Are Wide Tyres Better On A Motorcycle?

The Question is, are wider tyres better? And I hope by the end I have given you some information to help you make better choices.

The story made me think about how many misguided preconceptions we all have about tyres, and so I thought I would add my thoughts to a question that gets asked often, but maybe very rarely in the right way.

Sat there quietly minding my own business outside a cafe with a coffee one day, I was joined by a guy who had just arrived on one of the Victory cruisers. Fairly quickly the subject moved to tyres and in particular the rear tyre of the Victory.

I have heard similar conversations with Triumph Rocket 3 owners and others though to be clear.

The comment that got my attention was that the bike didn’t handle like a bike with a fat rear tire,

I didn’t say much. My Laverda SF2 with old school skinny tyres sat not so far away.

But it showed an insight into the fact that fat rear tyres aren’t always the best solution.

The Victory had a back tyre a just a little less than 10 inches wide.

For some, as with the Triumph Rocket 3 owners, this wide back tyre was a symbol of their manhood and they were honour bound to defend it’s superior performance, but this guy was different. He at least acknowledged the downfalls in some way.

Did I have the energy to discuss this convoluted subject that day, or try and explain some of the basic physics of the involved?

No to be honest.

It is a complex subject to say the least, and there is no one answer that explains the whole subject.

Above all, I had come out to ride not to chat.

In my years of riding motorcycles of all sorts, in all kinds of conditions, I have studied and learned many things about tyres. That relatively small band of rubber around each wheel is, I would say, without a doubt, one of the most misunderstood subjects in the motorcycle world.

I have watched a tyre engineer describe in detail how a tyre works. It left experienced racers, riders, journalists and even their own tyre reps baffled. Because, once you get down to the basic physics of when the rubber meets the road, it simply cannot be reduced to basic terms most of us can understand easily.

There are so many interactions taking place, that understanding the effect they all have on each other would be a lifetimes work.

In the end, one of the most significant elements of a motorcycles design, is also one of its least understood components.

Marketing may well have played a big part in why a particular manufacturer chose a particular tyre, and we all have favourite brands, but choosing the best performing tyre for you and your motorcycle really can be a minefield.

Without any real understanding, we make our minds up based on half truths and trends, as well as hopefully some good industry advice and a little personal experience.

We choose tyres, and tire sizes, based on sales pitches, fashions, and hunches as well as factory specs.

Even most tyre fitters and manufacturers can’t really be trusted for honest, informed advice much of the time. It is after all in their interest to drive sales of high ticket items, and a 10” wide tyre will always cost more to buy than a 4” wide tyre.

Here though I do have to say, there are a few seriously good tyre experts in most countries, but they are most often associated with the various racing types. If you want maximum grip with no compromise, go talk to someone in the road racing scene. The same goes for off road use. Go to the track and seek out the real experts.

Where this idea doesn’t work so well is with mixed use.

There are very few experts in multiple area’s of use and it is a very complex subject. Our roads arent as smooth or abrasive as a track and we sometimes carry luggage and ppassengers.

Tyres on motorcycles in the showrooms have become increasingly wide over the years. The reason we are told is you simply benefit from the bigger contact patch of a bigger tyre considering the weight and power of modern motorcycles.

You will be told that Superbikes of fifty years ago would only have made 70HP, so skinny tyres on 18 inch rims were enough. But that now, with 200HP engines they simply aren’t enough, and any argument or discussion gets difficult, because there is some truth to that particular fact.

But is it the whole truth of the matter?

The simple answer to that, is an emphatic no.

A wider back tyre will give you a bigger contact patch, so it will assist hard acceleration, but that is a small part of tyre performance and riding a motorcycle.

As the tyre leans that increased contact patch also improves side grip, to a point, and it can, if designed well, also give better feel after the point of adhesion is broken.

That will help better riders use that slide to tighten up cornering and get on the throttle faster, but that sort of limit is best kept just for the track in my opinion, except in emergencies of course.

However, and here it starts to get more complex.

If the rear tyre is significantly wider in profile than the front, when the motorcycle is leaned over, the geometry of the motorcycle will change with every degree the motorcycle is leaned.

Critical here is the difference in the widths of the front and rear tyre,

The proportion of the width of the tyre in relation to the depth of the profile from the peak of the tyre to the rim edge also plays a part, but for the purposes of this video, I am going to assume that all tyres have the same profile, so that part of the equation is removed.

With a wider back tyre set up, as the bike is leaned further over, the geometry of the motorcycle changes. It gets sharper, and this will make the bike turn more quickly, and can cause the rear tyre to break away faster than it would otherwise. It also makes it much easier to end up high siding the bike when the rear tyre starts to slide away then grabs again.

Try to imagine the changes.

From the pictures here I have tried to show a view of the position that tyres with different widths naturally move to as a bike is leaned into a turn.

In the left picture you can clearly see the 3 tyre widths as if they were running vertically on the same axle.

In the 2nd picture, you can see the same 3 tyres in the positions they would end up in when the motorcycle is leaned over. If you look closely, you will see that the widest tyre’s axle will be higher at the same angle of lean than the narrower tyre’s. You can also see that the difference is less when the tyres are more similar. The biggest difference is between the widest and narrowest tyres, and you can feel this when riding.

In the 3rd picture I have tried to show how the bike actually runs when the narrower front tyre and wider rear tyre are leant over in the real world.

