# Brompton 'Ticking' & Ratios



## cosmicbike (11 Feb 2017)

I bought my M3L last year, and so far have only covered about 130 miles on it, largely through not getting round to using it. All my other bikes have 'normal' gears, the Brompton SA hub.
In the lowest gear all is well, nice and peaceful. in 2nd & 3rd gears though it 'ticks' in the same way as it does when freewheeling. Is this normal, or does some adjustment need to be made?
One other question. I find the lowest gear not quite low enough for hills, and pretty much never use the highest. Can I change the ratio easily enough by swapping the rear sprocket?
Cheers


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## TheDoctor (11 Feb 2017)

That ticking is endemic to hub gears, as the various internal bits freewheel past each other.
And changing the chainring is the usual way of changing the gearing.
I think it's a 110 BCD, but your dealer should be able to sort you out there.


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## the_mikey (11 Feb 2017)

The ticking noise is entirely normal.


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## 12boy (11 Feb 2017)

It is unwise, I suppose, to have an opinion which differs from The Doctor but I am afraid I do. My price here is around $35 for a Vuelta chain ring which is about as cheap as they get and that is for a flat (not ramped nor pinned) single speed ring. I understand 130 BCD is the size of the removable chain rings that newer Bromptons are sporting. 
For about $ 8-10 you can get a different cog to fit on the SA hub. I know they go no smaller than 13 tooth but I am not sure how big they get. You did not mention what tooth cog your current set up is but a 2 tooth difference on a cog is like 4-6 teeth on the chain ring and cogs are so much cheaper. As far as the ticking goes I put a little 5/20 synthetic motor oil through the chain spindle side of the rear axle and it results in a far quieter running hub. In the olden days these 3 speed hubs had an oil port for this purpose but the new "improved" ones do not. Newer Sunrace/SA hubs are, I understand, made very well and work reliably but they require 2 different weights of grease lube whereas pouring in a little oil when it gets noisy works at least as well. ( maybe a cc or so when it gets noisy). From my reading oil lubed IGHs vs grease lubed ones are significantly more efficient, almost as good as a well set up and clean derailleur. It is a cheap fix to which the only drawback I have encountered is a little oil seepage after filling it up. 
BTW, last week I rode to work in 3 degree Fahrenheit weather on a 700c bike with studded tires and an SA 3 speed through slush and over ice and the hub worked like a charm. There are others, but I use Sheldon Browns gear inch calculator which makes it easy to figure what size cog/chain ring to go with: 
http://www.sheldonbrown.com/gear-calc.html


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## mjr (12 Feb 2017)

12boy said:


> For about $ 8-10 you can get a different cog to fit on the SA hub. I know they go no smaller than 13 tooth but I am not sure how big they get.


About £3 posted to the UK up to 22 teeth at http://www.starcyclespares.co.uk/st...3-14-15-16-17-18-19-20-21-22-teeth-3292-p.asp and I'm sure I've seen 23 somewhere... but rule of thumb is not to go far over 50% of the chainring teeth.



12boy said:


> almost as good as a well set up and clean derailleur


and a dang sight better than the caked derailleurs found on many folders like mine once it's done a few winter countryside miles


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## chriscross1966 (13 Feb 2017)

Max rear sprocket on an otherwise unmodified Brompton is a 16T, limited by the tensioner fixed arm. You can modify the fixed arm if you want to go bigger, with care (and a BIG hammer) you can get an 8-speed Sturmey hub into the Brompton rear frame and its smallest sprocket is a 20.


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## oldwheels (13 Feb 2017)

Brompton supply a 44 tooth chainwheel as standard if required. I changed this to 40 tooth which works for me.


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## TheDoctor (14 Feb 2017)

12boy said:


> It is unwise, I suppose, to have an opinion which differs from The Doctor but I am afraid I do. l


No problem! I was quoting the way that Brompton change the gear ratios. I assume there'll be no problem changing the hub sprocket instead, but changing the chainring doesn't require getting the back wheel out, which I always find a bit of a pain.
Ass Chriscross points out, the biggest sprocket is apparently 16T before things foul. I've got an M6R so I wouldn't know - I'm stuck with the standard sprocket set. Didn't stop me putting a 44/34 chainset on though! Suppose it's an M12R now...


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