Custom Wheel Building for Gravel Bikes

Gravel bikes are the trend of the moment. The relatively new genre combines the off-road capability and versatility of a cross-country hardtail with the straightforwardness, speed and aerodynamics of a road bike to create a whole new riding experience. Whether you’re pedalling at top speed over gravel, taking epic tours on pothole-strewn back roads, going on excursions into light terrain, bikepacking or making your commute more dynamic: the gravel bike is a real all-rounder. A custom wheelset can further enhance your overall riding experience. Depending on your what you’re looking for, you can use MTB or road bike components – or rely on the growing number of gravel-specific components. If you’ve got questions, we’ll show you what to look out for.

Know how you want to use it!

In the gravel world, there are three extremes and everything in between: 1. The roadie, who has no patience for honking cars and manoeuvring on badly-paved side roads, but who otherwise treats their gravel bike like a road bike. 2. The mountain biker who gets more enjoyment out of easier trails and forest-to-highway transitions with a gravel bike. 3. The adventurer who racks up mile after mile in the remotest corners of the world.
It is clear that no one wheelset shines equally in all fields. For example, do you want to ride root trails with your gravel bike? Then your custom wheel won't likely break any weight or aerodynamic records. As always, it is important to think carefully about what you are willing and not willing to compromise on beforehand.

Wheel size: 650B or 700C

The most important question you will probably face concerns wheel size. Many modern gravel bikes allow the use of 650B and 700C wheels. 650B corresponds to 27.5 inches in the mountain bike world for use with tyres with an ETRTO of 584 millimetres. The classic road bike size 700C corresponds to 28 inches in the road world, or 29 inches in the mountain bike world, for use with tyres with an ETRTO of 622 millimetres. Smaller wheels are more agile and often allow for the installation of wider tyres – which can be advantageous for more than just off-road use. To an extent, however, you are also largely dependent on the use of MTB or gravel rims. Road bike components in 650B are scarce, but it’s a different story with their bigger siblings. Here you can help yourself to products from the (29 inch) mountain bike shelf as well as from the (700C/28 inch) road bike range – despite the discrepancies in labelling, the sizes are identical. Bigger wheels roll better and can maintain speed. However, tyre clearance is lower on many frames with this dimension, and larger wheels are often heavier or flex more than their smaller siblings. What’s exciting, though, is if your bike allows the use of both wheel sizes right out of the box, you can radically alter its character with a second or new wheelset long after purchase. With slightly-smaller wheels, for example, the bottom bracket of the bike is moved slightly downwards, which improves cornering but reduces ground clearance off-road.

Rim shapes and materials for your gravel wheelset

In addition to rim width, rim height is an important criterion for gravel bikes. Depending on the front end of the bike and the cyclist, at the latest from a riding speed of approx. 15 km/h, the air resistance is higher than the rolling resistance. The faster you go, the wider the gap opens, as air resistance increases exponentially with speed while running and rolling resistance increase only very moderately. There are also good reasons to use aerodynamic high-profile rims used on road bikes with gravel bikes. However, since aero components are not usually combined with wide tyres (which would be counter-intuitive, since a wide tyre increases drag appreciably), a high-profile rim somewhat limits the choice in rim width. On the other hand, there are no restrictions in terms of choosing materials. No matter if you’re using products off the MTB, road or gravel rack, in principle you can put together every desired characteristic with aluminium as well as with carbon rims, even if not always in combination. Carbon rims allow for lighter wheels with the same degree of stiffness, or are generally stiffer than wheels with aluminium rims for the same weight. Aluminium is less expensive and more forgiving of minor damages such as dents.

Front and rear hubs: standards and dimensions

Gravel bikes are available – depending on the basic demands, see above – with different dimensions for hub widths and axle diameters. However, classic nine-millimetre quick-release axles in hubs with 100 or 135 millimetres over locknut dimension have become rare. Stiffer thru-axles with mostly twelve millimetre diameters in 100 or 142 mm hubs dominate the market. Off-road gravel bikes sometimes use Boost components with over locknut dimensions of 110 or 148 mm and axle diameters of 15 or 12 millimetres. Brand new to the market are Road Boost components, which combine higher Boost over locknut dimensions (110/148) with a smaller twelve-millimetre thru-axle diameter. The dimensions of your wheel are of course basically determined by your frame or fork. Most "non-Boost" components are compatible with each other via interchangeable sleeves. An adaptation between "Boost" and "Non-Boost" is not so easy due to different hub flanges or brake disc positions. However, special adapters such as the Better Boost Adapter from MRP can also help in this case – at least with common hubs.

Off on an adventure – or to the office!

Gravel bikes, as mentioned, are excellent long-distance or adventure bikes. Whether it's long laps across a variety of surfaces in the unknown back country or epic bikepacking adventures, having lights is a must here, as is a high degree of stability and easy reparability. The former can be provided by a modern hub dynamo, which, in conjunction with a charger such as the Plug5 Pure from cinq or the E-Werk from Busch & Müller, can also charge other devices such as a GPS or smartphone. The latter can be achieved primarily by using components that are as sturdy and widely-available as possible. Since adventure bikers often bear heavy loads, there is a lot to be said for 32 classic round spokes in combination with a well-sealed rear hub and robust alloy rims. Spare parts for these items are available almost everywhere worldwide. Everyday cyclists who enjoy the sportiness of a gravel bike during the week and who use it for training or touring on weekends appreciate the same advantages. Remember: you should not underestimate the value in everyday use in terms of material wear. During winter in particular, road salt and dirt can take a significant toll on the hubs.

How can I build my wheels?

Are you now inspired to build your own gravel wheelset? Find more background in our guide, "The basics of custom wheel building".