Brompton chain ring

clid61

Veteran
Location
The North
I bought a second hand brompton start of the year(It's a 6 speed , the guy I bought it off raced the damn thing.). TBH not been out on it a great deal at present, due to lockdown etc.
I'm a skinny bugger pushing 60 live on the edge of the Pennines. Needless to say I need a more sedate chainring than this Bin lid of a ring. Any suggestions? I was considering a 42 or 40 ring.
Any advice welcome.
TIA
 

mitchibob

Well-Known Member
Location
London, UK
I bought a second hand brompton start of the year(It's a 6 speed , the guy I bought it off raced the damn thing.). TBH not been out on it a great deal at present, due to lockdown etc.
I'm a skinny bugger pushing 60 live on the edge of the Pennines. Needless to say I need a more sedate chainring than this Bin lid of a ring. Any suggestions? I was considering a 42 or 40 ring.
Any advice welcome.
TIA
The standard Brompton 44T should be fine. It's about the equivalent of 35/32 on a 700c bike.
 
OP
clid61

clid61

Veteran
Location
The North
View attachment 537797

Or add a cheap stronglight Double 50/36.
i'll consider that ta
 

sdawila

Active Member
I bought a second hand brompton start of the year(It's a 6 speed , the guy I bought it off raced the damn thing.). TBH not been out on it a great deal at present, due to lockdown etc.
I'm a skinny bugger pushing 60 live on the edge of the Pennines. Needless to say I need a more sedate chainring than this Bin lid of a ring. Any suggestions? I was considering a 42 or 40 ring.
Any advice welcome.
TIA
did the previous owner change the cogs ? considering he's gone racing with it. if no, if you live in hilly area it should be alright using 44T chainring but if you aim for speed and agility in town then you opt for 50T Chainring.
 

Kell

Über Member
Just FYI (I know someone will be along in a minute to say that whenever anyone asks about gears, someone posts the Brompton ratio chart...)

So 'Standard' normally refers to the 50T on the front. -12% is the 44T and +8% is the 54T.

You can get other ratios by changing the rear sprockets (sometimes in conjunction with the front).

The good news is that even buying genuine Brompton parts, it's cheap to do.

I did recently change to the 44T on my 6-speed, but it compromised the top end too much for me. I have one killer hill where I live, but making it easier to climb that ruined the rest of the ride.

If I can find the thread on my experience, I'll post it, but even if you don't understand gear inches (I don't) you can see that on the 44T, your top end gear is only just longer than 5th on a 50T. For me, that wasn't quite enough as I tend to grind the gears round rather than spin them.



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Last edited:

Tenkaykev

Veteran
Location
Poole
Just FYI (I know someone will be along in a minute to say that whenever anyone asks about gears, someone posts the Brompton ratio chart...)

So 'Standard' normally refers to the 50T on the front. -12% is the 44T and +8% is the 54T.

You get the other ratios by changing the rear sprockets (sometimes in conjunction with the front).

The good news is that even buying genuine Brompton parts, it's cheap to do.

I did recently change to the 44T on my 6-speed, but it compromised the top end too much for me. I have one killer hill where I live, but making it easier to climb that ruined the rest of the ride.

If I can find the thread on my experience, I'll post it, but even if you don't understand gear inches (I don't) you can see that on the 44T, your top end gear is only just longer than 5th on a 50T. For me, that wasn't quite enough as I tend to grind the gears round rather than spin them.



View attachment 538475
It's always useful to have that chart Kell, I can never find it when I want to consult it.
I don't go very fast, so for me the 44 tooth conversion meant reaching the Pub at the top of the hill versus my previous "walk of shame" pushing the Brommie for the final 50 metres ^_^
 

12boy

Veteran
Location
Casper WY USA
I have 2 chainrings, a 58 and a 38. This is currently on a 3 speed chain pusher with 11, 14 and 17 sprockets. 85 to 36 gear inches. With my SA 177% hub with a 13 tooth sprocket I get a range of 96 to 35. The 3 speed chain pusher is quite a bit lighter. These both work fine where I live unless the steep parts,are blessed with stout headwinds. The 2 chainrings mean manually shifting which is pretty quick. I'm using a 110 BDC crank which has provisions for a 24 tooth 3rd chainring which runs fine except it doesn't fold. I'm sure a 34 would work as well as the 38.
 

rogerzilla

Legendary Member
A 14T sprocket in place of the factory 13T makes things a bit more spinny, but you have to add an inch of chain.
 
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