Advanced Riding Techniques Blog

Advanced Riding Techniques in Cape Town, South Africa | Learn to ride a motorbike with advanced driving skills.

Is Bigger Better?

How many times have you seen someone admiring the rear tyre of a motorcycle? Especially when it is super-wide. There is, unfortunately, a difference between cool and functional.

Motorcycles are assisted in a turn by tyre shape: as the bike leans off the centre of the tyres, the circumference becomes smaller. This is demonstrated easily by taking a styro-foam cup, putting it on its side on a table and pushing it. It goes in a circle, because the bottom has a smaller circumference than the top.  Motorcycle tyres work on the same principle, unless you are still riding that classic motorcycle which has original tyres that are virtually square in profile. That's how it was back in the day...

A smaller section tyre (the big number at the start of all modern tyre sizes) will allow the bike to roll into the turn faster, because it takes less effort to get it from the big circumference in the centre onto the smaller circumference on the side. Simple as that!

So, ignoring for a moment the effect of aspect ratio (the height of the sidewall vs the width of the tread and the second number shown on modern tyre sizes.) on overall handling feel, buying a bigger tyre to replace the standard ..e.g. 200/60..over 180/60 WILL change the ability of the tyre to move “quickly” in cornering situations and be particularly noticeable when trying to change directions through an “S” bend. Also, a larger tyre with the same aspect ratio will have a greater circumference , which will dull acceleration, but will eventually lead to a higher top speed..if you can ever get there with Cameras and Traffic Officers waiting for you.

So now factor in the potential choice of aspect ratios; say 180/55 vs 180/60 and again the overall circumference changes affecting top speed, acceleration ( via an effective gearing change ) as well as handling feel...so....

Is a big tyre faster in a straight line or does it offer better grip when leant over??  Nope, wrong again. The amount of traction you have is a product of  a bike’s geometry, weight and the co-efficient of friction.  In other words, the angles at which the tyres interface with the road, the stickiness of the tyre, and the weight of the bike. If you have a bigger contact patch, the weight is spread over a larger area, but the amount of traction does not change. Motorcycle & Tyre manufacturers spend large R&D sums on working out what size tyre will optimise the handling and transferring acceleration and braking forces at maximum efficiency.

Unless you are drastically changing the power output of your machine, or adept at understanding the affects that size and aspect ratio changes have on handling feel, it is best to stay with recommended tyre sizes...

Oh, but wide tyres definitely look cool.  No doubt about that…just gawp at any over-tyred cruiser or superbike and see the owner’s chest swell with pride..just don’t ask them how it feels now through the twisties..

As always, stay upright and in control ..

Mark




Mark

I have been riding all size motorcycles for over 30 years. I am lucky to have both Sport & Trail bikes to ride. The experiences gained on the road, track and trail have given me a great number of pointers and a unique perspective on safety and fun at the same time. I am originally from the UK, where I perfected my proficiencies with Royal Automobile Club and Advanced Motorcycling Association training, but currently based near Durbanville, Western Cape.

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