Diagonal vs. Radial
Next the classification of the different tyre types (sport, touring, custom, all/off road) is the most important distinction between diagonal and radial tyres. As long as there have been motorcycles diagonal tyres have existed, in point of fact, it is known as the mother of all tyres. The origin of the name comes from the pattern of the support construction - called the skeleton. The skeleton is constructed from multiple layers (mostly artificial) of material that is woven in a special manner. With the diagonal tyre the layers cross in a diagonal direction with each other. Such a layer of material is called a corded-layer and gives the tyre itís bearing capacity. Therefore the more layers, the more the tyre can bear. The conís of the diagonal tyre are that if the tyre is pushed in, the corded-layers move over each other with the expected results (unwanted) of rubbing and the tread has relatively little stability.
The radial tyre, which has become common since the end of the 1940ís, made itís debut in the motorcycle world only 20 years ago. The name is thanks to the squared directional position of the threads in the skeleton where they no longer cross over each other. From this you get less development of heat as the layers do not rub over each other. To give this construction more stability a zone/band of one or more layers is placed around the skeleton of the tread. The rubbing of the layers stays to a minimum for the tread. You can also see zones/bands in a diagonal tyre, the so called belted tyre, but then you get the rubbing of the layers. The con of this construction in the radial tyre is the side of the tyre, called the wall, the walls become weaker if they become the same height as that of the diagonal tyre. This has been resolved when a broader en lower tyre was designed. The biggest pro of the radial tyre is the lessened deformation, the so called growth of the tyre, the appearance of which gives more stability.
Since the introduction of the radial tyre there has been much experimentation which has given us many diverse variations of the radial tyre. One of the most well known is the nul grade tyre where the zone/band is laid in the same direction as that of the tyre. This resists the centrifugal forces (the forces directed from the centre to the perimeter of the wheel) this means less growth and deformation to the tread. A pro from this is the good forward stability at higher speeds and the lessened wear of the tread.
Description of the Tyre
About the walls of the tyre there is a sea of information available that explains how and why about the rubber that sits on the rims. Lets look at the important bits.
Generally the measurement and speed description of the tyre is given in metric:
180/55 ZR17 (73W)
| 180 ||Width of the tyre in mm |
| 55 ||Height of the tyre in percentage of the width |
| Z ||Speed Code |
J : tot 100 km/u
N : tot 140 km/u
P : tot 150 km/u
S : tot 180 km/u
H : tot 210 km/u
V : tot 240 km/u
W : tot 270 km/u
Z : boven 240 km/u
| R ||Tyre type |
B : Zone/band Tyre
R : Radial Tyre
- : Diagonal Tyre
| 17 ||Diameter of the rim in inches (1 inch = 2,54 cm) |
| 73W ||Load/Speed index |
This last number/letter combination (73W) requires further explanation. The Load Index indicates the maximum weight the tyre can bear. The speed Index indicates the maximum speed can be ridden during a short period. If the Speed Index is in brackets then the description of the Speed Code is valid.
LOAD INDEX SPEED INDEX
LI kg lbs LI kg lbs LI kg lbs code km/u mph
36 125 276 54 212 467 72 355 783 B 50 31
37 128 282 55 218 481 73 365 805 C 60 37
38 132 291 56 224 494 74 375 827 D 65 40
39 136 300 57 230 507 75 387 853 E 70 43
40 140 309 58 236 520 76 400 882 F 80 50
41 145 320 59 243 536 77 412 908 G 90 56
42 150 331 60 250 551 78 425 937 J 100 62
43 155 342 61 257 567 79 437 963 K 110 68
44 160 353 62 265 584 80 450 992 L 120 74
45 165 364 63 272 600 81 462 1019 M 130 81
46 170 375 64 280 617 82 475 1047 N 140 87
47 175 386 65 290 639 83 487 1074 P 150 93
48 180 397 66 300 661 84 500 1102 Q 160 99
49 185 408 67 307 677 85 515 1135 R 170 105
50 190 419 68 315 694 86 530 1168 S 180 112
51 195 430 69 325 716 87 545 1202 T 190 118
52 200 441 70 335 739 88 560 1235 U 200 125
53 206 454 71 345 761 89 580 1279 H 210 130
V/VB 240 150
(V)/(VB) >240 >150
W 270 167
(W) >270 >167
ZR >240 >150
The dot Description indicates that the tyre passes the requirements of the American Department of Transport and may therefore street worthy. After the Dot Description is a number that indicates when the tyre was produced. A .209 reveals the tyre was produced in week 20 in the year 1999. 1989 is in this case unlikely as that would mean the tyre is 12 years old and not suitable for use, but to exclude confusion you will find a symbol embossed on the tyre, the 1980ís indicated by a square, the 1990ís are indicated by a triangle, For the first decennium of 2000 I have yet to find a symbol.
The combination of different brands/models is not a problem as long as the correct size and speed category are selected. On the other side of the story is about the difference between two tyres of different brands/models. Combinations that are not permitted or are not recommended are:
- A Radial tyre on the front with a Diagonal or Belt tyre on the rear
- A Belt tyre on the front with a diagonal tyre on the rear
The other way around is permitted, thus a radial on the rear and a belt tyre on the front or a diagonal tyre on the rear and a belt tyre on the front is therefore no problem. The rule of thumb is the an Ďolder fashionedí type may be placed on the front than on the rear wheel.
Some general tips (more information welcomed):
- Keep an eye on the tyre pressure. Not only the handling and the grip but also wear and tear.
- During the winter often extra air is not necessary as the service temperature of the tyres, during riding, does not change significantly from summer In the winter the pressure is measured while the tyres are cold and can differ significantly if the air pressure is colder than 10°C.
- If the tyre does not suit you, then try a completely different brand. Which is of course easier said than done, you do not buy tyres like a pound of sugar. If you are not satisfied or are due for new tyres ask for the experiences of other riders. The difference in the types of tyres (radial or diagonal) can also vary widely. There are many Diversion 900 riders that have changed from the standard Exedra G601/G602 (diagonal) to the Battlax BT-020 (radial) and have an opinion to share.
- It is not recommended to change from the standard size, not counting the width of the tyre is decided by the width of the rim. Choose for a wider tyre then the heel (the innermost edge of the tyre) sits closer together with the result that the tyre will bulge. You shall miss part of the quality of the tyre design. You could also have a problem with legal responsibility if something goes wrong, so, be warned.
This is what I have found about tyres so far that would be of interest to Diversion Riders. The information was found in Moto73 and on various pages on the internet. May you ride many good and safe kilometres and keep the black rubber underneath.
Eugène van der Meer, Bemmel
Links Michelle Walton has used to understand and translate this article from Dutch to English:
, what is a tyre?
- Longstone Tyres
, what is a radial tyre?