Technical
Home » Technical » Data

Data

All Bromptons exceed the requirements laid down by British Standard BS6102, German Standard DIN 79100, and other relevant regulations in every other market in which they are sold.

In this section we have collected some of the more technical aspects of our bikes, ranging from general information about tyre pressures and lubricating the chain to detailed information on replacement parts and accessories.

GENERAL

Tyre pressures

We can not overemphasise the importance of keeping the tyres well pumped up: soft tyres lead to a lot more pedalling effort (which takes much of the fun out of riding), wear out quickly, and have an adverse effect on handling.

Recommended tyre pressures:

Brompton high-pressure
Front: 75 to 90 PSI, 100 PSI max.
Rear: 85 to 100 PSI, 100 PSI max.

Schwalbe Marathon
Front: 60 to 75 PSI, 85 PSI max.
Rear: 70 to 85 PSI, 85 PSI max.

Schwalbe Kojak
Front: 90 to 105 PSI, 115 PSI max.
Rear: 100 to 115 PSI, 115 PSI max.

Record (used on the C Type) (*)
Front: 50 to 70 PSI, 75 PSI max.
Rear: 60 to 70 PSI, 75 PSI max.

(*) Brompton no longer makes the C Type and no longer fits Raleigh Record tyres to any of its bikes

Gear ratios and ranges
GearsRatios (metric) RangeOptional higher gearing Optional lower gearing
1-speed 5.93m n/a NO -7% & -18%
2-speed 4.45m - 5.93m 133% NO -7% & -18%
3-speed 3.79m - 6.76m 178% +8% -12% & -18%
6-speed (BWR) 2.63m – 7.94m 302% +8% -12%

Wheel base

Every Brompton has a full-length wheel base of 1045mm (41.2"); pre-2003 models had a slightly shorter wheelbase of 1.02m (40.2").

Folded dimensions

585mm high x 565mm long x 270mm wide (23" x 22.2" x 10.6").

 

Measurements are based on a bike with folding pedal and a standard seat pillar and saddle; measurements will vary slightly by model - e.g. opting for a model without mudguards will reduce the height of the folded package.

The volumetric size of the folded package is approximately 3.1ft3 (0.089m3).

The chain

For smooth pedalling the chain has to be well lubricated; if the bike is used in the wet, this should be done frequently. The easiest way to cover the whole chain is to turn the pedals backwards while applying oil: make sure that the oil flows both onto the rollers and between the side plates: turn the pedals a few more times to allow the oil to work in, and then wipe off the excess.

Saddle height

Riding with a saddle even slightly too low is no fun. You can win around 15mm of extra height by moving the saddle-clamp up the seat pillar itself, and this may be sufficient. If not, there are three Brompton options which give you more height: an extended seat pillar, a telescopic seat pillar and the saddle adaptor pin (used pointing upwards).

Cables

Control cables on the Brompton are low friction but, with time, the linings can wear; deterioration in braking performance may be particularly noticeable. Fitting new cables cures this and is well worth doing regularly. Gear cables can also wear leading to poor selection of gears and, in the case of hub gears, risk of damage; as a pre-emptive measure, we therefore recommend replacing the gear cables at the same time as the brake cables.

Hub gear adjustment

Once any initial cable stretch has been taken care of, hub gears should seldom need adjustment. However, if you notice any slipping or other odd effects when pedalling, deal with problems as soon as possible to avoid permanent damage. Usually the problem will be caused by poor adjustment, but it could also be caused by a stiff cable run or damage to the little chain which goes into the rear axle. If you cannot resolve the issue quickly, avoid hard pedalling in the gear in question and take your Brompton to your authorised dealer.

DETAILED DATA

In this section you can take a look at the schematics for various parts of our bikes. The contents are, by necessity, fairly detailed and the complicated text (in particular our product codes) was not developed with the general public in mind.

Nevertheless, a good number of owners like to maintain and repair their Bromptons; while we would always recommend the services of our authorised dealers for all but the most basic cycle maintenance, it would be unreasonable to expect mechanically-competent owners not to indulge their passion for our bikes.

The schematics should enable anyone so minded to reconstruct a hub assembly after cleaning, or to fit a Brompton lighting system, etc. Please bear in mind that any spares and accessories must be ordered through a Brompton dealer, even if you are choosing to fit the items yourself; your dealer will have the full parts list and will ensure that you receive exactly what you need for a particular replacement or upgrade.