Edit: 10/26/15 – I’ve removed the link to the google Doc. The locked fields didn’t work, and people have defaced it pretty severely. Download this XLS file for your own use: Tire Pressure – salvaged doc
You can use the tire pressure Excel file to calculate pressures for different kinds of bikes. Put in your weight and tire width, and it gives you the optimal pressure for Road, Cross, Mountain Bikes, Low-trail randonneur bikes, Fat Bikes and Triathlon bikes.
Download the Bicycle Tire Pressure Calculator spreadsheet
You can fudge the numbers based on your experience, tire casing, riding style, and road surface. More info about the pressure calculator.
There is also an Android app available. You can save your bikes and easily access them later. You can even do custom calculations for cargo bikes, which the doc doesn’t do yet.
From Dave Adams, bsed on research by Frank Berto, as published in Bicycle Quarterly.
Thank you – I appreciate your making this available. Works very well for me.
My pleasure, Robert! We’re upgrading the Android app shortly, and have a design on paper for v 2.0 later this year.
What this doesn’t tell you is how to determine the actual pressure only the theoretical pressure.
Example:
My bike and I weight 210 lbs together – the app says my 23c tiers should be 130Rear/84 Front
My tires maximum PSI rating is 90 psi
Does this mean I need to find a tire that can handle 130 psi to use for my front tire?
You could get fatter tires.
Just run it at 90 psi, or get a different tire, or lose weight.
What is your cardsapp brand number?
I don’t understand. I did fix some busted links to the pressure app, though.
Thanks for the spreadsheet!
Question… A 23c tire could very well measure 22 on a narrow internal width rim or 24 on a wide internal width rim. Does this change actually affect the proper inflation pressure for a particular tire? Its seems like its still the same amount of rubber and therefore the same volume, just distributed “taller” on the narrow rim and “wider” on the wide rim. Therefore one would use the same pressures for both rims. But that doesn’t seem correct somehow. Thanks.
I think you could get a little more volume on a tire with a wide rim. I’d use the measured width, not the supposed width, but either will get you in the ball park.
All I saw was the inputs to 4 unknown bike styles and Low Trail. Will this spreadsheet ever show all the bikes you mentioned at the beginning of your blog?
Hi Steve,
No, probably not. Google Sheets couldn’t keep the protected cells protected, and the human visitors just made a giant mess of everything.
If you want to do Triathlon bikes, just use “Low Trail” and switch front and rear tire values.
Philip
Thank you for the xls, I’ve been looking for something like this.
Are you the app’s author/will you see revenue if I buy?
Many thanks, again.
Turtles, Man…
Excellent – enjoy the XLS!
I worked on the app, but my royalties have expired. If you have an Android phone, you should try it out.
Philip
I weighed my front and back wheel with me on the bike and a book under the other wheel.
It was 121 rear and 60 front lbs.
That is 33.2/67.3% ratio.
I love this spreadsheet, but concerned that it doesn’t factor in the front/rear weight distribution. How would my distribution effect the optimal results?
That’s a pretty big difference. Very upright bike? The old Google Docs had a couple settings for normal and low trail bikes with different front/rear weight distributions, but none as extreme as that.
I usually just run the front 5 lbs lower than the back. There’s less weight on the front, until you start braking.
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Didn’t work for 35mm Schwalbe road tires. With a load of 230lbs It gave a suggestion of just under 4,5 bars and the 4,5 bnars is the minimum pressure for the tire. Swhwalbes own chart suggests pressure of 5,7 bars…
I don’t know that that “didn’t work.” It sounds like you can run at the minimum pressure, and get that 15% drop.
If Schwalbe recommends a different pressure, try them both and see which one is faster or more comfortable for you.
Personally, I run my front tire about 10% lower than the back tire pressure, instead of the big difference the spreadsheet recommends.