Tyre Choices and Care
Two tiny contact patches are all that separate you from disaster. Here's some sound advice on what to look for when choosing and using motorcycle tyres.
Almost anyone who rides takes at least some interest in tyres. Bike magazines even run comparison articles on them that are every bit as detailed as the latest litre-bike group tests.
There are good reasons for this. Few things are more important to rider safety than tyres. The physics of motorcycle dynamics and stability are such that a loss of adhesion can lead quickly to a crash. That’s why grip matters so much.
Because adhesion features so strongly in our concerns, it can produce some unhelpful thinking. A lot of riders will say they want ‘sticky’ tyres and their assumption is that ‘racing’ tyres offer the most grip. And they do, if you can keep them at their proper operating temperatures. Usually that will be well north of 60ºC, and to keep tyres in that zone they need to be worked really hard. Fine, when you’re on a track day or racing, with the tyre surface forming an almost-molten layer.
Riding on the road will very rarely see your tyres operate at these temperatures. Blitzing the Col du Tourmalet on a searing hot summer’s day might do it, otherwise not so much. So tyres designed primarily for road use aim to provide maximum grip at lower operating temperatures. Everything is a compromise, of course, so the more road-biased a tyre is the more prone it will be to overheating on track. (Even so, modern road rubber can be surprisingly good on a track day.)
The other issue is wet grip. Rain not only reduces the available grip, it cools the tyres. Once again, a tyre designed for use in the wet will be formulated to warm up easily and grip well at lower temperatures. Tread pattern is another factor. Grooves and ‘sipes’ help cut through and disperse water, allowing the best contact between the tyre and the road surface. But again, grooves and tread blocks are not what you want in a track tyre because they reduce the tyre’s surface area and move around, generating excess heat.
You can see where this is going. ‘Sticky’ race tyres only really have one job to do: grip a dry surface at high temperatures. A road tyre has a more complicated job description, providing good grip across a whole range of scenarios and lasting a reasonable amount of time. It’s all about the right tool for the job.
Modern bike tyres from all the major manufacturers are unbelievably good. Almost without exception they warm up quickly, provide good grip even when cold and wet, cope well with heat and track-day antics, are long-lasting, provide good feedback and are predictable when losing adhesion.
It wasn’t always this way. Two-step changes created the modern miracle which is a motorcycle tyre. The first was the advent of radial ‘bike tyres in the late 80s. Until then, the vast majority of motorcycle tyres were of cross-ply construction, with a few bias-ply. Almost all cars had been using radial tyres for decades, and for good reason. Radial tyres last longer, keep more of the tyre in contact with the road and give better feedback. When Michelin launched its A59/M59 radials for motorcycles in 1987 it was a revelation.
About a decade later the next big step forward came in the shape of silica compounds. Blending these into the tyre formulation saw the creation of the tyre as we know it today, able to grip hot and cold, dry and wet, you name it.
Even just a few years ago it was still possible to find a ‘duff’ tyre from a big name brand…just. There were a few that were not all that grippy when cold or offered poor feedback. But today you can be confident that any tyre from any well-known brand will be excellent.
So how do you choose? That comes down to your machine and the type of riding you do. If you have a cruiser, your available tyre choice will be quite different to a full-on adventure bike. Similarly, if you have a sports bike you’ll be looking at something quite different to an old classic. The kind of riding you do will then start to narrow your choice. If you do a lot of kilometres longevity will be paramount. If you commute in all weathers you’ll need tyres that work well in the rain. So talk it all through with your tyre dealer: they’re your best source of specific advice on tyre choice. And, if they only do certain brands, have the same conversation with another dealer so you can gauge which would really be best. Tyre comparison test in the mags can be useful but they rarely measure how long tyres last. That’s something your dealer will have a handle on.
Features like dual or triple compounds can be useful and are increasingly common. This involves having a harder compound in the middle for longevity and softer compounds towards the tyre edge for grip when cornering. It makes sense, because motorcycle tyres almost always wear out in the middle and when the bike is upright it generates masses of grip because all the weight is pressing down through the contact patch. And who doesn’t want more grip when the bike’s leant over? In practice, however, even the toughest-wearing modern compounds generate massive grip in the dry. So don’t worry about a tyre being single-compound if it does what you need it to do.
