1992 KAWASAKI ZZ-R600

Q:My ZZ-R needs a new front tyre. Standard fitment is a 120/60/17; I am unfortunately on a very tight budget! I have a good used 120/70/17 tyre; would I be able to use this without upsetting things too much and providing I have enough clearance? I’ve been a reader since Motorcycle, Scooter & Three-wheeler Mechanics days! Malcolm Sutton

A:You’ve been reading the mag even longer than me! I bought my first copy as a schoolboy because the then-editor, Charles Deane, had tested the CB750 for the June 1970 issue. I do not see any great problems in using the bigger tyre providing it has the correct 55W rating, other than perhaps some subtle effect on the handling as it will probably be a little heavier and have a larger moment of inertia and gyroscopic effect but I do not suppose you will notice this in practice. In theory, your proposed tyre will have a radius 12mm larger than the correct one so you would need to check for clearance under the mudguard —though it should be okay on the width. However, one other effect will be on the speedometer reading as your bike has an old-fashioned mechanical drive and cable driven by the front wheel. It will read a little slower by about 14%, so as we are talking about a Kawasaki that would mean it would then be reading correctly!