Brompton Gearing

[LEE]

In standard form could someone explain the gearing, in inches, of the various options?

The Brompton site offers:

1 speed
2 speed derail
3 speed hub
6 speed hub/derail combo. (This seems fairly good value at +£42 over standard if there is some additional and useful gear range)

Edit, it is possible to get a low 30's to 90's range?

[delthebike]

1-speed   5.93m   
2-speed   4.45m - 5.93m    133%   
3-speed   3.79m - 6.76m    178%   
6-speed   3.22m - 6.87m    213%   

I'm sure you could convert to imperial.

[LEE]

I found this relating to the 2009 wide-range hub

This will mean an increased gear range of 33-95″ compared to the range of 40-80″ on the existing 6 speed system.

33"-95" is excellent and I would even consider knocking it down a few percent with a smaller chainring to get a real granny gear.

[rogerzilla]

They climb OK out of the saddle.

On standard tyres, the 3-speed is better with a 14T sprocket (middle gear 58").  Unfortunately this means changing the chain if you bought one with the standard 13T.  13T is OK with Stelvio tyres, which are a little smaller in diameter.

You'll have to check the specs carefully if you want to gear down a BWR - all hub gears have a torque limit, and a 20" gear might risk damage.

[LEE]

They climb OK out of the saddle.

On standard tyres, the 3-speed is better with a 14T sprocket (middle gear 58").  Unfortunately this means changing the chain if you bought one with the standard 13T.  13T is OK with Stelvio tyres, which are a little smaller in diameter.

You'll have to check the specs carefully if you want to gear down a BWR - all hub gears have a torque limit, and a 20" gear might risk damage.

Something around 30-80" would be fine I reckon.  Schlumpf drive anyone?

[Zipperhead]

8 speed?

[LEE]

8 speed?

Interesting.  I've sent them an email asking for gear range.

Personally I think the lowered ratio 6 speed 36" - 76" would suit me nicely.  I can just about squeeze my way up all the local hills in a 36" gear and 76" would have me moving along as quickly as I need to on 20" wheels (74" is the standard 1 gear option).

I'm really talking my way into a Brompton here.

[LEE]

[epa611]

8 speed?

Interesting.  I've sent them an email asking for gear range.

Personally I think the lowered ratio 6 speed 36" - 76" would suit me nicely.  I can just about squeeze my way up all the local hills in a 36" gear and 76" would have me moving along as quickly as I need to on 20" wheels (74" is the standard 1 gear option).

I'm really talking my way into a Brompton here.

I'd give Ben at Kinetics a call instead - he's a one man band and isn't the most responsive to email.  Really nice guy to talk to.  

[rogerzilla]

Brompton do their lower gearing in a strange way.  The smallest decrease is 12% lower on a 3-speed, done by fitting a smaller chainring.  Why not do what I did and fit a 14T sprocket for 8% lower gearing?  As well as being easier, this improves chain efficiency and reduces the risk of the sprocket cracking - the 13T is notorious for it, because there ain't much metal between the hub driver and the bottom of the teeth.

[duncan]

Something around 30-80" would be fine I reckon.  Schlumpf drive anyone?

I have a speed drive on my T6. I've forgotten what gear ratios I get though... I might have the email around somewhere.

Duncan

[LEE]

Something around 30-80" would be fine I reckon.  Schlumpf drive anyone?

I have a speed drive on my T6. I've forgotten what gear ratios I get though... I might have the email around somewhere.

Duncan

Any photos?