Rolling Resistance Testing
Smithers laboratories are ISO 17025 accredited and can perform a variety of tire rolling resistance tests on a range of different tire types and at varying temperatures including evaluations in accordance with UNECE R117.
What Fleet Rolling Resistance Testing Says About Fuel Costs
Rolling resistance is the energy a tire loses to heat as it flexes and recovers with every rotation. That lost energy must be made up by the engine, and it shows up directly as fuel burned.
For fleet managers looking for a fuel-saving lever that doesn't depend on driver behavior or route planning, tire rolling resistance testing offers something rare: a fixed, lab-verified number that translates directly into potential cost savings.
Why Rolling Resistance Matters to a Fleet's Bottom Line
A moving vehicle must overcome three main forces: aerodynamic drag, driveline losses, and rolling resistance. Drag is fixed by vehicle shape and driveline losses are fixed by the powertrain. But of the three, rolling resistance is one of the few a fleet manager can directly influence through tire selection and retread choice.This makes rolling resistance more stable than most other fuel-saving initiatives. It's a fixed, measurable property of the tire itself, so it doesn't degrade with driver behavior the way idling time or hard braking can. A fleet manager who optimizes tire and retread selection for rolling resistance is making a decision that holds regardless of who's behind the wheel.
Two variables are within a fleet's control here: which tires and retreads are purchased, and how they're positioned across axle positions. Everything that follows is about making those two decisions with data.
What Rolling Resistance Testing Actually Measures
Rolling resistance coefficient (RRC) is the force required to keep a loaded, rotating tire moving at a constant speed, normalized per unit of load. It's the standard metric labs use to quantify how much energy a given tire wastes as heat.
The detail that matters most for a fleet manager is that not all RRC numbers are measured the same way, so a number is only useful once you know which standard produced it.
Two test methods show up most often on tire spec sheets and lab reports:
- ISO 28580 (single-point, steady-state)
- SAE J2452 (coast-down)
SAE J2452 is a dynamic test that measures rolling resistance as the tire decelerates, similar to a vehicle coasting. It's generally used for vehicle simulation and fuel economy modeling..
Keep in mind that a SAE J2452 number and an ISO 28580 number for the same tire won't match, because they're measuring different things under different conditions. When comparing tires across suppliers, make sure the numbers come from the same standard.
Two related multi-point methods, SAE J1269 and ISO 18164, also appear on some spec sheets. They're worth recognizing if you see them referenced, though the ISO 28580 vs. J2452 distinction above covers what most fleet purchasing decisions hinge on.
For a deeper, engineer-level breakdown of these two standards, see Smithers' Navigating Rolling Resistance: SAE J2452 vs. ISO 28580.
How Rolling Resistance Testing Compares to On-Vehicle Testing
Lab-based rolling resistance testing is simpler than on-vehicle fuel consumption testing because it controls the variables that make in-fleet testing expensive and slower.
On-vehicle testing requires controlled trials across real trucks, real routes, and real drivers. Then you must statistically isolate the tire's contribution from everything else affecting fuel consumption. It can be vulnerable to weather, traffic, driver variation, and load changes, which means results can be difficult to trust and expensive to obtain.
Laboratory RRC testing removes those variables by design. Speed, load, inflation, and temperature are all controlled, so the result reflects the tire itself, not the conditions of a specific test week. That also makes the data reusable. One dataset can inform purchasing decisions across every truck running that tire size and duty cycle, where an on-vehicle test only tells a fleet what happened on the specific trucks and routes tested.
Bottom line: third-party lab testing eliminates the need for fleets to run their own complicated, expensive in-fleet trials, while still producing data that's directly applicable to purchasing and maintenance decisions.
What makes a rolling resistance number trustworthy
A rolling resistance number is only useful if it does the following for the fleet manager:
- The number is comparable: A single RRC value, generated under a controlled, repeatable standard. It lets a fleet stack Tire A against Tire B, or a new casing against a specific retread, on equal footing.
- The number isolates the tire variable: Fuel economy on the road reflects driver behavior, idle time, load, route, and weather, in addition to tire choice. RRC strips those confounding variables out, so a fuel-efficiency difference can be attributed specifically to the tire or retread combination.
Also, ISO 17025 accredited laboratories are audited to ensure that processes, procedures, and documentation follow internationally recognized standards. What makes laboratory rolling resistance testing so repeatable and consistent is the fact that these standards and test conditions are tightly controlled so a true side-by-side comparison can be made across multiple tires.
Another potential consideration is that standard testing runs at a fixed ambient reference near 24 to 25°C, and rolling resistance is known to perform worse in cold conditions. Fleets running cold-weather routes should consider this when interpreting a standard-temperature number. Smithers also offers testing at low temperatures to understand the true performance levels at varying conditions.
Find out more about our recent cold-temperature rolling resistance findings here.
If you're not sure where to start, Smithers can help identify which tire and retread combinations in your current fleet are worth benchmarking first. Contact our tire and wheel testing team to talk through your program.