MORE TYRE TIPS
I was interested in the letter about tyre age and performance in RC176, which made some very good points. However, it misrepresented how a tyre grips the road and how the coefficient of friction works. The coefficient of friction is independent of surface area and speed of contact, so it’s incorrect to bring tread patterns into the argument.
Tyres grip the road by ‘moulding’ to the surface. They grip better on a rough surface and less so on a smooth surface. This means that tread does actually reduce grip, but only in perfect conditions, dry and smooth. It becomes of great benefit in its ability to move water out of the way. So hard old tyres are bad because they are unable to mould to the surface. Bald tyres are bad in all except perfect dry conditions. Jerry, who wrote the letter, is right about fitting new tyres but it’s not a perfect world – good advice though.
Now what about mixing fork oil: do equal quantities of 10W and 20W make 15W or is the 20W still 20W? Discuss!