johngwheeler

I know some of us (myself included!) tend to get a bit hung up on categories and definitions, but I’ve started to wonder what exactly defines a “gravel bike”, as opposed to other types of bike that can be ridden on unpaved surfaces.

Wheel width is the obvious one, but the oft-mentioned geometry characterics seems to vary greatly across manufacturers, and it’s left me confused. I’ve seen gravel bikes advertised with 73.5 degree head-tube angles and 45mm trail, both of which aren’t out of place for race-oriented road bikes.

Giant’s TCX SX “gravel bike” is identicial in geometry to their CX bike (I own one), yet has a 60mm bottom bracket drop. Compare this to the Specialized Diverge that has a whopping 85mm BB drop.

Are they both gravel bikes, and if so, why? Does it matter? Probably not, provided they do the job, but it does make the selection process more difficult if you don’t know how the numbers will translate to real-world performance.

I’d love to hear your thoughts.

JonathanGennick 

Gravel includes a wide spectrum from racing (e.g., the Warbird), to mixed pavement and gravel (Marrakesh, maybe?) through to full on adventure like the Xsogn and the Fargo. Geometry's going to vary widely, and I don't know that one can point to a single set of typical numbers. What matters to me are a low bottom bracket and the ability to fit wide tires, say up to 50 mm. (I'm running 47 mm now).

Marcus_Ti

Drop bars and CX tire width at a minimum is just about all everyone agrees on. The rest is Run What Ya Brung, and whatever works for you.

Some people ride CX bikes, some people even ride road bikes are hard-packed MMR or chipped limestone. Others go more endurance/touring end of the spectrum.

Koyote

Hell, I bought a "do anything" bike - All City Space Horse Disc. Takes wide tires (up to about 43mm), has a stretched out wheelbase, and a geometry designed more for stability than quick handling. 'Course, it also has rack and fender mounts (front and rear) and a frame that can handle up to about 50lbs of cargo.

But it's a "gravel bike" because that's where I ride it.

tFUnK

Large tire clearance and low bottom bracket are the main points.

I like to ride light and fast bikes so I prefer geometry as close to road race geometry as possible (relatively steep angles, short chain stays, and light frame). Probably won't be great for riding on technical terrain/single-track, but great for crushing hard-pack fire roads with speed.

cs1

I really think all these sub catagories are just BS that bike manufacturers invented to sell more bikes. Do we really need bikes with such insignificant differences to enjoy riding?

Marcus_Ti

Eh. There's one thing to be said. The categorization has made it easier to find what you wanted for the purpose.

Rewind the clock 10 years-how would you have easily shopped for a high-tire-clearance, drop bar bike, with not-very-aggressive-geometry? You'd basically have to go through every brand and and look at each drop-bar-bike's frame specs one at a time to even find candidates.

Kontact 

It is likely always going to be a question like "what is MTB geometry?" While there is wide agreement about what pavement is, "gravel" is open to wide interpretation.


I don't think a rather long wheelbase bike to accommodate full racks is really in the spirit of gravel bike, which is supposed to be at least a bit about speed. Nothing wrong with it, just seems like more of a "do all" than a "gravel specific".

tyrion

I find the categorization of bikes much more fun than the actual riding.

HTupolev

A gravel bike is a bike intended to be capable of gravel.

A gravel bike geometry is the geometry on a gravel bike.

For various reasons, there are a lot of opinions about what a "gravel bike" should be capable of and optimized for. Some people are looking for a a high-performance road bike that happens to fit huge tires and has itsy-bitsy gears available. Some people are looking for simplified mountain bikes. Some people are looking for.... whatever. Lots of things.

Within any goal, there are a lot of different thoughts about how the goal should be reached.

Also, bike categorization can be affected not just by the engineering teams, but also by marketing. For example:
In the wake of the bike boom, everything was drop-bar road bicycles. So the 1983 Miyata 710, a mid-range road bike, was not just "ideal for sports riding", but also "commuting."
But through the early 1980s the mountain bike began to gobble up general-use markets and threaten road bikes. So although the 1984 Miyata 710 was basically the same bike as a 1983 Miyata 710 with a few upgrades and a new paint job, according to the catalog it now featured "TRIATHLON DESIGN." And somehow, it had lost its commuting usefulness.

Categories and definitions are fuzzy guidelines.

TugaDude

My gravel bike is a singlespeed bike that can fit wide "i.e. 38mm" tires. I don't currently have fenders on it so I put some 3M protective tape on areas I don't want ruined by churned up rocks. Only care to have one speed and the head tube angle is slack enough to avoid twitchiness. Works great for me.

Lazyass

How to choose a Gravel Bike: Part 2 ? Geometry ? Tekne

Koyote

You might be correct. Or you might be imposing your preferences. :-)

Sullalto

CX and touring categories would cover it.

Marcus_Ti

CX is the definition of aggressive geometry...and most companies 10 years ago were not selling many if any touring bikes, and the ones sold were friction-shifter only.

Metieval

Today you going to build a new home, and today you are going to frame up the walls, and add the trusses.

Quiz, do you grab your a. rubber mallet b. framing hammer, c. ball peen hammer d. finish hammer

tomorrow (next months tomorrow) you are going to finish the inside of your new home.

Quiz, do you grab your a. rubber mallet b. framing hammer, c. ball peen hammer d. finish hammer

are all the hammer options out there BS just to sell more hammers? Do we really need that many different hammers to enjoy building a home?

uh that might be lost on some people.
So the simple answer is yes, the differences are needed. Like the hammer thing, some might not understand the differences. None the less the differences are significant.

