Brompton with higher gearing / more top end speed - need new rim etc anyway

[AndrewP123]

I have a 6 speed electric Brompton with Sturmey rear hub. The gearing has always annoyed me - never use the lower gear cog as far too low and feels like it needs more top end pace. I am no mechanic so cost of buying a new rear wheel isn’t that different from paying someone rebuilding it. While I am doing this what is my best option to improve the gearing?

 

[Chris S]

Is it a 3-speed hub with 2 sprockets on the back? Put a smaller sprocket on it and shorten the chain. Sprockets start at a few pound on ebay. They're just held on with a circlip.
https://www.ebay.co.uk/itm/156469480155

 

[Schwinnsta]

You can get higher gearing by changing your chain wheel to one with more teeth.

 

[gom]

I don't have an electric Brompton, but assuming it's like my non-electric 6-speed:
The two sprockets (rear cogs) are designed to fill-in the 3 widely-spaced gears provided by the 3-speed hub, giving 6 evenly-spaced ratios. Gears 1,3,5 use the large sproket, 2,4,6 use the small. See something like
http://ritzelrechner.de/?GR=BWR6&KB=50&RZ=13,16&UF=1330&TF=90&SL=2.6&UN=MPH&DV=gearInches

Changing one sproket will break the even spacing.
As noted above, it sounds to me like you should just get a larger chainring.
Standard chainring is 50T. Brompton offer 44T & 54T as options, but you should find other makes and sizes will fit your crank.

 

[AndrewP123]

I don't have an electric Brompton, but assuming it's like my non-electric 6-speed:
The two sprockets (rear cogs) are designed to fill-in the 3 widely-spaced gears provided by the 3-speed hub, giving 6 evenly-spaced ratios. Gears 1,3,5 use the large sproket, 2,4,6 use the small. See something like
http://ritzelrechner.de/?GR=BWR6&KB=50&RZ=13,16&UF=1330&TF=90&SL=2.6&UN=MPH&DV=gearInches

Changing one sproket will break the even spacing.
As noted above, it sounds to me like you should just get a larger chainring.
Standard chainring is 50T. Brompton offer 44T & 54T as options, but you should find other makes and sizes will fit your crank.

I just use 2, 4 & 6 & the others are pointless. The spacing is absolutely fine (maybe might be different without electric). So I could by the sound of it change both the rear cog (swap large one out with an even smaller one) and change to a larger chainring. Any other downsides / issues to be aware of?

 

[Gunk]

You can get higher gearing by changing your chain wheel to one with more teeth.

Absolutely, as later Brompton’s have a spider crank, easy to fit a 52 or 54 teeth chain wheel

 

[Ajax Bay]

I think your 13t sprocket is the smallest available so a larger chainring is your avenue.
I guess swapping the 16t for a 14t would fit your apparent gear length range need better but it won't help with the spinning out.