I am working on my Brompton and therefor looking around the net for different convertions posted by others. Found this; https://www.atob.org.uk/folding-bikes/off-road-brompton/

I remember hearing about this some time back and have been thinking about it quite a lot.

Reason is that last summer I rode with another person on a muddy dirtroad. One Dahon curve, one Brompton. We swapped bikes just to compare, and I remember thinking the Dahon on its BA`s did much better than the Brompton, both for comfort and not digging as much into the mud.

After offroading on Bromptons last weekend plus riding quite a lot on the cobblestones of Copenhagen (resulting in my seatpost sliding down several times) I am once again thinking about it- just thinking, not doing.

May just do some measuring, trying to fit the curves front wheel and so on..

hmmm..

I like A to B and David Henshaw's sparkling little MTB conversion.

I place this kind of conversion in the same category as modifying the rear triangle to accept an IGH other than the 111mm OLD standard - you'd better really want it, as I'm not sure there's a way to turn back.

I'm a little dicey on the long reach brakes - my experience is that Cheng Star, Big Dog, etc. are not that great even compared to the brommie standard brakes.

Tektro was a name that kept coming up when I was researching this for the Bickerton. There are a few options. A place for ideas and possible makes: https://sheldonbrown.com/harris/brake...ers.html#70-88

I love 305 rims with Big Apples, super-snappy yet bouncy. When I first got my Brompton I was looking at the logistics of fitting them. . . I figured fork clearance would be too tight.
IMO a bike that folds as the Brompton does ought to be designed around wider tyres.

Best off road mod for brompton is called purchasing a birdie!
I have heard of people using suspension forks.
I. Have a suspension seatpost on my mezzo.
Front pantour hub results in full suspension brommie, done by evilv and stomatash.

And me.
It offers a small amount of cushioning; it's nice.

Or a Bike Friday Pocket Llama..

BTW , the Brompton rear stays are Parallel for quite a ways the width between them is limited,
and so Side to side clearance will still be limited to the 37 width tire, though the radial clearance under the Mudguard will increase.

& you lose ground clearance making hitting a Pedal More likely..