Getting a grip on motorcycling’s favourite conversation
Welcome to motorcycling. It’s a world of excitement, technology, innovation…and now and then, confusion. So let’s start with something simple, those black, round rubber things called tyres. Tyre stuff has gotta be pretty straightforward, right?
Well, on the face of it…no. Getting your head around tyres can have a lot to do with understanding a series of numbers and terms which, to the uninitiated, can make the Enigma Code look like a walk in the park. So let’s demystify some frequently asked questions so that you know what you’re looking at, and what to look for. We’ll cover the basics and some more advanced stuff as well in this brief Bikebiz tyre guide. Here goes!
My tyre is a 180/55/ZR17. What the hell does that even mean?
You can be excused for wondering what’s going here – and this code represents just the basics of the tyre’s size. Let’s break it down from front to back:
- 180 – this number is the width of the tyre at its widest part, expressed in millimetres.
- 55 – a bit more complicated. This number is a measurement of the profile or ‘side’ of the tyre, from the rim to edge of the tread surface, expressed as a percentage of the tyre’s width.
- Z – this first letter is sourced from an international speed rating guide for the safe speed at which the tyre can be used at its maximum load and inflated pressure. In this case, ‘Z’ means the tyre is rated at 240kph and up. (But don’t try using this as an excuse to the police, it’s unlikely they’ll buy it).
- R – this letter means that you’re looking a tyre that has radial construction, rather than bias belted.
What’s the difference between a Bias or Diagonal Tyre and a Radial?
So, we know that ‘R’ stands for radial and ‘B’ for Bias. It might sound a bit grim, but the foundation of a tyre’s construction is referred to as its ‘carcass’, and that’s what these terms refer to:
- The carcass of a bias tyre is a layer-upon-layer construction using ply cords, running to the centre of the tread. This creates a strong, uniform criss-cross structure all the way from the crown (the middle part of the tread) to the sidewalls.
- The carcass of a radial tyre is made up of ply cords that radiate outwards at an angle from the tread’s centre line. The crown is also made up of layers that form a belt.
- The construction of a bias tyre means that the crown and sidewalls of the tyre behave similarly. The softer sidewalls of a radial tyre, by comparison, allow the crown of the tyre to squish onto the road, creating a short, wide footprint or contact patch. At high speeds, radial tyres tend to be more comfortable. As a very broad guide, bias tyres are well suited to bikes travelling at moderate speeds, or bikes that are loaded up, such as tourers, while radial tyres suit powerful bikes with stiff chassis, such as sports bikes.
Can I just put any size tyre on my bike?
Nope. And a good tyre professional will refuse to do it for you, simply because it’s a safety issue. Obviously attempting to use the wrong diameter tyre for your wheel won’t work because it simply won’t fit. The more common concern is riders wishing to fit the correct diameter tyre, but in a narrower or wider sizing that the manufacturer recommends. While technically a different tyre can sometimes be successfully fitted and even inflated, how it fits the rim can cause significant issues including accelerated wear, poor handing and cornering grip. There’s also a danger of the tyre coming off the rim at speed.
Correct tyre fitment is especially important to beginner and LAMS riders. Fooling around with rubber outside the recommended types and sizes is not a good idea for any rider, least of all those new to the sport. Stick with tyres that are within the recommended range, and stay safe
Tread patterns – fashion or function?
If you’ve looked at more than a few motorcycle tyre tread patterns, you might be wondering what it’s all about. Tread patterns tend to be dictated by the focus of the tyre – is it a touring tyre designed for heavy loads ad big distances, a tyre designed to perform in wet weather, or a sports tyre designed with high speed grip as the number one priority?
The grooves and patterns in tyre tread optimize traction in varying road conditions, help the tyre carcass to flex and also help to shift or ‘pump’ water away from the contact patch so that grip is maximized in wet weather. Remember that every road tyre, to some degree, is a compromise, because riders will expect decent performance and grip in summer, winter, wet and dry. As a broad guide:
- Lots of tread grooves often indicate a tyre created to perform well in wet, cold weather
- Minimalist tread patterns point to a sporty tyre with a sticky compound designed for warm, dry surfaces and with little consideration for wet weather grip
- Knobby or chunky tread patterns bite into loose dirt or mud surfaces and are great for off road or adventure bikes, but don’t offer premium grip on tarmac
- Striking or interesting tread patterns are often designed to boost buyer appeal – yes, the cool factor sells tyres, too!
- Road tyres must have at least some tread so that ‘wear bars’ can be incorporated and we (or possibly the police…) can easily see when a tyre is past its best.
Race tyres – slicks, wets and why using them on the road might kill you…
Racing slicks are sticky, expensive, specialist tyres created for use by elite riders on clean, dry surfaces. They’re usually brought up to optimum temperature with tyre warmers, too. The compounds used in race slicks sacrifice longevity for grip. Even at club racing level, these tyres tend to last for just a few track sessions before they’re toast. Slicks offer spectacular grip across a narrow temperature range and don’t cope with rain, poorly surfaced or dirty roads. . So…they’re finicky, expensive and illegal on the road. But if you want to experience the magic grip of slicks in their perfect environment, contact us and book a Bikebiz track day.
Racing wets would be a great choice to get you through winter on the road, surely? Yeah…nah. Racing wets are designed for wet tracks only, and rely on plenty of surface water to keep cool. On dry surfaces they quickly overheat, after which they don’t just stop working, they literally start falling apart. Oh, and like slicks, using them on the road is illegal
Getting a grip during El Nina
Weather or not you buy into the whole climate change debate, The Bureau of Meteorology itself tells us we’re in the middle of a long-term La Nina weather cycle. This means changeable weather that’s also cooler and wetter than what we’re historically accustomed too. So we can easily find ourselves facing dry roads and wet in the space of the one ride. Without a pit crew standing by to conduct a quick tyre change, how do we cope, stay safe and still have fun?
- Stop, think, change your pace – you can’t safely carry on riding a wet road at the same pace that you ride in the dry
- Optimise your tyre pressures – this is a whole conversation in itself, but be aware that the pressures that work in the dry might not deliver the best grip in the wet
- Choose versatile tyres – tyre manufacturers are now creating amazing designs that perform superbly in the wet and dry alike – you can find out more now by contacting a Bikebiz tyre expert.
Knowing a few basics about tyres can make you more confident about your choices. There’s a good reason so many experienced riders come across as tyre obsessives – few other variables affect our confidence and performance as much as having the right tyres fitted for the bike we ride, the way we ride it and the conditions we experience.
We hope that this brief Bikebiz Tyre Guide has been helpful and if you have any questions at all regarding the right rubber for your ride, contact a Bikebiz tyre expert for more information.
Meanwhile, have fun and stay safe!