# Brompton Gearing



## Brommie77 (17 Feb 2011)

Hi there, this may be a strange question, but I am not too good at working out gearing ratios and things, so wondered if anyone could help here..

I currently have a Brompton S2L, but I find that I am often pedaling as fast as I can in top gear, wishing I could move the bike faster for the same pedal speed (if that makes any sense). What ratios could make this happen, or alternatively the expensive option if I added the three speed hub to make it an S6L, would this give me the speed I need, or just give me a broader range within the same limits.

I hope this makes sense as a question, any polite comments gratefully received.


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## ColinJ (17 Feb 2011)

I'll summon one of our resident Brompton riders for you. Hang on ... _*Shaun!*_


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## mickle (17 Feb 2011)

The answer, and I'm not being facetious, is to pedal faster. Bromptons are actually quite highly geared in standard spec.

I suspect that, like many bipeds, you are pedaling at a RPM rate close to walking pace. 

There are many benefits to high RPM rather than high pedal pressure - you'll reduce the load on your body, knees particularly, on the bike's transmission. You'll encourage cardiovascular fitness, be able to accelerate quicker and you'll go faster for longer.

Persevere with the gearing you've got, concentrate on turning your toes in fast circles rather than pushing down hard on the pedals. And check that your saddle is at the correct height, a too high saddle inhibits the ability to spin.


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## Rohloff_Brompton_Rider (17 Feb 2011)

go here and all your questions and dreams will be answered......



http://sports.groups.yahoo.com/group/BromptonTalk/


you can browse and search but to post you need to join.


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## mickle (17 Feb 2011)

why would that forum be any better than... say.... this one?..........




http://www.cyclechat.net/


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## mercurykev (17 Feb 2011)

The simple answer to your problem is to get a smaller rear sprocket or a bigger front chainring. Both of these changes would give you a bigger gear.


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## mickle (17 Feb 2011)

mercurykev said:


> The simple answer to your problem is to get a smaller rear sprocket or a bigger front chainring. Both of these changes would give you a bigger gear.



Yup, that's the simple answer awlright.


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## potsy (17 Feb 2011)

Or get a proper bike


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## Brommie77 (18 Feb 2011)

mickle said:


> The answer, and I'm not being facetious, is to pedal faster. Bromptons are actually quite highly geared in standard spec.
> 
> I suspect that, like many bipeds, you are pedaling at a RPM rate close to walking pace.
> 
> ...



I appreciate where you are coming from, but i really cannot be spinning any faster - if my cateye speedo is correct, I am pushing 18-20mph at my personal max rpm, but on my road bike I can usually get faster than that....




mickle said:


> why would that forum be any better than... say.... this one?..........
> 
> 
> 
> ...




Quite Right



mercurykev said:


> The simple answer to your problem is to get a smaller rear sprocket or a bigger front chainring. Both of these changes would give you a bigger gear.



Cheers, that was kind of what I thought, but wanted some expert advice 



potsy said:


> Or get a proper bike



Hmmmmm


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## Rohloff_Brompton_Rider (18 Feb 2011)

mickle said:


> why would that forum be any better than... say.... this one?..........
> 
> 
> 
> ...




simply because it SPECIALIZES in bromptons, or are you trolling?


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## Rohloff_Brompton_Rider (18 Feb 2011)

Brommie77 said:


> Quite Right




i assume you didn't look then? there's over 500 brompton EXPERTS on there, oh well up to you if want to take advice from non brompton riders. 

maybe get the baker in to fix the shower then


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## Rohloff_Brompton_Rider (18 Feb 2011)

mickle said:


> Yup, that's the simple answer awlright.



not that simple on a brompton, the rear triangle only takes up to 16 toothed sprocket unless you start grinding the rear triangle away (& voiding your 5 year frame warranty).

The front ring is a maximum of 54 (iirc), or it interferes with the fold. 


so unfortunately your not a brompton rider & have given duff advice


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## Rohloff_Brompton_Rider (18 Feb 2011)

potsy said:


> Or get a proper bike




mmmmm, there's always one  


you still up for waddington?


