This topic always generates a lot of talk and mixed opinions. Unfortunately understanding tyres in detail can be a complex subject.
So here are 10 things that might make things a bit clearer for you.
1 – Tyres have two main functions
· To provide support and act as part of the motorcycle’s overall suspension and deal with imperfections in the road
· To provide surface grip through a chemical reaction between rubber and road, yep it’s actually a chemical reaction!
Tyre companies’ employ chemist / chemical engineers to work on tyre design.
The biggest structural elements of a tyre are the tyre carcass and the tyre pressure.
The compound elements are designed to provide a chemical reaction with the road that in turn gives us surface grip.
Unfortunately, sometimes the requirements of each of these main parts will contradict each other.
Furthermore, they each deal with different sciences. The structural side is governed by the laws of physics, while the compound is more so governed by the science of chemistry.
Example: Lowering front tyre pressure to generate more compound heat will make the overall front suspension softer. Do this on a bike that has front suspension that is already too soft, then you’re going to get yourself in a lot of trouble.
SIDE NOTE: MotoGP commentators constantly referring to ‘cold tyres’ is just a far to simplistic way to look at it.
2 – Heat & Grip
As with their functions, tyres also have 2 different ‘working windows’ or design conditions.
Tyres have a ‘heat’ window (which every commentator on the planet bangs on about over and over again) and they also have a ‘grip’ window (which no one talks about enough)
Some people think, more heat = more grip. This is not always true because it is dependent on the tyre.
To think of tyres as SOFT, MED & HARD is a little too simplistic unfortunately.
Tyres need to be characterised by their GRIP & HEAT characteristics.
To explain this, we are going to compare REAR Pirelli racing slicks vs REAR Bridgestone racing slicks.
The soft from both companies are their most ‘grippy’ tyre. HOWEVER! The Pirelli soft is designed for hot conditions, while the Bridgestone soft is designed for cold conditions.
How they should be defined is like this:
Thus, to try use a Pirelli Soft in cold conditions would just be the wrong choice. Even if you want the most grip you can get.
3 – High Tyre Grip comes with side effects
While we all want as much grip as possible, there are some side effects that come with high grip tyres.
· The higher the surface grip, the higher the tyre wear and shorter life it will provide
· The higher the surface grip, the more likely tyre tear is. Tyres do not tear without high surface grip.
· The higher the surface grip, the smaller the working window for the tyre
· Too much grip makes a bike hard to steer on partial throttle and will result in SLOWER lap times
The highest performance race tyres are only design to do about 12 laps. So if you get 40-50 laps out of it, your doing awesome.
Higher performance = higher wear = higher costs
4 – Grip Coefficient
Coefficient is just a big word to quantify the overall effect of something. In this case we are talking about the overall surface grip that is provided by track and tyre.
This is really important to take into consideration
You cannot just consider the tyre grip, you must also take into account the track or road grip.
· Low grip tack with low grip tyre = low overall grip, but next to no tyre wear
· High grip track with high grip tyre = mega high grip at first. This might sound ace at first but think back to the side effects of grip. Very high chance of tear and can be slower
· High grip track with lower grip tyre = still high grip but not too high.
Some brand-new track surfaces provide very high grip. Especially with this new smooth ‘fine aggregate’ type of tarmac that is being used with all new track surfaces. Those that went to The Bend in the early days know exactly what we are talking about.
The new surface at Broadford is not as high grip as The Bend was in the early days, but it is still a very high grip surface. Thus using high grip tyres greatly increases the risk of tear.
This is because the overall grip coefficient will be very high
5 – Grip Coefficient PLUS
Now to add to what we just talked about. There is one more main element to the Overall Grip or Grip Coefficient. Your bike setup.
Thus, the real formula to understanding grip is: Track Surface + Tyre Grip + Bike Setup
Some setups will provide more grip than others. This is why in MotoGP bikes like the Honda will often use harder tyres in the race compared to the Ducatis. The Honda has a higher grip chassis setup so a less grippy tyre works better for them.
Even in our own Race Center stable of racers, some of our bikes have a higher grip chassis setup than others. So the result is some of our riders will use different compound tyres at the same track on the same day to one another.
Understanding if you have a high grip chassis setup or not is important.
6 – Your Suspension and Bike Setup has other work to do
Motorcycle suspension has a lot more to do than just manage your tyre wear. In fact, it has much more important things to do. In order of priority they are:
1. Provide the rider with confidence and feel in most of the riding conditions you encounter. This not only gives the rider confidence but increased safety too.
2. Produce fast & consistent lap times
3. For road bike, absorb bumps
4. Manage tyre wear, (least important)
You should never adjust your suspension based solely on tyre wear without considering the other 3 higher priority items & all the things we have already discussed.
Adjusting your suspension based on tyre wear without understanding the below things first is not right.
· if you have selected the correct tyre
· running the right pressures
· Using the tyre within both it’s grip & heat windows
· For track bikes, using your tyre warmers properly
Any person, article or video that talks about adjusting your suspension based on tyre wear without talking about all these things too should be ignored. It is misleading.
7 – No uniform method or terminology makes it even more confusing
As our example with the Pirelli and Bridgestone slicks shows, not all tyres are made in the same way, nor is the terminology used by each manufacturer the same.
This makes it confusing ☹
Scientists are great at really complex things, just not great at explaining it well.
