Brompton - Light & Cheap?

[timeout93]

I am building up my roadbike at the moment (Velobuild 066) which will be used for my trips and also my commute to work - 2x 30km. However I am pretty sure, I won´t take my bike for the commute every single time. Sometimes it´s just too cold, too rainy or I just don´t feel like it.
The only other option will be the train. But I need to get to the train (bike, by foot or bike) and also from the trainstation to work (bike or by foot). Because where I live I can´t take my bike into the tram and also I need to pay for an extra ticket for my bike if it´s before 9am, I was thinking of an folding bike.

(Of course) I was also watching for a Brompton. Because they are quite expensive, I also checked ebay and some other sites for used Bromptons and yeah... still quite expensive.... and heavy.

So I checked the Internet for some ideas. I found a good video on Youtube and two threads here on WW. In this Video (https://www.youtube.com/watch?v=rz24HOd ... stedWheels) he bought a used Brompton for 550 GBP, parts for 1300GBP and mostly from ali and sold the old original parts for 500GBP. So in total 1350GBP for a 8,98kg Brompton with 7 gears.

If money is a lesser problem than for me you can achive some pretty fancy sub 5 / 5kg builds with titanium frames:
viewtopic.php?f=10&t=168748&p=1728948&h ... n#p1728948
viewtopic.php?f=10&t=154985&hilit=brompton

So here would be my plan:

1. Find new parts for the Brompton - mainly from ali
2. Buy a new Brompton A-line - because it should be easier to sell parts and for higher prices
3. Check if all the new parts would fit me and the bike, when the Brompton arrives (for example handlebar etc.)
4. Buy the new parts and sell the original ones.

Try to be as costefficient as possible and save as much weight as possible. Also add some parts to the original A-line like mudguards etc.

This will be a theoretical thread (for now) to see where this would lead weight- and moneywise and also get your input. Also I am hoping this thread might help others with ther folding bike in the future.

[timeout93]

so first of all the Brompton:



999 Euro and 11,5kg.

To be fair I don´t understand what the difference between the a-line and c-line is. From what I understand it should be mostly the same bike, but you can´t choose different colours and handlebars, there are no mudguards and now bagholder (some more variations depending on which c-line model you choose). So all things I don´t need / I would change anyway.

[timeout93]

Parts to change - Wheelset

The original wheelset comes with an 3 gear hub. I think 3 gears will be more than enough for me as I am used to ride a singlespeed and won´t to climbing / descending on the Brompton.

Wheels I found:

1. Option
211 Euro / 733gr. / 305mm https://de.aliexpress.com/item/10050017 ... 7382v7t0nU

2. Option
260 Euro / 780gr. / 349mm https://de.aliexpress.com/item/40001702 ... mainSearch

3. Option
290 Euro / 830gr / 349mm / 7 gears https://de.aliexpress.com/item/40011915 ... bf3faJZiq0

4. Option
260 Euro / 800gr / 349mm https://de.aliexpress.com/item/40011965 ... bf3faJZiq0

5. Option
499 USD / 767gr / 349mm / carbon https://www.ebay.com/itm/352229052569

There are plenty more options, for example trispoke full carbon wheels, disc wheels etc. But these seem the most reasonable and I probably don`t want to go disc (for what reason?).

305 vs. 349
You can fit either diameter in the Brompton but I am leaning heavily towards 349mm. The original wheels are in this diameter, I don´t need space for bigger wheels and it should be easier to fit brakes.

aluminium vs. carbon
Because the carbon wheelset is much more expensive and no real weight savings I am leasing towars aluminium rims.

14 vs 16h front
I weigh aboud 80kg naked so more spokes are appreciated.

[timeout93]

Parts to change - Crank / Chainring / BB

Cranks

Option 1
37 Euro / 398gr https://de.aliexpress.com/item/10050032 ... mainSearch

Option 2
30 Euro / 366gr https://de.aliexpress.com/item/10050015 ... 5873XqFKCT

Chainring

Option 1
14 Euro / 80-100gr / 130BCD https://de.aliexpress.com/item/33014637 ... mainSearch

BB

Option 1
28 Euro / 165gr / 119mm https://de.aliexpress.com/item/40000147 ... mainSearch

Option 2
38 Euro / 155gr / 119mm https://de.aliexpress.com/item/32933118 ... mainSearch

This Setup would be pretty cheap and really light. The cranks won´t be stiff though.

[timeout93]

Parts to change - Chain tensioner and shifting system

Brompton uses their own(?) system and therefore options are limited. Also the rear triangle is only 115mm wide. Some people started to widen the rear triangle to 130mm to fit a Shimano Nexus for example.

