349-40 tires with Brompton

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Cynical idealist
Measure the gaps you currently with current tyres and what space is left should be self explanatory. I'd definitely have have the Fenders in hard case though and securely tied on the rear rack though.


Über Member
Berlin Germany
Can one run 349-40 tires on a Brompton with fenders?

Depends. With elderly Bromptons it can be a fit or not (undpredictable) with younger (MK4 since 2004) Bromptons chances are way better but still not a given. There's still a variability - not all will work out of the box, many will. W/o fenders it is usually no issue. I do run Scorchers on the front of a 2008 steel Brompton with fenders w/o the slightest issue (did not try on the rear on this bike). On another (2011) Brompton I have Scrochers front and rear, but w/o fenders, so not much help. User reports range from success over success with a bit of tinkering to "did not work".
Also, as over the years there have been various versions of the Scorcher (currently Greenspeed seem to offer a 120 TPI version along with a 60 TPI verison) - maybe they are not all totally identical in real world size despite all being 40/349. Relatively rectently there appeared a new kid on the block in 40/349: It is called "Mr Recumbents True Blue" and, as the Scorcher it comes from Australia. Not sure if it is the same tire under a different name or a different tire. Mr Recumbents sell various versions of it along with the Scorcher: https://mrrecumbenttrikes.com/parts/tyres/


Legendary Member
I used to run a Kevlar Scorcher at the front with a mudguard, but at the rear there were clearance issues, even after bending the stays (this was on 2014 bike with steel forks and rear triangle) and I did not persist with the rear Scorcher. However, I really liked the feeling of a wider front tyre and persisted with this set-up.

@berlinonaut is the clearance on the P-line with the new mudguards better do you know?


Über Member
There is an argument for using a slightly wider (than standard) tyre on the front, and standard on the rear. More tread, possibly better grip, better feel, perhaps. We're so used to bikes having a symmetry in sizes front and rear, for road use at least, that it seems strange at first acquaintance. Off road bikes regularly use wider on the front. My definitely non standard Linear recumbent has a wider tyre than standard on the front than the rear, and it works. Of course we're not all downhill racers but the principle still applies. A by product of doing this, at least with a Brompton, is that you are still more likely to be able to use mudguards.
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