tires size

HELLO GUYS I HAVE A 1978 KZ1000 Z1R JAPANESE VERSION WITH TIRE SIZE 3.50 18 FRONT AND 4.00 18 REAR. WHAT METRIC SIZE SHOULD I USE IN ORDER TO BE EXACTLY THE STOCK MEASURE, IM ALMOST CERTAIN A HAVE TO GO FOR 100 AT THE FRONT BUT DO I GO FOR 110 OR 120 IN THE REAR. WHATS BETTER? PLEASE ADVICE THANKS

100-90-18 front 110-90-rear will give you the exact sizes. In front you may substitute.
90-90-18 or 110-80-18

in the rear you may substitute
120-90-18 0r 130-80-18

You may refer to the following thread that covers exactly that subject.
kzrider.com/index.php?option=com_kunena&...ew&catid=5&id=365224

You won't get an exact size in a metric tire. That's like asking what size metric socket is exactly the same as a 1/2". A 13mm is close, but not exact. If you want exact get the 3.50 and 4.00. If you want metric tires that work you can do this. Get a 100/90-18 front. It will be a little smaller diameter as well as less width than original, or you can get a 110/90-18. It will be a little wider and larger diameter than original. On the rear you can get a 110/90-18 but it will be much smaller diameter than the original size although width will be close, or you can get a 120/90-18 and the tire will be too wide but the correct basic diameter. So there you go, that's the choices in metric to be "exact". Look for manufacturers that support inch size tires and support those companies. Metzler, Avon, continental among others offer correct tires, but few companies carry them. If you must a 100/90-18 is "OK", a 120/90-18 is "OK", but not exact.

thanks ron i want to g o for the stock ones,in what brand or where do i find the 3.50 and the 4.00

If you go on the Avon web sight they give you the exact sizes. in both metric and inch. The tire sizes i gave you are measured from those graphs and are with in a few mm of the inch sizes. Check it out for your self. They also have the tires in the inch sizes.

www.avon-tyres.co.uk/motorcycle/