KZ550A1 Tires

Hello Everyone,

New to the forum.
Did a quick search on the subject but didn't find anyone posted similar question.

I have 81 KZ550A, was wondering if anybody out there install 100/90/19 front and 110/90/18 bias tires.
Original calls for 3.25H-19 front and 3.75H-18, I can find 3.25H-19 front but seems like nobody makes 3.75H-18 anymore.
Can find 4.00-H-18 tires. Will 0.25 of a inch gonna make any difference? I am thinking not.

Thanks in advance

100 and 110 are fine. You may be able to go to 120 rear even, assuming the wheel is a 2.15 x 18. I'm not sure about clearance around various components is all.