rear tire size choices..
 

130/80-18 or 120/90-18.. i've always run the 130 on my 200. specs say 140/80-18! i would think the 140 is too big... what advantages would the 120/90 have over the 130/80??

i normally run s12's but am contemplating trying out mx31 or s12xc..... i hated the mx51 - it wore out so fast i could not believe it..

i like s12, will the mx31 work well in roots/rocks/some mud/wet??

i'm geting 2 2 hour races out of a s12 rear currently (reverse tire between races..)

I threw my S-12 away and went with a Michelin X-11 Trials tire,-4.00-18. I ride Arkansas single track with lots of rocks,roots etc. I love the hookup and so far the wear is good. My S-12 was about 1/2 used when I got the bike but it was shot after a 2 hour HS race.

i ran trials tires in the past (i ride trials bikes also...) - i don't like how the trials tires works for me at high speed, and i can't roost out of turns, and once it's wet i'm sideways. i gotta run a knobby for races..

i wish i could run trials tires, a 803 or x11 would last all season...

I used to run 140/80/18 in a S-12 on my 200. Nice fat tire....was a little big...But it fit with no problems. I used an S-12 for over half a racing season with good luck. I've now moved on to Maxis IT 110/100/18. In District 36 we get a really good deal on them.....and they wear good.

I buy what is on sale, as long as it meets my terrian requirements I'll run it...it's going to ware out, some faster than others...

I'm going to try Motoz next. I am hearing good reports on those as well, and they are at a good price.

i went and got a 110/90-18 mx31. i'll run one race on it and see if it works better than the s12..

Skinyier rear will give you less understeer, compared to wide in the corners and allow the bike to be leaned more, less footprint but more weight applied per knob will make the tire bite better in intermediate to hard conditions .Super wide tires are more suitable for less aggresive sit down riders usually prefered in super slow muddy conditions.