Helped some young friends of mine out with a car problem, saved them quite a bit of money. [View all]
A younger couple I know has two young kids with a third on the way, they're short on cash and their older Ford Aerostar minivan was feeling very unsafe to drive. I offered to help because I know neither of them has a clue about cars and I've been playing with them since I was tall enough to see over the fender into the engine compartment.
The little truck was pulling hard to the right when you were just driving down the road and pulled even worse when you put on the brakes, it was also making a loud noise that could have been any number of things, including a bad rear wheel bearing or perhaps brakes desperately needing attention. Another problem was that at about 40 mph the front wheels had a violent shimmy that made the steering wheel vibrate back and forth, the faster you went over 40 the worse the vibration, the wheel was moving several inches back and forth at 45, it felt like the front suspension and the steering were trashed and about to fall out from under the truck.
First thing I noticed is that all four tires were in really bad shape, they had been run underinflated for a long time (told you the couple was clueless about cars) and had a severe wear pattern that looked like this.. Tread in the middle and bald on either side.

Took the van up to the Hispanic tire store up the street where they sell remarkably good used tires for decent prices, got four Uniroyal tires that looked nearly new with lots of tread left for $175, including mounting and balancing..
Amazingly, the tires solved all the steering and vibration problems, it felt like a different truck to drive. However the grinding noise was even more apparent, it had actually gotten louder.
In the course of looking over the van after getting back from the tire store I happened to notice the the exhaust pipe had become bent to the point it was rubbing on the right rear tire and also the coil spring on the right rear suspension. I got a long cheater bar, stuck it in the exhaust pipe and bent the pipe back away from the tire and coil spring. Result, noise gone... The new tires had a lot more tread, particularly on the edges, than the old ones which was why the noise had gotten worse, there was more tire to rub on the pipe.
If this couple had taken their van to the average car repair shop they'd have been lucky to get out for $500 (money they really didn't have), instead we gave their transportation a new lease on life for well under $200. When I started I honestly thought the van was going to need front suspension work which could have been pricey. I've seen bad tires make a car drive poorly before but never to the extent this one was.