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## Brommie77 (18 Feb 2011)

bromptonfb said:


> i assume you didn't look then? there's over 500 brompton EXPERTS on there, oh well up to you if want to take advice from non brompton riders.
> 
> maybe get the baker in to fix the shower then




Yes I have just joined the group, and will post the question on there shortly, but I thought there would be some experts on this forum too.


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## John the Monkey (18 Feb 2011)

Would Brompton's own gearing page be any help?

http://www.brompton.co.uk/page.asp?p=3069


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## potsy (18 Feb 2011)

bromptonfb said:


> mmmmm, there's always one
> 
> 
> you still up for waddington?



Sorry, couldn't resist






I'm up for Waddy, not sure about my aching legs


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## mickle (18 Feb 2011)

bromptonfb said:


> simply because it SPECIALIZES in bromptons, or are you trolling?



Trolling?


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## mickle (18 Feb 2011)

bromptonfb said:


> not that simple on a brompton, the rear triangle only takes up to 16 toothed sprocket unless you start grinding the rear triangle away (& voiding your 5 year frame warranty).
> 
> The front ring is a maximum of 54 (iirc), or it interferes with the fold.
> 
> ...



I've owned several Bromptons over the years - we have one in the garage right now. But wait, there's more: My first industry job was as a Saturday assistant in the Victoria Bicycle company - C1983 when it was the one and only shop which sold Bromptons and before they had alloy rims. Since then I've served 23 years in cycle retail, twenty of which were in Brompton dealerships. I once held the unofficial speed record for folding a Brompton. I've written articles on them. I've given talks and I've demonstrated them to audiences of up to fifty people on cycling holidays. Worked on them, adapted them and hot-rodded them. Until recently I was responsible for the servicing and upkeep of a fleet of 400 bikes which included twenty assorted Bromptons. I've done the Brompton factory tour and shaken the hand of Andrew Ritchey. I even know Steve Parry. 

(iirc)


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## GrumpyGregry (18 Feb 2011)

^ now that _*is*_ a great comeback.


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## Brommie77 (18 Feb 2011)

mickle said:


> I've owned several Bromptons over the years - we have one in the garage right now. But wait, there's more: My first industry job was as a Saturday assistant in the Victoria Bicycle company - C1983 when it was the one and only shop which sold Bromptons and before they had alloy rims. Since then I've served 23 years in cycle retail, twenty of which were in Brompton dealerships. I once held the unofficial speed record for folding a Brompton. I've written articles on them. I've given talks and I've demonstrated them to audiences of up to fifty people on cycling holidays. Worked on them, adapted them and hot-rodded them. Until recently I was responsible for the servicing and upkeep of a fleet of 400 bikes which included twenty assorted Bromptons. I've done the Brompton factory tour and shaken the hand of Andrew Ritchey. I even know Steve Parry.
> 
> (iirc)




So...... would adding the three speed gear give me faster movement for the same pedal speed, or would I just have the same limits with more choice in between?


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## Rohloff_Brompton_Rider (18 Feb 2011)

GregCollins said:


> ^ now that _*is*_ a great comeback.




not really, all that pontification and he still didn't answer the question.

also i forgot earlier, the rear derailleur will only take up to a 18 toothed sprocket.

the lowest being 14 i believe, due to the chain snagging the rear triangle.

so personally, in your situation, i would go for the schlumpf speed drive or high speed drive. just a bit more cash for a perfect solution. the bwr is an option but i'd prefer not having an extra cable to play with. i have a schlumpf and it is so reliable and simple and no cables to foul and lose gears.


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## GrumpyGregry (18 Feb 2011)

bromptonfb said:


> not really, all that pontification and he still didn't answer the question.




my, we are tetchy today.


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## Paulus (18 Feb 2011)

As well as the various gear ratios, would the cadence be limited by the wheel size? I have a M3 which I use in town for work purposes from time to time, and even in top gear I find that I am pushing and spinning the top gear, yet not going nearly as fast as a large wheeled bike. Surely a 16 inch wheel, no matter what gearing will never be that fast?


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## GrumpyGregry (18 Feb 2011)

Paulus said:


> As well as the various gear ratios, would the cadence be limited by the wheel size? I have a M3 which I use in town for work purposes from time to time, and even in top gear I find that I am pushing and spinning the top gear, yet not going nearly as fast as a large wheeled bike. Surely a 16 inch wheel, no matter what gearing will never be that fast?