Here are Options from Ali for 3 Speed:

Chain tensioner

Option 1
127 Euro / 177gr https://de.aliexpress.com/item/40012760 ... 2368cOPYaf

Option 2
33 Euro / 140gr https://de.aliexpress.com/item/32885381 ... mainSearch

Option 3
36 Euro / 144gr https://de.aliexpress.com/item/10050041 ... mainSearch

Shifting System

Option 1
53 Euro / weight? https://de.aliexpress.com/item/10050014 ... mainSearch

Option 2
28 Euro / 45gr https://de.aliexpress.com/item/40013162 ... mainSearch

[timeout93]

Other idea for the shifting system.

In the search for some builds to get some ideas from I found this: https://www.bikeforums.net/folding-bike ... ioner.html

This Brompton uses a normal rear derailleur. The problem was, that the "normal" derailleur has not enough reach to tension the chain enough when folding the bike. Normally you can take a larger cage, but the small wheeldiameter limits this to an extend.
So his solution was to use an (ugly) OSPW System.

To use a normal rear derailleur you just need a separate hanger like this: https://www.ebay.com/itm/284490931687
There might be more to this, but I couldn´t find any informations about this option.

That gave me thinking. I have an old road bike at home with ans Dura Ace 7700 Groupset. I might could try to get the hands on one of this hangers and try to build it up with some of the DA parts. I mean ... don´t you think this would look super nice on a Brompton? But then I would probably go for more gears than just three, because there is no downside to it.. or I miss something.

[timeout93]

Parts to change - Seatpost / Saddle

Original weights:
Seatpost: 397gr (steel)
Collet: 100gr
Saddle: 385gr (post-2009)

Seatpost

Carbon

69 USD / 266gr https://www.ebay.com/itm/121434213513

Titan

76 EUR / 263gr / no collet https://de.aliexpress.com/item/32918827 ... 2809%22%7D

Aluminium

28 EUR / 330gr https://de.aliexpress.com/item/32850625 ... 9649%22%7D

Seatpostclamp
20 EUR / 37gr https://de.aliexpress.com/item/10050013 ... 4619%22%7D

Saddle

Because there is nothing special about the saddle and it´s also really personal, I won´t give any options.

[timeout93]

Parts to change - Frame / Fork

Sets

Steel
There are many sets from different Brands. For Steel you will find many different colours from Aceoffix starting at aroung 505 Euro. The set weigh about 4,1kg.

Titanium
Same goes for titanium sets. You can either swap single parts (rear triangle, fork, handlebarpost, mainframe) for titanium or go all in. Starting at about 2300 Euro and weigh about 2,4kg.

Some Informations about the weights you can find here: https://www.bikeforums.net/21059608-post22.html

You can also go for carbon. I could find different forks for rim and disc and one rear triangle, but only disc. Not sure if there are othere frameparts which can be bought in carbon. To be fair, carbon is probably not the way to go for a Brompton-like bike (design).

Headset
74gr / 11 Euro https://de.aliexpress.com/item/10050029 ... mainSearch

75gr / 78 Euro https://de.aliexpress.com/item/10050014 ... 2282%7Csea

75gr / 57 Euro https://de.aliexpress.com/item/10050037 ... 6040%7Csea

[timeout93]

Parts to change - Brakes / Levers / Cables / Housing

Brakes

For a Brompton different brakes apply. Because of the folding system only brakes which get pulled from the down right side are "usable". But I found a lot picture with a "normal" brake in the front. It seems here the problem which accures with normale brakes are not so problematic as in the rear.

Some people use their eeBrakes for a brompton by using 2 adapters. You can see them here: https://www.facebook.com/tipartsworksho ... 810672196/

You can find different adapters on ali as well. Don`t know about other brakes though. Also an option is to just use the frontbrake with a normal brake caliper. (not really safe though)

For cables you can use any cable/housing. Same goes for brakelevers.

[timeout93]

Parts to change - Accessories

To shorten it a little bit. On ali is no shortage of different accessories for you Brompton. There are mudguards in different materials, different sized racks in different materials, wheels, clamps etc. etc.

[sprazzler]

Any update on this?

[poulhansen]

Buy a Bike Friday bike. It has superior driving quality and uses mostly standard components. From new you can specify components but even used you can be quite certain it has usable quality components.

They have lightweight frames and gravel tyre options.

[OtterSpace]

timeout93 hasnt posted in awhile but I did something similar when a deal came up that I couldn't turn down.

It was a fun project because of how chaotic the design, aftermarket parts, and overall lack of documentation for everything. Most of the info online is from either brompton purists who think it's the best bike ever and nothing can improve it or Singapore Uncles that bling up the bike without a cohesive goal towards the final usability of the platform.

However the bike platform itself (wheel base, wheel size, weight distribution, weight, gearing) makes for a horrible riding bike that aftermarket parts can only partially address.

Unless you need to fold to a specific size get something as close to a normal bike as your use case can allow.

If you have specific questions feel free to ask and if there is enough interest I can post my build seperately to avoid cluttering up this thread so I'll limit myself to posting two images and then replying to any requests.

[mike]

great price for a brompton