Covering Dangerholm’s custom project bikes is usually about hunting little details that make them special, but this time it’s a bit more obvious – showing off a unique ultra-wide aero gravel wheel concept created with Faction. As gravel race tires grew from 35 to 40 to 45mm, rim widths have grown too, for both aero and handling performance gains. But Dangerholm questioned why wider gravel rim widths stalled around 32-35mm inside, when at the same time, gravel racers keep expanding to 50mm and up to 57mm tires depending on terrain.
So he worked with the creative minds at FactionBike Studio to go wider. How wide would you guess that these are?
2025 Bespoked Dangerholm wide aero gravel concept
At this weekend’s Bespoked show in Dresden, Gustav Gullholm aka Dangerholm, showed off two project bikes together with his online bikeshop partner R2, who is based in the city. And the carbon Dangerholm + FactionBike Studio concept wheels were very much one of the big highlights amongst a lot of modern handbuilt metal bikes.
But for now, this remains very much just a concept. And although they are real rideable wheels, you can see all 4 of the rims in existence in this photo above.
Dangerholm + FactionBike Studio concept for ultra-wide aero gravel wheels
Let’s first look at some of the project’s starting points.
Dangerholm wanted to try wider, and FactionBike Studio was happy to help figure it out.
The starting point was essentially that lightweight, fast-rolling XC mountain bike tires had become a viable option for fast, rougher gravel racing. But no existing gravel wheel was actually designed to be aerodynamic with a 29 x 2.0-2.25″ MTB tire. Most MTB racers have gone to 30mm or even 35mm inner rim widths, and stopped there. But mountain bikers experience different grip & cornering forces at different speeds than gravel racers – where a more lightbulb-shaped tire section may be more beneficial.
A lot of aerodynamic performance seems pretty sure about a smoother transition from rim width to tire width, reducing aero drag. So, even wider gravel rims for even wider gravel tires does sound like it could make even more sense.
They are how wide!
So, let’s look next at some key details of these concept wheels.
The Dangerholm + FactionBike Studio extra-wide prototype gravel wheels are 45mm inside and 52mm outside. They have a maximum depth of 70mm and a minimum depth of approximately 52mm.
Their construction is two-part. Inside, there is a conventional low-profile carbon mountain bike rim that defines the 45mm hookless tubeless inner width. And outside of that FactionBike Studio’s LX Lab crafted a custom aerodynamic carbon cowl that creates the undulating aero shape we can see – designed to smooth air over those wide tires.
We don’t have any aero data, and neither Dangerholm nor FactionBike is yet making aerodynamic claims. Faction & Dangerholm agreed on this shape out of about 8 different aerodynamic concepts. But the goal of the project is more about drumming up interest in going wider, more than saying that this is the ultimate aero design solution.
Ultra-wide gravel tire aerodynamics, in theory
That construction creates the 52mm wide shape that transitions rather smoothly to these 57mm/2.25″ Maxxis Aspen ST and Schwalbe Thunder Burt cross country tires.
But it is also the reason that we see wider openings to allow the spokes to pass through to the nipples that are in the internal rim. Plus, it also means that these wheels are quite heavy. Dangerholm – a notorious weight weenie – didn’t want to talk about their exact weight, really, because obviously a purpose-built production wheelset using this ultra-wide concept could be built much lighter when engineered from scratch.
He did mention that the outer carbon shells were strong enough to be set up with tubeless valves, although he didn’t have time yet to do so before the Bespoked show.
What’s next for the Dangerholm + FactionBike Studio ultra-wide gravel wheels concept?
The result is undoubtedly a massive-looking wheel. But it is proportionate to the wider XC MTB tires that continue to be adopted for rougher modern gravel racing.
Now we (Dangerholm, Bikerumor, and you the readers) just wait and see what the rest of the bike industry thinks about ultra-wide aero gravel wheels?
Gustav clearly is convinced that wider rims are the way forward for gravel riding – and says he won’t go back to conventionally narrow gravel wheels, even accounting for the obvious weight penalty.
OK, so yes, this story is mostly ‘not about the bike’ but since Dangerholm is involved, it is also always about the bikes too…
Dangerholm’s latest drop bar gravel build is a full-suspension Scott Spark RC.
Dangerholm put the new ultra-wide prototype aero gravel wheels on two custom bike builds for the 2025 Bespoked show.
First up is the more straightforward Scott Spark – a 120mm travel full-suspension cross-country mountain bike. But of course, with a dropbar build.
I think Dangerholm really likes to write “Technically A Gravel Bike” on something outside of what you would expect. We saw it just last month with his ultralight Scale dropbar in Girona.
