Auto Q&A: Proper tire inflation is vitally important

Tire pressure should be checked once or more per month, first thing in the morning, even on vehicles equipped with a tire pressure monitoring system.

Tire pressure check by car mechanic outdoor

I thought I’d do something a little different today. Retirement from my automotive technology teaching job was short-lived, as I missed playing with kids and Monterey Peninsula College had an opening to staff an afternoon introduction to automotive technology class. It’s a bit of a drive from the Santa Cruz Mountains, but a pleasant one, and results in a highly enjoyable part-time activity!

MPC’s auto technology program is incredibly well-run, with a strong emphasis on teamwork, collaboration and professionalism. Each day I’m there brings challenges to step up my game to their high standards! Yesterday’s topic was tire inspection, which brought up many items to share.


Proper tire inflation is vitally important for proper vehicle handling, safety, and tire life. Even with the advent of tire pressure monitoring systems (since 2008), there are still a great many vehicles on the road driving on underinflated tires. A tire that is low on air doesn’t properly support the load placed upon it, runs at a higher temperature due to sidewall flex, has an inefficient contact patch, and creates an adverse affect on vehicle handling. Tire pressure should be checked once or more per month, first thing in the morning, even on vehicles equipped with a tire pressure monitoring system. Such systems are only required to illuminate a warning light when a tire is 25 percent or more below the inflation specification. Some vehicles employ an indirect monitoring system comparing wheel speeds to infer low pressure (potentially less accurate). A dial type, or preferably an electronic gauge, is more accurate than the pencil type tools.

Students also learned the many procedures and precautions and became certified in the proper methods to safely elevate a vehicle, using a floor jack and jack stands, and a professional vehicle hoist. Prior to servicing their vehicles, they created an electronic repair order, entering all pertinent vehicle/owner information, and the applicable procedure to perform. Attention to procedure is paramount at MPC, seat protectors, wheel chocks, and other steps to protect the vehicle and participants are followed precisely.


Once airborne, tires were checked for tread depth (approximately 10/32″ is new, 2/32″ is minimum), lumps/bumps, unusual tread wear, embedded objects, cracking, and other defects, as well as inflation pressure. When a vehicle is driven previously, tire pressure will rise by about one pound for each 10 degrees in temperature rise, so this was factored in to the readings taken.

Proper documentation is important to accurately convey results to the customer and for shop records. Students also confirmed proper tire size, load, and speed ratings per the manufacturer’s door placard.

Upon vehicle completion/departure, attention to detail again included safe hoist practices, a check/correction for fingerprints, and meticulous tool box and service bay restoration. Students then were awarded Pro-Points for professional procedures observed, proper lifting procedures observed, service estimate thorough and complete, tire pressure correct and valve caps in place, and repair order completed to industry standards. These pleasant and amazing young people are on their way to becoming highly desirable candidates for employment!

Parking brake may be triggering light on dash

By Bob Weber, Chicago Tribune

Q: I am an 83-year-old lady who is having a problem with a brake light coming on on my dash. I brought it to two mechanics. They gave my car a going over, and each said there is nothing wrong with the brakes or the pads. They thought maybe I had my hand brake up a little. After I left them my brake light did not appear.

Now when I start the car, the brake light comes on, so I turn the car off. When I start it again it does not come on and stays off for that day. Can you give me an idea what might be wrong? The brakes feel fine, but I am apprehensive to drive the car.


— C.R., Chicago

A: The parking brake may be triggering the light. Jiggle it to see if the light goes off. Another possibility is the brake fluid level sensor. If the fluid is low, the light may come on briefly. If the level checks out full, the sensor may be the culprit.

Q: I own a car that came equipped with wider tires on the rear than the ones on the front. The dealer service rep said that there is no benefit to exchanging tires left-to-right (in lieu of normal rotation). The manual is silent on this issue. I’d like your opinion.

— R.R., Lisle, Illinois

A: Although you might be able to swap the tires right to left, there is not a whole lot of advantage in doing so. In some cases, this is not even an option. If you look closely, you may find that the tires may be directional.

Look for an arrow denoting the tire’s rotation when driving. If so, the right wheel will be going clockwise and the left counter clockwise when driving forward. (My apologies to those who can only tell time with their smartphones.)

Q: I come from the school that you were supposed to turn the key on before cranking over the engine, in order to give the fuel pump time to start flowing. I have my very first push-button car (2019 Trax), and there is no way to do this. I assume the engine can handle it, or they wouldn’t make it, but I notice an issue when I first drive the car for the day. As I start to accelerate, the engine seems to lurch and almost stall a bit before it settles in and drives smoothly.

Could it have something to do with the quick engine turnover from the push-button? I’m not even sure how I can have the dealer check it, since it only happens after the car’s been sitting for about 12 hours, and only that first drive.

— J.K., Grayslake, Illinois

A: Not to worry. In the past, it took a couple seconds for the fuel pump to pressurize the system. Even if you didn’t wait, the engine started rather quickly. With today’s technology, engines often start within one revolution of the crankshaft.

Push the start button (no need to continue pressing; just poke it once) and the engine seems to magically flash to life faster than Harry Potter’s wand. The starting system is probably fine. But during initial warmup, the transmission may hunt a little and that is OK, too. An option is to leave the car overnight so the tech can experience the behavior.

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