We Made A Crazy Gravel Brompton... How Scary Is It?!

The humble Brompton bicycle. The most iconic folding bike, suited for short and easy commutes. So what would happen if you created an off-road, monster Brompton? Si and Alex take their Brompton bike build to gravel tracks and mountain bike trails to see how well it shreds!
00:00 Intro
02:48 Ride start
05:30 Top speed test
08:39 Road review
09:37 Mountain biking
13:20 Summary
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📸 Photos - © Velo Collection (TDW) / Getty Images & © Sprint Cycling Agency
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[@gcn]

Would you convert your Brompton? 🚲

[@philipcooper8297]

Sure, into a TT bike.

[@dhtmbowen]

Definitely. I love this. I have to replace the gears on my Brompton anyway. I’m thinking a gravel / road bike build and take it up Sa Calobra at Easter.

[@reecedawson6113]

I'd love to see a GCN Brompton TT or 100 km ride

[@Richarddraper]

No, but I would love to have a go on that bike.

[@dimrub]

Absolutely not. I use my Brompton for commuting, and it's brilliant for that. I wouldn't want to make it worse for its main purpose in order to create a below average gravel bike - I have a separate great gravel bike for that, that didn't cost much more than that conversion kit.

[@andrewmcalister3462]

Alex and Si looked like they had an absolute hoot on the MTBrompton. Can't wait till Blake gets his hands on it. 😂

[@gcn]

What should Blake do with the MTBrompton?🫣

[@MacMasore]

@@gcneverything!

[@paulsslightlyactivelife]

​@@gcnWell he's tackled the Mega on everything else... 😂

[@two-eyedRoy]

@@gcn Honestly, Leave him to his own devices. He can't help himself, he will try to find the limits of it, or him.

[@PereAndreuUbachdeFuentes]

Give it to Blake so that he performs his jumpy thing with it. And then give it to Sam Pilgrim, to give it a proper test 😂

[@Nebulacore98]

Finally another Brompton video! GCN needs to see the mods done to Bromptons in Singapore... ...carbon wheelset with bladed sapim spokes, external gearing, TPU Tubes, Schwalbe Pro One Tyres, Titanium parts, etc. Definitely pit the T-Line against a road bike of the same price too!

[@Gravel-Cult]

Let's see Blake free ride it. Legend bike and rider!

[@gcn]

Maybe we will let him have a little go...

[@TheBirchCreek]

​@@gcnI wanted to write just this! Pretty please...

[@Seppster58]

I was thinking the exact same thing while watching this. Then Si mentions it at the end...Bring on the Blake!!!!

[@nukedathlonman]

I'd like to see him attempt to get some big air on it...

[@doernerrr]

Maybe a TT Brompton conversion would be something to try. Such a bike would simplify travel to distant triathlons.

[@ajthmmht]

Good idea

[@PRH123]

I'd like to see a tandem Brompton :)

[@simscape7869]

What is "TT" please ?

[@bimblingalong]

I'm always pleased when GCN does science and Si has his safety specs on

[@PaulHolder]

I took my regular Brompton off road once thanks to some overly optimistic route planning. Nothing quite as wild as you ended up on but it managed much better than my friends Touring Bikes did and I felt confident in the bike the whole time. I also utilised the 'dropper post' on the down hills. The 11-speed option would be great though.

[@gcn]

You're braver than us! Would you convert your Brompton in any way?

[@patricecantin2797]

The look on the lady when they did the rock/paper/scissors was great… “what are these guys doing?”😂

[@Jayneflakes]

That looked like so much fun, it is too easy to get wrapped up in all of the serious stuff about sport and forget that we do this for fun. Well done GCN on carving those corners like pros, also I loved the video. 🤣 Now go and give it to Blake, he may be adorable, but he rides like a lunatic.

[@gcn]

We love cycling! This means cycling of any kind... folding off road mountain bikes included 😂 - Would you ride this MTB-Brompton ?

