Tire woes, sub-compact advice, backup lights, adding a plow to a Jeep

Q. I have a 2016 SRX Cadillac with 17,500 miles on it. When on the highway at high speeds above 40 miles per hour, I hear wind that sounds like when I have an open window in the rear. My dealer checked the wheel bearings and say they were okay and said it must be coming from my tires, which are Michelin. The sound increases with the speed of the car. Could it be insufficient insulation at the rear door or around the windows?

A. As a general rule Michelin tires are quiet unless like all tires they have worn unevenly. A simple test would be to swap out the tires off another SRX to see how your vehicle sounds. At this point, the technician needs to determine the source of the noise. A technician using a vibration tester will be able to see if the noise is related to a mechanical part such as a bearing, transmission component or even a vibration from an exhaust pipe or another component touching (grounding out) on the body of the vehicle. These testers that were once mechanical, but now incorporate an oscilloscope and measure the frequency of the vibration. You mentioned the possibly a wind noise and that needs to be investigated as well.

Q. What is the best sub-compact to buy used for reliability? My budget is $8-$12,000 and I need a small car that will last a long time and be cheap to keep?

A. My first choice would be the Honda FIT, in your price range, you should be able to purchase a 2011/2012 model with reasonable mileage. The FIT is economical, reliable and quite practical for a subcompact. As something, a bit different I would then look at the Scion xD or Prius C. The Scion although not made now is a Toyota so reliability is excellent. The hybrid Prius C gets fantastic mileage and has been very reliable. If you can use a slightly bigger car the Kia Soul is a good choice and if you drive a manual shift can be a very good value.

Q. I have a GMC 2500HD pickup and the door sticker states the front tires should be at 65PSI and the rear tires should be inflated to 75PSI. I just had an oil change and tire rotation at my dealer, at about 11,000 miles. I checked my tires and they are all at around 63psi.  Should I set the tires at different levels?

A. I believe in setting vehicle tires at the pressure recommended by the vehicle manufacturer. The only time I would vary the pressure is if you were carrying a heavy load for a long distance.

Q. I have the factory trailering (pull out, folding) mirrors GMC truck and they have what looks like a LED-bulb in the lower left and lower right corners, on both mirrors. I have questioned my dealership numerous times and searched the internet as to what these are. My dealership said they were backup lights – but they do not light up in reverse! I’m guessing they are for side collision avoidance?

A. I’m surprised the dealer didn’t know the answer. The lights are auxiliary back-up lights and they activate when you turn the cargo-bed light on.

Q. I’m thinking about buying a Jeep so that I can place a small homeowner plow on it during the winter to plow my own flat driveway. Can I get away with the Jeep JK or do I need a vehicle with a beefier suspension?

A. People have been adding plows to Jeeps for years and it is even easier today. Now there are lightweight “homeowner” style plows that are fully functional and very lightweight. Meyer, a long time plow manufacturer makes a lightweight power plow that attaches to a front trailer hitch, making installation quick and simple.  

John Paul is AAA’s Car Doctor. He is an automotive expert who has been writing and talking about cars for more than 30 years. He also hosts the Car Doctor radio program on WROL radio in Boston. Email John at jpaul [at] aaanortheast.com.

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