Indirect TPMS attractive for volume car models – strong European, North American growth expected in 2014

Come November, every new car and light commercial vehicle sold in the European Union will need to have a tyre pressure monitoring system, making the region the second behind the US to make TPMS fitment mandatory. The question vehicle manufacturers must answer is which type of TPMS is best for them. While direct TPMS systems have enjoyed a lot of attention since the first phase of the ECE R64 legislation came into force in November 2012, one indirect TPMS manufacturer expresses confidence in a growing presence in the high-volume market.

“Indirect systems offer customers the distinct benefit of no additional lifetime costs as the lifetime of the system lasts for the lifetime of the car,” comments Bernd Schuchhardt, general director of Dunlop Tech GmbH, a German subsidiary of Sumitomo Rubber Industries. Presenting the case for indirect TPMS (or iDWS – indirect Deflation Warning System, as Dunlop Tech calls it) at February’s Tire Technology Expo conference in Cologne, Schuchhardt outlined its advantages and drawbacks, and opined that although direct systems may initially look like they’re winning the TPMS war, in the medium and long-term the indirect approach will gain a strong following.

The principle behind Dunlop Tech’s iDWS (Dunlop Tech is one of three key suppliers of this technology; the others are Continental and NIRA Dynamics) is straightforward: The dynamic loaded radius of each of a car’s four tyres are compared and lower pressure is detected by the presence of a tyre rotating more quickly than the others. This system first entered the market in the 1990s (with Toyota and BMW early adopters of the technology) and Schuchhardt says it has been very successful, with no customer claims received. More recently, the system evolved to accommodate the US FMVSS138 and European ECE R64 legislation, which requires TPMS systems to detect the unlikely but possible simultaneous deflation of all four tyres – something the original iDWS couldn’t achieve. “This system responded to a deflation very quickly,” Schuchhardt comments. “For example, a 30 per cent deflation under normal speed conditions could be detected in less than one minute. But the demerit was that it couldn’t detect simultaneous deflations like diffusion effects or, very hypothetically, if all four tyres are punctured at the same time. To address this, we developed our RFM (Resonance Frequency Method) module.” RFM detects tyre deflation by comparing the resonance frequency between normal and deflated pressure. The DLR and RFM software modules run in parallel and thus can detect all possible tyre deflation conditions. A regulation-compliant system employing both modules first saw light of day in the North American market on the Honda Accord and Mazda 6 in 2012 and was followed in Europe that year with the Honda CRV and Mazda 6. “We now have a lot of other new projects, more and more car makers are adopting it, especially for high volume models,” Schuchhardt shares. “In the near future we will bring it to the market in a very high volume.”

As mentioned above, the DLR and RFM modules are software applications, and this is a major point of difference between iDWS and direct TPMS – indirect systems such as those developed by Dunlop Tech utilise no hardware of their own. “Our iDWS uses existing ABS/ESC vehicles systems and sensors,” explains the Dunlop Tech general director. “No additional electronic components or batteries are required.” Dunlop Tech acts as a second-tier supplier and supplies its software to ABS, ESC and ESP manufacturers.

Indirect systems are very attractive in terms of costs for high-volume car models. “Once the software is applied to all the tyre brands and tyre sizes and one or two parameters are set (depending on type of tyre) and applied to the vehicle, the cost per vehicle is rather low.” But Schuchhardt admits there are always a plus and a minus when comparing rival technologies: On the positive side of the equation, cost is accompanied by ease of maintenance. “There is no aging effect, nothing wears out and nothing must be replaced. It is rather simple – if you’ve inflated the tyre correctly you push a button and that’s it.” But Schuchhardt notes that iDWS lacks the absolute pressure detection (and accompanying dashboard status display) that direct systems offer. “This means a customer using the indirect system has the strict responsibility to fill the correct inflation pressure into the car, push the button – and then it will work. A manufacturer can set a direct system to an exact level, whereas the indirect system always calculates its warning level by itself – you push the button, and this tells the system that this is the pressure you want to have.”

While this appears to leave indirect TPMS open to errors caused by incorrect end-user adjustment, Bernd Schuchhardt says this drawback doesn’t lead to unsafe situations. But he also adds that Dunlop Tech is continuing research to improve its software. “There are several modules under investigation, for example to address what happens when a customer pushes the button when the tyre is too deflated or if the customer tries to ignore a warning and pushes the button, resetting it to a lower pressure. Here our software structure is under investigation, and partly already on the market, to avoid this misuse of the system. Indirect systems have a cost merit, but cost shouldn’t equal less safety or less comfort.”

The Dunlop Tech general director concedes that direct TPMS is seen as the system of choice for some vehicles – he notes that the dashboard display with exact pressure is a desired feature on upmarket models – but he is equally certain that the added cost of installation and maintenance will work against the direct system at the cost-competitive end of the market. And he also believes it is too early to speak about one system or another holding a greater market share in Europe. Schuchhardt admits that the direct system has enjoyed the limelight in Europe following the requirement for TPMS fitment on newly-homologated models from November 2012, and he sees this continuing in the near future – but he is quick to explain why he believes the pendulum will swing back following this early success for the rival technology.

“After November 2014, the majority of fitments will initially be the direct system because everyone has to install something in their cars, and we have not yet by far applied the indirect system to all these cars.” Once this is done, Dunlop Tech foresees that car makers producing mass-market models that are sold both in Europe and other global markets will be interested in iDWS, particularly as further regions introduce their own TPMS legislation in the coming years. Volumes in Europe and North will also continue to rise; last year 777,000 vehicles in Europe and North America were fitted with regulation-compliant iDWS systems, and Dunlop Tech projects that this figure will more than double to 1,810,000 units this year and further grow to 2,320,000 units in 2015.