There are lot’s of Brompton clones and Brompton modifications. People like how it folds but want more, like disk brakes, generic cassette/derailleur/hubs, thicker tires, bigger rims, different forks, different OLD rear triangle etc etc. I wander why asian producers do not offer a Brompton like frame sets like Fhnon?Offer a frame and separately few versions of fork/rear triangle/handlebars. Let people buy the rest and assemble the bike they want.

Have you checked Aliexpress? There are many frames, forks, parts for folding bikes and minivelos made of steel, aluminum or carbon.

Ti parts yes, but I didn’t see listing with main frame made of metal. Also not sure about handlebar stem made of metal.

All parts of the Brompton frame are available in titanium including the stem on ebay or aliexpress.

And there are several types of rear frame, with the original OLD or 135mm OLD, with or without disc brakes calipers mounting points.

Of course, you never know in advance the quality of the parts you will actually receive and the price of a complete frame when you add the prices of all parts isn't really cheap.

CEBEP, is this what you are looking for? The knockoff steel frame components for a Brompton? Check out the SungDa Outdoor Shop on Aliexpress.

SunDa

Thanks, for some reason these didn’t popup in my Aliexpress app.

There are two mods I’d want to have on my Brompton: disc brakes and big apple tires. The rest is not critical, like RD with cassette or 20’ wheels. But even to do what I’d like to upgrade I’ll need to buy new fork and rear triangle. And I don’t want to modify the Brompton I already have, so it seems like a good idea to go for new frame, triangle, fork. I may look into it some day. I agree it’s hard to say about quality, but Aceoffix is the brand I heard of and is widely available in Aliexpress. The only other option that I know of would be Kinetics but it would be the whole other price points and they don’t sell main frame afaik.

The problem is that to go to wider 50mm tires like the Big Apple, either you must accept smaller diameter wheels (ETRTO305 with 50x305 tires, even with these wider tires the overall wheel diameter is smaller than the original 35x349 diameter) or must accept to have a bigger folded size with 50x355 tires.

I’ve seen modified Bromptons with 20’ wheels, folding size is not all that bigger, so it’s fine.

If you talk about the Kinetics 20" mod, it makes the folded Brompton higher and longer.

It remains one of he smallest 20" folding bike but its bigger than original, as big as a Birdy 3. This because the folded rear wheel comes against the frame tubes and bottom bracket box. If the wheel diameter is increased by let say 50mm, then the rear triangle length must be increased by about 25mm and the folded length and height are increased by about 50mm too.

So a part of the Brompton advantage is lost.

After my Birdy I really miss disk brakes and a bit more cushy ride on Brompton

Yes, I understand that even if in practice, good caliper brakes like the Ridea for Brompton provide sufficient braking.

The drawback of disc brakes is that they will always increase the weight, to have the real power of disc brakes, hydraulic disc brakes are needed (I have TRP disc on my Ti Birdy, they are lightweight but cannot compete against the cheap Shimano Deore of my Birdy 3) and even higher end, very expensive hydraulic disc brakes, weight more than lightweight rim brakes like the Ridea (and its possible to mount eebrakes that weight less and provide top notch braking).

Something like...

https://eu.dahon.com/bikes/curl-i4-3/

Brompton converted to 305x50s:

You can try going bigger than 50mm wide tires on 305 rims. You can try, for example, 57-305 which is only marginally shorter than 37-349, but substantially cushier.