Gravel Bike Fit: Maximising Comfort and Performance for Thunderbolts and Beyond

Images: Ready Aim Media

Written by Nicole Oh, Physio & Bike Fitter at the Body Mechanic, Sydney

So, you’ve entered Thunderbolts, got your gravel rig ready, and are now wondering if you should get a bike fit to get the most enjoyment out of the event?

Certainly, if you are experiencing pain, discomfort, or injury, it is a good idea to check that your bike isn’t contributing to your issues. And if you’ve never had a bike fit on any bike before, it can go a long way to maximising your efficiency and performance.

Many people will base their gravel set up on their road bike fit, as the sizing and fit on a gravel bike is quite similar to that of a road bike, but with some key differences. In fact, many people will use an endurance geometry road bike with wide tyre clearance for their gravel adventures, particularly if the roads are more champagne than spumante / single trail.

So, what are the main differences between a gravel and a road bike?

Gravel bikes are designed for a combination of on-road and off-road riding, unlike Cyclocross and Mountain bikes which are essentially used off-road. Their versatility means they are suited for mixed terrain, long-distance rides and multi-day bike-packing. They are aimed at maximising comfort, handling, and stability, whereas road bikes are more about performance and speed.

In terms of geometry, gravel bikes will have a longer wheelbase and slacker head tube angle, moving the front wheel further out from the bottom bracket, which makes the bike more stable over technical and less predictable terrain. The slack head tube angle helps the gravel bike handle better at lower speeds.

Gravel bikes will also have a more relaxed geometry, with a higher stack and shorter reach, which places the rider in a more upright position, which is generally less demanding on the body and improves handling.

Gravel bikes have wider tyre clearance compared to road bikes. This allows for the use of wider tyres, anywhere from 30-50mm, with a variety of tread patterns suitable for varied terrain. Wider tyres can be ridden at lower pressures, providing more traction and comfort.

Drop handlebars are still the norm for gravel bikes, although they tend to be wider and are often flared, which provide more control and stability on rough terrain.

Keeping these differences in mind, there are a few things to consider in terms of fit between a road and gravel bike. As with a road bike fit, a gravel bike fit needs to be individualised to your particular characteristics and limitations. Two people can have completely different gravel bike positions depending on their needs.

The choice of saddle for a gravel bike may be different, one that is suitable for a more upright position. The more upright we sit, the less our pelvis rotates forward, meaning the pelvic contact area with the saddle will be wider. Some people may also opt for a slightly more cushioned saddle to help improve comfort on rough terrain.

The position on the saddle may also vary, with some riders preferring a lower and slightly more rearward saddle position (which will maintain a similar range of knee motion). This will be slightly more stable but also make it easier to put your foot on the ground should it be needed for bailing out!

The Q-factor for some gravel group sets is wider, for example both a GRX and SRAM “wide” crank are 5mm wider (2.5mm each side) than their standard road cranks. This will mean that your cleat position may need to be adjusted to ensure you are riding with the appropriate stance width and alignment and help to prevent knee and foot pain. For those who need a particularly narrow stance width, narrower can be achieved by moving the cleats all the way to the outside of the shoe. Shimano make an XTR pedal that has a spindle length of -3mm (compared to standard).

Whilst wider handlebars provide more stability, you need to ensure the bars are not too wide for your riding position. Handlebars that are too wide may cause the rider to bend the wrists back (hyperextend) to try to achieve a narrower shoulder position, which places tension on the ulnar nerve. Ulnar nerve palsy is a common cycling injury for long distance and multi-day events.

Handlebars that are too wide can also cause over-reaching, which can also result in neck pain. The shorter reach geometry of a gravel bike in combination with a tendency to ride a shorter stem should hopefully compensate for wider bars.

In summary, both road and gravel bikes can be adjusted for proper fit based on the three contact points. However, the specific adjustments may vary slightly based on the bike's intended use and the rider's preferences.

If you are interested in having a fit on your gravel bike, The Body Mechanic in Milsons Point is offering Thunderbolts entrants $60 off an Initial Bike fit. Details can be found here.