[TRWSHSHLX]

For FTC most teams will have issues with too little traction due to the limited tire selections. All regular tetrix wheels have little to none and they easily slide or spin out when pushing something. Traction also helps with autonomous since the wheels are not going to skid / slide out as much when paired up with the encoder.
The tires that JesseK was mentioning are great for traction. I saw them at World's last year and in one of the matches (they posted the video on youtube), they scored in end game then pushed TWO robots on their sides and successfully prevented from scoring. Also in the divisional finals they pushed team Tiki (can't remember team number) with only 2 wheels contacting the ground during autonomous. If I remembered correctly team Tiki's robot weighted almost 50 lbs so it's obvious that the traction helps.
For additional traction on the 3'' wheels, there are the tires that Jessek was talking about. As for the 4'' wheels, there's this tire that team 3531 the short circuits, another divisional finalist last year. The first kind (I won't mention the part# or specs) fits prefect with the original tires on there; for the second kind the tires must be taken off the 4'' rim and the tire must be stretched to fit.
Traction are good until it starts slowing down the robot's agility and turning ability. But other than that, it's a great asset and if correctly utilized it will be a game changer.
The last way to increase traction is just simply put more wheels on! Dualies (putting two wheels side by side) helped two of our teams last year and they were a huge part of the strategy in the state finals where all three teams from our school were on the same alliance and take out the first seed.
Good luck teams!