear load platform for top bagsOptional integrated rack for panniersOptional standard Brompton rack
Optional integrated rack
Colours?Adventure Orange, Traildust White, Forest GreenAny 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 backBrompton-specific bags, or full-size panniers front, and rack top bag
Material?Steel mainframe and rear triangle, aluminium fork and stemSteel mainframe, stainless rear triangle, Columbus steel forkSteel 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 upgradedExisting Bromptons can be upgraded from £1435Existing Bromptons can be upgraded from £1275
Made?Made in the UK and other countriesHandmade in ScotlandHandmade in Scotland
Cost?From £2499 (with rack and mudguards)From £2635From £2660 (with mudguards)
*measurements and weights are for a G-Line with rack and mudguards, and a MTBrompton with 2.4″ tyres and wide wide bars
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Brompton Hub Comparisons

With a bunch of different hubs available for the Brompton, I thought a comparison would be a good idea:

KindernayRohloffAlfine 11Alfine 8Enviolo
NuVinci		Sturmey 8
Number of gears1414118n/a8
Gear range543%525%405%307%380%325%
Weight1.4kg1.7kg1.6kg1.7kg2.4kg1.8kg
Gear ratios18″-98″19″-100″24″-99″24″-74″25″-95″29″-95″
ShifterThumbTwist
or Thumb		Lever*Lever*TwistTwist or Thumb
EfficiencyVery goodVery goodGoodMediumGoodMedium
AxleSolid 10mmQuick releaseSolid 10mmSolid 10mmSolid 10mmSolid 13/32″
Disc brakeYesYesYesYesYesNo
Kit cost£1795£1595£795£725£725£395

Gear ratios are the most common possibilities – with the Rohloff and Kindernay, they are with the smallest possible rear cog and largest Brompton front ring (54t). With the Alfine and Enviolo, it’s 18t/50t. So getting higher gears is possible on the Alfine and Enviolo hubs, more difficult with the Kindernay and Rohloff.

I know it seems a bit odd that the Kindernay has a wider range than the Rohloff but has very similar gear ratios, but it’s because the difference between 18″ and 19″ at the bottom end is a much bigger difference than between 98″ and 100″ at the top end.

Other factors are harder to quantify in a table: In terms of fitting, the Rohloff is easiest – it’s a simple quick release hub (though I usually use an Allen key skewer) and cable fitting is very simple. The Alfine and Enviolo hubs are nutted, so need a spanner to fit, but cabling is pretty simple. The Kindernay is the most complex, with a nutted through axle, and hydraulic shifting that has to be cut and perhaps re-bled to fit.

*A rapid-fire shifter is available, but I strongly recommend the Jtek shifter for the Brompton handlebars.

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Why Ride a Folder?

Why Ride a Folder?

Bikes can be very inconvenient when they are not being ridden. You need to find somewhere to park them safely or squeeze them onto some other form of transport. By contrast a folding bike is there when you need it, and when you don’t it packs away easily under seats or in lockers. You can commute by train using the same cycle at both ends, and a folding bike can be taken anywhere, even into a bar or restaurant with you for security.

Folding bikes have become very sophisticated – the old Dawes Kingpin of the 1960’s with it’s heavy frame and simple hinge has been replaced by a wide range of lightweight high performance cycles which fold much smaller and are far better to ride.

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Why Ride Recumbent?

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Why Ride Recumbent?

 

There are some very good reasons for reclining. You rest on a supportive and comfortable seat, rather than perching on a saddle. Your diaphragm can expand freely, improving your breathing. Weight is taken off your wrists, your neck does not have to strain to see where you are going, and you have better all-round vision. Recumbents are quite often very beneficial to cyclists with back or knee problems, who would otherwise need to restrict or stop cycling altogether.

Recumbent bikes and trikes come in many flavours, and are often very fast machines, partly due to the improved aerodynamics of having your legs in front of you not below you. And with a firm supportive seat to push against, a recumbent cyclist produces just as much energy as an upright cyclist. It is also argued that recumbents are safer than upright cycles – for one thing, the first part of your body to hit an obstruction is your feet, not your head. Brakes can be pulled as hard as they will go with no fear of diving over the handlebars, and car drivers seem to be much more wary of recumbents. Read lots more on the General Info page….

Which Recumbent?

That all depends on what you intend to do with it 😉 Two-wheelers are generally lighter and faster, and happier in traffic. Three-wheelers are more stable, especially at very low speeds, and can be a lot of fun to play with as they’re like pedal-powered go-karts.