Brompton 3-speed hub internals

[kais01]

there are many ways to rome, but if you are willing to put in some uncompromising effort a serious multigear bike for do it all street use should in my preferance have about 30 gear inches on the lowest and over 100 on the highest.

and not more than 18 percent between gears over 70, no more than 10 percent over 100.

for decent wear and efficiency no less than 12t sprocket on the rear wheel, and max one planetary gear in the driveline.

thats the wish list, and i have fullfilled it on one of my bromptons.

have fitted it with a 2x10 dura ace/shlumpf speed drive 30-120 gear inches. 12 percent max step between gears. needless to say its a highly competent blast.

with less gears you have to compromise, nothing wrong with that.

a drastic example is my 2speed brommie commuter where i have done away with all low gears and have only 71 and 95 on hand. like having only gear 4 and 5,5 on a bwr 6sp, or 2,5 and 3,5 on a 3sp. nothing for hilly areas, but the greatest fun elsewhere.

then the surprice; almost as fast as the 20sp on longer distances in reasonably flat landscapes.

 

[Kell]

then the surprice; almost as fast as the 20sp on longer distances in reasonably flat landscapes.

it shouldn't really be a surprise. If the gearing matches the terrain, then you could do it with just one.

 

[kais01]

absolutely Kell. and the hour record is witheld with just one gear.

but i am with this minimalistic approach really glad to have a second gear for going on and about. and with brompton and its chain tensioner/derailer its more or less built in.

and also glad for the 2x10. it is of course the better more versatile bike.

and is easier on the knees

 

[12boy]

there are many ways to rome, but if you are willing to put in some uncompromising effort a serious multigear bike for do it all street use should in my preferance have about 30 gear inches on the lowest and over 100 on the highest.

and not more than 18 percent between gears over 70, no more than 10 percent over 100.

for decent wear and efficiency no less than 12t sprocket on the rear wheel, and max one planetary gear in the driveline.

thats the wish list, and i have fullfilled it on one of my bromptons.

have fitted it with a 2x10 dura ace/shlumpf speed drive 30-120 gear inches. 12 percent max step between gears. needless to say its a highly competent blast.

with less gears you have to compromise, nothing wrong with that.

a drastic example is my 2speed brommie commuter where i have done away with all low gears and have only 71 and 95 on hand. like having only gear 4 and 5,5 on a bwr 6sp, or 2,5 and 3,5 on a 3sp. nothing for hilly areas, but the greatest fun elsewhere.

then the surprice; almost as fast as the 20sp on longer distances in reasonably flat landscapes.

How did you manage 95 gear inches on a 2 speed?

 

[kais01]

like this

the lower gear is around what most single speeders have to barely make it up the hills, but then on this there is one more to go

climbing is also made easier by the spd pedals, regularly pull the pedals then, rather than mush my knees.

 

[12boy]

What is that chain ring? Huge! Do you have any folding issues? I have 58/ 38 chain rings and 12/17 sprockets which with the 38 allows for some hills. No front derailleur, just the greasy finger shift, which isn't too much trouble since I don't need the lowest gears often.

 

[kais01]

its a gebhardt.cz 69t. they can make any size up to 75t, and with any bcd.

no problem with fold, but you have to do away with the hook at the left of the front hub, and replace with older style s1e hook that mounts on the fork. there is a small pipe brace-on there for that purpose. such a hook catches the chain and not the chainstay. i chose to make a hook myself from a piece of wire.

upper limit i believe would be about 72t. with original hub hook in place i have previously used 61t, but one or two more teeth could work.

 

[the_mikey]

Also consider changing the front chainring from a 50T to a 44T, this will also need a new chain but it brings those gear ratios down to something easier to turn, I generally dont have trouble with the standard 6S arrangement except for the very top gear, which is just hard to turn in most circumstances.

EDIT: this has already been mentioned! (I've read the whole thread now)

 

[Oren_Hershco]

Update:

Eventually I decided to purchase a 3-speed wheelset, from BrommiePlus (http://www.brommieplus.com/portal_c..._word3=&bool1=&bool2=&search_type=1&up_page=1)

It was very easy to install. I got rid of the two-speed derailleur mechanism.

Front chainring is the original Brompton, I think it's 50t; rear sprocket is 14t. The gears in the system are perfect for my almost-flat 20km commute.

I'm not going to do any hills with this bike, so these 3 gears are enough for me.

I also changed the handlebar to a lower-rise carbon one, and the seatpost to a black alloy one (both from Aliexpress)

Changing the handlebar was the roughest challenge in the process:

a. It didn't quite fit in the Brompton stem... I had to use some violence, which left some visible scars. Everything works, but I wouldn't install that bar again on a brompton.

b. A lower handlebar means you need to re-calculate all the cables lengths. And unlike normal bikes, where only "too-short" is really a problem, on a Brompton there's also "too-long" (because of the fold).

Anyway, the result is almost 1.5kg lighter than the original M6L model! The riding posture is much better now for my needs, and the simple 3-gear system is swift.

I hope I'll be able to post some photos soon.

 

[Oren_Hershco]

Photos:

Rear 3 speed hub

• Oren_Hershco
• 15 Sep 2019

Seatpost

• Oren_Hershco
• 15 Sep 2019

Shifter

• Oren_Hershco
• 15 Sep 2019

Bike

• Oren_Hershco
• 15 Sep 2019