On my 99 fazer I have a 110/70 on the front and a 160/60 on the rear.
I get that the big number is the width of the tyre but the 2nd number is the “Aspect ratio (90%) (Section height divided by Section width as a percentage)”, lolwot?
If I want to fit a 120/60 on the front instead, how will that affect how the bike works? I’ve been told that the extra width will make it more stable but harder to lean in corners? what about the other number?
Idiots guide for an idiot would be much appreciated.
Stick with the manufacturers recommended sizes (service manual)
and try different tyre brands if you don’t like your current ones.
Would never mess around with incorrect sizes…
I’m no expert and don’t know much… But I too have '99 Fazer and my front is 120/60 and have had no problems at all. Not that I have anything to compare mind you. I only noticed the size a short while after the first time I replaced the front - I trusted the workshop to fit the right thing. I believe that on later Fazers 120/60 is the right size.
As for the numbers, the second is the profile of the tyre, i.e. a percentage of the width. So as I understand it a 120/60 would mean the tyre profile is 60% of 120, so 72mm. But as I said I’m no expert so I stand corrected… 
aye, you’re there… although the 120 will mean it would be slightly slower steering, the 5mm reduction in ride height should make up for it - you get less ride height , which tightens the rake, giving sharper steering with the trade-off of less stability.
110/70/17 110mm width 77mm height
120/60/17 120mm width 72mm height
steering head goes 5mm down, front tyre diameter 10mm down.
cheers guys. road pilot CT2’s it is then!
I’m a silly sod, I was looking at the wrong bloody model! gonna get the road pilot 2’s tomorrow.
Turns out if you run the wrong size tyre not recommended for the bike, you invalidate your insurance! You might want to watch out LegendOfG. you’re screwed if someone crashes into you
is this what your insurance company told you, or man in the pub? OEM tyres are not always the best choices but a compromise. yamaha’s 04 r6 recommended choice was inferior to what most people changed the front to and as a result they changed their stock tyre the following year.
changing the tyre ratio is a similar modification to changing suspenion and geometry. they would have to prove that the tyre choice was unsuitable for the bike and as a result contributed to the accident, especially as the change is to suit the bikes usage. not only would i be very amazed if that was even checked in the event of an accident, i’d be very surprised if many insurance co’s actually had this as a stipulation.
the rear tyre on the 06 r1 is a 190/50 but many people (including myself) switch for the 190/55 as it gives a steeper taper and more responsive steering (and is a stock size for many comparable litre bikes now). 180/55’s aren’t uncommon either.
woman on the phone at essential rubber told me
