On my 1990 K75 I have a 100/90-18 tire on the front and a
130/90-B17 on the rear, even though they are only 6 yrs old the side walls are starting to crack so I'm going to replace them.
Just wondering if I have to stick with these exact sizes or if I change them a bit like you can do with car tires?
Thanks,
Chris

100/90-18 or 110/80-18 front

130/90-17 or 140/80-17 rear

The 110F/140R combination was used on some of the later RSs on the same sized rims.  With the larger sizes you might be able to move to radial tyres.

Al

You can go up 1 size front and rear and they will still fit.  Your bigger limitation is the 2.5" / 2.75" rims that limit what you can fit on the rim

Thanks Gents,  not many tires in our sizes anymore.
I'm thinking about this combo,
http://www.fsmotorcycle.com/tires/sport-tires/pirelli-sport-demon.html
Anyone using these?
Thanks,
Chris

AL-58 wrote:100/90-18 or 110/80-18 front

130/90-17 or 140/80-17 rear

The 110F/140R combination was used on some of the later RSs on the same sized rims.  With the larger sizes you might be able to move to radial tyres.

Al

Will the lower aspect ratio front (110/80) end up with a smaller overall wheel diameter than with the 100/90?  I've problems with my front Avon 100/90 tire almost hitting the fender; I have barely 5mm clearance, even with spacer washers to raise the fork cross brace (K1100 Marzocchi stanchions). I have K1100 3-spoke 3X18 front rim so tire selection would be more varied than the K100 snowflake rims.

87m6chris wrote:Thanks Gents,  not many tires in our sizes anymore.
I'm thinking about this combo,
http://www.fsmotorcycle.com/tires/sport-tires/pirelli-sport-demon.html
Anyone using these?
Thanks,
Chris

they work great chris

quite a few members have them on....road surfacing compounds differ across our country's  so you might find different wear rates and expected killometers- miles out of them

rob the lower profile does give a little more clearance

i notice that with the 140 on the back ( or even the 160 on the wide rim ) im doing 4100 at 100 kph ....where as with the 130 x 90  im doing 4k for 100 kph ...if that helps any (still confuses me though )

additionally i have slightly more lift off the ground on the centre stand with the wider profile tyres ....with the 90 sizes both wheels touch the ground ...just ...;.so just a bit of difference in overall diameters
hope that helps

robmack wrote:

AL-58 wrote:100/90-18 or 110/80-18 front

130/90-17 or 140/80-17 rear

The 110F/140R combination was used on some of the later RSs on the same sized rims.  With the larger sizes you might be able to move to radial tyres.

Al

Will the lower aspect ratio front (110/80) end up with a smaller overall wheel diameter than with the 100/90?  I've problems with my front Avon 100/90 tire almost hitting the fender; I have barely 5mm clearance, even with spacer washers to raise the fork cross brace (K1100 Marzocchi stanchions). I have K1100 3-spoke 3X18 front rim so tire selection would be more varied than the K100 snowflake rims.

90% of 100mm = 90mm tyre height
80% of 110mm = 88mm tyre height

There's not much in it.

Al