• nick

The future of Gravel Bikes?

Updated: Feb 23

In 2019, just before I embarked on my NCN route #2 adventure, I built an "Adventure bike". The name was really just to inspire me to get out and explore more of the UK, but the bike itself had to be a "do-it-all" machine allowing me to enjoy the best of our beautiful scenery in what I feel cycling in the UK is all about. And it's built around a Hybrid bike.

The Mk 1 Adventure bike


Why a Hybrid? Well, in my experience, riding in the UK means crossing every type of terrain and encountering all four seasons, including an obligatory dose of mud, all in the space of a few hours. Much of our "off-road" is access via journeys "on-road" so for me the beauty is combining both terrains into day (or longer) adventures. And if you look past the "Hybrid" title, then you start to uncover some interesting aspects that, in my opinion, make them the perfect platform for a do-it-all, go anywhere, all terrain bike for the UK.


I also think this is where the current UK Gravel bike trend is heading and I think they'll eventually become the best all terrain bikes for UK riding, although they still have a degree of evolution to go.


Some of the hidden gems overlooked on Hybrid bikes:

  • Built around a 50mm to 65mm suspension fork and a 700c (29'er) wheel size

  • Can run 700c or 27.5" (650b) wheels

  • Clearance for a circa 50mm tyre

  • Long wheel base which is good for trail stability

  • Long and sloping top tube which increases stand-over height, cockpit manoeuvrability and great for avoiding toe strike.

  • Classic 73° seat angle and 69°-70° head angle - a sweet spot for riding both on and off-road

  • Circa 450mm seat stays - great for stability but still short enough for efficient climbing


I've recently re-built my original flat bar Adventure bike, and in order to fund the build I sold my road bike. Although I was sad to see my old Planet X Pro Carbon go, riding on 25mm wide tyres, with no suspension and rim brakes (and being an MTB'er at heart) just wasn't doing it for me anymore. However, as my plan was to build the Mk2 Adventure bike with drop bars, I'd still have a bike with my preferred hand position for long days on the road.


Ergo the new Adventure bike would take the place of both the old road bike and the original flat bar Adventure bike.


And this is it...


Like it's predecessor, it's based around a Specialized CrossTrail Hybrid frame. Real world aspects like 'budget' and 'parts availability' featured heavily in the build. Other than the frame, all the components have come from the Mk1 Adventure bike, been purchased new or found by rummaging around the parts bin.


Spec:

  • Frame: 2018 Specialized CrossTrail Elite Carbon

  • Fork: Rockshox Paragon Gold RL with (Oneloc) lock-out activated from the left GRX brake / shift lever, incorporating a 2:1 ratio cable pulley hack.

  • Wheels: DT Swiss RR521 rims on Shimano XT 11sp hubs

  • Groupset (Shimano): XT 11 sp rear derailleur, XT 11-46t cassette, GRX810 40T crankset, GRX600 levers, Ultegra 68mm BB. And the magic part - a Wolf Tooth Tanpan which handles the GRX to XT shifting ratio conversion.

  • Brakes: GRX600 levers, GRX 400 160mm rear and Deore 5100 180mm front

  • Bars: PNW Coast 52cm

  • Stem: Specialzed 45mm (was a Felt 90mm)

  • Seat post: PNW Coast suspension dropper with bar mounted lever

  • Seat: Ergon SR Comp

  • Pedals: Shimano XT T8000 trekking

  • Tyres: Schwalbe Landcruiser 700 x 45 (running tubes at present)



How does it ride:

Smooth and fast like a 29'er on steroids! The tyre width just soaks up the awful UK road bumps and cracks and the suspension seat post and fork do a fantastic job of smoothing out the off-road trail lumps. It's not quite an XC MTB but it's not far short. The frame is just how I like it, fast accelerating and it loves to climb.


Cable pull ratio's between brands make mullet hacks really tricky but I'm impressed with the Wolf Tooth Tanpan which effortlessly converts the GRX road shift ratio to XT MTB shift ratios.


And the left hand shifter actuating the lock out on my fork via a 2:1 ratio pulley wheel is perfect for flitting between road and trail.



The 1 x 11sp 40T x 11-46t range gives me around 25 to 103 gear inches, which although not quite the spread I would like, is good enough for now. I've been running 1x set-up's since 2004, primarily due to the amount of mud a front derailleur attracts in the UK. My my previous 2 x 11 set-up on the mk1 Adventure bike was perhaps a bit optimistic so it's back to a 1x this time around.



Wide bars give me more control and Pacific North West's (PNW) Coast bar at 52cm does exactly that. I've gone from a 42cm road drop bar to this new wider size and honestly it feels so much more natural, particularly as I'm used to 660mm+ flat bars.


The dropper post was a must. The hybrid geometry does a superb job of shifting the riders weight backwards into a less aggressive / less front heavy position, but the dropper just adds that extra weight shift capability when the terrain starts getting steep. Plus it has built in suspension, something I've been running on all my hard tails (road bike included) since the early 2000's.


What I also love about this frame is it still has a decent amount of lugs and fitment points, allowing me to attach my bespoke rear rack and multi position water bottles to head off for a bikepacking adventure whenever I feel the urge.


And its flexibility doesn't stop there - all I need to do is swap the suspension fork for a rigid carbon version and stick a set of 28mm or 32mm slick tyres on and I've got my road bike back again, albeit better suited to riding on UK roads.


What’s more, I still have a set of flat bars, shifters and levers that would allow me to swap the drop bars out for a flat bar set-up if I felt the journey necessitated.




