Q: Can you resolve a long-standing disagreement I have with my father about rearview mirrors?
He insists on adjusting them so that he can see only his own rear fenders in the outside mirrors. I like to set them so I can see only the edge, not with the whole fender filling half of the mirror.
A: I had a long chat over dinner with an engineer from a major auto company a couple of years back about this very subject. In addition to being an engineer, this guy holds a Ph.D in psychology, specializing in human factors and ergonomics. And we both agreed that people often don't adjust their rearview mirrors correctly.
The interior mirror should be set to see straight back along the road, as most people do. But most drivers set the mirrors mounted on the doors to duplicate this view.
The engineer suggested that the proper use of these mirrors is to let you visualize the blind spots flanking your car, not to see straight back. Here's his procedure for adjusting the mirrors, and it's what I have always done myself:
1. Adjust the driver's seat to the correct position. Lean your head and torso over to the left until your head contacts the window glass. I know, that seems too far, but trust me.
2. Adjust the left-side mirror outward until you can barely see your own fender in it.
3. Lean over to the right a similar distance, and adjust the right-side mirror so that you can barely see your own rear fender.
4. Sit up straight.
Your mirrors are now set to allow you to see other cars in your blind spot. You won't need to swivel your neck around to be aware of traffic hiding at 60 miles per hour right beside you, and the interior mirror will still let you see the traffic directly behind you.
Q: My truck gets very little use. Two years ago the left-front disc brake began sticking whenever I applied the brakes. It was just enough to heat up the wheel and cause a noticeable slowdown. You could smell the pads burning. The brakes would eventually release after the wheel cooled down.
So I replaced the caliper, inner and outer bearings, and brake pads. I greased the caliper sliders and bled the system. Amazingly, the brake still sticks.
A: Any small friction in the sliding parts of the caliper or in the inner pad's path can cause drag. Try to push back the piston with a screwdriver. If it's hard to move, crack open the bleeder bolt and try again. If it moves more easily now, there's pressure in the line holding the pads down.
If not, something is dragging mechanically in the caliper/pin/pad assembly. That leaves the rest of the hydraulic system to consider. The proportioning valve, the master cylinder, or even a pinched brake hose could be retaining pressure in the line.
You'll have to chase down which one is causing your problem. I'd start by checking the rubber line to that caliper, because, if it were anything else, both front calipers would be affected, not only the left one.
You've checked the brake hose for blockage? Next check the pedal to see if it is sticking, and check the pushrod from the pedal to the master cylinder to see whether it is misadjusted or sticking.
Still smoking? Every once in a while you can get a bad new or rebuilt caliper right out of the box. I've lost days diagnosing problems caused by bad new parts.
Q: The closest Top Tier gas is hundreds of miles from where I live. Are there any alternatives?
A: You can get the same detergents in Chevron's FI cleaner Techron. Follow the directions on the label.
Q: I have a 2000 Nissan Frontier with around 162,000 miles. The heater/AC blower fan operates only at the highest speed, and the three low speeds do not turn on the fan.
Is the problem with the sliding switch or with some relay?
A: It's a bad resistor block inside the A/C plenum.
Mike Allen is a senior editor for Popular Mechanics magazine. Questions should be sent via e-mail to driveit@nytimes.com.
