EU rating: ECB
Without even knowing which test each letter is assigned to in ECB, I can categorically state that I would not recommend that tyre to anyone, as at best wet grip is B, which is poor.
The euro labelling is pointless wank anyway, as its not in depth enough, and concentrates on fuel economy. Who gives a toss a bout fuel economy, we drive big barges, and over the lifetime of the tyre, the difference between A and G is about a gallon of petrol. Noise I can accept. But safety, ie grip levels, should be the most important thing to anyone... ...and what does this labelling give us? A straight line stop in the wet. Crap.
actually the calculation of the wet grip rating is quite complicated and is based on the ISO standard originally developed for bus and truck tyres ISO 15222:2011
if you're interested in the science there is plenty on the net e.g. have a read here
https://www.unece.org/fileadmin/DAM/trans/doc/2011/wp29grrf/GRRF-71-10e.pdf and here
https://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r117rev.2E.pdfof course you can always rely on opinion and manufacturer advertising if you prefer
.
here's an extract anyway
Test procedure for measuring wet grip
1. General Test Conditions
1.1. Track characteristics
The track shall have a dense asphalt surface with a gradient in any direction
not exceeding 2 per cent. It shall be of uniform age, composition, and wear
and shall be free of loose material or foreign deposits. The maximum
chipping size shall be 10 mm (tolerances permitted from 8 mm to 13 mm)
and the sand depth measured as specified in ASTM standard E 965-96 (2006)
shall be 0.7 ±0.3 mm.
The surface friction value for the wetted track shall be established by one or
other of the following methods:
1.1.1. Standard reference test tyre (SRTT) method
When tested using the SRTT and the method given in paragraph 2.1. the
average peak brake force coefficient (pbfc) shall be between 0.6 and 0.8. The
measured values shall be corrected for the effects of temperature as follows:
pbfc = pbfc (measured) + 0.0035 (t - 20)
where "t" is the wetted track surface temperature in degrees Celsius.
The test shall be conducted using the lanes and length of the track to be used
for the wet grip test;
1.1.2. British pendulum number (BPN) method
The averaged British pendulum number (BPN) of the wetted track, measured
in accordance with the procedure given in the ASTM standard E 303-93
(2008) and using the pad as specified in ASTM standard E 501-08, shall be
between 40 and 60 after temperature correction. Unless temperature
correction recommendations are indicated by the pendulum manufacturer, the
following formula can be used:
BPN = BPN (measured value) + 0.34 · t - 0.0018 · t² - 6.1
where "t" is the wetted track surface temperature in degrees Celsius.
In the lanes of the track to be used during the wet grip tests, the BPN shall be
measured at intervals of 10 m along the length of the lanes. The BPN shall be
measured 5 times at each point and the coefficient of variation of the BPN
averages shall not exceed by 10 per cent.
1.1.3. The Type Approval Authority shall satisfy itself of the characteristics of the
track on the basis of evidence produced in test reports.
1.2. Wetting conditions
The surface may be wetted from the track-side or by a wetting system
incorporated into the test vehicle or the trailer.
E/ECE/324/Rev.2/Add.116/Rev.2
E/ECE/TRANS/505/Rev.2/Add.116/Rev.2
Annex 5
50
If a track-side system is used, the test surface shall be wetted for at least half
an hour prior to testing in order to equalize the surface temperature and water
temperature. It is recommended that track-side wetting be continuously
applied throughout testing.
The water depth shall be between 0.5 and 1.5 mm.
1.3. The wind conditions shall not interfere with wetting of the surface (windshields
are permitted).
The wetted surface temperature shall be between 5 °C and 35 °C and shall
not vary during the test by more than 10 °C.
2. Test Procedure
The comparative wet grip performance shall be established using either:
(a) A trailer or special purpose tyre evaluation vehicle; or
(b) A standard production passenger carrying vehicle......................
Author
Topic: WARNING tyre question (Read 10633 times)