Widest tire on STOCK Brompton?
 

What is the widest tire that can fit on a stock Brompton and without having to mod anything?

Greenspeed Scorcher, 40mm wide. It is AFAIK at the same time the widest tire available in ETRO 349 (Brompton Size).

tightest clearance is the rear, drive side chain-stay.. notice they had to dent it for what clearance it has..

Thanks. I took an older generation 3-speed M-style out for a spin yesterday and really liked the smooth feel of the ride, especially the geometry of the front fork, and they fold so small, they're convenient to travel with. I was hoping the newer generation models might fit a fatter tire.

So you should define what a "STOCK" Brompton is in your opinion... The space for tires has only changed very slightly over time but this may offer a more convenient fit for the Scorcher. It will fit even on an MK2 as far as I can judge but there's no guarantee. You might geht into trouble if your Brompton has mudguards - it might be an easier or harder fit and it will be tight anyway. So: does a "STOCK" Brompton have mudguards? :foo: Depends. Again: In Brompton size there is currently no wider tire than the 40mm Scorcher so even if newer models would offer more space it would not make a difference.
Apart from that: Which problem are you trying to solve? If you want a folder with the widest tire possible (just because you like wide tires) than the Brompton is not for you. If you want to solve a different problem it would probably good to name it instead of "wide tires".

By stock I mean not requiring a swap-out of the fork or rear triangle and replacement with an aftermarket frame assembly, to accommodate the tire. Mudgards can be removed.

I'm not up to speed on what's available in all tire sizes. I seem to recall seeing some pretty fat looking tires on Bromptons which had been heavily modded ($$$ on top of $$) so I assumed fatter tires were available.

The specific problem I'm trying to solve is finding a folding bike whose feel my wife likes (she really likes the feel of the Brompton's M-style but she does not care for the Swift or the Birdy BD-1); it has to be a bike which is capable of riding well not only on pavement but also on gritty/sandy/gravelly/grassy paths (no roots and rocks, just light off-roading on surfaces that can be rather soft) and ideally one which also folds fairly small, since it will be sharing the trunk of the car with a Birdy or a Swift. I will probably be selling the one or the other of those to buy this new bike for her.

What bike's ride-feel is closest to the M-style Brompton, and can support a fatter tire?

A Brompton is pretty useless off road and even more in soft sand. This is a consequence of the small tires in combination with the limited tire-width. Each of the two would be a limiting factor on it's own, in combination avoidance is the logical consequence. What's especially bad about sand is that it will infiltrate the chain due to the small distance between chain and ground and wear will go up dramatically.
So what you can do with a Brompton w/o any issues is to ride unpaved roads as long as they are not too soft or too uneven. The softer the ground and the more uneven the surface the more useless it becomes. This goes for sand, for deep gravel, for mud and also for nature trails.

For the terrain in question (as I understand it) I'd not go below 20"/Etro 406. Maybe with he Birdy with it's 18" suspended tires as an exception, at east to a degree. But this heavily depends on how offroadish your trails really are. Even a 20" bike will be not so much fun on an uneven path full of roots, mud, deep gravel and sand.

Nope , as mentioned Green speed is about it.. The company is also the wholesale distributing importer for Australia

37 to 40 you only gain , (math) 3mm.. is the search and expense of trying to get green speed tires worth it? only you can decide...


I have 406-47 tires on my bike Friday pocket Llama , its a bit more cumbersome to fold.. ..

Bromptons are not made for deep mud, gravel, roots, large stones etc. My swift with 2" tires is a little better but litle wheel bikes are not mtn bikes or much good in loose gravel. People ride them in all kinds of sketchy environments, though , and sometimes paved streets with cracks and potholes are plenty sketchy. In my opinion, what contributes to the plush Brompton ride is the long wheel base.

In January this year I rode my 6 speed Brompton for 32 miles on the Hauraki Rail Train in New Zealand. This is mostly a gravel track. It was hard going in places, but definately doable. Plenty of photos of this famous trail on the internet. I was using the stock Schwalbe Marathon tyres. I have since fitted Greenspeed Scorcher tires front and back. My bike does not have mudguards any more due to my fondness of light off road riding. The ride comfort and handling I find is much improved with the fatter tires.

Schwalbe Marathons are usually pumped up high. Dropping the pressure can help on unpaved surfaces. Brompton wheels are 349 but there is also a 16 inch 305 rim. Those wheels will fit with larger tires and wind up about the same diameter as the 349s with 37 mm tires.

Even the stockers would benefit from a quick release on the brakes, as they require deflation or pad/cable removal to remove the wheel.
Are there aftermarket brake QR's available for the stock calipers?
Adds tools and time to flat repair not to have them.

You should mention that apart from the need to respoke the wheels with smaller rims you also run into issues with the brakes - the arm length with the stock brakes is not long enough. There are solutions to that via adaptors or other brakes but that is extra work and investment. Also I would not be sure if 305 Big Apples fit an unmodified frame. The Bromptons with 305-Big Apple that i know of had at least a modified rear frame, but the modification was due to the hubs, so maybe it would fit with a stock frame and maybe not.

Jonesey359 any photos of your trip ? Thanks

In that case, the Brompton is the wrong bike. Although they fold bigger, so that could be an issue with the trunk, you should look at other folders like Dahon, Tern, etc. They're usually cheaper too. One with a Nexus 3/7/8 instead of a derailleur would make it even easier to use.

If the rides are not long too long and on mostly flat areas, what about the Dahon Curve with 305 16" wheels, 2" tires, and a smaller fold than those with 20" wheels?
https://cimg2.ibsrv.net/gimg/bikefor...aa75a77794.jpg

https://dahon.com/bikes/curve-i3-2/

I have been riding backroads of Africa on Brompton with stock tires and it has been fine. To add perspective, you might sure find better bikes and tires for the sandy backroads, but nobody in Africa will ever have resources to optimize their tires and just ride on whatever their bike came with, usually a low level bike made in Asia - India or China. People do fine, even when things are not quite optimal. First thing is to have a bike where you need it. Otherwise don't check your pulse too much :D.