So is it perfect?

It’s certainly getting there, and that's the fun of pioneering something new and experimenting with bikes not readily made for the mainstream. If I had an unlimited budget then a non mullet hack, 1 x 12 speed, 10-50 ish setup with thru axle hubs and carbon rims would be on the list... which would then necessitate a frame change.... which I’d then spec with more luggage fitment points… and so on…


I’ve recently swapped the 90mm stem for a 45mm version which has tightened the steering up immensely. At 90mm (the only one I had in the parts bin) it felt a little front biased, I think also due to the weight of the fork compared to the frame.



I've also been running a set of Soma Cazadero 700c x 50 tyres this winter which have been amazing. I’m now more convinced that narrower, rather than wider tyres, are better for UK winters as they don’t get so bogged down in all the slop.




So is this the future of the Gravel bike?

I believe the Gravel bike will continue to evolve into the perfect go anywhere, adventure / bikepacking bike for the UK, fitting neatly between a road bike and an XC MTB. They will become the final incarnation of the Hybrid.


They will evolve to be longer and slacker, but more importantly with less aggressive geometry, shifting rider weight up and back. 700c wheels with 45-50mm wide "all-terrain" tyres, 60mm front suspension (with lock-out capability), either flat or wide drop bars, suspension / dropper seat posts, MTB gearing and brakes.


Geometry

Less aggressive and more upright. Longer top tube, shorter stems, longer wheel base, longer chain stays, sloping top tubes etc. Pretty much as the 2018 Specialized CrossTrail!

Details from Specialized concept store - CrossTrail Elite Carbon


Front suspension

In 2016 I toured the Isle of Wight with a bunch of mates, wild camping and mixing the route between off-road trails and road sections. I'd re-built my old Cannondale CAAD3 for the retro trip and it served me well enough. I'd put my old rigid "Pepperoni" forks back on and ran 26" x 1 1/4" Schwalbe Marathon tyres. Although it was primarily an on-road adventure, there were a number of off-road trails. It was perhaps the first time I'd ridden off-road in around 15 years without front suspension... never again. It was too jarring and too slow!

From that point on I made a pact with myself that any bike I owned, that even vaguely ventured off road, would have front suspension.


So, if 100mm travel is still XC MTB territory, I think the sweet spot for Gravel will be around 60mm with lock-out capability.


Wheels

700c / 29'er is the place to be. 650 is only really there, in my opinion, because of the need for more tyre volume to dampen the ride due to a lack of suspension and a 700 x 50mm + doesn't always fit in the frame due to current Gravel bike geometry.


In terms of rim width, I reckon anything around 20 - 23mm inner width depending on the tyre and the type of tyre profile you're comfortable to run. (see below)


Tyres

Dual purpose tyres are never going to be good at the extremes of road and off-road. I run anywhere from 23mm to 2.6" rubber across a number of my bikes and 45 - 50mm feels about the right balance. As the terrain and speeds get more challenging there needs to be a shift towards slightly heavier MTB style rubber with better all-round damage protection. Unfortunately this will forego some of the 'supple' feel, but when you're running suspension it's not so noticeable.


I think tyre treads for a UK "all terrain" application need to become more 'all-round' with a raised solid central section for tarmac, intermediate knobbles and larger outer lugs for bite when the terrain gets loose or muddy. The rubber compound needs to match the various knobble profiles. Firmer to the middle, softer towards the outer. Some good examples are the Soma Cazadero and Schwalbe's, old school Landcruiser and perhaps the Teravail Washburn.


In terms of tyre pressure - 40psi feels about the right balance between road and trail. I currently still run tubes (with added sealant) in my road / gravel biased bikes and am probably not likely to change for the time being.


Gearing

Forget the current road gearing, which in my opinion is completely over geared for anyone less than a professional UCI cyclist anyway. Real world ratios with an added dose of off-road hill climbing squeezed in. Ideally 20 to 110 gear inches with as smaller gaps / jumps as possible. 2x set-ups work really well with the lower range for off-road and the higher range for on-road. I prefer 1x set-ups and with the right range they also suit a gravel bike. Perhaps something like 12sp 1 x 40T x 10-50 ish?


Brakes

A firm shift towards XC MTB brakes with 180mm front and 160mm rear rotors and perhaps twin pot brakes on the front. The hand-on-the-hood position isn't great for braking but bigger discs or more powerful brakes will compensate for this.


Bars

Options for either drop bars or flat bars depending on your adventure or riding style.

  • Drops: 50cm+ wide with 40mm - 50mm long stems

  • Flats: mid-range flat bars, say 660mm to 720mm wide with 50mm - 70mm stems

Seatposts

As riders push the terrain limits of current Gravel bikes, I believe we'll see more suspension and / or suspension dropper posts, anything to dampen the terrain and also help shift weight back when going down hill.



So what next?

Firstly, I have a huge amount of respect for forward thinking companies like Wolf Tooth Components and PNW Components who make the kind of stuff that allows people like me to build bikes like this.

https://www.wolftoothcomponents.com/

https://www.pnwcomponents.com/



I believe in a just a few years time, if you're looking for the perfect do-it-all bike for UK riding, it will possibly look something like this and the only real choice will be whether you opt for flat or drop bars.


"Gravel" will become the new word for "Hybrid" and Roadies and MTB'ers will sit happily together swapping tales of baggy shorts & leg shaving, drinking beer & expresso's!


(Ok, maybe not the last part!)



#gravelisthenewhybrid

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