Prototype 20" Brompton

[Origamist]

Seen at the junction with Caledonian Rd, London.

I've heard talk of a 20" model for many years. Looks like we're nearly there? This version looks to be electric...

Lots of talking points...

Image courtesy of @dr_brompton

 

[Kell]

I've pondered whether or not this would be possible for years.

Combined with the discs, I could see me opting for something like this.

Price dependent of course.

Is this just a frankenbike though? Or a genuine thing?

Just googled dr_Brompton as I genuinely thought it was on the guy's tights.

 

[rualexander]

Looks good.
Kinetics in Glasgow have been making 20" Brompton conversions for a few years now but this isn't one of theirs. Their 20" conversion doesn't take tyres that fat.
There's also Eerdermetal in Netherlands who makes conversions with 20" fat tyres.

 

[404 Not Found Anywhere]

The stem is definitely not stock Brompton and that triangle in the main frame looks a bit bigger than usual…

 

[cougie uk]

More details on his site


View: https://twitter.com/dr_brompton/status/1613899241801539584?t=_RNIH_nF2DsheZumF65wrQ&s=19

 

[rafiki]

Looks good.
Kinetics in Glasgow have been making 20" Brompton conversions for a few years now but this isn't one of theirs. Their 20" conversion doesn't take tyres that fat.
There's also Eerdermetal in Netherlands who makes conversions with 20" fat tyres.

Ben is making wide tyred 20" models now. Mine is almost complete. It can take tyres up to 2.35", I have specified 2.15" Big Bens, I don't want knobblies.

 

[Origamist]

I've pondered whether or not this would be possible for years.

Combined with the discs, I could see me opting for something like this.

Price dependent of course.

Is this just a frankenbike though? Or a genuine thing?

Just googled dr_Brompton as I genuinely thought it was on the guy's tights.

I know most of the work of the main Brompton modders in Europe and Asia and this is not like anything I've seen before.

I think one of the biggest tells are the tyres. They appear to be Schwalbe G-One All-Round in a 406 flavour and in the 50mm - 55mm range. No such tyre is commercially available at the moment (to the best of my knowledge) and I suspect Brompton have cut a deal with Schwalbe.

 

[berlinonaut]

This is definitively a factory prototype. For a long time no one really believed that a 20" Brompton would be possible. The first of it's kind was the famous Bromptosaurus, made in 2017 by Juliane Neuss as a one off (that later got a brother called Bromptosaurus Rex, so basically became a two-off):

Much later Vincent van Eerd with his very sexy Explorer entered the scence and Ben Cooper also started to offer 20" options, in the beginning limited to slimmer tires. However: The bike in the start post is different from all of them and has a lot of details using the design language of P- and T-line Bromptons.
Interestingly - in opposite to Ben Cooper and Vincent van Eerd, it does seem to have a modified main frame as well. The small curved helper tube seems to be way longer than usual. The Bromptosaurus does have that as well as in oppsite to Cooper and Eerder it is built on a stretched main frame.

 

[404 Not Found Anywhere]

I know most of the work of the main Brompton modders in Europe and Asia and this is not like anything I've seen before.

I think one of the biggest tells are the tyres. They appear to be Schwalbe G-One All-Round in a 406 flavour and in the 50mm - 55mm range. No such tyre is commercially available at the moment (to the best of my knowledge) and I suspect Brompton have cut a deal with Schwalbe.

Pity, I thought they would be good on my Trice recumbent!

 

[404 Not Found Anywhere]

The Bromptosaurus does have a massively high bottom bracket. I think I’d need steps to get on and off! Comparing the two I’m afraid the original looks better proportioned to me, but that may just be familiarity.

 

[berlinonaut]

The Bromptosaurus does have a massively high bottom bracket.

Indeed it does. It needs a bit getting used to and is uncomfortable at traffic lights but else no issue in practice. When "entering" the bike it is really a bit like climbing a horse.
I think other 20" Bromptons do have the same issue when i.e. looking at the Eerder Explorer:

clearly, Ben Cooper's 20" suffers from the same thing:

Brompton would have to overcome this with their 20" in my opinion and they are probably aware of that. Judging from the photo in the start posting hard to tell if they suceeded already.

 

[Origamist]

This is definitively a factory prototype. For a long time no one really believed that a 20" Brompton would be possible. The first of it's kind was the famous Bromptosaurus, made in 2017 by Juliane Neuss as a one off (that later got a brother called Bromptosaurus Rex, so basically became a two-off):

View attachment 674758

View attachment 674759

View attachment 674760

Much later Vincent van Eerd with his very sexy Explorer entered the scence and Ben Cooper also started to offer 20" options, in the beginning limited to slimmer tires. However: The bike in the start post is different from all of them and has a lot of details using the design language of P- and T-line Bromptons.
Interestingly - in opposite to Ben Cooper and Vincent van Eerd, it does seem to have a modified main frame as well. The small curved helper tube seems to be way longer than usual. The Bromptosaurus does have that as well as in oppsite to Cooper and Eerder it is built on a stretched main frame.

Ben C doesn't modify the main frame, but Vincent does when converting the frame to accept 2.6 inch tyres - he reduces the length of the head tube (although you could argue that is not the main frame, but you get my point). It looks like the Brompton prototype has a similarly shorter HT, but also a longer support tube as you say - it will be interesting to know the BB height.

 

[rogerzilla]

A high BB is not good in what is (normally) a town bike. Back in the 60s, Moulton ruined the series 2 by giving it rear forks which are stronger, but raise the saddle by about 3/4". That's the difference between being able to get a foot down at traffic lights, or having to dismount.

 

[Origamist]

A high BB is not good in what is (normally) a town bike. Back in the 60s, Moulton ruined the series 2 by giving it rear forks which are stronger, but raise the saddle by about 3/4". That's the difference between being able to get a foot down at traffic lights, or having to dismount.

Yes, that's true. It does look like the Brompton team have adjusted the frame design/geometry to compensate for the 20" wheels. It's pure conjecture, but I imagine the BB height will be somewhere between a standard 16" Brompton and a Kinetics 20" conversion, for example.

I'm also interested to know how this model will be marketed. Will it be a "Brompton Gravel muncher" where a higher BB would arguably be less of an issue, or more of a town/off-road crossover. I like the way the frame has clearance for Big Apples/50mm Contact Urbans or knobblies.

I also imagine there will be electric and non-electric versions.

What do people think is going on here: internal cable routing, a head tube guide, or just a trick of the light and a cable?!

 

[ianrauk]

What ever it is, it looks way better then a normal Brompton. I'll be in the market for a new folder later this year. Not going to go down the Brompton 16 again, so may have a look at one of these if they are released by then.