There is a lot going on recently in the gravel bikes market in terms of comfort. Bikes like new Cannondale Topstone Carbon with KingPin rear suspension or BMC URS with soft-tail suspension capabilities are advertised as a revolution in riding comfort. And I am very much into finding out if this is true but for now all of my previous tests of suspension seatpost (Ergon CF3 Pro Carbon and suspension stem – Redshift shockstop) makes me think that all of this wonderful engineering can translate to rather modest improvements when we take into consideration of how much we can gain by simply putting less air into our tires.
If you don’t believe in this statement just try to lower the air pressure by half and feel the difference for yourself. Or even better, just look and the charts below where I compared the results riding with 40psi and 20 psi air pressure. Both with and without additional comfort improving solutions like flexing seatpost and suspension stem. Spoiler alert: there is no bigger contribution to the overall bike comfort that lowering its tire pressure.
Let’s start with the bike equipped with both suspension stem and a suspension seatpost. You might think that this kind of combination leaves nothing to the tires itself yet lowering the pressure from 40 psi to 20 psi brings a whopping 35,4% improvement at the front and not too shabby 17,8% at the back. When we ride on fast gravel the numbers are very similar (a bike with lower tire pressure will be over 34% more comfortable in terms of the front of the bike and 13,9% in terms of the back of the bike).
If you are familiar with Cervelo’s chart (https://www.cervelo.com/en/ride-quality) describing different bike parts’ impact on overall ride comfort those results will not be surprising to you. Tires are the biggest contributor to the bike overall comfort. Both front and rear.
Without suspension stem (with standard rigid FSA stem) lowering the pressure from 40 psi to 20 psi improves the front end comfort by 32,5% on a fast gravel road and 28,9% in the woods (which is comparable to what a shockstop flexing stem gives you in terms of improved comfort).
Without suspension seatpost (using FSA K-Force no setback carbon seatpost) lowering the tire pressure from 40 psi to 20 psi gives you between 17,5% (forest) and 10,5% (gravel) improvement. Yet again more than Ergon CF3 Pro Carbon usually offers.
These numbers clearly show that your first step towards better ride comfort of your gravel bike should be buying a bigger tire and lowering its air pressure. That is why I am really excited about this new trend among bike manufactures to allow gravel bikes using 700x50c tires (new Ronto Ruut is one example).
But my tests also show that you should not stop there and use another comfort inducing bike parts like suspension stem and suspension seatpost. Along with comfortable saddle, comfortable shorts and gloves. Because only when they all work together you can really enjoy the most comfortable ride possible.
UPDATE: To conduct this test I used a 40 psi and 20 psi air pressure but I know that 20 psi is very low so to explore the topic I did also a test at 30 psi (using both Shockstop stem and Ergon CF3 Pro seatpost).
Below you will find the results. They are not as big as comparing 20 psi to 40 psi but still you will achive a far more comfortable ride just by lowering air pressure by 10 psi from 40 to 30.
SIDE NOTE: please bear in mind that all of those results were achieved on my bike with a very narrow inner rim and using inner tubes so treat them more as a guideline and inspiration rather than a final and decisive conclusion.