Having selected and paid for some shiny new hoops you’ll want to look after them properly to get the most out of them. Checking pressures, cold, at least once a week will not only show if you have a slow puncture, it can save you money. Keeping tyres at the correct pressure ensures they grip well and don’t wear prematurely.
The pressures recommended by the bike manufacturer and tyre manufacturer may differ, so who to trust? We’d tend towards the bike manufacturer, because they're specifying what works for their individual machine. Weight is a factor here. The same set of 120/70 and 180/55 tyres could go on anything from a 180kg supersport to a 280kg tourer, and it’s a fair bet they won’t be specified at the same pressures. So use the pressures given by the bike’s maker as your starting point. You’ll find them in the handbook (if you no longer have it you should be able to find it on the manufacturer’s website). Japanese bikes use “kPa”, Euro bikes use “Bar”, and American bikes go for psi, which we use here in NZ. Ironic, given that NZ went metric in the 70’s. Whichever one you have, your smartphone will quickly convert it for you.
Sometimes you’ll find the pressures on the bike’s swingarm. Yamaha is decent enough to do the conversion for you. Normally they suggest a pressure for rider only riding, and something higher for rider and pillion riding.
This one, on a Yamaha MT-03, is a bit odd, as it recommends 29F/36R regardless of pillion. But hey, Yamaha must know something about how it works, so use it as a benchmark.
On the same bike, the tyre has this written on the sidewall. It’s almost more about a weight limit than a tyre pressure thing. It only says that the maximum you can go to is 41 psi. No mention of the minimum.
You can, of course, experiment with pressures to optimise how they perform for you. If you’re a svelte 50kg you probably won’t want the same pressures as a 110kg bruiser. Other considerations are wear versus grip, ambient temperatures and your riding style. Lower pressures, within reason, can produce more grip, while higher pressures generally deliver longer tyre life. If you are going to try different pressures do it gradually (no more than 2psi at a time) and feel for any difference. And don’t go mad: pressures in the 20s (psi) are seriously low and really only worth considering for track riding, and approaching 50psi will badly affect grip and feel. Again, if you don’t feel 100% confident changing the pressures stick to those specified for your bike.
There are other checks you should do too. Give the tyres a good visual inspection and run a hand over them before every ride. You’re looking for anything sticking into the tyre, splits, bulges or other damage. If you find anything like this get the bike straight into the tyre dealer, preferably without riding it! Sometimes a small puncture can be safely repaired so it doesn’t always mean shelling out for a new tyre. Check for wear, too. Minimum legal tread depth is 1.5mm in all the principal grooves around the complete circumference of the tyre. The hard truth is that anywhere close to 1.5mm the tyre won’t clear water well, reducing grip in the wet, and it will be more easily punctured.
Cracking or crazing of the tyre sidewall is another red flag. The tyre may not be on the verge of destroying itself but it’s a sign of a tyre that’s weathered and probably too old. Modern tyres have a four-figure code surrounded by an oval line on the sidewall, e.g. 4818. They indicate the date of the tyre’s manufacture. The first two numbers show which week of the year it was, in that example week 48, so early December. The second two are the year, so 4818 would be week 48 in 2018. Tyres, even left unused, do not last forever. That clever chemistry that makes modern tyres so good begins to deteriorate over time, leaching oils and silica compounds, and drying out. Manufacturers say tyres will last five years no problem but will then require ‘professional inspection’ yearly after that, up to a maximum of ten years. The inspection will involve a durometer test to check the tyre’s hardness. In reality, the longevity of a tyre can be severely compromised by the number and scale of heat cycles it goes through, meaning some tyres can be toast after three or four years even if they have legal tread depth. If your tyres feel ‘wooden’ or the grip is suspect it’s simply not worth the risk. Invest in some new rubber and revel in the enjoyment and confidence that come with them.
Another thing to watch for, especially at this time of year, is flat spots. If the bike has been left standing on its tyres over winter it may have deformed the carcass, leaving a flat spot. Sometimes these will come out with a bit of air pressure and a ride or two. But be honest with yourself. If there’s still even a hint of judder replacement is the safe option, and you’ll enjoy riding so much more.