They would have a different hub; high end trials would have a stronger hub then freestyle, and sometimes more aggressive pedals. But basically I guess it’s the tire and tire pressure on a lower end unicycle.
Trials unicycles have a 19" trials rim and a special fat tire that fits that rim. Overall wheel diameter is about the same as a regular 20" freestyle wheel.
Freestyle unicycles us a regular 20" BMX rim and a regular 20" BMX tire.
You cannot fit a 20" BMX tire on a 19" trials rim. You cannot fit a 19" trials tire on a 20" BMX rim.
To confuse matters the 19" trials tires say 20 x 2.50 on their sidewalls. They are not a 20" tire no matter what the sidewall says.
A Trials unicycle is more specialized than a Freestyle one. In other words, you can do some pretty serious Freestyle on any old "regular" unicycle. But if you used the same unicycle for some serious Trials, you'd destroy it pretty fast. The most important different (at least on the higher-end ones) is the crankset. Then the tire/rim, then the pedals.
One modification you might want to make for a Freestyle uni is to remove the handle from the front of the seat. This can get in the way for some tricks. A bumper without the handle is better.
-- johnfoss - The wilder Wilder
John Foss, the Uni-Cyclone "jfoss" at "unicycling.com" -- www.unicycling.com
Other differences include: 1. Crank length. Freestyle unis have shorter cranks. 2. Frame. A freestyle frame usually has a square crown which is very close to the tire to make gliding and stand-up skills easier. It should also have a long neck, to get the seat post clamp out of the way for various skills. 3. Pedals. Freestyle unis should always have plastic pedals with no pins.
