# Brompton higher gearing option



## Holeshot (14 Apr 2018)

Hi guys. 
Have been away from the forum for years but have viewed regularly - so first post for a long time. 
Anyway.....

I have a 6L at the moment with the 8% higher gear option which I’m happy with. 
I’m considering changing this and taking advantage of Evans’ discount on the raw lacquer 6LX (titanium) but trying to weigh up the pros and cons. 
The thing I’m not clear on is how Brompton achieve the increased gearing: Is it done through a larger chainring, rear sprockets or is it in the hub? 
I’d like to have the higher ratio but wondering how much it would take to change from the standard ratio that this bike will come with(the offer is only available on the standard bike build....not a bespoke build) and whether I may spend the money I save on modifying it to how I want it. If it’s a simple thing like changing just the chain ring then that’s OK. 

Hope this makes sense. 

Cheers.


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## Pale Rider (14 Apr 2018)

The standard, low and high gearing on factory Bromptons is achieved by different sized chain rings at the front.

As far as I'm aware the rear sprocket - or sprockets on a six speed - and hub gear is the same on all bikes.


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## Cycleops (14 Apr 2018)

@chriscross1966 is your man regarding modding the gears on Bromptons. 
If you want a wider gear choice why don't you consider a Dahon or Tern?


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## mickle (14 Apr 2018)

Or learn to spin. Bromptons don't fare well when muscled along by tall gears.


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## Holeshot (14 Apr 2018)

Ah, thanks Pale Rider. 
That’s great - and an easy fix. Not expensive either. 

Cyclops - Good thinking and thanks for telling me about Mr Cross. I’d be interested to see what other gear options there are but really, I need a Brompton purely because of the fold size and the ease in which it is achieved. Just suits my needs for getting to work and stashing it under my desk etc. 
I’m pretty happy with the spread of gears on the 6 speed with the higher ratio option but my only niggle is the overlap of ratios when changing into the higher 3 which involves a bit of a juggle between levers. 
Have read about the 8 speed mod but not sure what to think. Interesting thought though. 

Anyway, thanks again for the replies chaps


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## Holeshot (14 Apr 2018)

mickle said:


> Or learn to spin. Bromptons don't fare well when muscled along by tall gears.



Haha! Too true....though ‘muscle’ may not be the term that applies to me!


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## 12boy (14 Apr 2018)

Perhaps you already are familiar with gear inch calculators, but if not I like Sheldon Brown`s (RIP). Plug in the wheel size, chain ring and sprocket sizes and if there is an IGH, that too. You can easily see what would happen as you change sprocket and chain rings. Or, you could simply use what is one your .existing bike to duplicate the 8% increase.


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## chriscross1966 (16 Apr 2018)

The +8% is achieved with a 54T chainring, you can go up to a 60T chainring before it becomes an issue with affecting the hook that locks the front fork during the fold. Next easiest options would be a toss-up between fitting a Schlumpf speed drive to the bottom bracket or an 8-speed Sturmey hubto the rear... about equal complexity... finally there is the whole-hog go bananas option and fit an aftermarket rear triangle from Kinetics or Vostok and put either a Shimano Alfine 11-speed or Rohloff 14-speed hub in it... The Sclumpf unit costs about the same as a cheapo Brompton 3-speed on eBay, the Sturmey setup is a bit cheaper, you could buy a recent Brompton for the cost of an 11-speed conversion once fitted and you could by a new top-end one for the cost of the 14-speed. The Sainted Sheldon's Gear Calculator shall be your One True Word...


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## chriscross1966 (16 Apr 2018)

A +8% 6-speed is 34 to around 103 gear inches through the range. A Sturmey 8-speed set up 44T chainring to 20T sprocket is 35 to 114 inches with slightly closer ratios through the range.

The Schlumpf is a x1.65 increased gear on the bottom bracket, so you'd probably go to a smaller chainring, a 40T chainring would give you the equivalent of a 66T when the increased is engaged, whilst giving you some serious granny gears when not...

The Alfine 11 set up 60 to 16 gives 31 to 129 gear inches and a trendy big chainring. 

To get really big ratios out of the Rohloff you'll need to get a BikinGreen 70T chainring and mod it to get the fork hook to fit.. 70T to 13T gets you 24 inches to 129 and a very trick Brompton... as in be prepared for other Brompton owners to want to talk to you about it.


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## chriscross1966 (16 Apr 2018)

Cycleops said:


> @chriscross1966 is your man regarding modding the gears on Bromptons.
> If you want a wider gear choice why don't you consider a Dahon or Tern?



Thanks for the mention :-)... but wash your mouth out for suggesting a D***n or T**n :-)


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## Kell (16 Apr 2018)

Don't know if this is still true, but I think it is...