For this one, it’s mostly the ultra-wide Faction concept wheels and integrated Darimo Nexum flared dropbar cockpit that makes it a gravel bike – even when almost everything else is pretty clearly XC, including automatic SID Ultimate Flight Attendant suspension front & rear.
While this bike isn’t about being crazy light, I do really love the simple ultralight Alpitude Stelvio Correto out-front GPS mount – the ‘world’s lightest’ when it launched a couple summers ago.
Drivetrain is gravel too, with the mid-tier SRAM Force AXS Xplr transmission setup – combining a 46T aero Garbaruk custom 1mm offset chainring to the 10-46T Xplr cassette. But outside of really big gearing, that’s almost XC race worthy with a 460% range compared to the standard 34T x 10-52 setup this bike would come with in its normal XC guise.
Dangerholm is still a weight weenie at heart!
Even on a bike where weight is not the primary concern, Dangerholm’s weight-weenie tendencies do creep out. Like this Mcfk carbon saddle that can weigh as little as 69g. The Darimo T1 Loop seatpost that weighs just 90g, even in its largest & longest 31.6 x 400mm size, thanks to a loop of dyneema rope that clamps the saddle rails in place. And finish it off with the Darimo Sub4 carbon seatpost clamp that weighs <4g.
The rideable prototype rims might not be the lightest ever just yet. But Dangerholm has them laced into a set of modular Extralite HyperSmart3+ hubs that share intricately machined hub bodies across all axle spacing standards to shed grams. The front is 75g and the rear is 150g, including Boost axles and the ultralight 3g carbon spacers that align your rotors to the correct place.
Yes, it is technically a gravel bike, but anyone who has ridden a Spark will know that this Dangerholm creation is capable of some serious off-road racing, as long as you have the leg power to get that massive gearing up the steeper hills.
This Scott Scale+Foil gravel race bike is a classic Dangerholm mashup!
This one feels even more like a Dangerholm creation, because it’s more of a frankenbike.
Let’s call it a Scott Scoil maybe? (Fale probably doesn’t work.)
Yes, this started as Scott Scale, the first lightweight rigid cross-country mountain bike that Gustav asserted was actually a gravel bike. But this time he wanted an aero seatpost to match the aero cockpit and aero concept wheels. So, he chopped up a new Foil aero road bike to get its seatclamp, and its neat multi-part Duncan SL Aero CFT seatpost with an integrated taillight inside.
It’s not entirely obvious how this used a Foil seatclamp, because this isn’t a frame shape that exists exactly on the new Scott aero road bike. But Gustav explained that he cut the seat cluster and clamp out of a crash-damaged frame, placed it on top of the Scale’s toptube, added a separate sloping section of carbon tube in front, and had his local carbon repair shop wrap the entire thing to make it strong and safe enough to ride.
Gustav says he was almost proudest of the way the small rubber cover he made over the seat binder, turned out.
Conventional SRAM Red gravel drivetrain hides all-new Wert ti cranks
This bike is more of a lightweight build, so it more appropriately gets a full SRAM Red Xplr transmission setup.
Just a standard Red direct-mount chain ring and power meter up front over… wait, an all-new ultralight CNC-machined titanium crank arms! Yep, that’s a Belgian-made Wert StW-G ti crankset. It’s a project that’s been going on for more than a decade to create the ultimate, ultralight crankset – in various materials, via both conventional machining and 3D-printing technologies. And now, this one is said to weigh as little as 292g for the arms, spindle & hardware without a chainring.
We’ve got a bit more info and will go into more detail later this week. But it is now finally something you can actually buy, if your wallet can handle it.
Custom carbon and ultralight parts to finish the build
Another slick Darimo Nexum integrated cockpit for this Dangerholm Scoil project bike. Darimo had to add a new 80mm long x -17° stem angle size to their offering to match the MTB fork angle. We also asked Darimo founder Damià Rizo Morant what he thought about Gustav adding heavy gold paint to a bar that probably only weighed around 200g to start with, and he laughed saying he was always interested to see what the next Dangerholm project bike would look like and was happy to work together to build such unique bikes.
A bit more classic Dangerholm attention to detail finishing comes with CarbonTi rotors with a one-piece carbon carrier. Gustav suspects that a simple laser-cut stainless rotor is probably more aero, but it’s hard to argue with the unique look of these. As for the boxy German-machined 612 2-piston brake calipers, they certainly aren’t aero but do tuck in nicely behind the big rigid Scott fork legs. And claim improved brake performance that can be fit to most lever types and most brake mounts.
And again, those same modular Extralite HyperSmart3+ hubs with Boost axles and carbon rotor spacers.
The custom Scale+Foil looks a bit more like a conventional gravel bike while maintaining that classic Dangerholm contempt for manufacturers’ warranties.
