ANATOMY OF AN ADVENTURE BIKE
Despite surface similarities to road machines, gravel bikes have lots of subtle differences
1. WHEELS
Most gravel bikes can accept 700c wheels or a smaller 650b wheel size borrowed from mountain biking. Its advantage is that you can fit a bigger tyre into the frame for better comfort and grip, but at the expense of speed.
2. HEAD TUBE ANGLE
Gravel bikes tend to have more relaxed head angles than racy road bikes, and more fork ‘rake’ too, which increases ‘trail’. Trail is the distance between the steering axis and tyre contact patch. More trail slows the steering, making for greater stability over uneven terrain.
3. WHEELBASE
Gravel bike geometry means increased wheelbase (horizontal distance between the axles). This is to accommodate bigger tyres in the frame and also contributes to more stable handling.
4. FIX TURES AND FIT TINGS
Fork legs usually have triple bosses – these are for the latest ‘anything’ style cages, which can carry kit from water carriers to tents. Top tubes can have triathlon style bento-box mounts for a carry bag mounted just behind the stem. Mudguard mounts are standard and triple bottle-cage bosses on the down tube are also common.
5. DRIVETRAIN
Gravel bikes are all about gearing choice. Some favour mountain bike style 1x setups where you have a fairly small single chainring, usually 40 or 42-teeth, matched to a very wide-range cassette like an 11-42, which gives a low gear at a 1:1 ratio. For 2x systems many gravel bikes use a compact 50/34 chainset with an 11-34 cassette. New ‘adventure’ drivetrains pair a smaller 46/30 chainset with a wide 11-34 cassette.
6. REAR MECH
If you’re serious about going off-road then a clutch-equipped rear mech is essential. The ‘clutch’ retains the tension in the derailleur at all times, which keeps the chain tight and stops it bouncing off the chainring. Shimano have a family of clutch mechs in the GRX range and a special version of Ultegra, the RX. All SRAM’s 1x groups come with a clutch mech.
7. HANDLEBAR
Gravel-specific drop bars are designed with a ‘flare’ to the drop – the hook and lower portion of the bar are angled outwards and sit proud of the tops. This gives greater wrist clearance, which enables you to shift your bodyweight around more – exactly what you want when navigating steep off-road slopes, loose surfaces or off-camber tracks. The wider flare also gives you more leverage to boost your climbing prowess.