The world of gravel cycling has recently seen the introduction of a bigger wheel standard, called 750d.
Having thought road and gravel bikes had largely settled on 700c wheels, I wondered what all the fuss was about.
With that in mind, I set out to analyse the theory behind the new standard and find out how these wheels ride.
First though, let’s get up to speed on what 750d wheels are, their positives and negatives and what you’ll need if you want to try them yourself.
The theory behind 750d wheels for gravel bikes
When 29-inch wheels entered the world of mountain bikes, the internet melted.
Although they promised faster speed, and better rolling over roots and rocks, many decided they hated 29ers before they’d even tried them – as with most new standards in the cycling world.
Eventually, though, the benefits became clear and 29ers were widely adopted – mostly by the Lycra-clad XC crowd.
According to their proponents, such as WTB, Moots and Merit – which makes the Jumbo 750d gravel bike I used for testing – the theory behind 750d wheels for gravel bikes is essentially the same.
The larger 660mm rim diameter (compared to 622mm for 700c wheels) is meant to roll more easily over rough terrain, for example.
The additional inertia of the larger wheel could also help retain speed.
Because they have a larger contact patch, 750d wheels are also claimed to increase grip, leading to better braking and handling.
Bigger wheels are also meant to help custom builds for taller riders. Merit, for example, feels that “in L-XXL sizes the [Jumbo gravel] bike looks best with 750d [wheels]”.
How are 750d wheels different from 700c wheels?
When paired with 750d gravel tyres around 40mm wide, 750d wheels are designed to have an overall diameter similar to that of 29in mountain bike wheels with larger mountain bike tyres.
A standard 700c or 29in wheel has a rim diameter of 622mm, while a 750d wheel has a diameter of 660mm. Other than that size difference, though, 750d wheels are similar to regular 700c wheels.
The Merit Jumbo bike I rode uses road Boost spacing. This equates to 110mm at the front and 148mm at the back.
The spokes are a bit longer than you’d usually find on a rim of this depth, but the internal rim width is a rather standard 25mm. The wheels are also tubeless-ready.
Unfortunately, the bad news is you’ll almost certainly need a new bike to fit 750d wheels.
The Merit Jumbo 750d I used for testing was designed specifically for use with 750d wheels. As with bikes designed for 700c and smaller 650b wheels, though, this bigger frame enables you to fit standard 700c wheels too.
750d wheels ride impressions
To test out the theories, I took the Merit Jumbo 750d for a short spin at Ashton Court – a trail centre in Bristol. It has plenty of tarmac paths, open gravel roads and some excellent blue mountain bike trails.
I went straight onto the stony trails, which – covered by leaden skies and thick tree cover – were slick and strewn with puddles.
Despite the conditions, traction was good both when coasting through corners and under heavy braking. The WTB Nano tyres, supplied in a 45mm size, bit well, but I wouldn’t say there was a huge difference in traction with the 750d wheels compared to 700c ones.
The trails provide plenty of flowing and techy corners, and it was here that I noticed the bike felt unusually tall. I didn’t feel able to move myself around the bike as I typically would.
Getting my centre of mass lower in faster corners and back for more technical terrain is how I would usually ride, but with the larger wheels, I felt more like a passenger.
As a rider of average height (173cm), I may be more sensitive to the feel of larger wheels, so this would be something I’d advise watching out for if you’re under the 6ft mark.
To test the wheels’ ability to absorb shocks, I took the bike over as many rough sections as possible and even hopped down a few drops. Was the latter strictly necessary? No. Was it fun? Yes.
Over rougher parts of the trail, where smaller rock sections were exposed, the 750d wheels seemed to soak up a good amount of chatter. That said, they weren't a great deal better than 700c wheels and, as ever, tyre size and tyre pressure optimisation matters more.
Onto some more open gravel stretches and the bigger wheels seemed to confer a small speed benefit. However, I wasn’t transformed instantly into a pro racer, and I’d need to do some comparative testing before concluding 750d wheels are measurably faster than 700c ones.
One thing I did notice, however, was a slightly sluggish feeling when trying to accelerate from slow speeds.
Finally, I took the 750d wheels over as many roots and rocks as I could find. In these scenarios, the larger wheels felt less susceptible to getting bogged down in rooty sections at slow speed.
Big impacts still come through the bike when riding at higher speeds, though. If you’re looking for proper bump-taming, a gravel suspension fork is still the way to go.
Do we need 750d wheels for gravel bikes?
With my short ride done, I was left seeing some potential benefits, but the question remains whether they’re enough to warrant investing in an entirely new bike.
That said, there isn’t anything wrong with having a choice.
Taller riders, for example, might enjoy the most significant benefit from the larger wheel size, enabling them to ride a bike with similar handling characteristics to smaller bikes and 700c wheels.
Whether there are enough tangible benefits for riders of more average height is unclear, though, especially because you’ll likely need a new bike to even try it.
In my experience, 700c wheels aren’t noticeably hard to handle over technical terrain, and offer a good balance between speed and acceleration. Given this, it’s likely going to be hard to convince many riders they need to buy a new bike just to get slightly bigger wheels.
As things stand, there are only a handful of brands making 750d wheels, tyres and compatible bikes.
It’s hard to see any serious momentum gathering behind riders switching until more brands support 750d wheels.
But what happens if the bike industry simply decides 750d is a better standard for all gravel bikes, regardless of size? It happened with disc brakes, after all…
Maybe next time you upgrade your gravel bike, you’ll have a choice to make.
For now, though, I think 750d wheels are something to keep an eye on. I certainly don’t feel the need to rush out and replace my Specialized Crux just yet.
