For those with any tyre queries. This is off another thread which other people could use as a guide.
87Y is the speed rating and load capacity.
87 is the load capacity, and the Y is the speed symbol.
e.g. W = Higher speed rating in conjunction with load index e.g. 83W, are suitable for speeds in excess of 240km/h up to 270km/h. (Load index is given at 210km/h, load must be reduced 5% for every 10km/h over up to 270km/h).
H - 210km/h (130mp/h)
V - 240km/h (150mp/h)
W (ZR) - up to 270km/h (168mp/h)
Y (ZR) - 300km/h (186.4mp/h)
Z - over 240km/h (150mp/h)
ZR is the Radial Construction. The ZR will come with all Y rated tyres which means your tyres are capable of 300km/h (186mp/h). If your tyres didn't have the Y rating, then they would only be ZR's alone ... capable of above 240km/h (149mp/h). Not as fast as the ZR Y's. Only the W's and the Y's come together with the ZR's as one package. The ZR W's are only capable of 270km/h (168mp/h), so your tyres are faster then them!
Sidewall Marking Explanation
205 - Width of the tyre in millimetres
50 - Height of the tyre sidewall as a percentage of the width. In this case 50% of 205mm. Also know as the aspect ratio.
R - Radial Construction.
15 - The diameter of the tyre's inner rim in inches
91 - Load Capacity of Tyre. In this case its 615kg
V - Speed Symbol. Indicates the max. speed for the tyre at full load. In this case 149.1mph.
E4 - ECE type approval mark, which demonstrates the tyre has been tested as high quality by the European Regulatory Authorities. All Tyres sold by Black Circles carry this mark.