CRR at Different Temperatures: Examining Temperature Dependence of Rolling Resistance
Contents
- Introduction
- Test Set up and Conditions
- Average Test Results
- Individual Test Results (Pro Members)
- Conclusion
- Comments
We've been using our standard test protocol for all tire tests that you can find on this website since we started testing tires in 2014. Sticking to the same protocol for all tires, regardless of their category, has given us unique data of over 240 tires that can be compared relatively easily.
We've always stuck with a controlled ambient air temperature of 22 °C - 71.6 °F for the rolling resistance tests. We feel that temperature is a good compromise of the temperatures experienced during a cycling season in most parts of the world. Another advantage that should not be forgotten is that this temperature can be sustained easily in our test lab year-round.
Of course, there will be many situations with higher or lower temperatures. The test results presented in this article should give a rough indication of what to expect when the temperature changes.
The temperature tests are the last part of our trilogy of articles that goes into how CRR is affected under changing conditions. Next to the temperature tests, you can also find our speed and load tests below:
This test was requested, supported, and voted for by our Pro Members. We've done temperature tests at tire surface temperatures (see below) of 20 °C - 68 °F, 30 °C - 86 °F, and 40 °C - 104 °F with 6 tires: Vittoria Corsa Speed G+ 2.0 TLR, Continental Grand Prix 5000 S TR, Michelin Power Road TLR, Vittoria Corsa G+ 2.0, Schwalbe Pro One V-Guard, and the Continental Grand Prix Urban. We've averaged the data from those 6 tires and made that available for free for anyone.
Pro Members can open the individual tire data and dig into the results further. We found consistent results among all tires, but we found 1 tire that was much more sensitive to temperature changes than the other 5 tires.
Test Set up and Conditions
We've performed all tests on the same day to get the data as accurate as possible. The load and speed during all tests were our standard load and speed of 42.5 kg - 94 lbs and 8 m/s - 28.8 km/h - 18 mph.
To stay in line with our other CRR articles, we mainly provide the CRR numbers here. As the temperature is not a part of the CRR formula, we also provide the rolling resistance in watts as that's what we usually provide in our other tests.
We tested at tire surface temperatures of 20 °C - 68 °F, 30 °C - 86 °F, and 40 °C - 104 °F. Please note that the tire surface temperature can not be directly compared to our regular test ambient temperature of 22 °C - 71.6 °F. Our regular test ambient temperature usually results in a tire surface temperature of somewhere between 24 °C - 75.2 °F and 26 °C - 78.8 °F depending on the self-heating of the tire (rolling resistance loss).
We're using the tire surface temperatures here as we cannot change the ambient temperature to such a large degree in our test lab. We used a heat gun to heat the tires while recording the tire surface temperature with an infrared thermometer.
We tested only a single air pressure to make the data understandable and easily digestible. We chose 90 psi - 6.2 bars for the 25-622 tires and 60 psi - 4.1 bars for the 35-622 tire.
To stay consistent with our other CRR articles, we used the same selection of tires that we also used for the speed and load tests:
- Vittoria Corsa Speed G+ 2.0 25-622
- Continental Grand Prix 5000 S TR 25-622
- Michelin Power Road TLR 25-622
- Vittoria Corsa G+ 2.0 25-622
- Schwalbe Pro One V-Guard 25-622
- Continental Grand Prix Urban 35-622
Test Conditions
- Total wheel load of 42.5 kg / 94 lbs
- 700 x 18 mm wheel
- Diamond plate drum surface
- 77 cm drum diameter
- Excludes aerodynamic and bearing drag
- Air pressure of 90 psi for 25-622 tires
- Air pressure of 60 psi for 35-622 tires
Test Results - Average Results of 6 Tires
| Tire Surface Temperature | Average CRR | Average Watts | % Decrease (over previous) |
|---|---|---|---|
| 20 °C - 68 °F | 0.00398 | 13.3 | |
| 30 °C - 86 °F | 0.00357 | 11.9 | 10.5% (10.5%) |
| 40 °C - 104 °F | 0.00328 | 10.9 | 17.6% (8.1%) |
| Average CRR of 6 tires at different temperatures | |||
The averaged results of the 6 tires we tested clearly show that rolling resistance goes down at higher temperatures. For general purpose calculations of what to expect at different temperatures, the averaged results will give a good indication of the expected rolling resistance.
When looking at the individual tests, all tires follow the same pattern of lower rolling resistance at higher temperatures. We did find 1 tire that seems much more sensitive to temperature changes than the other 5 tires.
The best performing (or worst if you care about lower temperature performance) tire saw a total reduction of 27.1%. In contrast, the worst (again, or best if you care about lower temperature performance) saw a total reduction of just 11.4%.
Test Results - Individual Rolling Resistance Data (Pro Members)
The next section is only accessible by our highly valued Pro Members. This section includes all test data of the individual tires used for the temperature tests.
Conclusion
Our test results clearly show that rolling resistance decreases at higher temperatures. On average, rolling resistance decreases by 17.6% when the tire surface temperature is increased from 20 °C - 68 °F up to 40 °C - 104 °F.
All 6 tires we tested show a decrease in rolling resistance at higher temperatures, but some tires seem to be more sensitive than others. The least sensitive tire rolls 11.4% faster at 40 °C - 104 °F, while the most sensitive tire rolls 27.1% faster at 40 °C - 104 °F.
With the limited number of tires we tested, and only 1 tire showing a substantially higher temperature sensitivity, it's hard to conclude why some tires might be more sensitive than others.
When looking at our standard test protocol where the ambient air temperature is set at 22 °C - 71.6 °F, which results in a tire surface temperature of roughly 25 °C - 77 °F, the possible differences among the tires will be limited as we expect the tire surface temperatures to be somewhere between 10 °C - 50 °F and 40 °C - 104 °F for 90-95% of the tire mileage.