André Rijnders1 Dutch proposal on tyre conditioning DTP-LabProcICE November 2012 WLTP-DTP-LabProcICE-169

DTP-LabProcICE November 2012 André Rijnders 2 The tyre condition plays an important role in the rolling resistance (RR) of the coast down test. The tyre rolling resistance of a tyre in real world should not be dominant worst than the tyre rolling resistance of a tyre in the coast down test. For the tyre selection we choose the worst case class concerning RR. For the tyre condition for the cost down we should also choose a kind of worst case of what we see in real world. During TA, the manufacture will use the tolerance in the provision and is tendering to the best case for RLD. For robustness of the provision of RR the tolerance of the tyre condition for TA should not be too wide and tender to the worst case. Tyre conditioning and Road Load Determination

DTP-LabProcICE November 2012 André Rijnders 3 Items of the tyre condition which play an important role in the rolling resistance (RR) Aging: Tyres do deteriorate with age, which improve the rolling resistance (harder tyre). Forced aging (heating) should be forbidden. No test tyres which are special treated to be used for the coast down test. Tyre tread wear and tyre tread depth Tyre conditioning and Road Load Determination

DTP-LabProcICE November 2012 André Rijnders 4 Tire Tread wear and tread depth and the effect on RR Information on NHTSA Fuel Efficiency Consumer Information Program Development: Phase 2- Effect on Tire Rolling Resistance Level on Traction, Tread wear, and Vehicle Fuel Economy (August 2009) Tyre conditioning and Road Load Determination Research & Test Center (VRTC)/ca/Tires/ pdf

DTP-LabProcICE November 2012 André Rijnders 5 Effect on Tire Rolling Resistance Level on Traction, Tread wear, and Vehicle Fuel Economy (NHTSA August 2009) Tyre conditioning and Road Load Determination 2.10 Indoor Tire Treadwear Testing The FMVSS No requires all passenger tires (with some exceptions) manufactured after April 1, 1980, to be graded for tread life. However, advances in radial tire tread compounding since 1980 have resulting in longer life treads that exhibit only a marginal amount of wear after running the 7,200-mile UTQGS treadwear course. To evaluate the effects of bulk treadwear on tire rolling resistance, additional tires were subjected to a more aggressive indoor treadwear test developed by Smithers Scientific Services, Inc. in Ravenna, Ohio

DTP-LabProcICE November 2012 André Rijnders 6 Tyre conditioning and Road Load Determination “A slight reduction in rolling resistance may be observed, however the change is less than the scatter of the data”

DTP-LabProcICE November 2012 André Rijnders 7 Tyre conditioning and Road Load Determination Tire tread loss change tread surface and will estimate a negative effect on the rolling resistance.

DTP-LabProcICE November 2012 André Rijnders 8 NHTSA : Effect on Tire Rolling Resistance Level on Traction, Tread wear, and Vehicle Fuel Economy (August 2009) Tyre conditioning and Road Load Determination “For all tire types except B13 the quadratic term was statistically significant, indicating that the wear rate tends to change (either increase or decrease) as the tire wears.”

DTP-LabProcICE November 2012 André Rijnders 9 Items of the tyre condition which play an important role in the rolling resistance (RR). Tread depth Less tread depth positive for RR Tyre conditioning and Road Load Determination Source: Goodyear Computer Fuel Economy Model Chart 9 illustrates the effect of tire wear on fuel economy improvement as each of the vehicle wheel position tires are worn out and replaced over 350,000 miles. (Trucks)

DTP-LabProcICE November 2012 André Rijnders 10 Tread surface and tyre tread depth If the tyre is treated by a grinding machine “you will get what you want”. The tyre tread surface can be optimal shaped or smoothened to the maximum allowed tread wear, which probably will not reflect real world. Tyre conditioning and Road Load Determination Grinding: Optimized for RR Minimum tread depth Optimal shape and smoothened surface

Tyre conditioning WLTP-DTP-LabProcICE-139 modified NL proposal Tyre condition The tyres used for the test shall: - not be older than 2 years after production date, - not be specially conditioned or treated (e.g. grinded or heated), - shall be run-in on a road for at least 100 km, - shall have a constant tread depth of not less than 80 per cent of the original tread depth over the full tread width of the tyre. DTP-LabProcICE November 2012 André Rijnders 11