2011 was such a great year for Craftsman that the manufacture ran out of rear 20x8x8 tires for the YT3000 and YT4000 tractors. To keep your new tractor coming to you they substituted a larger tire.
This larger tire was primarily used on some of the Model 28851, 28856, and 28866 YT Yard Tractors.
If you are planning on installing tire chains this winter these larger tires need a different tire chain than what is listed in the fit-up chart your local Sears store has.
In short, to get the correct chain you need to look at your rear tire and get the ACTUAL tire size off the tire.
Tire Chains for 20 x 8 x 8 Wheels
Tire Chains for 20 x 10 x 8 Wheels
Yes, You need to remove the deck to use tire chains on the YT3000 and YT4000 with 20x10x10 tires. The chains will rub on the deck.