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## Holeshot (16 Apr 2018)

Wow, thanks for the replies everyone.

That's absolutely answered my questions!

chrisscross1966 - thanks for taking the time to explain the gear system options - I'm liking the 8 speed Sturmey idea best.
Presumably with this, it would do away with the derailleur set-up?
Forgive my ignorance on these things, but what would the preferred changing mechanism be for these on a Brompton? (Twist grip vs. lever etc).
Also, where might one find the 44T chainring? 

Thanks again for everyone's time


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## Kell (16 Apr 2018)

Holeshot said:


> chrisscross1966 - thanks for taking the time to explain the gear system options - I'm liking the 8 speed Sturmey idea best.
> Presumably with this, it would do away with the derailleur set-up?
> 
> Thanks again for everyone's time



It does away with the chain pusher, but you still need to chain tensioner (the bit that looks like a derailleur with the jockey wheels) to allow the fold.


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## CopperBrompton (18 Apr 2018)

Also, remember you're not limited to Brompton's standard options. Others available include:
- Sturmey Archer 8-speed
- Alfine 11-speed
- Rohloff 14-speed


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## Kell (18 Apr 2018)

I cannot confirm or deny this, but the mechanic at my local Brompton shop (an ex-engineer) rates the Alfine way more than the Rohloff and cited various reasons including cost, serviceability (i.e. because it's a pressurised unit, you have to take it to someone who knows exactly what they're doing and has the right tools, and ease of use due to the spread of gears.

On the last point, I disagreed as he said it's a twist shift and no-one has a wrist that can twist that far. But then, realistically, when do you ever go from 1st to 14th in one hit anyway?


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## Holeshot (18 Apr 2018)

Thanks again for all the info - I'm learning all the time.

Just spoke to Kinetics about the Sturmey 8 and Alfine 11 speed conversion - all down to cost really (and that the Alfine requires a slight rear triangle re-shape to accommodate it).

Any thoughts on either of these?
In reality, is the Alfine a smoother ride?

Cheers


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## Cycleops (18 Apr 2018)

Just to let you know @Holeshot if you put @ before the members name they will get a notification that you mentioned them.


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## Holeshot (19 Apr 2018)

Thanks @Cycleops  ....I'm learning


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## Pale Rider (19 Apr 2018)

The Alfine 11 is not one of Shimano's finest efforts.

Many early ones broke - mine did, replaced under warranty.

Even when working, it always felt fragile and was prone to missed changes if the cable tension wasn't spot on.

Newer ones might be better.


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## chriscross1966 (19 Apr 2018)

Pale Rider said:


> The Alfine 11 is not one of Shimano's finest efforts.
> 
> Many early ones broke - mine did, replaced under warranty.
> 
> ...


They're sensitive to shift cable setup, I find the Jtek shifter to be more reliable than the Shimano rapidfire..


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## bikegang (21 Apr 2018)

If you are not a fan of internal gear hub or gear box chainring (schlumpf or Efneo) ... this one probably the widest range you can get so far for push chain type tensioner.

12-16-22T cogs example (11-xx-23 possible)


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## Holeshot (23 Apr 2018)

bikegang said:


> If you are not a fan of internal gear hub or gear box chainring (schlumpf or Efneo) ... this one probably the widest range you can get so far for push chain type tensioner.
> 
> 12-16-22T cogs example (11-xx-23 possible)
> 
> [



Wow, very nice.
What make are these?


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## stephenjubb (25 Apr 2018)

https://clevercycles.com/blog/2017/...rompton-the-ti-parts-workshop-triple-cog-kit/

available at SJS. site down when you see the price

https://www.sjscycles.co.uk/gear-sp...um-rear-cassette-sprocket-set-w-chain-pusher/


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## e-rider (27 Apr 2018)

a simple answer to the OP question is:

if the Brompton from Evans comes with standard gears and you want to convert it to the Brompton +8% higher gear option, all you need is the 54T chainring and a longer chain that Brompton sell. It's a cheap simple swap out of 2 parts.


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## Holeshot (27 Apr 2018)

e-rider said:


> a simple answer to the OP question is:
> 
> if the Brompton from Evans comes with standard gears and you want to convert it to the Brompton +8% higher gear option, all you need is the 54T chainring and a longer chain that Brompton sell. It's a cheap simple swap out of 2 parts.



Thanks for that.....

Just been advised my new Superlight is ready to collect so have done a bit of prepping as you described above. The chains are Powerlink so are a doddle to swap along with just undoing the allen bolts on the chainrings. Just for those that are concerned about swapping old chains onto new sprockets....the 'old' ones have only done 100 miles 

Am excited to see how the new, lighter version feels.......


