When gravel first hit the mainstream, we talked about the ‘huge’ tyre capacity of bikes such as the GT Grade at 35mm. Soon, the industry told us we needed bigger tyres, more volume, more grip and more comfort.
This led to the adoption of Road Plus – remember that? – using a 650b wheel with a big tyre for better off-roading.
The combination saw some brilliant bikes released at all price points, from Marin’s long-standing Nicasio+ to the Rondo HVRT (a do-it-all, road-cum-gravel bike I loved and still own). The original Open U.P., released over a decade ago, could fit 700c wheels with 40mm tyres, or 650b wheels with 55m tyres.
Bikes then evolved, making 650b an afterthought, and 700c became the norm for gravel. Then, a few riders, and a few brands mooted, tried and preached about 29ers, big clearances and even bigger tyres.
Hold on a second
When I started thinking about this, I was testing some of the latest and best gravel bikes. They all fit the 700c gravel mould, but have relatively big clearances compared to the original gravel template.
That made me bring out my 2015 Cannondale Slate, with room for 42mm tyres on 650b wheels, and my 2020 GT Grade, which can fit 45mm tyres on 700c wheels. I rode both over a few days with the cutting-edge 2026 bikes still in my mind.
Are they as good as the new bikes? Possibly not. Could I ride the same gravel loops and singletrack trails on these older bikes? Absolutely. Was I slower? Yes, in some conditions, but not by any significant margin. Was it harder? Yes. Did I have less fun? Categorically, no.
But over the last year or more, we’ve seen riders pushing for larger and larger tyre clearances, and on the industry side, a push towards larger wheels.
Are wheel sizes evolving?
To put that in perspective, the gravel bike in its relatively short mainstream history – 12 years from 2014 to 2026 – has had 700c skinny, 650b, 700c wide, 29er, 750d and now 32in wheels.
In comparison, mainstream mountain bikes have, in 45 years, had 26in, 27.5in and 29in wheels. There’s been a small deviation for dirt-jump bikes with 24in wheels, and now 32in is coming.
Bear in mind mountain bike design is one of the freest and fastest-changing of any type of bike. Rigid, front suspension, full suspension, with countless variations for all sorts of terrain and riding styles… yet it’s had fewer wheel sizes in close to half a century than gravel has in just over a decade.
Road bikes have been 700c since the 1970s for racers, and since the very early 1980s for consumers. Racers used tubular-compatible wheels with glue on the tyres with a shallow rim and 622mm diameter; older road bikes had sidewalls for clincher tyres and a marginally larger 630mm diameter commonly called 27in.
Simply put, road bike wheel sizes have remained unchanged for longer than I can remember, and don't look to be changing anytime soon. So why can’t gravel bikes settle on a standard?
Bigger is better
Baum recently announced its Gravel DBM 32 with 32in wheels as a solution for taller riders, because the wheel size means the Australian brand can build a bigger frame with better proportions. However, that’s not the reason being pushed for a switch to these large wheels by the industry.
At 6ft 2in, I'm taller than average, but not excessively so, and I admit I'm intrigued by the prospect of trying a bike with 32in wheels. If the claims of stability and increased grip bear out, it could be a great option for an all-round gravel bike.
Darren Baum explained to me that his extensive testing of the 32in prototype has given him Strava PBs on climbs and descents he’s ridden for decades, and that he hasn’t yet found the limits of the bike's handling and grip, so he believes 32in wheels and tyres have a bright future.
I thought similarly of 750d, which was generating some buzz this time last year.
At the start of 2025, WTB and Moots, among others, purported the benefits of 750d, even going so far as to produce bikes with this in-between wheel size that's larger than 700c and 29er mountain bike rims. The 750d size (660mm diameter compared to 622mm for 700c) was pitched as a better-rolling and more stable alternative for gravel.
When it comes to 750d and 32in, I’m going to reserve judgment until I get a chance to ride some bikes equipped with these oversized wheels.
But I’m intrigued to hear what you think. Has 750d become a footnote? Is 32in the future for gravel? Or should we just stick with 700c? Let me know in the comments below.