Let’s take the below graphic from Pirelli, even this can be misleading. Practically the bit about ‘smooth’ tarmac vs ‘severe’ tarmac.
Tracks like The Bend and Broadford’s new surface are smooth right? (well except for all the new bumps at Broadford)
However, they are actually quite severe in terms of wear. It’s misleading because of the word smooth. You need to treat these tracks as Severe not Smooth.
But there is even more wrong. On a stinking hot day, like stinking hot, you could use an SC0 on a Severe track but this graphic doesn’t show that.
In fact the graphic indicates you might use an SC0 on a severe track when it’s cooler and if you did that it would tear itself to shreds in a lap or 2.
What you really need to know is the tyres heat range and it’s grip profile. If a tyre is high grip, don’t use it at new high grip track unless you are ok with tearing it. Simple.
High grip track with high grip tyre = high chance of tear.
The good bit of news is that in generally terms while their temp ranges will be different, all soft tyres will wear faster, while all hard tyres will wear slower. It’s just they have different target temperature ranges.
8 – Tyre Selection
This is not always easy unfortunately. The good news is for beginners or intermediate riders it is less critical in terms of tyre tear.
If it all seems a bit confusing, its always best to speak to an expert in the area and someone you trust.
Tyre selection is one of the most important things you will do from a bike setup, lap time, safety and cost perspective. Again, adjusting suspension or pressures for an incorrect tyre selection is not right.
While we might grave it, there is no set-in stone specific number to use. You must take all factors into consideration and make an educated decision based on the information you have.
Here is the formula to help you decide: Track Surface Grip + Bike Setup Grip + Performance vs Cost
And here are some examples on how to apply it. Providing you have the information that is ☹
*NOTE: The higher the overall grip, high chance of tear and wear rate will be faster
Example 1:
You have a high grip bike setup, going to a high grip track like Broadford, its 15degC and you do not want to tear tyres. The only choice you have is the SC2. Anything else will be too high grip and will tear
Example 2:
You have a twitchy low grip bike setup, going to a high grip track like Broadford, its 15degC and you are chasing lap time. The SC1 is for you and you probably will not tear it either.
9 – Cold Tear & Hot Tear
There are some key things to know:
· To tear a tyre, you must have a lot of grip. You will never tear any tyre on wet tiles, will you?
· Once a tyre is torn it is damaged. Trying to ‘clean it up’ is hard and can lead to misleading info for next time. The missing bits of tyre from the tear have been left on the track, they are not coming back.
· It’s much better to properly understand why the tyre tore in the first place and resolve those issues rather than try to fix the damaged tyre.
Cold tear is a situation where a tyre isn’t just ‘too cold’ but that it is producing so much grip that it tears. While the temperature may have something to do with it, it is more important to realise it has too much grip and focus on that as well, not just the temperature.
For example, doing something like letting out some air pressure to generate more heat is a bit silly. Why because lowering rear tyre pressure will also increase grip.
Instead what you want to do is focus on removing some grip rather than just generating more heat. The best solution would be to select the tyre designed to work in those temps.
However, let’s say we can’t do that. Making a setup change that give the bike more mid corner rotation and would spin up the tyre slightly easier will both reduce some grip and generate extra heat too. So that is a much smarter thing to do then letting out pressure.
Hot tear. When a tyre gets too hot it will blister rather than tear.
Instead the thing we know as hot tear is just another form of a grip tear. It’s very common on new tracks. Where it comes from is from a tyre losing grip and then re gripping. On a less grippy track in the same situation it would just spin nicely and predictably. However, on a high grip track where it would normally wheelspin nicely there is just a bit too much surface grip still because of the tarmac and it tears.
It looks different because the tyre is actually in a good heat range or to the higher end of heat range. So it just tears different. Sure it might be really hot but its not the heat alone causing the tear, it’s the grip.
10 –Overall Grip and Riding Grip are different things
This may be a little bit different to what you have learnt and hard to get your head around at first but clear your head and have a think about it.
Too much overall grip can actually feel like a lack of grip to a rider when pushing hard. What? Yep that is correct. Too much grip can make you feel like you have no grip.
Why? Because ultimately what you perceive as grip and feel, is the bike doing what you want.
If for example you have too much mid corner grip, subconsciously without even realising you will be forcing the bike to turn better on the throttle than it actually wants too.
It can also make you carry more lean angle than is ideal to help it steer.
So you’ll be doing these things without realising it and the bike might let go a bit just because it can’t follow the lines you are asking of it.
Yet when it let’s go, you’ll think ‘I don’t have enough grip.
Understanding if a bike is letting go because you have too much grip or because not enough grip can be hard.
Here is a little bit of gold for you. Remember the stuff we have already covered? What if you see what you used to think of as cold tear as too much grip. If you have those symptoms and your bike is letting go, it’s likely you have too much grip rather than not enough.
Look it would be nice if you could look at the wear pattern of your tyres and concluded what you need to do with setup. However that’s just not realistic. It’s not because tis so complicated but rather because there are so many factors at play in this. So you need to take your time to understand it properly and that takes a lot of experience. So lean on people with it 😊
If you want some great tips on specific things you can try when you have these tears plus get our latest tyre data including pressure for the new surface at Broadford, join our Race School. Race School has this data and more and is still at our introductory price of just $99 for 12 months.
Ride safe & fast 😉