Talk to a wounded soldier ( -1719, -599, -1219 ) /waypoint -1719.06, -598.54, -1218.78 to be told the wheel has been taken by the bugs.
Pick up a broken wagon wheel at ( -2713, -546, -1158 ) /waypoint -2713, -546, -1158 and receive a recipe called Wagon Wheel Reconstruction, scribe it (requires Level 10 Artisan).
Destroy 2 treants and get a Supple Treant Branch and a Large Strip of Treant Bark as a treasure chest drop
Go to a Woodworking table, which can be found at the New Combine Foothold at ( -3781, -783, -79 ) /waypoint -3781, -783, -79 and repair the wheel.
NOTE: if you don't want to learn trade skills to level 10 in order to make this recipe, make sure you have the components and recipe in your bags then talk to Porto Bunglefoot (Master Chef) right at the back of the tradeskill cave in the New Combine Foothold. Dialogue: "Hail, Porto Bunglefoot" "Yeah, yeah, yeah... I can see that wheel needs fixin' and you want me to fix it... Luckily it's an easy fix. There ya go. Now leave me be, I am really busy today!". Discovered 1st August 2013.