[@doggylover1958]

Hey great video guys, a lot of fun! For my part, I got fed up of having my work bikes stolen (lost 2 in the space of 2 weeks) so I bought a fold up bike and took it into the office and stashed it under my desk. Then I thought if I put better tyres on it I could ride home down the canal tow paths. Viola! I put 20 inch bmx tyres on and it became a demon bike, jumping over obstacles no problem, I sought out dirt tracks and trails to ride home on. It got me blooming fit as I didn’t want to stop riding it, and looked forward to the commute. I’ve retired now but still love my folder, it’s definitely a versatile throw in the boot of the car fun bike. It comes away to the seaside with us now so I can get my cycling fix. Love my road bike and my mountain bikes too (don’t want them to feel left out!) Cheers, keep up the great work!

[@LittlePixelTM]

These are super fun conversions. Ben at Kinetics is a great bloke. Thoughts having built my own custom Brompton: - 1) You can get more 'gravel bike-y' tyres in 20"/ISO 406 size that are probably better all rounders (ie Schwalbe Billy Bonkers) that would be great for commutes that involve canal tow paths and light gravel - but less rolling resistant on tarmac than full knoblies 2) you could put something like a Crud catcher mudguard on the back by attaching it to the seatpost. Would look dorky, but would work :) 3) some Ergon grips and an adjustable stem would make for a better cockpit for grunting up hills 3) There's so much room with the bigger forks and triangle, that one could make a really nice 'fast' road Brompton with this kit using the larger 20" size (ISO 451) with skinny road tyres - yes the fold would not be as good, but make for more long-legged bike that's less crashy in the potholes. Could be a good Triathlon bike for same reasons.

[@kevincross9206]

Brompton’s will definitely take more than they’re designed to (maybe not long term!). Such great bikes, and the initial twitchiness you soon get used to. The standard wheels / tyres can catch you out, not so much pot holes, but I managed to ride out of my drive one morning and got the angle wrong crossing a drain cover. Result - front wheel drops into the groove, stops dead and I’m pitched over the bars into the road 🤦🏼‍♂️

[@cruachan1191]

Can we get Betsy the BMXer from Manon's recent vid to do the speed run on this? She'd get some insane top speeds with the power she can put down!

[@oliviant2235]

Great idea!

[@donnajago]

😂love that Si got further on the Brompton then Alex when going up the hill 😂

[@trisrossin7614]

90% of my Brompton rides are on gravel and bridal paths. To be honest, aside from being a tad more careful, it already handles this type of terrain surprisingly well. I wouldn't go full off-road like in this video but they're tough little machines already!

[@casakaiser]

Totally agree. My Brompton as well is reasonable happy on mellow gravel. And on the tarmac and as city bike.

[@stephenturkLA]

Bridal paths? Those must be a lot more fun than bridle paths!

[@joelhenderson3723]

I'm looking into a folding bike (tern, not brompton), and this is actually something I was worried about. Do you feel like they will hold up long-term to small bunny hops (as over potholes or up a curb) and riding on gravel roads? I have no plans to treat it as a mountain bike, but I do want a bike that I can go on minor adventures with. The folding aspect would be extremely welcome since I'm getting ready to move into an apartment, but I am a little worried that it might be limiting for longer rides or rougher roads.

[@timevans9195]

I think you may be doing the stock Brompton a bit of a dis-service. Yeah they’re used on smooth tarmac in towns and cities, but they’re also used by a lot of people for some pretty rough stuff. All you need to do is put a 39t chainring on the standard 6 speed and you’ve got yourself a bike that will get up most hills, even with a load! I regularly take mine into the Welsh hills on rough lanes and also on canal paths and gravel tracks and it works just fine. Still, it’s interesting to see what can be done but at the end of the day with all the changes, it’s not really a Brompton anymore !…why not just test a Bike Friday all-packa which is a ground up, properly designed 20” off road folding bike?

[@wjp555]

I love all the filming around Bath and god that is a magnificent bike.

[@ihatenegi]

I'd never do this conversion myself but I'm so glad GCN did. So much fun! You guys were genuinely laughing like kids! Great fun video!

[@noamross]

You should do a video on the Bike Friday All-Packa: a 20-inch folder, with geometry designed for gravel and light MTB bikepacking.

[@DvhhCfsghh]

They won't because Time Warner [Brothers] is the parent company and they want money for advertising

[@JeremyLawrence-imajez]

Yup, the All-PAcka seems to be an amazing bike. I want one and I no interest in folding bikes. Bike Friday bikes in general seem very highly regarded.

