In this case, an eighth of an inch cost us an additional 3 hours. Yesterday afternoon, a group of guys from the lab came over to my parents' house to do some car brake work. Pieter's 1999 Jeep was suffering from some poor braking and so he asked me for some help in fixing it. Since Jason's dad is a mechanic and he practically grew up with a torque wrench in his crib I asked him to come along as well. Mohammad came along to learn and get his hands literally dirty.

Pieter had previously purchased all the parts beforehand from Autozone, so we expected the work to be finished in one hour. The work went by without a hitch and everything fit like it was supposed to. We finished putting everything back together and Jason gets into the car to pull it out of the garage. He starts the car and puts it into reverse and lets off the brake pedal.

The car doesn't move.

He eases on the gas pedal, and the car still doesn't move. He revs the car hard. You can see the car lunging back as if it desperately wanted to move, but it's not going anywhere. The wheels are firmly planted on the ground.

We were dumbfounded. Never has this happened to either Jason or I when doing brake work. We had no idea what was going on. Did we break something? Why were the brakes permanently engaged? We started going through the problem-solving method, trying to narrow the problem down to a specific part or area. The emergency brake was off, there was no wheel chock behind the tires, and the brake cylinder had the proper fluid level.

We took the front tires back off to see if the brakes were permanently clamped, which we still didn't know why that could happen. The rotor/hub turned freely. I started to put the tire back on and as I tightened the first lug nut, I tried to spin the tire. It was stuck.

The rotor was too big and therefore it was engaging the brake pad when the tire was on the car. But the Autozone guy had sold Pieter the rotors based on him saying that he had a 1999 Jeep. By this time, it's been two hours and the guys had no choice but to go back to the store. Turns out Jeep engineers changed the specification in the middle of 1999 and some Jeeps got rotors/hubs from the new 2000 model. The difference? One-eighth of an inch. And the worst part is that there's no way to know which rotors you have without physically taking the wheel off and visually inspecting the rotor.

By the time they got back and put everything back together it was 10:30pm: a whole 3 hours from when we could have been done.