hihi2u2

Hi there,
I'm thinking to convert my Brompton to take external gear with a 130mm rear dropout without getting a new rear triangle.
I'm thinking to take it to a local steel bicycle workshop to see if it's possible.

The bike is still on-order hence I'm here. It seems like there are only rear triangles designed at 130mm and can't see anyone converting one.
Has anyone tried and is it physically impossible to do hence there is only mod with changing the rear triangle?

Thanks,

Roland

squirtdad

I really am not sure I understand your question.

The Bromptons I see are 3 speed hubs, so you would not have derailler hanger.

the seat stays are short which would complicating cold setting

Why try to modify a purpose built bike?

If you want deraillers get folder designed with those like a bike friday
https://bikefriday.com/product/bike-...t-folding-bike
https://bikefriday.com/product/bike-...road-bike-2019
https://bikefriday.com/product/bike-...t-folding-bike

tcs

I read that it's possible through the standard technique...but naturally, all risk is yours.

hihi2u2

I saw a video on YouTube, and it seems like a standard techniques. Will try it with a steel bike repairer so at least they know what they are doing with the steel.

hihi2u2

​​​​​​
the only folder that folds in a similar compact size with similar folding time and a normal derailleur is a Mezzo/Ori but they are still bigger than Brompton when folded. The Bike Friday are too big to take on a daily commute in London and the fold is not as fast. Don't really get on with hubs, they are heavy and quite limited hence wanted more options with a normal 130mm OLD.

CliffordK

Hmmm...
You'll have to be careful that you don't mess up the folding. Some of the larger internal gear hubs are even 135mm spacing.

Whatever you do, also make sure you realign the dropouts after spreading them.

2_i 

Tensioner in a standard derailleur will have a problem collecting slack for the folded bike. I suggest living with the bike and listening to it first and not watching too much of YouTube - it could be detrimental to more than the bike alone

squirtdad

the Brompton is not light at 23+ pounds so it is not light to start with.
as to weight you are subtracting an igh, but adding hub, cassette, derailler, derailler hanger I compared the weight of these against a sram ddr hub and in total they weigh more by about 100 grams than the igh

Brompton does offer a front shifter to get 6 speeds with the 3speed igh

you bike your choice, but overall this does no look like something that is going to be simple and work smoothly. Good luck

Iride01 

Wouldn't a Shimano Nexus IGH fit within the rear triangle with no fuss? And if the OP only has a 3 speed IGH currently, then Nexus can probably put 7 or 8 speed inside the same space if the rear is 126mm spacing.

Being a folding bike, I'd hate to make it where it might not fold up properly and also I'd be worried about the DR hangar getting bent.

tcs

Best advice: take your inquiry to the Folder Forum where folks know the bike, understand the question and have even done this before.

jgwilliams

Have you looked at what Kinetics do? It may give you an idea of what's possible. I would have thought, though, it would make more sense to put a different IGH hub on.

hihi2u2

You just need a tensioner added to the rear derailleur and a chain guide/hook at the chainring to take the slack. It's very similar to the Mezzo when folded which relies on the chain guide/hook at the chainring

hihi2u2

Good point 👍

hihi2u2

I just don't want a hub, had them before just heavy. The Kinetics basically is evidence that it can be done and doesn't affect the fold. They sell the rear triangle on its own and before I comission a Steel Bike Workshop to do it (basically I'm not doing it myself but asking someone who works with bikes day in and out to do it). Is there any show stoppers e.g. does the widening reduce the wheel base up to a point where it doesn't accommodate the rear wheel? Basically the material on the rear triangle is finite and it doesnt work unless you ask the workshop to solder on additional length for the drop out?

It's a folding bike, if it's messed up it only cost £70 to get another rear triangle. It's easily replaceable by undoing a bolt.

2_i 

Let's meet here in a year from now and see where your project stands.