I noticed a slight loss going to the 26" from the 25" tires. But, they are good for the extra 1/2" of clearance and pull through everything. My 489s didn't fail me but the XTRs are tons better. I haven't had any slippage in mud unless I jabbed the throttle to spin the tires. I even got to play in some clay type mud after a skidder chopped up an area in wet weather. Did fine in 1.5' deep mud.

 

So will 28" tires impact my trail riding quality? Wonder if an 850 would take a noticeable hit. Really want the 27.5 (measure out at 28"), but not at the cost of quality trail performance. Thoughts?
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Edit: I found the below on the Web and really makes me wonder about going to 28s. Too bad, really wanted some bigger tires for the nasty, although rare mud holes we have around here.

Quote....

"What about 28" or taller ATV tires? Will they fit?


We do not recommend 28" tires...Now with that said...

Very few stock machines can actually fit 28" tire sizes without having fitment issues. These include fender rubbing and suspension interferences at full compression or tight turning.

Be prepared to do other modifications such as install a lift kit and possibly a set of wheel spacers if you are looking at a 28" or taller ATV tires. These larger tires will require more power to turn, especially when the going gets muddy. Many people compensate for this by doing engine upgrades to increase power.

Also understand that there will be a loss of bottom end power and increased drivetrain stress. These large diameter tires will ultimately cause premature wear on your suspension components due to their additional weight and gearing effects. Many machines with equipped with 28" and larger tires, end up purchasing heavier suspension components and axles as a result of failure. As the saying goes..."Closed Course, Professional Rider". This setup is for the extreme machines only!"

 

My Thundercat took 28's without a single filament issue
I lost 20km/hr top speed (with GPS guys!) and tore the transmission to pieces but it sure looked good LOL!
I then sold them and went with 26"

 

Hummmm. Another nail in the coffin for my 28" tire idea. Thanks for the input Thunder. Makes me wonder about the 27s being to big for a good trailing riding rig. Wish the 26" Pitbull rubber came in 9s and 11s. Only the 27s are that wide. 26s are 8s and 10s.