[@chagas99z]

Being underbiked is a lot of fun. I ride my brom off road fairly often. Also a fixed wheel 1976 Raleigh 20 makes a great towpath / BOAT blaster. And Ben at kinetics is a wizard - it’s a huge design exercise to get the rear triangle of a 20 inch brom right.

[@callumk5]

I’m always in awe at what a bike designed to be taken on the underground can do.

[@alexredhair]

Great video. We in fact did something similar with a Buxton Pro E folding bike. Put on gnarly 20inch tyres, altered handlebar/grips and its managed perfectly well on the hardest MTB trails. Lake district gravel epic, King Alfreds way etc. it does make other riders stop and stare mind you .

[@chrisbaum998]

That was a fun video Alex and Si!!!

[@jeremypewterschmidt664]

really a good tire the smart sam. I wonder why there are not many videos to introduce it.

[@hackfabrication139]

Si and Anton off on another bonkers adventure. Brilliant!

[@alexgraves6842]

Brilliant! in my opinion. If I had a Brompton, that would be exactly what I modify mine into.

[@manemisdonmalasnemissalata6324]

this was fun to watch, it was like that unplanned event you and your friend just wanna do in an impulse

[@lesstroddenpath3726]

Brilliant fun watching you two doing that!!😂

[@TimR123]

That seems like the most genuine fun y’all have had on one of these challenges in ages. 😂

[@bikeskimawk670]

Glad to see you give Hank some time off from crazy challenges.

[@fwod1867]

Alex and Si, absolute insane, riding that downhill path 😅

[@gcn]

Not sure who was more scared😂

[@bentara0]

Epic! That was a blast.

[@zukzworld]

MTB Brompton! What an idea! 💡 🙌🏾❤️✌🏾

[@eliknowsbest4946]

You made my dream build 🤩 👏🏾👏🏾

[@idrissamorehouse322]

Freekin awesome !! Really excited to see more kinetic kits in action !!

[@geoffreyhoney122]

What a HILARIOUS video! I was peeing myself laughing! Love this content gcn! Especially funny, in addition to the downhill bits was Si and Alex fighting not to ride the 'FrankenGrompton'! It goes to show that you can ride just about anything anywhere. Don't believe me? Answer how mountain biking got started? Richie, Fisher et al riding 'clunkers ' down mountains. Paperboy cruisers, single speed, coaster brakes down California mountains! More extreme bike challenges please gcn! Totally wrong bike for the job and make it work. (Si & Ollie do it every day commuting on Pinarellos!) LOL

[@patricklui6834]

You made my dream come true! I always wanted to know if a brompton will be capable to go off road! Amazing video! Thumbs up!!

[@robbchastain3036]

Considering how much more susceptible to pothole endos a rider on 16" wheels can be, I think beefy 20s are brilliant and better and I totally applaud and understand this Brompton mod. Thanks for showing us, Si and Pierre. And history lesson, until '75 or so and the introduction of production BMX bikes, a generation of kids in the States rode 20" Schwinn Sting-Rays everywhere, streets and dirt and downhill and just everywhere and we finessed and figured it out and made the most of it. Lots of adventures, too, everything was an adventure, really, so much fun to ride for hours and see what was down the road or trail.

[@ryankarr7109]

It might be dangerous but the smiles per miles...off the charts!

[@gcn]

And that is the main reason we cycle!

[@xosece]

10:27 those leaves are soap, it's like tree roots, pure soap. I can see the cold on your faces. It's raining here (Galicia) and it's relatively cold but not much, although you both look just as my sister described when she was in London the other day, it was humid but it was a extremely cold humidity there, you can see droplets hanging from Alex nose just like in the japanese mangas xD . Si was having lots of fun I can tell, the beauty of mountain biking, going almost anywhere and those autumn landscapes, it's beautiful although "soapy"

[@markbooth6745]

Looked great fun guys.😃👍

[@thilo1berg]

Very cool build!

[@TheAegisClaw]

Ben at Kinetics in Glasgow is a genius... And a mad man, in the best possible way. Top bloke.