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## Holeshot (27 Apr 2018)

stephenjubb said:


> https://clevercycles.com/blog/2017/...rompton-the-ti-parts-workshop-triple-cog-kit/
> 
> available at SJS. site down when you see the price
> 
> https://www.sjscycles.co.uk/gear-sp...um-rear-cassette-sprocket-set-w-chain-pusher/




Very kind of you sir - thanks!

Quite mouthwatering stuff!

I'll see how I get on with the new bike and the revised shifters.

I like the idea of a sequential set of ratios (as per Alfine conversion) rather than the juggling of ratios between the 2 sets of shifters on the standard set up.
I love the trickness of the triple rear sprockets but slightly worried it might take that juggling to another level. Am trying to calculate the inches that the 12/15/18T sprockets would give with the 3 speed hub


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## lyndsayp (17 Oct 2018)

chriscross1966 said:


> The +8% is achieved with a 54T chainring, you can go up to a 60T chainring before it becomes an issue with affecting the hook that locks the front fork during the fold. Next easiest options would be a toss-up between fitting a Schlumpf speed drive to the bottom bracket or an 8-speed Sturmey hubto the rear... about equal complexity... finally there is the whole-hog go bananas option and fit an aftermarket rear triangle from Kinetics or Vostok and put either a Shimano Alfine 11-speed or Rohloff 14-speed hub in it... The Sclumpf unit costs about the same as a cheapo Brompton 3-speed on eBay, the Sturmey setup is a bit cheaper, you could buy a recent Brompton for the cost of an 11-speed conversion once fitted and you could by a new top-end one for the cost of the 14-speed. The Sainted Sheldon's Gear Calculator shall be your One True Word...



@chriscross1966 - I've got a 2 speed Brompton that I'd like to increase the gearing off. I'm considering replacing it's 54T chainring with a 60T one, but unsure of what other specs to look for (other than 130BCD). Is this suitable? https://www.ebay.co.uk/itm/Fast-Shi...075-Alloy-10-11-Speed-Chainring-60T-BCD-130mm

Thanks


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## rogerzilla (17 Oct 2018)

7-9 speed chainrings, possibly 10 and 11 too, are all 2mm thick - only the thickness of the chain side plates and rivets differs. So yes. Even if the 10/11 speed ring is thinner, it will work. You are better off getting a singlespeed ring with no ramps or cutouts though. Just avoid 1/8" track stuff.

I'm running a "7 speed" NOS Sugino 56T on a 9 speed Moulton.


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## 12boy (17 Oct 2018)

Vuelta sells fairly inexpensive flat chain rings up to 60 tooth. You can certainly use a 130 BCD crank and chain ring and you can use a 110 also. I've used both a 58 and 38 tooth chain rings on a JIS taper 119 bottom bracket although this requires "dirty finger shifting". The newer cranks/chainrings are 130 BCD and JIS. Even with 58, though, you have to be a little careful when folding or unfolding since the edge of the chain ring sticks out more towards the hook which locks onto the chain stay when folded.


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## rogerzilla (20 Oct 2018)

One thing to watch for is that the LH folding pedal won't push over the end of all cranks. Try before you buy, or get a "diamond" rather than a "square" taper crankset in case you have to go snd buy a LH Brompton crank.later.

Of course, if you use a non-folding pedal this isn't a concern


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## lyndsayp (20 Oct 2018)

Thank you both @rogerzilla and @12boy . I've replaced the folding pedal with SPDs, so should be okay there. I'll probably try a 58T first, before going up to 60T. I'm curious why a single speed chainring, with no ramps or cut outs would be better though (I don't know much about this area)?


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## chriscross1966 (21 Oct 2018)

lyndsayp said:


> @chriscross1966 - I've got a 2 speed Brompton that I'd like to increase the gearing off. I'm considering replacing it's 54T chainring with a 60T one, but unsure of what other specs to look for (other than 130BCD). Is this suitable? https://www.ebay.co.uk/itm/Fast-Shi...075-Alloy-10-11-Speed-Chainring-60T-BCD-130mm
> 
> Thanks


Er.. the link isnt working for me.


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## chriscross1966 (21 Oct 2018)

lyndsayp said:


> Thank you both @rogerzilla and @12boy . I've replaced the folding pedal with SPDs, so should be okay there. I'll probably try a 58T first, before going up to 60T. I'm curious why a single speed chainring, with no ramps or cut outs would be better though (I don't know much about this area)?


The ramps are just missing material in our use, it is effectively just getting a ring that already has wear...


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## chriscross1966 (21 Oct 2018)

58t is about half the price of 60t and has an integrated guard. You can also get different colours.

www.ebay.co.uk/itm/263793828868


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## rogerzilla (21 Oct 2018)

A ring with full height teeth is less likely to unship the chain over bumps, especially if it's a large ring (conversely, those new 1 x 11 setups with a tiny ring need a special clutched rear mech to maintain chain tension). And yes, it'll last longer.


