Got my first Brompton (S6L).



It came with standard gearing, but thanks to the new 2013 cranks, I was able to slap a 39t Ultegra chainring for about $25 (removed 3 chain links). Now it has a similar gearing range as my MTB in middle gear (32t middle w/ 11-34t rear).

Getting it ready for a ride with the kids this weekend:



Small enough to store inside (along with the kids' Skuut / Razor), so there's no excuse for me not to ride around with the kids.

nice hard wood (?) flooring ..

Welcome to the world of Brompton. You will love riding it. I've had mine now for a number of months and have put hundreds of miles on it. It rides as beautiful today as the day I bought it. One of the best purchases I have ever made.

Nice! Congratulations just this week I chose a black Ori M10 Superlight over the Brom... but it was a very, veeeeery hard decision. I even posted a thread here as I couldn't decide

Nice bike.

To be clear, if you have the same chainring and cassette as you mountain bike, it's geared much lower. Wheel size needs to be factored in.

So your highest gear on the mountain bike would be 75.6", while on the brompton it's 46.7".

https://www.sheldonbrown.com/gears/

(gear inches is how big the front wheel of a penny-farthing would be to cover the same distance with one spin of the pedals)

You forgot the internal gear multipler of the BWR hub , In High.. So high gear is (39:13 x 16")x1.57 so 75.6''

https://sheldonbrown.com/gears/internal.html tire =35-349

I used the Brompton Gear Calculator: https://xldev.co.uk/bgc.html

With a 39t front chain ring, the Gear Inch range goes from 25.7" to 77.8".

Using Sheldon Brown's calculator for my Reign w/ 26x2.125" tires, 170mm cranks and a 32t middle gear with 11-34t cassette, I get 24.4" to 75.7".

That's pretty close and more importantly, it feels just about right. Can't wait for the weekend to pull that weeride co-pilot trailer. should be fun.

the 6 I get using 13t/ 16t [1,2,3 ..]

[TABLE]
[TR]
[TD][TABLE]
[TR]
[TH]30.8[/TH]
[/TR]
[TR]
[TH]25.0[/TH]
[/TR]
[/TABLE]
[/TD]
[TD][TABLE]
[TR]
[TH]48.2[/TH]
[/TR]
[TR]
[TH]39.2[/TH]
[/TR]
[/TABLE]
[/TD]
[TD][TABLE]
[TR]
[TH]75.6[/TH]
[/TR]
[TR]
[TH]61.4

[/TH]
[/TR]
[/TABLE]
[/TD]
[/TR]
[/TABLE]




You missed the OP saying they substituted a 39t , perhaps? a non standard Brommy chainring
the new B spider crank allows any 130 BCD chainring to be used. they got an Ultegra one.

I got this (direct copy / paste). Did I do something wrong?

[TABLE]
[TR]
[TD]Chainring: [/TD]
[TD] Factory sizes are 54/50/44 teeth (+8%/standard/-12%) [/TD]
[/TR]
[TR]
[TD] Tyre: [/TD]
[TD] All Brompton high-pressure tyres [/TD]
[/TR]
[TR]
[TD] Hub: [/TD]
[TD] BWR
[/TD]
[/TR]
[TR]
[TD] Schlumpf: [/TD]
[TD] Direct Drive
[/TD]
[/TR]
[TR]
[TD] Units: [/TD]
[TD] Gear Inches
[/TD]
[/TR]
[/TABLE]

[TABLE]
[TR]
[TD="class: tblTopLeft, colspan: 1"]Gear Inches[/TD]
[TD][/TD]
[TD="class: tblHdr, colspan: 3"]Hub Ratios[/TD]
[/TR]
[TR]
[TD][/TD]
[TD="class: tblSubHdr"]64%[/TD]
[TD="class: tblSubHdr"]100%[/TD]
[TD="class: tblSubHdr"]157%[/TD]
[/TR]
[TR]
[TD="class: tblLeft"] Rear sprocket-Low: [/TD]
[TD][/TD]
[TD="class: tblCell"]25.7[/TD]
[TD="class: tblCell"]40.3[/TD]
[TD="class: tblCell"]63.2[/TD]
[/TR]
[TR]
[TD="class: tblLeft"] Rear sprocket-High: [/TD]
[TD][/TD]
[TD="class: tblCell"]31.7[/TD]
[TD="class: tblCell"]49.7[/TD]
[TD="class: tblCell"]77.8[/TD]
[/TR]
[TR]
[TD="class: tblRange, colspan: 5"]Range: 302%[/TD]
[/TR]
[/TABLE]

Successful first ride with the tandem trailer bike attachment. Here I am checking out this old van while the little one enjoys his ride.