[@two-eyedRoy]

Twitchy you sayyy... ? Needs wider bars or more stem? So after GMBN: Dr. Olivier Breegewoo' to TT the heck out of it. Wireless Di2. Some cardboard sheets to cover the spokes, bigger chain ring, h̶o̶m̶e̶m̶a̶d̶e̶ "artisanal" teardop fairings for the steerer and seat post. Maybe get some tunnel time in? ...some sneaksy Tom Sturdy 3d prints :D

[@toojeys]

I have sold my gravel bike and maintained only the brompton. Made some few simple modification to ride as good as the gravel bike, so far so good! Everyone who cycles should have a brompton!

[@independentmind1977]

I'M SO GLAD YOU DID THIS, just so I didn't have to! I had the fleeting thought, but then came to my senses.

[@lukewalker1051]

Great fun. Love the humor. Glad you guys didn't break your neck on the Mtb-Brompton. That thing is made for smooooooth road. Big tires FTW.

[@niklasa.5622]

Beautiful glasses from Si, in my chemistry lessons we had similar "small" ones on ;-)

[@ehuremovic526]

The lady in the hat at 2:39 made me chuckle. She seemed really invested in who won rock paper scissors

[@ayclarke1880]

Love it!

[@deanpurcell7771]

That looked like a hell of a lot of fun! I love it when you guys do crazy shit🤣🤣

[@mitchpaliga4851]

2:36 "Ooh am I on the telly!?"

[@hangkook]

Nice set up! It will be interesting to see GCN does a head on challenge of a Brompton P or T Line Explore 12 speed against a road bike. The first of its kind challenge.

[@slowwerthensnot]

I adore my Bike Friday All Packa!

[@slowwerthensnot]

Long live 406 wheels!

[@goldenmath4091]

I am actually building my own version of this style of bike.. From scratch a BMX/MTB/folder so this was great to watch, you need a dropper Si And . yes..give it to Blake!

[@Likelybiking]

Don’t let anyone bring down your spirits Si, those glasses are awesome!

[@asambatyon]

You should have tried the Vello Gravel, which is a foldable bike which comes from the factory in a gravel version

[@Avatar1983]

This ....! Absolut Love my Vello Gravel from The First Sec. ❤

[@Dan_Kornfeld]

Throw on some 800mm bars and a 200mm dropper post and I'm. ready for the trails 😜👍‼️

[@gcn]

You'd be flying down the trails!😂

[@jonathanbenn2241]

Modern internal gear hubs are great-in some applications.

[@paulgordon7526]

Wicked !! rather you than me down the off road MTB bit 🙂

[@derkapellmeister]

THAT woman during the rock-paper-scissors! Smooth cameo! LOL!

[@nevillepretorius8948]

Very cool video! 😂

[@rudolphpyatt4833]

Fascinating. As a devotee of geared hubs, I'm curious about your thoughts on the Shimano Alfine as well as the standard hub on the Brompton.

[@obirad4071]

Sweet... Changed my Muli Muskel Bio-Cargobike, to Gravel😂: 1. Changed Tyres to Schwalbe Big Ben 2. Handlebar and stem from BMC Fourstroke. So S0 Trails, no Problem

[@chrisfurby8241]

Alex trying to get to that hill 🤣🤣🤣 Good stuff 👍

[@gcn]

It took him a bit of effort😂

[@jasondoust4935]

You mad buggers! Keep it up... Biking should be fun; and this is.

[@madmick9205]

Bloody good fun I think:)

[@designfcs]

gravel full suspension folding bike 20 inch, MT-Brompton..., love it...

[@jascollinscork]

Only seeing this now….. video would better described as Alex made a Brompton off roader 🤔🤣 great video Mr Si Windshield 👓 😂

[@robstevens2152]

I want one!!! 🤩

[@bcschafer]

Watching Si going down that mountain bike trail was mildly terrifying.

[@anthonylloyd6094]

Before I heard of Kinetics and Eerdermetal, I had a similar train of thought. I called it The Brompton Dirt Dog.

[@maximiliano8540]

Bartholomew did great job (re)building the Brompton, liked the tech vid too :)

[@r0bv123]

Lol such a hilarious fun video. But would love to see the GMBN boys really put the MTB-rompton to the test!! Please share that monster with them and do a ride together to share the action!!

[@BernardManansala]

Since the launch of this channel, I think this is the first ever video on a Brompton the most Brit Bike out there.

