Making a fairly old (c15 years) 6-speed Brompton easier on hills

Mr_T_Wales

Regular
Hi all - I'm looking for some advice. I have a nice 6 speed Brompton and where I now live has a fair few hills, so it's a struggle sometimes. I've literally never used the higher gears so I'm thinking of changing the chain ring to something smaller as I don't care about riding fast.

After looking into this, my my bike has the older crankset and bottom bracket so I'd need to do some replacing.

Right now, I'm thinking of this (plus a new bottom bracket, plus some tools as I only have a crank remover) https://brilliantbikes.co.uk/brompt...pton-crankset-with-44t-spider-chainwheel.html

My chain is fairly new, as are the rear sprocket things, so I'm hoping I could remove some chain links and get away with not changing the sprockets. Not sure if this is sensible?

My real question is whether I can go lower than 44T. This is the lowest that I can see for specific Brompton kits, but I wonder how much difference it will make. Something like 38T or 40T would be better if it would work and not mess up the folding etc.

Any advice would be great!
 

berlinonaut

Senior Member
Location
Berlin Germany
Sure you can, just that Brompton themselves don't sell these parts. With the older crankset you may be able to simply mount an additional chainwheel directly onto the existing one. Has for a while been relatively common years ago and is the cheapest solution (greasy finger shifting applied). Anyways you can safely contiue to use your existing chain and sprockets if they are in good shape, even if you choose to seitch to the new crankset completely.

Regarding the effects of a smaller chainring: have a look at http://ritzelrechner.de
 

oldwheels

Legendary Member
I have a 40T chainring on my 6 speed which limits my top speed to under 20mph. Suits me fine as I have a lot of shortish but steep hills to climb and not bothered about much above 12mph anyway.
Cannot remember where I got it but not a Brompton part.
 
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Mr_T_Wales

Regular
Sure you can, just that Brompton themselves don't sell these parts. With the older crankset you may be able to simply mount an additional chainwheel directly onto the existing one. Has for a while been relatively common years ago and is the cheapest solution (greasy finger shifting applied). Anyways you can safely contiue to use your existing chain and sprockets if they are in good shape, even if you choose to seitch to the new crankset completely.

Regarding the effects of a smaller chainring: have a look at http://ritzelrechner.de
Thanks. I need to look at that website when I have a clear head! My understanding is limited to: easy hills means small front cog and large back cog.

I did notice from a Google that some people have the two chainwheels but it may be beyond me, plus to be honest I only use the lower gears anyway.
 
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Mr_T_Wales

Regular
I use a 50/34 Stronglight Chainset on my 6 speed and gets me up most things with a heavy load.
I tend to replace chain and sprockets regularly (they're not expensive) and I certainly would if fitting a new chainset to an old bike.
Thanks. The bike is old but I did change the chain, chainring and sprockets a while back (actually I guess it was 6 years or so but I've hardly used the bike since then as I stopped commuting to work, but want to cycle more going forward).

I did just order this cheap chain set: pliers, breaker and weird measuring thing. The latter is supposed to let you know if the chain has stretched but I have my doubts to be honest. I just can't face changing the rear ones if I can help it.
 
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Mr_T_Wales

Regular
I have a 40T chainring on my 6 speed which limits my top speed to under 20mph. Suits me fine as I have a lot of shortish but steep hills to climb and not bothered about much above 12mph anyway.
Cannot remember where I got it but not a Brompton part.
This is what I want really.

I'm getting confused though. Eg this on eBay seems suspiciously cheap but I think it would work if I had the correct bottom bracket thing? I don't mind paying a bit more for better quality though.

https://www.ebay.co.uk/itm/352870424372?hash=item5228b75f34:g:wwAAAOSwcbpd1Qnm
 

berlinonaut

Senior Member
Location
Berlin Germany
I'm getting confused though. Eg this on eBay seems suspiciously cheap but I think it would work if I had the correct bottom bracket thing? I don't mind paying a bit more for better quality though.

https://www.ebay.co.uk/itm/352870424372?hash=item5228b75f34:g:wwAAAOSwcbpd1Qnm
In principle it should work. In today's world you often only have the choice between very cheap stuff and very expensive stuff - which does not necessarily mean that the cheap stuff would be of bad quality or endurance. In many cases it is just heavier. In your example it does have a steel chain wheel and seems generically to be made on the cheap side. So the price should be about right and the weight probably relatively high.

You should be aware that todays cranks are in 99% of the cases designed for JIS bottom brackets while you do have an ISO bottom bracket. You can use the newer cranks on the old bottom bracket, however pesonally I would exchange it for a JIS one (not expensive).
Furthermore, in most cases the left crank does need a bit of treatment with an angle grinder to make the folding pedal fold it not using Brompton cranks.
 

oldwheels

Legendary Member
I got the kit from tillercycles.co.uk. Their address is in Stockton but no idea if they are still in business as it was some time ago. It was a ring which fits on to the existing cranks. Easy job to fit.
 
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Mr_T_Wales

Regular
In principle it should work. In today's world you often only have the choice between very cheap stuff and very expensive stuff - which does not necessarily mean that the cheap stuff would be of bad quality or endurance. In many cases it is just heavier. In your example it does have a steel chain wheel and seems generically to be made on the cheap side. So the price should be about right and the weight probably relatively high.

