‘Cats Claw’ Theory – Motorcycle tyre grip

We’ve been working on this for a while at The School, trying to show riders the amount of grip available when cornering, in a simplified straightforward way. Many thanks to Martin Knox for the concept.

It must be stressed that this is the theoretical maximum amount of grip available when cornering, dependent on lean angle, on a flat consistent surface, for an expert rider.grip-final-plus-logo

This illustration combines the radial (centrifugal) forces from John Bradleys work, with Mohr’s Circle for the relationship between radial and tangential forces.

The dark green area shows the further you lean, the less cornering grip is left.

The light green areas shows the available tangential grip at angles of lean which is used in braking, accelerating or steering.

Both start to drop off rapidly after 45 degrees of lean.

So at 45 degrees of lean you have in theory 45% of your maximum radial grip left for cornering, (which seems reasonable), and 80% tangential grip for braking and steering (which doesn’t). In practise there is significantly less tangential grip apparently available, particularly when braking, although we know there is enough grip to wheelie a bike out of a corner at 45 degrees of lean.

We got a literal ‘thumbs up’ from Vittorre Cossalter (Motorcycle Dynamics)

We’ve worked backwards, assuming the maximum lean angle is 60 degrees (zero grip), which is only available on a dry race track with soft race rubber.

To stress again this is theoretical, assumes ‘steady state’ on a race track with slicks, ignores the effects of bumps and dips, variations in road surface etc. or extra loads due to sudden steering, braking or accelerating which all need to be smoother the nearer you get to the limit to avoid going over the edge.

You need also to consider weight transfer and tyre slip – which we will discuss later.

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