tyre size - 120/70 and 150/70?

hi all has anyone tried a 160 70 17 with a 120 70 17 and if so is it better that the 60 profile, i dont like them they feel ok until you lean to a certain degree then you feel your on a knife edge and i was wondwring if you could get away with a 150 70 17 rear looks as if theres loads of overhang on the 160 cheers

[NedSVS]

Originally Posted by lh25

hi all has anyone tried a 160 70 17 with a 120 70 17 and if so is it better that the 60 profile, i dont like them they feel ok until you lean to a certain degree then you feel your on a knife edge and i was wondwring if you could get away with a 150 70 17 rear looks as if theres loads of overhang on the 160 cheers

Quite a few people on this forum run 120/70 fronts, including myself. Reasons for this vary - I started because I was using "race scrubs" (ie peoples ex track tyres with lots of road life left) and racers almost exclusivey prefer the 120/70 over the 120/60. A 150/70 on the rear I believe would work fine and your observation is correct that the 4.5 inch wide rim is a bit skinny for a 160 wide tyre. All the last generation sports 600's ran 160 tyres on a 5 inch rim.
Hope this helps.

[yorkie_chris]

120 70 on front is fine, I haven't heard of anyone using 150 70 on rear but sounds like it could be worth experimenting.

Could you elaborate on the "Knife edge" description? Which tyres are you using?

The 120/70 has a bigger contact patch when leant over and a different profile so maybe you're feeling it as easier to tip into a turn.

Are you running a matched pair? Some tyres don't like being mixed (and for the worst possible combination try a Metzeler wet front with a Bridgestone wet rear !!! Scary!!

Have you tried different pressures? I know the difference in feeling with conti road attacks was vast with only three degrees less pressure in them. At 36 psi front the bike would fall on its side in a bend, at 33psi it was completely neutral.

Remember too that there's a difference between "horrible" and "new" in terms of feeling. Changing tyres feels "different" for a short while until you get used to the new feeling. Changing back to what you had then feels "different". You might not like the "different" feel but it soon fades.

C

[MrMessy]

I have ran a 150/70 on the rear with no problems.

cheers guys i am running pilot road 2ct 120 60 17 and 160 60 17 matching pair they feel fine untill im about 1cm away from the edge of the tyre then its like a knife edge with no confidence at all. i used to have 120 70 17 and 190 50 17 on my old zx9r and using the pilot power 2ct tyres i could use all the tread on those and they never felt like this so im presuming its the 60 part thats making all the difference on this bike. im happy with the grip of these its just the profile how it rounds off really sharp at the last 2cm. Im deffo going to try a 150 70 17 rear and will keep you posted how i find this size.

I still don't get what you mean by knife edge. Are they Sliding? Are they braking away? If they are then you've found the edge of the tyre

... and as I asked above, have you tried different pressures as this is a whole lot cheaper than buying a new tyre. I found the Pilot Powers superb and very very confidence inspiring. Definitely no knife edge. They do however have a triangulated rear profile that means they fall to a set lean angle quickly and then take up a very stable lean. But this was right to the edge of the tyre. If you are trying to lean past that point then maybe you are just riding off the edge of the tyre. Or your rear tyre is over inflated.

C

[yorkie_chris]

Or if either one has squared or cupped then it can give a very nervous feeling.

yes the pilot powers are superb with a great profile but i have the pilot road now and are different profile which i cant get past the last 1 cm of lean angle due to this feeling. The pilot powers i had before were a 70 profile i could use all the tyre up and was confident to do so, but the pilot road is a different story for me cheers for all your help again guys

ps there not squared off and they have plenty of tread all round not sure about the cupped please explain