Designing a gravel bike that doesn't lie : Geo

Full disclosure, I love riding all types of bikes; if I am pedaling, I am happy. I was raised on BMX and mountain bikes, so naturally I am happiest when my tires are on dirt, rocks, and roots. I only rode road bikes for cross training, and by default. I really wanted to like road bikes, but it was just so boring.

When I worked for CSG, a well known brand of ours called GT launched a bike called the Grade, which promised to be a road bike with a bad attitude. Looking back it was actually one of the first mainstream gravel bikes. It wasn't a road bike with knobby tires, (CX bike) it had slack angles and wide bars. This was a bike that wanted you to take it out and get off of pavement.

So I picked one up, and fell in love with what GT called "EnduRoad" riding. Later dubbed Gravel, All-Road, mixed terrain, etc. Finally I could enjoy riding "road".

Since then, I have been bouncing around from different gravel frames while I continue to fall in love with the idea of going out on an exploratory ride that can take me from pavement, to mud, cobblestone - really wherever I want to turn. I have ridden probably about ten different "pure" gravel frames to date. They were all truly wonderful bikes, and were well designed products.

Here's the thing though, I learned something that all of them share, and it's an unfortunate truth, but

gravel bikes are all liars.

Let me explain.

Gravel bikes are not new by any stretch of the imagination. One could make the argument that the klunkers that started the mountain bike movement were the first gravel bikes of the age. Riding gravel is definitely not new either. The road segment of the bike industry was seeing a steady decline in sales, to the point where it was the lowest performing market segment. The industry needed something to bump up sales and gravel bikes fit that bill beautifully. Repacking and rebranding something that already exists into something new and fresh. Nothing new there.

There lies the lie though - gravel bikes are too much road, they are lying to themselves about what they are. Afterall, where is gravel typically found - rural areas that are too far from city centers to warrant paving services. What is also out there in those areas? Singletrack, rocks, roots, dirt. The gravel movement started with this idea that you could be riding road and see a twisty turny gravel road off to the side and you could be like "my bike can handle that".

Gravel bikes were never meant to be slack road bikes with room for really knobby tires. In reality, they weren't even meant to be rigid mountain bikes with slightly narrower tires. They have always been something that should embody the best of both worlds. The frame design of the road bike is terrible and archaic, which is partly why the road segment was declining - no innovation. Companies like Giant had started making more progressive style road bikes, to be sure - but falling short of radical.

Frankly I'm sick of it, I know geometry enough to know how a bike will behave with certain measurements, so I'd like to sit gravel down and say "who are you, really?"

Last year I started playing with some designs and here I'm going to talk about the unnamed radical design that I am referring to as the unofficial future of gravel. It should be noted, that in the time since I started designing, coordinating with a builder and solidifying the geo - brands like Hudski and Surly have also released bikes that are really similar to my design - so I'm not the only one who thinks the time has come.

Let's start with the front end. Most gravel frames are between 70-72 on the head angle. Generally speaking, slacker means slower steering and more stability at speed. My 69.5 degree head angle is aimed at achieving that stability, but it also takes advantage of a slacker head angle's ability to roll over objects on the trail without treating the front wheel as a fulcrum.

I designed the geo around a fork with a 440 axle to crown measurement, I am having a rigid fork made, but I expect to experiment with a suspension fork between 40 -60mm of travel, so this measurement gives me some wiggle room while not messing with the rest of the geo.

Top tube and reach are pretty synonymous with a build direction that I am going for, but also just because longer bikes are a lot more fun to ride. Longer top tube = longer wheelbase = more stable. Most road bikes (and by default gravel bikes) use a longer stem and this a shorter top tube. But this isn't a road bike, so. That 180mm headtube is going to bring the stack up a bit and keep my position upright, and leave some space between the bar and the tire so I can fit a sizeable bar bag there for bike packing. Another strategy of having a slightly longer headtube is to increase the torsional rigidity of the front end.

My seattube is more mountain bike than road bike. Tall seattubes are dumb, and archaic. Dropper posts are the new hotness. I did 47cm as I fully intend to run a long dropper post. Having a longer toptube, and wheelbase, means that if I go with the standard 73 degree seattube angle, my center of gravity is going to make that front wheel feel lofty. On most of my fits, I end up using a zero offset seatpost and slide the saddle fairly forward to get my hips over the BB. So combine those two and I came up with 74.5 degrees, which is much steeper than most bikes, but this is much longer than most bikes, so.

The chainstays of this bike are short, at 420mm. This is going to make the bike very nimble and snappy on acceleration. Then on the BB, I have a -55mm drop. This is a bit higher than most, I wanted extra clearance under the bike. I also gave myself some room to raise or lower the front end without messing with the BB height too much.

Overall, I designed this geo with the best in mind from both types of bikes. Steep angles and short distances where they will give me the best results, slack and long where it matters. I want to be able to bunny hop this bike over a downed tree, and I want to be able to rip down a gravel road at speed without the steering getting twitchy. Where typical gravel bikes are designed like a roadbike that squeezes in components for the best case scenario, this bike designs the frame for the worst case scenario, while allowing a variety of components to suit any scenario.

The frame is currently being built by a custom frame builder and I should get to see the prototype here soon. More details to come!