Finding Your Ideal Tire Pressure

[cantunamunch]

That would be cool. Are you thinking that it would measure some aspect of vertical travel on a higher psi tire? It would be interesting if that respective app gave a graph of each run. I could where a section that might be a bit sandy would have a totally different read that one with fist sized rocks.

It's a bit phone and orientation dependent, but yes. On my phone it does pretty well up to 100Hz.

 

[cantunamunch]

More for @Ron to catch up with:

https://www.bicyclerollingresistance.com/specials/grand-prix-5000-comparison

 

[Ross Biff]

No... actually the testing protocol boiled down the below. However you are probably more familiar with the article than I am.

"How do we make this information actionable? With a roll-out test. At the most basic level, you will need a stopwatch, a digital pressure gauge, and some tape, cones, or a stick in the ground to mark the start/finish of your course.

Look for a gradual downhill run over several hundred meters of terrain that’s consistent with the terrain you typically ride. In my case, I ride long loops that involve Forest Service roads and singletrack. My test run is a slight downhill of gravel road leading to singletrack. Its total length is about 500 meters.

First, inflate your tires to a few psi over the manufacturer’s maximum recommended tire pressure. Mark your course. Ride your bike a bit to get the tires warmed up before your first run. Then bleed the tire pressure down to the manufacturer’s maximum recommended tire pressure with your gauge’s bleed feature. Take a run, record your time, and record the tire pressure you started with.

Second, repeat while lowering psi. From this point forward, your goal will be to take identical runs. Focus on laying your tracks down on top of your last run so that your line is the same, and maintain an identical body position. Wind will have an influence on results, so a light-wind day is ideal.

As per Vorm Walde, Specialized bleeds down in 0.2 bar (approximately 3 psi) increments for 2.1- and 2.3-inch tires.

Record your times for each run while gradually lowering tire pressure. Note that in your first few runs, especially if you are lighter weight, you will likely not see any time differences. Keep doing what you’re doing — you’ll hit a tipping point where your tires don’t bounce you and your bike, instead becoming more compliant and forming to the ground.

At that point, your times will drop. Continue making runs until a pattern has formed and your lowest time has been established. Congrats, you’ve found your sweet spot!"

I'm sure that few psi difference is fairly controllable compared to the line you could duplicate repeatedly. Riding the same line repeatedly would also change the compaction and condition of the dirt( assuming we are not talking about a sealed surface). Having said that, I'm sure there would be a point when it just unscientifically " felt better". I had a pinch flat during a dh race and there was about a 1 second window were the traction felt awesome as the tyre deflated....hard to reproduce and find that ideal as EVERYTHING constantly changes. Bottom line-- if it feels good, do it!

 

[martyg]

I'm sure that few psi difference is fairly controllable compared to the line you could duplicate repeatedly. Riding the same line repeatedly would also change the compaction and condition of the dirt( assuming we are not talking about a sealed surface). Having said that, I'm sure there would be a point when it just unscientifically " felt better". I had a pinch flat during a dh race and there was about a 1 second window were the traction felt awesome as the tyre deflated....hard to reproduce and find that ideal as EVERYTHING constantly changes. Bottom line-- if it feels good, do it!

The problem with relying on it just feeling better is that there is huge subjectivity to it, and it often conttidicts the objective metrics of what is most efficient. It is not the way that factory teams competing in UCI events operate.