I have a CBR 1000F-J 1988 the manual says a 170/60/17 is the right size tyre for the rear but several dealers say the right size is 140/80/17 can I use a 170/60/17 as I have just bought one as I followed the sizes in the manual.

Are you looking at the right year in your manual? A 170 sounds a bit wide for 1988, most bikes had fairly skinny rims back then, the wider section tyres really came in in the early 90's and the CBR thou range covered all that time.

Top bike by the way, bullet proof battleship that was never accorded the respect it deserved (bit like the RF 900 really )

The one 170/60 - 17 could be correct.

My old VFR750FJ originally had a 110 front and a 140 rear but somebody changed the wheels for CBR1000 ones.

Here's my VFR, does that look like the same type of wheels.



If its the SC21 model, its a 140 rear. If its a SC24, then its a 170 tyre.

My rear wheel is also marked as having a 5.5" rim on it. So you could check for that as well.

The wheel sizes took a change around that time, check what size rims you have, written on the sides around the spokes. once you know the sizes it is easy to get the correct tyre size. Don't make the mistake of going for the wider size as this can slow down the steering and make the bike harder to turn.