[@muratmustafa4532]

I am tall and I do ride my Brompton with lycra :) My top speed is 42 km/h on flat 69 km/h on a decent. And I do like a spider on it :) :) :)

[@charles0414]

The price you modify this Brompton can just buy a Birdy, which can be used as a MT folding bike. But the biggest problem is there is a hinge spindle on your Brompton main frame, if you ride your Brompton like this, pretty soon that hinge needs to be replaced. Worse than that, the hole will be getting bigger. Eventually you will need a new main frame. PS: I do like Brompton with disc brakes. I have 4 Kinetics Brompton with disc brakes. After watching this video, I think I might take one of them to replace the wheels from 349 to 355 so that way I can use Schwalbe Black Jack tires and see how it works.

[@91dave]

Should have been a halloween video 🤣😱 Great video as always, team.

[@leeellis3382]

And i got those exact parts fitted to an Airnimal Rhino by Ben at Kinetics… small foldable but suspension front and back it’s ace !!

[@lennymccartney1]

40k along the narrow kennet & avon canal path? you guys are nuts!

[@talos935]

I'm amused to know Blake saw it out and about. I'm actually surprised you didn't get Hank to ride it. I thought he or Ollie are your go to guys for any off road shenanigans 😁

[@andrewmcalister3462]

Have we ever seen Ollie leave the tarmac? (No disrespect to Ollie - his Tour de Stations ride this year was beyond epic).

[@LesterBenjaminLin]

Would love to see you guys try a 20" tern or dahon!

[@andrewchalke1078]

Great Video. I’ve got a couple of Bromptons, and have been looking at kits to convert to the Afline or Rohloff rear hub. Think I’ll keep the smaller wheels tho. 👍🏻

[@gcn]

Not going to take them down any trails any time soon?

[@wurzlitzer]

Fun video so much fun, but I finished the vid wondering where did Si get the barn door clear glasses ideal for riding in winter

[@richardluvsford7849]

Hey. Try a viscoset headset bearings from cane creek(if the size is available) it is an integrated steering dampener. May tame the twitchiness. I mentioned these a few years ago for gmbn when they tried narrower and narrower bars.

[@daveblakney6787]

39t crankset, a set of vee rubber goodie goodie tires- my brompton sees lots of dirt roads and single track just getting around

[@neilmdon]

I loved that time Emma went and won the Brompton championships whilst filming a GCN video.

[@JasonInMelbourne]

Blake sending it on a Brompton: now THAT would be a sight! 🤣

[@Stormi1991]

Playstation Access Podcast Music at 2:49 - coincidence? :D Great Video, I own 3 bromptons, C-Line- E-Pline and T-Line. Love them all. But allways questioned myself if it is possible to do MTB-Trails with a brompoton ^^

[@gcn]

Will you be giving your own MTBrompton a go?

[@on2play736]

ummm...I want one now. Damn, that looks cool!

[@maheshv1395]

I have an MT brompton (from kinetics) and for cities it is fun for sure.

[@fentuz]

Si should ride it in the next western league CX race!

[@bradleyjones5932]

Knobby bits on Bmx sized tyres will always be better than any sort of slick tyre.

[@grahamlongley8298]

I went for a 5 mile ride with my mates around a very large lake. I had my Brompton E bike & I did not know that about a mile of the ride was off road. Similar to that enduro road in the video. I fell off about 5 times. Once I hit a tree root & went over the top of the handlebars. Bar stewards thought it was funny. I certainly did not. Bromptons are not off roaders, but they are strong, because amazingly no damage was done.

[@steelcup]

This is a good test to see what it must be like for our kids when we send them on the trails on their 20" bikes

[@capio78]

I've never seen on a Brompton, but I've always been surprised how quick over riders on them seem.

[@kain12343]

Video idea: GMBN presenter on MTBrompton vs GCN presenter on 29" MTB. Downhill, flat and climbing segments.

[@gcn]

Who do you think would win?

[@gcn]

Who do you think would win? And which presenters would you choose?

[@junaid42465]

The "TRP Spyre" seems to have performed pretty well. Dual piston mech disk vs hydraulic disc need a comparison now.

[@brannmacfinnchad9056]

An unbiased one.

[@cchangg]

I'm curious to see GCN compare a few more folding bikes on gravel/ENDURO trails. Montague Paratrooper, maybe?

[@barnabywoods5403]

I would like to see a TT Brompton