In Part One of this Monster Gravel series, I showed you how we went from a simple gravel bike to having a version for everything from racing to exploring to bikepacking and more.

And how all of that quickly led to this latest category, “Monster Gravel”.

Drop Bar MTB vs Monster Gravel

Below, you’ll see how I’m designing a Monster Gravel bike. But first, let’s talk about two key differences between a mountain bike and gravel bike and why they matter if you’re thinking of converting your current hardtail into a Drop Bar MTB. 

Each bike is designed to tackle the terrain slightly differently, mainly due to two factors:

1. Bottom Bracket Drop
2. Front Center / Reach. 

BOTTOM BRACKET DROP: Because mountain bikes are designed around longer-travel suspensions (even hardtails!), they have a much higher BB to avoid rock strikes and to make the bike more nimble in the singletrack.

Gravel bikes have lower BB heights to make the bike more stable on high speed gravel sections while also having positive handling characteristics whether the rider is on road or gravel sectors.

Side note: When you’re looking at geometry charts, more BB drop = lower BB height…the “drop” is measured as the distance below the horizontal plane drawn between the axles.

FRONT CENTER: Mountain bikes have a much longer top tube and shorter stem combination than a gravel bike. This style of geometry evolved as wheel sizes grew from 26” to 29”, and then further still as we’ve progressed to larger tires, longer travel forks, and slacker head angles for steeper terrain.

Gravel bikes (even “Monster” ones) simply aren’t as slack or long travel, and even on the roughest courses aren’t going to traverse as technical of terrain as a typical MTB trail. So, they don’t need to push the front end out quite as far, which keeps you in a more comfortable cruising position for long miles in the saddle.

At the end of the day, it’s horses for courses. The guys at Leadville proved the benefits of bigger tires on a more aggressive drop-bar setup, and the aero advantages of a drop bar over flat bars are clear.

Now it’s time to combine the two and make something really special! 

How to design a “Monster Gravel” bike

In this Part Two, I’ll explain how I would design a Monster Gravel bike, taking into consideration the goals, opportunities, and limitations based on the following assumptions:

1. The bike has to fit 29×2.2” or 700×56 tires
2. It will have a 50-60mm travel suspension fork
3. It has to have proper chain clearance for both 1x and 2x gearing
4. Geometry is pure gravel bike, not a drop-bar mountain bike

I’ll also dive into the current component options (and limitations!), even though I’m designing around the ideal and not necessarily what’s currently on the market. You could say I’m a bit hopeful that the rest of the industry is as interested in making Monster Gravel a reality, too. Read into that what you will… 😉

Monster Gravel Geometry & Components

I thought about breaking these two things into separate sections, but the reality is that both geometry and components both play into the design. Tire width and fork height dictate chainstay design and head tube height and angles.

And lots more…you can’t design a bike without knowing what type of parts you want to put on it.

So, here are the key considerations in designing a Monster Gravel bike:

TIRE SIZE:

IDEAL: 700×56 or 29×2.2”

NOTES: Tire sizes are getting bigger on everything for good reason. More volume lets you run lower pressures, which are smoother, more efficient (aka faster), and have more traction.

For everything but the smoothest courses, it’s likely the 29×2.2” tire size is going to become the norm in the next two years or so. Rims are already wide enough, and tire brands are quickly optimizing casings and tread patterns for wider tires.

FORK TRAVEL: 

IDEAL: 50mm to 60mm of suspension fork travel.

NOTES: Some forks on the market do offer 50mm (Fox TaperCast) and 60mm (MRP Baxter) of travel, but none currently clear tires larger than 700×50. A true Monster Gravel fork would need to clear 700×56 (29×2.2”) tires.

Travel longer than 60mm is pushing into short travel XC forks territory and gravel bikes just don’t need that much travel. 

In contrast, a drop bar mountain bike is still a mountain bike, so its geometry is built around 80-100mm travel.

That much travel means you’d need to set up your handlebar with more upward rotation at sag than you’re typically used to, because you need to have enough grip at full compression to safely keep your hands on the bar. But that wouldn’t be as comfortable on mile after mile of less technical terrain.

