Two speed + larger chainring

The two speed is an obvious choice to save weight, but with the limited gears you need to pick you options well or be left churning a massive gear or spinning out too quickly! 


The stock ratio / MPH for RPM/cadence of 90 is - 3.38-4.5 / 15.1-20.1 mph.

It is very common to increase the chainring size, 60t seems to be the biggest option without too many issues. Larger hits the front fork hook / the chainstay. On my personal bike I now use a 122mm BB to stop the chainring contacting the chainstay when folded. 


The following ratios and MPH90C are per increased ring sizes;

56t - 3.5-4.67 / 15.6-20.8mph 
58t - 3.63-4.83 / 16.2-21.6mph 
60t - 3.75-5.00 / 16.7-22.3mph

The BWR with 50t has a gear range of 302%, ratio of 1.99-6.03 with MPH per 90 RPM (cadence) at 8.9-26.9mph.

So with a 60t x 12/16 you would need to pedal at 108.5 RPM to equal a BWR hub using 50t 13/16 at 90 RPM.  

2 Speed Hub Drivechain Alternatives

A page about various non stock gearing systems..

Converting a 2 speed to 3 speed - non IGH 

Stock hub - simple and easy 

Simply using a thinner snap ring will allow a third sprocket to be fitted to the stock hub! 
Stock snap ring is 2.2mm and the replacement needs to be 1.5mm. 
This allows you to then use a combination of sprockets such as 12-14-17 making a 2 speed ratio a lot more usable! 
You can simply use a friction shifter or other shifters may work depending on the set up. It is common to need to modify the cable run, with an inner cable going straight through the spring of the anchorage and fastened with a barrel nut / grub screw.

- On a Ti triangle you are limited in sprocket size to 18t without modification.

Hubsmith hub - 11t capability! 

Using a Hubsmith rear hub, you can replace the free hub body to one that accepts a locking, such as on traditional cassettes, rather than a snap ring. 
This allows you to fit an 11t Shimano style cog, meaning you can widen that gearing range! 

http://www.brommieplus.com/portal_c1_cnt_page.php?owner_num=c1_343119&button_num=c1&folder_id=44131&cnt_id=708310&search_field=&search_word=&search_field2=&search_word2=&search_field3=&search_word3=&bool1=&bool2=&search_type=1&up_page=1

Converting a 6 speed to 9 speed 

Simply convert the external cogs from 2 to 3 and change the shifter - see - "Converting a 2 speed to 3 speed - non IGH"



Suitable for BWR hubs, or BSR*/SRF3*/SRF5 hubs that have been converted to a dual sprocket driver.
* These hubs offer ratios of 0.75, 1.1 and 1.33, compared to the BWR which offers 0.638, 1.1 and 1.567.

Aftermarket Brompton Components + Weights

A list of common additions / upgrades and their weights! 

Pedals:

Chainrings:
Litepro 53t with bash - 105 grams 

Cranks:
Ti Parts Workshop - Forged, 53t, with bolts, - 477 grams 
Thorn Triple Solo Alloy - no ring/bolts - 140mm- 1673L140 - 484 grams 

Bottom Brackets: 
Shimano BB-UN55 - 309 grams

Front Hubs:
Jtek superlight - Xgrams
SP dynamo - sv-9-fb - Xgrams

Rear Hubs: 
Hubsmith R015R 28h - 227g
Rims:
Joseph Kuosac 38mm Carbon - 28h - 342 grams 

Spokes:

Front Wheels:

Rear Wheels: 
Sturmey Archer SRF3 / Jtek spokes / Sun CR18 - 1410 grams 

Wheel Fittings:
Jtek Allen key skewer - Front - 26 grams

Tyres: 
Nexo - 37mm - Solid - 420 grams 

Tubes: 

Rim Tapes:
Jtek Yellow Tape 349mm - 10 grams

Seat posts:

Seatclamp/clips;
Ti Parts Workshop - easy large handle - 53 grams 

Saddles:
Joseph Kuosac - wide - 273 grams 
Brooks Cambium S17s carved - 404 grams

Suspension Blocks: 

Easy wheels:

Racks:
RJT Alloy - 190 grams 

Handlebars: (All 25.4mm)
Joseph Kuosac - flat - 195 grams
Joseph Kuosac - full rise - 239 grams
Litepro Ghost - 580mm - 144 grams 

Grips:
Joseph Kuosac - 75 grams

Brake levers:

Shifters: 
Sturmey Archer - SL30 3 speed - 79 grams 

Brakes:

Headsets:
Joseph Kuosac - sealed bearing - 100 grams 

Derailleurs:
H&H Derailleur + fittings - 9 grams

Hinge Clamps:
Joseph Kuosac knobs - 124 grams 

Other; 
Ti Parts Workshop Ti hinge spindle/bolts - 23 grams 

Stock Bike Weights

One of the most common questions is how much does it weigh? So here we are, all of the weights are the standard bike, with Marathon Racer tyres, mudguards and a standard seat post. 


S1 - 10.7kg
S2 - 10.9kg
S3 - 11.5kg
S6 - 11.6kg

P1 - 11.3kg
P2 - 11.5kg
P3 - 12kg
P6 - 12.2kg

H1 - 11kg
H2 - 11.2kg
H3 - 11.7kg
H6 - 11.9kg

M1 - 10.8kg
M2 - 11kg
M3 - 11.5kg
M6 - 11.7kg 


Electric! 

Fitted as stock, marathon tyres, lighting, mudguards, standard seat post/saddle. 

M2 - 13.7kg (16.6kg total with battery)
M6 - 14.6kg (17.5kg total with battery)

H2 - 13.8kg (16.7kg total with battery)

H6 - 14.7kg (17.6kg total with battery)

Battery - 2.9kg 

Notes

- The Brompton two speed hub uses:

6900-2RS in the non-drive side
6901-2RS in the drive side

And in the freewheel body:

6900-2RS
6000-2RS

Brompton SL front hub bearings:

6900 / 61900 - 1 either side

- The dimensions of a Brompton when folded are 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.)

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").

Torque Settings

Let me know if there is anything missing! 


Aluminium brake lever - 3mm Bolt - 2Nm
Aluminium brake lever - 4mm Bolt - 2Nm
Grips - (foam lock on) - 1.5Nm
2017+ Shifter - brake lever bolts - 2Nm
Pre 2017 shifter band clamp - 5Nm

Stem Bolt - handlebars - 18Nm
Stem expander bolt - 15Nm for cone style / 30Nm for wedge style. 

Front wheel nuts - 15Nm
Rear wheel nuts - 18Nm
Chain tensioner Nut - 5Nm

Front brake - 10Nm
Rear brake - (stop disc) - 10Nm
Brake pads - 5Nm
Brake cable clamp - 8Nm

Seat clamp - 4-7Nm
Pentaclip - 15Nm

Left folding pedal - 30Nm
Right pedal - 30Nm
Crank bolts - 30Nm
Bottom bracket - 24/30Nm
Chainring bolts - 10Nm

Rear hinge bolts - 10Nm

Mudguard fittings - Secure these screws firmly 
Rack fittings - Secure these screws firmly 

Chain Length

The list below states the required chain length for each chain ring / sprocket choice. 


44t Chain Ring

12t - 96 link
13t - 96 link
14t - 96 link 
13/15t - 98 link 
12/16t - 98 link
13/16t - 98 link

50t Chain Ring

12t - 98 link
13t - 98 link
13/15t - 100 link 
12/16t - 100 link
13/16t - 100 link

54t Chain Ring

12t - 100 link
13t - 100 link
13/15t - 102 link
12/16t - 102 link
13/16t - 102 link