bruce19

I've been experimenting with my 25 mm Mavic USTs. I weigh 185 lbs and have been running 80 psi (rear) and 70 psi (front). Just wondering what others are doing and if there's some "scientific" way of finding your optimal psi. Talking about road bike for recreational rides.

Iride01 

Science involves experimentation. So experiment and see what works best for you. Noting your perceived effort for rides you do and what tire pressures you used is one simple scientific way to go.

Just keep the same tire pressure for six rides and record how you felt both energy wise and comfort wise. Then change the tire pressure and do six more, and repeat till you have an answer tailored to you.

WhyFi

Sure, there's a scientific way of finding it, but very few of us (with the exception of guys like RChung) are equipped to do so and it's going to change depending upon the conditions. There are various calculators online now, like the new one from Zipp (https://axs.sram.com/tirepressureguide), but those just get you in the right area, it's still up to you to tweak based on conditions and preferences.

If you really want more info, there's a good Cycling Tips Podcast about tire width and pressure (https://cyclingtips.com/2016/08/cycl...and-pressures/) from a few years back. It's about an hour, though, so those with ADHD need not apply.

bruce19

This is what I've been doing. The Zipp chart suggests 65psi (rear) and 55 psi (front). That's a big difference from where I am now but I'm going to try it.

sfrider 

That actually gets very close for me and my actual empirical preferences. It suggests 73/78 when I ride 70/75 for comfort and 75/80 for performance with 25mm tires on a hooked TL 21 inner width. Looks pretty good for 28mm as well.

I can see taking their suggestion, rounding it up to the next 5 or 10, and then let some air out on the first ride until it feels right.

bruce19

Oops. I rechecked and there was an error in one of the values used. It's a lot closer to what I'm currently using.

Iride01 

Don't be so caught up in charts and formulas that you don't try higher or lower pressures yourself. They don't know what your riding conditions are like. Nor do that know exactly what you consider comfort.

bruce19

As I have said, that's exactly what I have been doing. I just thought there might be other ways to calculate an approximate value.

Sy Reene

Yeah, the best way to calculate it is to use a calculator. YMMV. I like the Silca Pro version.. link below. For access, you have to register by giving an email address.. nbd

SILCA TIRE PRESSURE CALCULATOR

bbbean 

Best advice I've heard is to pick a level, ride. Drop pressure 5 lbs, ride some more. Repeat until tires get "too" squishy and corners get iffy. Increase pressure another 5 lbs and you're good to go.

Ultimately, though, if its just for pleasure (i.e., you aren't trying to squeeze every single watt out of your bike), then ride what's comfortable! No need for more qualification than that.

thecycleclinic

60 psi works for.me. experiment and see what you like. Anything more than 80.psi is really too high though.

JohnJ80

I've found Silca's tire pressure calculator to work extremely well for me. Takes into account road surface, rider weight, bike geometry etc...

Goes without saying though, you need to make sure your pump gauge is accurate. Most aren't in my experience.

https://info.silca.cc/silca-professi...ure-calculator

noodle soup

The SRAM link works well

bruce19

Very good point. My recent experiments tell me that 80-85 psi (rear) and 70 psi (front) works nicely for me.

JohnJ80

Fascinating and entertaining story here about designing Zipp carbon wheels for Roubaix which ultimately had a big impact on racing. There is an anecdote here that they kept blowing up wheels and couldn't get it right. Traced it down to the variance in pressure as read out on the pump gauges. Getting inflation right within a fairly narrow range (less than 5psi) makes a big difference especially tubeless and on wider tires.

https://blog.silca.cc/road-to-roubai...lete-story-1-0

FWIW, I have a ridiculous number of pumps (don't ask) and when I checked them against each other, there was nothing resembling consistency although most pumps generally seem to be repeatable even if their gauge is wildly off. What that means, of course, is if you take your favorite setting and borrow a friend's pump at the start of the ride, there is no guarantee that you're even close to the pressure you read off your pump.

J.