More than 30 people were killed or seriously injured in motorway accidents in 2016 in the UK due to illegal or faulty tyres (Source: Highways England). Tyres that are running underinflated is the most common cause of tyre failure. Incorrect inflation leads to an uneven distribution of heat within the tyre which not only leads to premature degradation of the tyre but will ultimately result in a tyre blowout. FACTS sat down with the team at Celerity DRS to learn about the damaging effects of improper tyre inflation and how the PSI Automatic Tyre Inflation System serves as a solution for many of the UK’s commercial vehicle fleets.

What are the safety risks incurred by a commercial trailer tyre blowout?

A tyre blowout presents three main safety risks. Firstly, the risk to the driver and the load as the vehicle loses control. Secondly, the risk to other road users as a result of the explosion itself, debris on the road and the vehicle losing control. Finally, there is also a risk associated with the vehicle and driver being at a standstill on the side of the highway. In a recent Highways England paper, it was reported that over 100 people are killed or injured from being stood on the hard shoulder every year. The August 2018 wildfire in California is a real-world example of the potential catastrophic implications of a blowout. The Carr wildfires were the sixth most deadly wildfires in the state’s history and were started by a vehicle towing a dual-axle trailer. One of the tyres on the trailer blew out, the sparks from the rim ignited dry vegetation along the edge of the highway which was the catalyst for the fire. How does underinflation effect tyre wear and tyre life and what are the implications? A recent report from Bridgestone highlighted that around 25 % of tyres in a fleet are operating with at least 10% underinflation; approximately 5% are underinflated by more than 20%. Underinflation causes degradation of the tyre sidewall which prevents remould or retread opportunities. This leads to premature removal of a tyre and increased costs for a fleet. 10% underinflation leads to a reduction in tyre life by approximately 10%. A 20% underinflation leads to a reduction in tyre life by 25% (Source: Bridgestone). Tyre wear caused by underinflation also presents huge safety risks for a fleet. Uneven tyre wear reduces traction with the road, increasing the vehicle’s stopping distance and potentially resulting in a collision.

Fuel is a principal expenditure for hauliers – how can the PSI system reduce fuel costs?

Underinflation has a significant impact on fuel costs. A tyre which is underinflated by 20% leads to a 12% larger footprint on the road resulting in an increase in fuel consumption of 4% (Source: Michelin – Michelin X Mutli Trailer 385/55R22.5). The PSI system maintains optimum pressure in tyres at all times eradicating this cost altogether. The cost saving differs for each fleet and vehicle dependent on load, mileage and fuel consumption. However, we have a comprehensive savings calculator available on our website ( where you are able to input your own variables to calculate the potential savings gained by introducing PSI. In general, we state PSI will typically provide a fuel saving somewhere between 1.4-6% annually depending on the vehicle and tyre specification. Steve Page, Managing Director at Kingswood Pallets, said: “We have seen significant fuel benefits with the tyre inflation system fitted on our new trailers. On the same route from the UK to Germany, we were seeing 10.4 mpg on our trailers without PSI, and with PSI we are now seeing 10.7 mpg – these routes were at the same time of year in the same conditions carrying exactly the same weight.”

Image 01: a metal shard which punctured the tyre of a tipper vehicle. Through the PSI system, the tyre was able to withstand the severe puncture and maintan the correct operating pressure.

How does the PSI Automatic Tyre Inflation system account for punctures?

The PSI system not only prevents slow pressure loss over time, it also works to inflate a tyre under extreme stress such as a puncture. Image 01 (pictured above) highlights a recent example of a tipper which, through PSI, was able to withstand a severe puncture. Despite the metal shard pictured being embedded 4 inches into the wall of the tipper tyre, the PSI system maintained the correct operating pressure keeping the vehicle safely on the road for three working days. If a tyre is punctured, the PSI system will immediately notify the driver of a drop in pressure via a warning light fitted to the trailer behind the cab and the pump will kick in to maintain optimum pressure despite the puncture. A driver is then able to keep driving and plan the repair on the tyre into a scheduled break for the vehicle – avoiding any unplanned downtime.

How can the PSI system protect against tyre blowouts?

As a tyre becomes underinflated, the heat of the tyre increases. Eventually this overheating will result in complete tyre failure – a blowout. PSI ensures a tyre is consistently inflated to optimum pressure, stabilising the temperature of the tyre and thus preventing blowouts. The owner of French fleet maintenance company ‘Maintenance Poids Lourds’ (see image 02 below) recently told us that 50% of his fleet call-outs were tyre blowouts as a result of underinflation. After experiencing the benefits of PSI, he has now fitted the system to all of his trailers in order to prevent this. In recent years, many fleets have safeguarded against blowouts with a TPMS system. TPMS helps to reduce occurrences by warning a driver when there is a detection of underinflation. However, the current regulation on TPMS prescribes a detection time of up to 10 minutes (Source: TNO). With TPMS, the driver is also required to take action (which is not always immediate) and this action is dependent on the availability of a nearby filling station. From the point of underinflation to the action to re-inflate, a tyre could become severely underinflated, overheated and the chances of a blowout are significantly increased. With a PSI system fitted, the pump kicks in immediately on detection of a loss in pressure of 0.2 bar. The system regulates the tyre at optimum pressure preventing a catastrophic blowout. Unlike TPMS, PSI does not require human intervention. The system thus supports the inevitable path to autonomous driving.

Image 02: The owner of French fleet maintenance company ‘Maintenance Poids Lourds’ told Celerity DRS that 50% of his fleet call-outs were tyre blowouts as a result of underinflation.

What can you tell us about your work with Walmart and FedEx?

In North America, FedEx Freight have been specifying PSI on all of their trailers since 2006 and FedEx Ground since 2008. The two together take approximately 6000 trailers specified with PSI every year. In total, the company has purchased approximately 50,000 PSI systems. Walmart has been specifying 100% of their trailers with PSI for the past three years and has taken approximately 6000 trailers each year. Next year, we anticipate this number to increase.

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