620cc 2004 - Anyone try rear tire higher than recommended size

[koko64]

Going oversize can be bad safety wise if you go too far, but one step up should be ok. If you tried a Pilot Pure you would have a light tyre, but its a light construction which means getting advice on tyre pressures. You dont want too much "flexion" on the more extreme angle of the side wall on an oversize tyre.

The other thing to consider is a more triangulated profile on a 170 so it has the width but a quick steering profile. Ask your tyre guy about this, (mind you he may say to run stock sizes as an indemnity issue).

Get advice about the best tyre that will stand up to running ovrrsize and have a profile that promotes quicker steering, or mitigates slower steering. Another thing is that the narrow rim sometimes pulls in the sides of the wider tyre and changes it's profile in a good or bad way. I have seen 190/50/17 tyres on a 5.5 inch rim that grew out to 55/60/65 profile. Some huggers barely cleared the tyre, some huggers wouldn't fit and strange handling sometimes ensued. Sometimes it worked well. By working well I mean the rider felt the security of a bigger contact patch but the increased profile maintained agility. By strange handling I mean unpredictable turn in, heavy response to steering inputs and dangerous tyre wear. It depends. Get specific advice from the tyre guy regarding pressures and application.

Its a little complex what has to be considered, but its tyres we are talking about and you are considering going outside the oem size.

[koko64]

Another thing to consider, tyres from different manufacturers but with the same sizing say 180/55/17 for example will have different profiles and widths.

I ran a Dunlop Q2 which barely cleared the chain and looked like a 190, while the Pirelli Diablo Rosso Corsa rear I'm now running looks like a 170. Both have 180/55/17 on the side.

So why don't you try a 160 Dunlop Q2? Then you will have the correct tyre that is more the look you want. Be careful, it's only a 4.5" rim not a 5". Don't think about a 180.
The 5.5" rim on the 900 Monster usually specifies a 170.

This begs the question, how many 900 owners run a 180?

[Roaduser]

i run a 900 ss rear wheel on my monster. 5.5in with a 180 road pilot 2 tyre. this is from a 4.5 in wheel and 160 road pilot 2 tyre i had originally. disregarding the bearing and innertube changes it fits fine. the chain has eaten a little of the extreme edge off the tyre but its nothing, many modified bikes do that. i havent put the rear hugger back on since.

as for handling, i havent been on a track but spirited street/forrest riding i cant put any blame to the rear tyre. i am still playing with ride heights and geomety, the issue im chasing is the front end feeling unstable in mid corner bumps. i did change both wheels to five spokes and rear to 5.5in, sbk forks (sprung and valved previous owner a bit too heavy for me), rear shock (re sprung to me) and triples at the one time.