Finally done with the rebuild of my daughters Sportsman 90. Rear-end swap due to cracked welds, new carb, new one way clutch, and cleaned out kick-start, and custom hydrographics. However the ground clearance is just terrible. The front has plenty, however the rear at the chain guard only has just north of 3 1/2 inches. We do a lot of trail riding, and hit some ruts. The rear tires are 18x9.5-8's, I was looking at getting 20x9.5-8, no taller than a 21. I figure width can be a 10 to 10 1/2. However, looking at the hubs I am unsure what options I really have. From the information I have read, I think the bolt pattern is a 4/110. The tricky part seems to be the inner diameter of the hub, I have no clue what the mm's is (maybe 90mm). I have done a lot of digging and have only come across a couple of tires, and they are OEM Chinese quad tires. I really do not want something too big, I think it will too much rolling mass for such a small engine. I see the RZR 170’s have a similar style hub, I wonder if they will fit on the Sportsman 90 unsure of the spline axle size?

 

Did you ever install the larger tires? I was going to try installing 19 or 20 inch tires on my son's 2011 to increase ground clearance but I was concerned about overheating and loss of low end power. Thanks for any help.

 

I just purchased a pair of rear tires from EBay 20x11-8 Nanco N606 4Ply. From all that I have read, there is no noticealbe power loss. My daughter is only 9 and is about 60lbs, not to worried. We will have the quad for a few years, then she will be ready to move up. I will keep you updated. Should have them mounted in about a week.

 

Try "Carlisle All Trail" they have them in 20x10-8 you could go to even 22x10-8 since both size weigh the same at 16lbs each. Carlisle All Trail
Power loss is more about weight then the tire size.
Some tires are just much lighter then others even if they are larger.
or
20x11-8 "ITP Trail Wolf" they weigh only 14lbs.http://www.mud-throwers.com/inc/sdetail/24151/1572 also are wider and cost less.
Either way you avoid rim shopping.

There are more then I thought for 8" rims. http://www.mud-throwers.com/inc/sdetail/6593/515 Mudlite 22x11-8 (14.6lbs) compared to Dirt Devils of the same size at 18.7lbs http://www.mud-throwers.com/inc/sdetail/6596/225