Abe_Froman

Totally lost. Hammers have a hard end, and a handle end, right?

Metieval

Exactly just like bicycles have 2 wheels, and a handle bar of some sort.

johngwheeler

.... except this doesn't necessarily seem to be consistent across manufacturers, or even the same manufacturer. My Giant TCX is supposedly a "CX race bike", yet has a 71.5 degree HTA and 430mm chain stay, which (as far as I understand) are relatively "relaxed".

The same geometry in the guise of the TCX SX is magically classified as a Gravel Bike.

So I guess there is still some latitude in the definition!

In the end, I don't really care what they call it, but it is helpful to have a label to know what the intention of the bike is, and also to understand how the specs translate into the actual real-world experience on the track.

chas58

I think you mean 45mm offset, as 45mm trail is highly unstable.
Some manufacturers use the same frame for Gravel and CX (partially because CX and mountain bikes are gravitating to longer/lower/slacker).
I use CX geometry because I like the agility (and loath pedal strike I get with less than 70mm drop). But if I lived in Iowa or even somewhere mountainous, I would rather have something that leans more towards mountain bike geometry.

You need to decide if you want an agile bike or a stable bike, a lighter race bike or something more sturdy, and how important touring or bikepacking is to you to determine what side of the spectrum will fit your needs. The biggest question often is, what tires do you want to run? If your favorite tires will not fit your frame, then its time to start all over.
Personally, I don’t like low bottom brackets (I thought the old Diverge was too low, and its gotten lower). I find a low bottom bracket makes the bike feel sluggish, and I like to power through turns without pedal strike (and to do singletrack). But others prefer the low center of gravity and stability that low bottom bracket provides (not to mention that it is easier to sit on the saddle when stopped, lol).

Then again, I like to have one bike that adapts to all of my riding – getting too specialized in a way makes it too easy and too boring. But one man’s “too easy” is another man’s comfortable.

chas58

You are right - lots of latitude and overlap. Some mfgs take the same frame and use it for both CX and Gravel. The components and accessories might be slightly different to fit the intended usage.

CX bikes often are getting more gravel like - longer and slacker with larger tires. Or there is specialized which has done a fair amount this year to make the Crux (CX) and the Diverge as different as they can. I think the older Crux was a great gravel bike, but now its a bit to CX specific IMHO.

u235

Marketing aside.. "Gravel" bikes a few years ago were too limited in gearing for everyone in my opinion. Compact with a 28 rear and a soft/med derailleur that could not officially do much more was the norm, 32 being the exception. If you were coming from a road background and considering a "gravel" bike you would be right at home with most of the choices. People coming from the MTB or flat bar that wanted a drop bar or never previously considered one wanted even wider than 32 or CX and more flexibility with gears and geometry. That eventually changed with choices and the reason why the definition of a gravel bike means a lot of things now. There are probably 50 different bikes you could line up next to each other to illustrate the transition from pure road time trial to pure MTB downhill. You just pick the range in that lineup where your current void is. That can be confusing or a benefit depending on how you look at it.
Just mentioning the Stuntman, definitely on the fringe but I'm sure for someone that is the perfect bike

One area that might need some more options is the >700x37 tire choices. Options now mainly consist of city/hybrid/comfort/touring/gravel tires. You could put your favorite 28 road tire or 33 CX tire on but an equal quality 37-47 tire would be a nice choice to have.

Metieval

I wouldn't want to hit 30-40 mph descents on loose gravel on a few CX bikes. Which has more to do with wheel base, and HTA/trail.

Gravel is also a very diverse environment. What California, Nebraska, Ohio, Australia all call gravel is as diverse as what manufactures call 'gravel bikes'. I wouldn't know, but I bet gravel across Australia has it's own diversity going on?

What I find interesting is a few years ago Trek called their Crossrip a gravel/adventure bike. They now call the Crossrip an Urban/Commuter. With gravel bikes being Domane gravel, Boone, and Crockett. Yet, their boone and crockett are also their CX bikes. Good job Trek on not even knowing what you were selling! lol

My Point..... It might be best to go research wheel base, trail, rake, HTA, STA etc... Then take a look at your environment. Pull from what you liked dislikes about your previous geometries, and Go shopping. the labels kind of gets you close enough. But the Ultimate bike for you will be the one that has the geometry you need/want.

johngwheeler

Yes, you're right. The spec I saw for a "Planet X Gravel bike" incorrectly listed trail as 45mm, but it's clear from the geometry diagram that they meant fork rake, and mis-labelled it in the table.

You'd probably like my bike with its 60mm BB drop. I did wonder about the 2018 Spec Diverge with its 85mm BB drop - apparently it is not recommended to go below 32mm wide tires to reduce the risk of pedal strike by lowering the BB height too much. To my mind, this limits the bike somewhat, as one might well want to put on 25-28mm tires to use for road riding. I have 28mm tires on my Giant TCX for road / commuting, and can probably go up to 45mm for off-road, which makes it multi-purpse.

johngwheeler

I had a 2016 Crossrip, which at the time was marketed as a CX bike. I didn't really know what Cyclocross was at the time, but I think my bike would have been hard work in this role (it weighed about 11.5kg, and had a long relaxed geometry). The 2017 model was re-classified / marketed as an "adventure bike". Now it looks like it's moving on to Urban/Commuter, which was what I used it for!

So, 3 different categories all for essentially the same bike (AFAIK, the geo hasn't changed).

As you say, it's a safer bet to study geometries and understand what effect each measurement has in different environments. I'm still learning this bit!