Pull a big enough/right gear and in theory no reason why 16" wheels can't make a bike go as fast as a 700c wheeled one surely?

Is such a gear available for, and within the constraints of, a Brompton? ( I have visions of a huge chainwheel gouging the tarmac). That I don't know


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## Rohloff_Brompton_Rider (18 Feb 2011)

Paulus said:


> As well as the various gear ratios, would the cadence be limited by the wheel size? I have a M3 which I use in town for work purposes from time to time, and even in top gear I find that I am pushing and spinning the top gear, yet not going nearly as fast as a large wheeled bike. Surely a 16 inch wheel, no matter what gearing will never be that fast?




there are theories that smaller wheels are faster, eg, less aero drag, less rotational mass etc etc. not sure on that theory myself. but, didn't some world speed record get set by a 16 inch wheeled moulton? and didn't moultons do really well in racing until they got banned?


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## RecordAceFromNew (18 Feb 2011)

According to their spec the 2 speed's highest gear ratio (which I figure is 12T x 54T on something like a 16 x1 3/8 tyre) is 74 gear inches, which is roughly equivalent to a 15T x 42T on 700c. Requiring 100 rpm at the pedal to hit 22mph, I can appreciate that it can be a little too busy for some.

However if the OP hasn't already he might want to check if he has 12T (and 16T) x 54T at the moment - it seems some come with a 13T at the back and 44T or 50T up front.


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## Brommie77 (20 Feb 2011)

Cheers for the comments people, I will have to make a tooth count later - it was a standard spec when I bought it, but goodness knows what that actually was. I am contemplating upgrading as I want more speed  but just trying to make sure I don't spend loads to get no improvement. 

Paulus - pedal faster! I frequently leave other bikes behind (although not the really serious ones) its great fun to see their reaction when they realise I'm on 'one of those folding shopper bikes'

Will have to do some more persuading of Mrs B that the money is well spent upgrading!


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## suecsi (21 Feb 2011)

Glad I'm not the only one that gets that - apparently I am going at a fair clip according to my hubby as he sees me ride down the road from home to the station, but I am just at a pace that is comfy for me, I'm not actually trying to go particularly fast. I had to do my first overtake last week which was interesting.

I have found that my balance on the Brommie is a little better when at a higher speed, although my slow balance is getting better through experience (I have to go pretty slow, or sometimes get off and walk the bike, at night as the shared ped/cycle path is chaos when the shops are open).


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## Wobbles (22 Feb 2011)

Hi Brommie 77.
I was in exactly the same position a while ago having bought the same 2 speed version as you. I bought it as I only intended to use it around W1 instead of taxis at work.
Of course, I got hooked and it's sheer versatility meant I was using it for up to 20mile+ commutes etc and twiddling away in top(2nd) gear started getting very frustrating very quickly....in fact I never even used 1st!
I did a load of calculations ....even considered getting a custom larger front ring but in the end settled for upgrading to a 6 speed as I was using it regularly for my 26mile per day commute and could justify the expense. 
The 3 speed hub alone would have given a little more speed for the cadence, but I really wanted something that would keep up with , _ahem,_ 'proper' bikes so went for broke and got the 6 speed. This meant a new hub and changer, but because I already had the rear deraillieur, I didn't have to fork out for it.
It weighs a bit more(I feel that I do notice the difference) but this is more than compensated for by the extra vroom.

I put the slimmer, lighter slick tyres on it and it really flies.....tho I was puncturing at least once/twice a week 

BTW I put mini bar ends that really make a difference when on the rivet. £20 well invested.

Not sure if I've answered your question but good luck with your choice.

Cheers.


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## Brommie77 (25 Feb 2011)

Thanks wobbles, sorry for the delay, I've been away for a day or two.

You have given me the answer that I wanted - so cheers. Bromptons are very nippy, but as you say, sometimes you just want that bit more. I was concerned that the 3 speed would not be enough, so its nice to know that you have had success with the 6 speed.

I've also added some bar ends (a while ago now, and really notice the difference, my other bike is a tourer, and I was missing the drops, but the ends give a change of grip now and again)

Now I definately need to butter Mrs B up!!


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