GAR | TPM-03-07

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Document Title	OICA Study of factors involved in the low tire pressure warning threshold
Reference Number	TPM-03-07
Date	19 Jun 2008
Source(s)	OICA
Rulemaking Area(s)	UN R64 Spare Tires
Meeting(s)	TPM \| Session 3 \| 19-20 Jun 2008
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Excerpts from session reports related to this document
TPM \| Session 3 \| 19-20 Jun 2008			OICA presented an investigation about the influence of various tolerances on the accuracy of TPMS warning thresholds. (TPM-03-07) The main factors which influence the tyre pressure are: • ambient temperature change (daily, weekly, monthly) • tyre warming up by driving • pressure gauge accuracy at filling stations • TPMS sensor accuracy • natural pressure loss by permeation All these tolerances must be taken into account when setting the warning thresholds. OICA deems a pressure drop threshold of at least 25% necessary to avoid false alarms. Experience in the USA shows that there are many customer complaints if the warning threshold is too narrow. Pressure gauge accuracy at filling stations is an important item which cannot be influenced by a regulation for TPMS. The governments and the EU-Commission should find a way to guarantee minimum accuracy of these devices in all countries. OICA presented its informal paper “TPMS OICA position” (Doc. TPM-03-08). The main items of this informal paper are: • Comparison of direct and indirect TPMS • Proposal for a revised test procedure (pressure drop related to pwarm instead of Prec. cold) • Introduction of TPRS (Tyre Pressure Reminder System) • CO2 benefits of TPRS • Proposal for 2 different routes – Route A: TPMS for CO2 and safety – Route B: TPRS for CO2 and TPMS for safety • Open issues ETRTO explained that from their point of view CO2 and safety could not be separated completely because driving with an under-inflated tyre for a longer period (CO2) also affects the durability of a tyre which means safety. The government representatives from D and J declared that they can agree in principal with the OICA position, NL and UK were not satisfied with TPRS, also the representative of the EU-Commission had doubts about the efficiency of TPRS. There was general agreement that no specific design of TPMS should be required and each manufacturer could choose his own way to achieve the target of CO2 reduction and better road safety. The representative of the EU-Commission informed the group that a European Safety Directive will be published which also includes TPMS. There could be a reference to an ECE-Regulation on TPMS, if this appears satisfying but an own European Directive on TPMS would also be possible.