Tyre Sizing Help

Your tyre size can be found on the side-wall of the tyre.
Sizes are made up of many different combinations including various numbers and letters.

For example, 185/55R16 100V:

  • 185 represents the tyre section width in millimetres (the width of the treaded area)
  • 55 represents the aspect ratio (side-wall height). The number is a percentage of the tyre width.
  • R denotes the tyre’s construction type. In this case, Radial.
  • 16 is the diameter of the wheel in inches.
  • 100 is this tyre’s load index.
  • V is the speed rating for this tyre.
Load Index

The load index is a code showing the maximum load a tyre can carry at the speed indicated by its speed symbol.
You will find your load rating as shown: 185/55R16 100 V

Load Index Max. Load (kg) Load Index Max. Load (kg) Load Index Max. Load (kg) Load Index Max. Load (kg) Load Index Max. Load (kg) Load Index Max. Load (kg)
60 250 71 345 82 475 93 650 104 900 115 1,215
61 257 72 355 83 487 94 670 105 925 116 1,250
62 265 73 365 84 500 95 690 106 950 117 1,285
63 272 74 375 85 515 96 710 107 975 118 1,320
64 280 75 387 86 530 97 730 108 1,000 119 1,360
65 290 76 400 87 545 98 750 109 1,030 120 1,400
66 300 77 412 88 560 99 775 110 1,060 121 1,450
67 307 78 425 89 580 100 800 111 1,090 122 1,500
68 315 79 437 90 600 101 825 112 1,120 123 1,550
69 325 80 450 91 615 102 850 113 1,150 124 1,600
70 335 81 462 92 630 103 875 114 1,180 125 1,650
Speed Rating

The speed rating represents the maximum permissible speed for which the tyre is rated.

You will find your speed rating as shown: 185/55/R16 100 V

Rating Max Speed Rating Max Speed
N 87mph H 130mph
P 93mph V 149mph
Q 99mph Z 150+mph
R 106mph W 168mph
S 112mph Y 186mph
T 118mph Above Call for specialist applications
U 124mph

You should replace your tyres with those of the same size, load and speed rating as recommended by the vehicles’ manufacturer.Increasing the value of both the load and/or speed rating is acceptable practice but it is not recommended that lower value products be fitted.

The tyre should be able to withstand the forces applied to it at the vehicles maximum rated top speed.
There is currently no legal requirement for speed ratings but it is advised to check with your vehicle insurer of any potential issues that may arise when significantly altering specifications.

If you require any further information in respect of these issues, please do feel free to give us a call – we will be happy to check all the technical requirements of your specific vehicle (where available).

Further Tyre Information

As well as the size, speed and load rating there is further information available to you when selecting the right products for your vehicle online. Certain vehicle manufacturers work very closely with tyre manufacturers to create a particular product which best suits a given vehicle. Mercedes, for example, may select CONTINENTAL tyres as original equipment for a particular model. These tyres would have been developed by CONTINENTAL to deliver the best overall performance for that specific model. The tyre will then be branded with an ‘MO’ classification and provided as an after-market product for you to buy when the original tyres become worn out or damaged.

It is not absolutely necessary to purchase a tyre classified in this way, and indeed an MO tyre, for example, could also be fitted to other models and makes of vehicle without issue – it is simply that these products may best suit that make of vehicle…….

N-Rated Porsche Tyres

Original Equipment Porsche tyres have to undergo considerable lab tests in order to prove beyond doubt that they would be able to perform underneath a Porsche running at top speed in both dry and wet weather conditions. Following this work, they are produced and handed over to ever-stringent Porsche engineers to test them to the extreme. If all testing is approved and passed, Porsche will officially approve the tyres for OE fitment on each new model. For every revision, the tyre is reclassified with a new ‘N’ rating. The process begins with N0 and runs through sequentially to N4 as developments are implemented.
Porsche recommend that only tyres of the same make, model and N rating are fitted to thier vehicles. While it is possible to buy exactly the same looking tyre in exactly the same size and speed/load rating – it is not the optimum product and the car should be driven accordingly….

Other Tyre Manufacturer Related Coding

Tyres developed and denoted as Original Equipment by manufacturers carry additional coding for identification:

( – ) or – Peugeot / Volvo LOTUS Lotus
( * ) or * BMW / Fiat M Maserati
( 1 ) or 1 Bentley / Maserati M0 / MO Mercedes
1Z Toyota M3 BMW M3
5Z Ford MB Mercedes
( a ) or a Audi / Seat / Volvo / VW MZ Mitsubishi / Toyota
( A ) or A Alfa Romeo N0 Porsche v.1
AU Audi N1 Porsche v.2
AZ Alfa / Fiat / Subaru / Toyota N2 Porsche v.3
B BMW N3 Porsche v.4
BM BMW N4 Porsche v.5
BZ Audi / Honda / Mazda / MercedesOpel / Skoda / VW (P) of P Peugeot / Porsche
C1 Chrysler / Daimler / Dodge PZ Ford / Mazda / Mercedes / VW
CZ Subaru R Renault
DC Chrysler / Daimler RE Renault
DZ Honda / Mazda / Toyota RU BMW / Ferrari / Lexus / Mercedes
EZ Audi / Mazda 6 SMART Smart
(f) or f Fiat SZ Mazda MPV
(F) of F Ferrari / Ford TZ Mazda 6
FE Ferrari UV VolksWagen
FO Ford UZ BMW 3 Series / Skoda
G1 Mercedes Volvo Volvo
GZ Subaru VW VolksWagen
(J) or J Jaguar VW Golf 3 VW Golf mk3
JZ Seat / Subaru VW Golf 4 VW Golf mk4
L Lexus XZ Nissan
LZ Lancia YZ Hyundai / Kia / Mazda / Mercedes
K1 Ferrari Z Mazda / Toyota
KZ Nissan / Toyota R01 Audi