It is mandatory that your tyres conform to the following rules:

• Tyres must be kept in good condition without bulges, splits or breaks.
• Pressure must be maintaining to recommended levels.
• There must be 1mm of tread depth throughout a continuous band measuring at least three quarters of the breadth of the tread around the entire circumference OR if the grooves of the original tread pattern did not extend beyond three quarters of the breadth of the tread any groove, which showed in the original tread pattern must have a depth of at least 1mm. AND
• The base of any groove, which showed on the original tread pattern, must be clearly visible.

What You Should Be On The Look-Out For

• Foreign objects sticking out of the tyre (esp. bits of glass or flint in the grooves of the tread).
• Cracks in the side walls - very important if the bike has been laid up for a while.
• Tread depth (see above)
• Pressures - these need to be checked while the tyres are cold at least every fortnight using a good quality tyre pressure gauge.
  N.B. the gauges found in most petrol stations are notoriously unreliable.
• Uneven wear in the tyre - especially any 'flattening out' in the middle, which leaves a ridge.

More About Pressures

This is the first thing you should check if the bike starts handling badly. Even a couple of pounds difference in the pressure can make a huge difference and tyre wear becomes ruinous. The effect of over or under inflation can be shown thus:

Also, if you go to a different make from the one originally fitted you may find the pressures have to be different as well. For example the Honda Gold Wing runs on the following pressures for the makes indicated