I have a 2008 Polaris sportsman 500 ho and I need some help figuring out what size tires to run and not make it unstable.everything on quad is stock rite now and it only has like 300 mile on it so everything is in good shape. It has the stock 25 in 489 tires on it now and everyone I ride with has a rzr and I get so sick of getting stuck in the mud going behind them. Also is there a way to add any stability to the quad as well I am a big guy I weigh 295 and on hills it feels like the suspension is kinda weak. I was thinking about 28 in Zilla tires on 14 in wheels 9s on the front and 11s on back. I am ready to buy everything I need today but I have never really changed all that stuff and don't want to order the wrong stuff and waste a bunch of money. Thanks

 

Sounds like just need more traction, your 25" tire size is fine but you may need a taller more aggressive lug. Two bang for the buck trail/Mud Tires is the ITP Mudlite (XL) and the Maxxis Zilla but with the Zilla you need to move to a 26" to get the aggressive lug which is no problem on the 500. My 350 Grizzly handle them without power lose.
Here is a good site for tire specs.
Hard to believe a Sportsman is getting stuck behind a wide heavy SXS. Your tires must suck.
http://www.mud-throwers.com/atv_mud_tires

Your rear suspension is probably not dialed to the stiffest stetting .
Twist your pre load collar on your rear shocks to #5 which is the stiffest. If that's not enough you may need to get HD Springs.

 

Would you go with a 12 in or 14 in Rim

 

Why change rims? You all ready have 12" rims. I like 12" rims better because the give you more side wall cushion which is a nicer ride plus you have a 1" more rubber before a rock dents the rim. Low profile tires belong on a sports car.

If you go 28" tires you may need to watch if you have the clearance and you will notice a good amount of power and speed loss. Low rang will be you best friend.

 

Thanks for the help ended up going with 27 in Zilla tires on 12 in ss wheels,the only reason I went with the aftermarket wheels was I wanted the off set so I didn't need to buy the spacers. Ended up buying them from the company you sent on the link.

 

Bigger wheels are heavier too. Not to mention more expensive as well as tires for 14" rims. Even in 27" size, the Zillas are probably the same weight or lighter than many 25" mud tires. Those 489's were ok for a factory stock tire but were never meant to be a decent mud tire. I think you'll be much happier with the performance of your machine with this new wheel/tire combo. Probably a lot better looking too, no doubt about that. The 500 engine should be plenty powerful enough to handle these bigger tires.

 

You should get better 4 wheeler tires my suggestion would be Mudzilla or Mudlite. Also make sure to fill the tire with an appropriate tire pressure.