32” wheels only suit average height, white, male riders - my CAD drawing shows you why

Cam Jones (Scott) lines up on Saturday as the defending Unbound 200 champion, riding a Scott RC Gravel prototype rolling on 32” wheels.

His Scott team mate, Robin Gemperle, is on a second 32” prototype. Both riders are talking about levitation, revolutionary cornering; "I'm genuinely scared how fast I'll be able to corner once on a course with proper descents," Jones said. The theory is that a larger wheel just rolls faster.

The brand behind the bikes was keen to communicate that this machine "will never be released on the market." And yet, it was clear at the recent Sea Otter trade show that a plethora of wheel and tyre brands are keen to see 32” wheels become mainstream.

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Whilst these larger diameter wheels have always had a legitimate place in custom bikes designed for riders exceeding the ‘average’ height, I would consider 32” wheels arriving on the mainstream market to be a major backwards step for cycling, and its accessibility.

Jones is 6’ and Gemperle is 5’10”; the latter falls right into the ‘average white male’ bracket with the former exceeding average. Baum Cycles’ new DBM 32” bike looks great in its marketing images - but that bike would suit a rider around 5’7”. The geometry of a 32” wheel just doesn’t work at smaller frame sizes. This means a massive chunk of the market – plenty of women and almost all of Asia – is locked out of 32” completely.

Having designed and built bikes for decades, I hope I can demonstrate why, with a quick CAD (computer aided design) sketch.

Building a 54cm 32” wheel bike in CAD presented major issues

I modelled my CAD image on a 54cm frame, which would typically suit a male of around 5’8”, much taller than the average Western female of around 5’4”. CW’s US editor Anne Marije-Rook rides a 49cm Specialized, and digital editor Michelle Arthurs-Brennan a 52cm.

The main values I sought to preserve were the stack and reach, relatively to the bottom bracket, as these coordinates dictate a rider’s position. The result was a struggle to fit everything else in.

To create my designs, I chose an arbitrary 440mm axle-to-crown length for the fork, which I judged as giving me enough crown clearance for a 50mm tyre on a 32” rim. To get the rear wheel in, I’ve had to extend the chainstays out to 485mm, some 35mm longer than a downhill mountain bike. The impact on front and rear centre and overall wheelbase could – potentially – give rise to incredible stability in terms of forward progress, but it will pay big time in agility. Even before you consider the extra mass.

To retain the reach, I pushed the effective top tube as far as I could - the horizontal distance from the center of the head tube to the center of the seat post. To get the reach working at all the head angle now sits at 68 degrees, that’s very shallow for a gravel bike - the same as a Specialized Chisel XC MTB. This would create overly slow handling and hinder precision, turn-in in fast corners, and the kind of positional changes we see in bunch riding.

The headtube is left with only a couple of thumb widths of space, and the whole front triangle is compromised to the extent that I simply don’t think it’s possible to physically make it work. I even struggled to illustrate it correctly in my drawing.

And then there’s the toe overlap. Despite slackening the head angle as far as I dare. At slower speeds and in very technical terrain, the rider’s foot is going to come into unavoidable contact with the front tyre.

I could go on.

You could go some way to solve some of the geometry problems resulting from the 32” wheel with offset forks, or a longer top tube paired with steeper head angles. A shorter fork crown might help, and could likely be designed, but the downtube quickly comes into direct conflict with the front tyre as the fork gets shorter. It's a fools errand, as any result is an unavoidable compromise.

Remember, a 54cm frame isn’t an unusual or even very small size in our home markets. In Asia, it's a large.

My brief and ragged design study – please excuse the presence of the double chainset – is a crude visual device to support my point. But what is clear is that each compromise trades away handling, adds complexity, or makes the bike slower handling or heavier in any sensible analysis. And on a 52cm or equivalent, there is simply nowhere for the front wheel to go at all.

The business problem

My point is simple: 32” wheels are not going to work on smaller bikes. Therefore, if 32” wheels were to become mainstream, the industry would be left with two choices: produce 32” bikes for larger riders and maintain existing 700c sizes. Or, majorly disadvantage some already marginalised customer groups, such as women who are already a minority group the industry claims to want to reach.

Given the bike trade has spent the last year or two complaining its ranges are too sprawling - Cannondale’s “one bike to rule them all” pitch in the WorldTour, followed by Giant with its Propel now shading out the TCR - the appetite for increasing SKUs with twice as many wheel sizes seems limited.

The most frustrating component in all of this is that on the question of whether 32” is actually faster, we have nothing empirical at all.

So far, we have a few field tests, a handful of runs in each, with a ton of variables in play, and one independent comparison that Vittoria offered at Sea Otter, quickly clarifying that the few seconds saved came with some major caveats.

Even if a 32” bike does cross the line first at Unbound, it proves nothing about the speed of these larger wheels. The fastest rider in any gravel race is, by definition, the fastest rider in the race.

Scott has been clear that there are no plans to create a consumer model of this bike, and I’m pleased. Gifting the vast majority of the female and Asian riding population with serious toe overlap and compromised handling, based on a data point of one, would be a travesty.