Bikelab.cc is finally fully operational. After some significant changes required to do measurements with the bike itself (without the rider), I am ready to start measuring the impact of different things on the overall riding comfort. The first thing is the impact of air pressure. If you were wondering how big is the impact of this parameter on the overall comfort, wonder no more. Just see the results!
Let’s start with the obvious (should be obvious) fact that the easiest, yet one of the most beneficial thing in terms of improving riding comfort is lowering the tire air pressure. I have said this many times that you should always start with experimenting with air pressure before buying, usually quite expensive, comfort improving parts like suspension seatpost or suspension stems. I know that from my testing but I was never sure exactly what kind of level of comfort improvement you can expect just by lowering the air pressure. Thanks to my bikelab we can, once and for all see the exact numbers and then, base on that, just lower our tire air pressure a bit to get more comfortable on our bikes.
The testing scenario: bike with load simulating a rider approximately 75 KG in weight. WTB Byway 700x44c tire (just shy of 42 mm on Spinergy GX wheel and rim) set up tubeless to exclude inner tube’s vibrations affecting the end result. Vibrations were recorded at the handlebar level with a rigid aluminum stem (110 mm).
The first chart shows you the overall impact of air pressure on riding comfort. I have tested this with two speeds, 5 and 10 miles per hour. Please bear in mind that due to the fact that on my treadmill there are a lot of small and big obstacles (ranging from 5 mm to 18 mm in height) I have found that the 5 miles per hour ride on my treadmill equals a 10 to 15 miles ride on bumpy terrain (the more bumps the lower speed). 10 miles per hour ride equals a very fast ride on bumpy roads. So what does this mean?
First, you can definitely see that the higher the speed, the more negative impact on the overall comfort higher air pressure has. At lower speeds, 50 PSI seems to be a threshold above which the overall comfort is not changing that much. But when you are riding really fast, there are always the negative effects of pumping the tire more and more. But what about the exact numbers? Here they are!
At 5 miles per hour, we can see a steady increase in the level of vibrations when we pump the tire by 5 PSI. The biggest increase is between 25 PSI and 30 PSI (where you can even subjectively feel the real difference but not everybody likes to ride a bike with so low air pressure). What is more important is the fact that lowering air pressure from 50 PSI to 30 PSI results in 34,4% fewer vibrations. This is HUGE and believe me (or not, because there are a lot more tests coming showing you the effectiveness of different suspension solutions) you will have a really hard time gaining this kind of comfort by buying expensive suspension stems etc. But how about riding at really high speeds? What then?
With highs speeds the biggest negative effect on overall riding comfort has pumped up the tire from 35 to 40 PSI. Above that level, we can see that every 5 PSI more is lowering the comfort at a lower margin. Yet, even above 50 PSI, there is still a significant negative effect of getting even higher air pressure. Interestingly, going down from 50 to 30 PSI resulted in very similar comfort improvement as with 5 miles per hour test (42% to be exact). Again, this is a HUGE difference and I really encourage you to feel it by yourself. You just have to pump the tire to 50 PSI and then 30 PSI…
So there you have it! Tire air pressure is the most important thing in terms of overall riding comfort and also the easiest one to experiment with so I really encourage you all to go out and try to find your sweet spot regarding traction and overall riding comfort. For me, the sweet spot is around 30 PSI at the front and 35 PSI at the back. And for you?