How Much Does Tire Pressure Increase in the Sun?

• Posted on 15 July 2025
• By Antonio Gonzalez
• Posted in bicycle tech
• 0

Exposed pavement can easily reach temperatures of 130 ° or higher on a sunny day. If you have your bike tires near maximum pressure, there is a risk they can burst due to the increase in internal gas temperature.

How Much Does Tire Pressure Increase in the Sun?

We field a lot of questions about tire pressure here at Tri Town. One of the most common is: What pressure should I run in my tubeless tires? While that depends on many factors, the Silca Tire Pressure Calculator is a great tool for dialing in a starting point.

Another frequent topic is how much tire pressure increases when a bike is left in the sun. I’ve heard plenty of theories over the years — some reasonable, others less so — so I decided to test this myself.

The Test

I set several tires on our exposed pavement on a hot summer day and used the highly accurate Silca Truth Gauge to measure pressure changes. The tires were left on the pavement for 2 hours, and I took pressure readings approximately every 30 minutes. Pavement temperatures ranged between 115°F and 125°F, depending on cloud cover.

Here are the results:

Findings

The results showed a consistent ~10% pressure increase for a 40°F rise in temperature. This was surprisingly uniform across different tire types and widths, and as it turns out entirely consistent with the Ideal Gas Law (which I had to look up!), which predicts that tire pressure increases by about 2% for every 10°F rise in internal air temperature (assuming volume and gas quantity stay constant).

What About Blow-Off Risk?

This led me to research the engineering safety margins built into modern bicycle tires. While most companies don’t publish exact blow-off data, industry guidance suggests that tires are typically tested to withstand at least 20% above their stated maximum pressure.

So, if a tire’s max pressure is listed as 100 psi, it’s generally expected to hold at least 120 psi before failure. In practice, most riders should be running well below max pressure anyway, especially on rough chip-seal roads, where lower pressures improve comfort and reduce rolling resistance.

A Practical Example

Let’s say your tire has a max pressure of 80 psi, and your optimal race-day pressure is 70 psi. If the bike sits in transition on a hot day and the tire heats from 70°F to 130°F, the pressure could rise to around 79 psi — still within the safe range and under the tire’s max rating. No need to panic.

That said, if you’re the type who runs tires right at the maximum, a 10% reduction before racking your bike in transition is a wise precaution. Just as important: bring a reliable pump and pressure gauge on race morning to fine-tune before the start. Flat repair gear is always a good idea, too.

About the Author:

Antonio Gonzalez is the owner of Tri Town Bicycles in Boise, Idaho. He is an endurance coach, bicycle fitter, and veteran of the cycling and triathlon industry for over 20 years.