CHAINSTAY LENGTH:

IDEAL: 425mm chainstays

NOTES: Both our Storm King (gravel) and Optimator (XC MTB) frames have 425mm chainstays and fit 29×2.25” tires thanks to two things – a bent seat tube and our custom 3D-printed chainstay yokes.

We could use a straight seat tube, but that would mean longer chainstays, which would feel very stable but lose some of the snappy race-like performance we’re looking for.

Our 3D-printed chainstay yoke creates maximum tire clearance, but to fit a 2.25” tire you’re limited to a 1x chainring, which leads me to…

GEARING OPTIONS:

IDEAL: 1x wide range with 2x compatibility for those who want it

NOTES: It’s not hard to have both 1x and 2x compatibility on a bike. Current bottom bracket and chainring offset standards make either possible. The real limitation is chain-and-tire clearance and maximum chainring size.

For 1x setups, a wider chainring offset can easily clear a 2.25” mountain bike tire even with 425mm chainstays. But, the chainstay yoke’s wider stance limits the maximum chainring size to 44-46 teeth. That may sound small by road standards, but most mountain bike frames max out at 36-38, so you’re going to get a much taller, gravel-worthy gear here than on a modified hardtail MTB!

For 2x setups, the front derailleur’s cage is the limiting factor as it protrudes rearward into the space otherwise used by a wider tire. So, your drivetrain choice is at least as much dictated by how big of a tire you want to run as it is your gearing.

If you want the biggest possible tires, you’ll need to go with a single chainring.

HEAD & SEAT ANGLES:

HEAD ANGLE: The Head Angle directly impacts the handling of the bike by interacting with the fork’s offset to create Trail. (Check out this edition of Bike Design 101 for a deep dive on how that works)

Fortunately, a Monster Gravel bike’s head angle is a bit slacker than typical gravel bikes because of the increased fork travel and its rambunctious intentions, which helps with front tire-to-toe overlap clearance.

Ultimately, we have to design the head angle to eliminate front wheel/toe overlap, which sometimes means playing with reach, front-center, and even stem lengths (see below) to achieve good handling and safe clearance.

SEAT TUBE ANGLE: Here we have some wiggle room. If we need a steeper or straighter seat tubes to add tire clearance, rider can use setback seatposts to get further back. Or straight seatposts if we need more of a bend in the seat tube.

Since these bikes are likely to have dropper seatposts, we’ll want a straighter seat tube (or at least one with a longer straight section at the top) to make room for longer travel droppers.

And we want to keep the upper tube’s seat angle from getting too slack so that we’re pushing the dropper down as vertically as possible to reduce friction on the slider.

INTENDED STEM LENGTH:

IDEAL: Shorter stems

NOTES: Wider tires also get taller, which means their edge sits further back from the front axle…and closer to your pedals. That means your toes are more likely to overlap the front tire, and that’s bad.

While we can tweak the head angle a little to help push the wheel further forward, there are better ways to do it. Stretching the top tube to increase the reach lets us move the front end forward without moving your toes forward.

But we don’t want to stretch you out too much, so adjusting your actual reach with a shorter stem keeps you in a comfortable riding position while also eliminating toe overlap.

A shorter stem also gives you snappier handling, which helps offset the stability of more tire grip and typically longer trail and wheelbase. In the end, it ends up feeling very balanced. (read more about Stack & Reach here)

Why is the Monster Gravel category so interesting?

Or, why would I put the time and energy into drafting a bike in CAD for something that’s not real?

Here’s why: Because at its heart, the MGR shown here would be a wicked fun bike for anything.

Race it on rough trails, load it up and go explore, or just rip around your local trails and paths with friends. It’s a bike that embodies all of the best things a bike can be. Namely, FUN!

WANT ONE?

Reach out if you’re interested. The MGR could be real, and it could come sooner than later. Email me if you’re interested and I’ll open up pre-orders if I get enough interest.