Very cool!

(For what it's worth, I wouldn't call that a tandem trail-a-bike as it's just a single. As opposed to Adams Tandem trail-a-bike:
)

or you might say that he is pulling a trail-a-bike in tandem and what you are suggesting is a tandem trail-a-bike attachment... also, that looks dangerous.

Wow, didn't even know such a thing existed... and with gearing too.

Can I call the Weeride Co-pilot (official name of the one I got) an instant kiddie tandem kit?

I used a trail-a-bike type thing to pull my granddaughter along and it became more difficult to manage as she grew and got heavier. I can't imagine a tandem version being much fun to schlep along.

[QUOTE=tk1971;16454724]Got my first Brompton (S6L).

It came with standard gearing, but thanks to the new 2013 cranks, I was able to slap a 39t Ultegra chainring for about $25 (removed 3 chain links). Now it has a similar gearing range as my MTB in middle gear (32t middle w/ 11-34t rear).......................[QUOTE]

Nice bike! It's identical to my 1st Brompton(2012). It also had the standard gearing, 50T chainring and I swapped it for the
44T chainring/crank combo from B'ton. I got the reduced gearing for my 2nd B'ton. But I still want even lower gearing for the
hills. I have a 39T Dura Ace ring on order, actually wanted a 38T but the dealer said they can't get it.

How do you like your Ultegra ring? You had to lose the protector?

[QUOTE=1nterceptor;16466587][QUOTE=tk1971;16454724]Got my first Brompton (S6L).

It came with standard gearing, but thanks to the new 2013 cranks, I was able to slap a 39t Ultegra chainring for about $25 (removed 3 chain links). Now it has a similar gearing range as my MTB in middle gear (32t middle w/ 11-34t rear).......................The 39t is good, especially for my wife when lugging the Weeride. Like I described above, the gearing with the 39t is similar to my MTB in middle gear (32t) and 11t - 34t cassette. Should be good enough for leisure / travel, which is what this bike is for.

The wife liked it so much that she commandeered the white Brompton, forcing me to order another for myself. I'm getting a black one with standard gearing. I will swap out the chain ring with another 39t Ultegra as soon as I receive it.

Yep, I did loose the chain guard. I've recently bought two 42t 130 BCD chain rings that I plan to machine the teeth off of. With longer chain ring bolts I should be able to mount it on the outside of the cranks as a chain guard. It's just a shame to grind off teeth from perfectly good chain rings. I may resort to placing a WTB ad for worn out 42-44t 130 bcd chain rings.

I like Surly's Stainless steel chainrings in single speed drive trains (Brompton is such)
I have a 38-110 on a bike ..

why 2,? the chainline is awfully close to the frame hinge plate , it will be way off line
if you stick a chainguard flange on there instead.

Cyclocrossworld,com and others has nice ones made for the their purposes
I have one the companion for that 38t 110.. if you feel a trouser guard is needed..

I have not had the chain bounce off (54t,mountain drive crank)
on my Bike Friday Pocket Llama.. i added a 'chainminder'. it fits with a hose clamp
holding on a plastic finger ..


have one on bikes with triple cranks too..

You married well!

One for each bike. I'm nixing the idea. I don't think the 42 is big enough to act like a chain guard with the teeth milled off.

I think I'll leave it as is.

cyclocrossworld.com heres the link https://www.cyclocrossworld.com/thorn...hainring-guard

If it says 42 on those then its larger than the tips of the teeth..

But yea, as your Brompton spider crank is machined to just have the chainring on the inside face ..

Its different from a double crankset that you also could install .. there the shoulder for the outer chainring
seats a chainguard disc perfectly ..

Alright-y...

Snow White's evil twin now joins the stable... I thereby name thee Black.

Have fun...