As the bike leans, the narrower front tyre tries to cut into the corner faster, immediately altering the angle of the chassis very slightly. The wider rear tyre also effectively lifts the rear of the chassis slightly higher off the surface than the narrower front tyre.

That slight change in the angle of the chassis in relation to the surface and the direction of travel, tightens up the cornering. This is emphasised by the effect the braking also has on geometry as you slow and lean into the corner. The effective centre of gravity is moved further up and forwards, changing the effective weight balance at the same time as the whole chassis is angled more sharply into the corner.

Now I’m going to steal a phrase from the Superbike Surgeon who runs a great channel I will link below and say, I hope that makes sense.

At the point shown in the 3rd drawing, if a racer applies controlled countersteer it will increase both the angle of lean and the change in direction of travel even more, often pushing the rear tyre past adhesion limits. At this point, the rear tyre slides and the angle of the motorcycle in relation to the turn is increased. This allows a good rider to stand the bike up faster and get back on the gas sooner to take advantage of the bigger contact patch.

All of this happens instinctively with a good racer and it is all done very quickly but smoothly.

As the motorcycle stands up again, the width of the rear tyre becomes less relevant to geometry, and the depth of the profile, becomes more important. This is where the tyres profile and pressure begin to play the most important role, especially in Sport tyres.

The angle of a line drawn through the front to rear axle in relation to the road will generally become slightly less as the power is applied, moving the effective centre of gravity slightly down and rearward, helping the bike to gain better traction as it rises towards the vertical and the size of the contact patch increases.

Purely from a geometry perspective, the most true running set up, is to have the same tyre width both front and rear. It means however far you lean the bike over, the chassis geometry stays the same, so the turn in both front and rear are the same. The bike will track in a neutral way, without tightening up the corner for you.

2 tyres that are matched in width will make it easier to achieve a fast, smooth line around the corner, whereas a wider tyre on the rear of the same bike, will make a fast in, slow apex, and fast acceleration out of the corner “Point and shoot” approach work much better.

This is where it starts to get personal, and the reality is, each combination will work better for different riders and different bikes.

With the front, again a wider tyre will give more side grip because of the bigger contact patch. A slide with a wider front tyre is again more susceptible to grab again after it has begun to slide, so it is more likely to be susceptible to a highside, whereas a narrower profile is more likely to suffer a lowside type spill when pushed past its limits.

So, for a rider who is hard on the brakes, and fast out of the corners, a wider front and rear tyre will aid stopping and acceleration, but for a rider who likes to carry extra corner speed, a more matched profile front and rear will help them do that more smoothly.

Narrower tyres will always turn in faster, especially when using counter-steer.

Having ridden many bikes hard, and thinking in particular about a Triumph Daytona track bike I rode very hard indeed. I have felt those effects first hand.

The Daytona had a very wide rear tyre set up, I have tested and passed its limits on more than one occasion, sometimes saving it, sometimes not. I love the bike and it has many qualities that help the rider, but it is sharp steering at the best of times, and the wider rear can make it even more twitchy at high lean angles.

Conversely, the older Yamaha FZR1000 has a much more balanced tyre set up front to back. It helped me learn how to carry more speed through the corners in a way I found much harder on the Daytona.

The Daytona just worked better with a hard in, hard out technique.

And here we get the bit that gets missed the most.

As I have said, a narrower tyre actually requires less of a lean angle to produce the same radius of turning circle. Wider tyres are also heavier, so will always be harder work as well as requiring a greater lean angle to make the same turn.

So you see both set up’s have their own pro’s and con’s, and this is emphasized even more with a classic bike like my old Laverda SF2, which runs smoothly through the bends, turns in quickly and holds it line around corners.

Because narrower tyres require less of a lean angle to produce the same turning radius and weigh less, The Laverda, with tyres that are narrower and similar widths front and rear, is just more agile. It changes direction faster and with less effort than the newer bikes. The narrow tyres on those old Borrani rims will never have the extra side grip a wider tyre set up has, simply because of the smaller size of the contact patch, but it doesn’t need that side grip to achieve the same turning radius.

Now this is only one small part of a huge equation that makes choosing the right tyres for you and your bike a very complicated affair. Tyre profile plays a huge role too, but that is a story for another day. That and the rubber compound is often where our affinity with different manufacturers comes from.

Rotating mass, unsprung weight, rake, trail, air pressure and many other things can also have a major effect, but after seeing a recent article on the subject that left everyone speechless in the comments because it was so inept. I thought I would add this small conclusion.

This is a conclusion drawn from sound scientific principles and discussed long and hard with many experts. Many could simply not agree with each other, despite having similar years of experience in the industry.

That alone shows how much this complex subject is both misunderstood, and very subjective.

These are my thoughts after listening to all those people I have had the conversation with, and after many evenings of contemplation.

You may not agree, and that is fine. Tell me in the comments what your conclusions are?

One of the things I learned was that even with the same use, some bikes just liked different tyres to others. Bridgestone S20’s worked best for me on the Daytona but the EXUP just preferred the Conti’s, whereas the Michelin 2CT’s probably worked equally well on both,

Tyre use plays a huge part, and here I am simply looking at the performance of the tyres on a sound, tarmac, road surface. The tale of what is best on rutted roads, in the dirt and in sand is a completely different rabbit hole.

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