Mixed surface - tire pressure?

My last race for the year is a mixed surface circuit on an 8 mile loop than it 60% paved, 20% hard pack dirt, and 20% loose, chunky gravel. In years past, I’ve been able to take advantage of my road fitness to stay in the lead pack on the paved and hard pack sections, but I consistently gap the leaders in the deep/lose gravel section. This isn’t a big problem for the first lap or two - I can bridge the gap without too much trouble, but by the 3rd or 4th lap, the extra effort takes its predictable toll, and I find myself in a solo chase looking for other stragglers to work with.
I have updated my setup and added a 40mm file tread tubeless front tire (CX frame only accepts a 35 on the rear), in hopes of improving my gravel performance enough to stay with the front pack and contest for the win.
I’m not sure how to approach air pressure. If I run the 40s at 50psi, they handle ok on pavement, but they still get a little squirrely in gravel. If I knock them down to 30-35, they handle much better in gravel, but they create a lot of extra work on the road.

1 Like


50 psi for a 40mm tire seems like a lot….FWIW, I run my tubed 35’s around 50psi on the road and light gravel. I’m ~70kg / 155.

For me, I would gladly run mid-30’s on the road for a tubeless 40….but I also run that tire at ~25psi for gravel.

1 Like

I use the SRAM Tire Pressure Calculator. I find it simpler than the Silca one and the numbers are very close.


That doesn’t help me with balancing the pavement and the gravel.

I would find the recommended tire pressures for your setup (tire width, inner rim width, etc) and run the calculator for both gravel and road, then split the difference.