HOW TO DECODE TYRE MARKINGS
The markings on a tyre’s sidewall contain much important information, hence we should equip ourselves with them.
Who knows, you may meet an unscrupulous workshop that tries to recommend tyres that are not suited to your bike. Or they just made a mistake. But mistakes can be costly for us bikers.
Let us begin.
Let’s use this tyre as the example:
Michelin Power5, 160/60ZR17 M/C (69W)
It denotes the nominal width of the tyre measured at the widest point of the tyre, in milimetres (mm). You may have noticed that one brand of tyre in the same segment may be wider than another. That’s because manufacturers may vary the width to tune for different handling characteristics by +/- 4%.
Indicates the tyre’s aspect ratio or in other words, section height. It is expressed in percentage, not a direct measurement. So, 60% of 160mm is 96mm. Just as with the width, different manufacturers vary the aspect ratio by +/- 4%.
The two letters represent two different meanings, although joined together.
“Z” is the tyre’s speed rating which in this case is above 240 km/h.
“R” means radial construction, NOT racing. The letter is omitted if the tyre is a bias-ply type (usually on dirtbikes, dual-sport, older cruisers, and kapchais).
The wheel (rim) size in inches.
The tyre is for motorcycles.
There are two parts to this as well.
“69” stands for the tyre’s load index. It is the code that states the tyre’s maximum load at maximum inflation pressure. Referring to the graph, this tyre’s maximum load is 325kg.
“W” is the tyre’s speed index, 270 km/h in this case. This is where it gets confusing, since the “Z” lettering already indicates that the tyre can exceed 240 km/h? That is why the load index and speed index are married to each other.
It works like this: The maximum speed at which you should ride while carrying 325kg at maximum pressure is 270 km/h.
However, the brackets around “69W” means the tyre can go faster than 270 km/h (provided you’re not carrying 325kg, of course).
Tubeless. Certain tyres may carry the “TL” designation. Conversely, tube tyres may carry the “TT” symbol. No, “TT” DOES NOT mean the Isle of Man TT.
You may come across a tyre with the GT marking after the above markings i.e. 120/70 ZR17 M/C (58W) TL GT. “GT” means the tyre is designed for heavier motorcycles such as the BMW R 1200 RT, Kawasaki 1400GTR, Yamaha FJR1300, among others. It’s not recommended to mount it on your middleweight bike just because “the GT version lasts longer,” as some mechanics try to con you. Yes, it does last longer on your Versys 650 because the tyre’s compound and construction are meant for heavier bikes.
Refer to (69W) marking above. Virtually all tyres carry this marking. See what this one says? Just like what the load and speed indexes indicated. Also note the maximum pressure, which is 290 kPa or 42 psi in this case. DO NOT ever exceed this.
Hence, going back to the (58W) rating, this tyre can support a maximum of 236 kg when the tyre is inflated to 290 kPa (42 psi).
Four-digit numbers in an oval or rectangle
Together, they denote the manufacturing date of the tyre. The first two digits tells the week, while the last two are the year. For example, “2918” means the tyre was produced in the 29th working week of 2018. While there are 52 weeks in a year, there may not be production during every week.
Rotation or Direction
Every tyre has an arrow to mark the direction of rotation for the tyre, hence it should be mounted as such. DO NOT mount it against the intended direction – even if it “feels better when mounted backwards.” (You may laugh, but we have had riders telling us so.)
So, there you are. There are still more markings and symbols but these are the most important ones.