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## 12boy (21 Oct 2018)

So yesterday I am going up a hill which required I get off the 58 and onto the 38. But as I start grinding away the chain slips and does that whenever the effort goes up. I stop and examine this and can see that either the 38 or 58 has a warp which has the 58 nudging the chain as it travels back to the tensioner. Perhaps a 130 would be better than a 110 as there is more crank spider and less chainring. Probably is the 58 which is warped and which I can try to straighten or ditch the 38 and just go with the 58. Once going up a hill with a headwind the extra gear inches don't appeal quite so much. Has anyone else encountered chainnring warpage?


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## rogerzilla (22 Oct 2018)

It's easy to straighten chainrings with a big adjustable spanner. if it's flex rather than warp, that's (as you say) a case for a bigger BCD.


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## 12boy (22 Oct 2018)

I spent some time looking at this closely and the problem is different than I had thought. I like the big chainring on the inside which gives a straight chainline to the rear sprocket and makes it easy to shift from one to the other. But the 38 tooth chainline is out far enough that the chainline is far from straight and the chain hits the 58 tooth chainring just a little. I never had this issue with a 54 or 53 tooth and a 38, so I can go back to that, get a shorter BB, say 117 mm, or put some spacers between the 58 and the crank spider so it is closer to the frame a bit. Other than the rubbing issue, the chainline with the 38 has seemed to work very well with no skipping. I would like to have both chainrings as close to correct as possible so probably the shorter BB will be the best option.


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## chriscross1966 (23 Oct 2018)

12boy said:


> So yesterday I am going up a hill which required I get off the 58 and onto the 38. But as I start grinding away the chain slips and does that whenever the effort goes up. I stop and examine this and can see that either the 38 or 58 has a warp which has the 58 nudging the chain as it travels back to the tensioner. Perhaps a 130 would be better than a 110 as there is more crank spider and less chainring. Probably is the 58 which is warped and which I can try to straighten or ditch the 38 and just go with the 58. Once going up a hill with a headwind the extra gear inches don't appeal quite so much. Has anyone else encountered chainnring warpage?


I wonder if the chain tensioner isnt causing issues trying to take up 20 teeth of difference and still work normally... remember it isnt so much a tensioner as a take-up device to stop the chain unshipping when folded.


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## 12boy (24 Oct 2018)

You may be right that the span is just too much. The chainline appears to be 43.5 mm with the 58 on the inner part of the crank. The little one is the thickness of the spider further out and definitely looks crossway a bit. Since I primarily use the big one and reserve the 38 as a granny gear it seems best to have the correct chainline on the 58. I was toying with getting a BB 3 mm shorter than the current one as there is a 5mm gap between the ring and frame and mount the 38 on the inside. It does seem better with a 53 and 38. I have tried to find out what the standard chainline is supposed to be but haven't found that. It is getting to be winter here and I have studded tires but the 58 will definitely be too high for me to pedal with the extra work they require. Perhaps next year I will just go with the 58 alone and try to get stronger.


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## rogerzilla (25 Oct 2018)

Bromptons are quite hard to modify because of the fold. If you fit an alternative crank, the ring normally has to go on the inside of the spider; Bromptons have a large Q-factor to allow the crank to clear the rear triangle during folding. The LH pedal is amother possible complication, as I mentioned above. The headset needs to be a pretty low stack height - a Chris King 2Nut will fit if you are aggressive with the facing tool and grab 1mm extra stack height. Anything bar-related has to clear the front wheel when folded. It's an interesting challenge.


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## 12boy (26 Oct 2018)

Rogerzilla, do you know what the chain line is exactly? I can figure out the front fairly easily but the back.is harder. I am thinking if I can get the front crank out far enough so the chain line falls on the middle of the crank arm between the two chain rings I can avoid any rubbing of the chainrings
Thanks, Ron


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## rogerzilla (26 Oct 2018)

I used to but I've forgotten! I think about 46mm. You can adjust it a little at the back by moving sprocket spacers and also the washers under the jockey wheels of the chain tensioner. I initially tried a Sugino XD2 double with 107mm BB and the ring on the outside, but the crank hits the rear triangle when folded. So I used a 110mm with the ring on rhe inside, and got the sprocket a bit more inboard at the back to.match. My chainline is about 43mm now. I had the 110mm anyway; I could have bought a 117mm and it should have Just Worked with the ring on the inside. Disclaimer: I'm not using the Brompton black plastic spacer/dust shield under the sprocket as mine has AM hub internals with the usual metal labyrinth seal and two 1/16" spacers.


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