MOTORCYCLE TYRE MARKINGS: THE WRITING’S ON THE WALL!!
LIKE any trade, the tyre business has its own jargon. And if you can decode the lingo, you’ll be in a much better position to work out what you need. Luckily, most of it is quite logical and scientific, and much of what you need is actually written down – on your bike, outside, right now!
No, we’re not talking about the owner’s manual under the seat (though that does have some good info in there). It’s even easier than that: by law, tyres have to carry a load of detailed information stamped onto the side of them, about size, speed and weight ratings, and much more. Understand these numbers, letters and symbols, and you’ll be well on the way to being a tyre genius. Here’s our quick-yet-comprehensive guide to what it all means.
• As ever – we’re ready and waiting to help you with any queries at all! Give us a shout here on 0207 205 2205
SIZING (1,2 and 4 on our pic)
This is a good place to start – the actual physical size of the tyre, which is the most obvious text on the sidewall (after the branding). A typical front tyre size is 120/70 17, a common rear is 180/55 17. There are three parts to this – the width of the tyre in millimetres, and the ‘aspect ratio’, which is basically how tall the tyre is, as a percentage of the width, plus the diameter of the wheel the tyre fits (in inches, curiously). So that typical 120/70 17 front tyre is 120mm wide (1), 70 per cent (2) of 120mm (around 84mm) tall, and fits onto a 17-inch rim (4). Easy.
Type – radial or crossply (3)
These are the two main types of internal tyre construction: radial tyres have bands of strengthening cords arranged radially from one edge of the tyre rim straight across the tread to the other, so they sit at 90 degrees to the direction of travel. Crossply tyres are an older technology, which uses different arrangements of ‘plies’ or material which cross over each other under the tyre tread. Crossply tyres generally have taller sidewalls and are more suited to older bikes, commuter and off-road machines.
Radial tyres have a letter ‘R’ after the speed rating. So a 120/70 16 ZR is a radial with a Z speed rating.
Load index (6)
Like the speed rating, tyres are designed to cope with certain loads in terms of weight, and again, you need to make sure the tyre is suitable for your bike. Check the load you’ll be carrying, with pillion and luggage if relevant. Remember the weight allowed is per tyre.
The load index is a two-digit number, but the permitted weight is also marked on the tyre. Give us a shout if you have any queries on Load Index.
Speed rating (7)
The forces going through a tyre get very serious as speeds increase, so they have a maximum speed rating. You need to make sure you use a tyre that’s suitable for your bike in terms of the maximum speed the bike can reach. The speed rating is a single capital letter next to the size – so our typical front tyre might be a 120/70 17 Z – which is suitable for over 150mph.
Here’s a list of the speed ratings:
Z Over 150mph
Tyres can be tube-type, which aren’t airtight themselves, and need an inner tube to hold the air in, or tubeless type, which have an airtight lining so they don’t need a tube.
The choice here depends on your wheels. Old-school wire-spoked rims need inner tubes, like a bicycle, because the wire spokes aren’t sealed where they join the outer rim, and air would leak out here. So tube-type rims need to be used with an inner tube – but you can use either a tube-type or tubeless tyre. Some modern designs have tubeless wire spoked wheels now – the spokes attach to the outer edge of the rim rather than through the centre, so the rim is air-tight.
The tyre will be marked on the outside to tell you if it’s a tube-type or tubeless.
Rotation arrow (9)
Most tyres are designed to be used in one direction only, so they have an arrow on the side. Make sure the arrow points the right way when the tyre is on the bike and moving forwards! Getting this wrong is an MOT fail, and can be dangerous, so do check when you buy a bike or get tyres fitted.
The arrow usually has ‘front’ or ‘rear’ written in it, so you know which end to put it on! This is pretty simple: don’t use a front tyre on the back wheel or vice versa. No matter how cool your matt black retro Bobber Brat Scrambler Rat creation looks with a 200-section rear tyre squashed onto the front.
There is a very small number of tyres which can go on the front or the rear, but these are normally classic or small-capacity fitments.
Date code (10)
Tyres, like cans of beer, last quite a long time, but they will go bad eventually. So, like cans of beer, it’s best to use them as quickly as you can – then buy some fresh ones!
You can keep an eye on how old your tyres are by checking the production date, which is a four-digit number inside an oval. The numbers are a two-digit week and two-digit year – so ‘2319’ would be a tyre made in week 23 of 2019.
E marking (10)
Letter ‘E’ with a number, which tells you which country in Europe has approved the tyre construction.
DOT mark (10)
DOT stands for the US Department of Transport, and the DOT mark shows that the tyre is road legal and has passed statutory homologation testing for safety.
Brand/model/logo marks (11)
It’s literally a rolling advert for the maker, so they stamp the model and their name as big as possible on there. Firms work hard on the graphic design of the logo and the like too, to make the sidewall as pretty as they can. And why not?!?!
Country of Construction (12)
That’s a simple one!