You should be aware that todays cranks are in 99% of the cases designed for JIS bottom brackets while you do have an ISO bottom bracket. You can use the newer cranks on the old bottom bracket, however pesonally I would exchange it for a JIS one (not expensive).
Furthermore, in most cases the left crank does need a bit of treatment with an angle grinder to make the folding pedal fold it not using Brompton cranks.
Thanks, I never even thought about the folding pedal being restricted.

Just looking around, the problem I have is that most options don't seem to have a chain guard and I want one for sure.

Just been looking at this, and it comes with the bottom bracket. It looks like it may be better quality, or at least lighter.

https://www.bike-discount.de/en/buy/shimano-alfine-fc-s501-crank-with-single-chainguard-1080150
 

Fab Foodie

hanging-on in quiet desperation ...
Thanks. The bike is old but I did change the chain, chainring and sprockets a while back (actually I guess it was 6 years or so but I've hardly used the bike since then as I stopped commuting to work, but want to cycle more going forward).

I did just order this cheap chain set: pliers, breaker and weird measuring thing. The latter is supposed to let you know if the chain has stretched but I have my doubts to be honest. I just can't face changing the rear ones if I can help it.
Changing the rear cogs is simple, easier than any regular bicycle.
 

T4tomo

Guru
if you wnat a chainguard and dont want to have to mess around with an angle grinder or file to get the pedal to fold, then you want the brompton spinder crankset you linked. If 44T still isn't low enough (is your current one 50T?) then you can either change to a small chainring (such a spa cycles will do you a standard chainring, but no chainguard)

or some places have thought of them problem you face,,,, (tad pricy though)

or you can up the size of the two rear sprockets and keep the standard 44T brommie chainring. Not sure what you have on your rear sprockets but up 1 or 2 teeth is similar or even lower than going from 44 to 40T on front. so can change 13/15 to 15/17 for example
 
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Mr_T_Wales

Regular
if you wnat a chainguard and dont want to have to mess around with an angle grinder or file to get the pedal to fold, then you want the brompton spinder crankset you linked. If 44T still isn't low enough (is your current one 50T?) then you can either change to a small chainring (such a spa cycles will do you a standard chainring, but no chainguard)

or some places have thought of them problem you face,,,, (tad pricy though)

or you can up the size of the two rear sprockets and keep the standard 44T brommie chainring. Not sure what you have on your rear sprockets but up 1 or 2 teeth is similar or even lower than going from 44 to 44T on front. so can change 13/15 to 15/17 for example
Damn, that's great advice. I didn't consider the rear sprockets, mainly as I'm never sure about having to re-tune the gears etc if all that gets removed and I've found the tension arm thing a bit fiddly (hence getting a solid rear tyre last time I changed a tyre, which I have to say I 100% love). It sounds like you guys manage to change in about 5 mins though so I must be making a meal of it somehow!

Just looking at my email history, I have "Brompton sprocket / disc set 13 / 15 tooth for SRAM rear wheel Item Number 414" as my sprocket set. Not sure if it's the relevant calculation, but 44/17 is lower than 40/15 (even 39/15) so I guess it must be an option.

Right now I'm thinking about either:

(1) Get the Brompton 44T spider set and bottom bracket, and 15/17 sprockets (if I can work out which ones to get). My chain is fairly new but I'm thinking that if I get a new chain, to save hassle, then it may not be a standard size though so I'd have to remove links anyway?

(2) Get something like this https://www.bike-discount.de/en/buy/shimano-alfine-fc-s501-crank-with-single-chainguard-1080150
I think this looks great, and I guess I'd have the option of bigger sprockets if I wanted to go even lower at some point. I have an angle grinder, and file sander for that matter, so provided it doesn't remove the colour and look silly I don't mind fiddling around a bit.
 

byegad

Legendary Member
Location
NE England
Not solely Brompton related, but, in the days I rode uprights I often found a new bike was seriously over-geared for a fat, only reasonably fit, older guy in County Durham where we have some 'decent hills'.

On recumbent trikes, on the other hand, the top gear is often too low and the bottom gear too high. However re-gearing a trike is easy enough as not only are you not limited from using all the available options regarding crossover but I've also discovered that the recommended capacity of mech's, both front and rear, are very conservative. My old QNT ran 55-40-24 to 11-34 and I could and did use all 27 possible combinations when need be to no ill effect in well over 20000 miles of riding.
 

berlinonaut

Senior Member
Location
Berlin Germany
Btw: The sprocket-set for the SRAM is no longer avail. from Brompton for some time already. No issues to get a single 13t as this is used on the 3-speed as well. Getting a 15t can become a bit of a task and you won't get it from Brompton apart from maybe a longterm Brompton shop that has old stock. As it is an ordinary 3-spline sprocket there are other sources, namely Sturmey Archer but you should check thickness and form of the sprocket if it fits what is needed. If you lack an oldschool Brompton dealership SJS can be a source as can - as others mentioned - SPA be for chainrings and chainsets. Tillercycles has been out of business already for a while but Graham handed over at least the chainring side of his business to another small shop and I remember the webpage used to be forwarded to this shop. This is no longer the case but this is the shop in question: https://www.brommiemods.co.uk/
 
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