For the past few weeks, my mom's 2002 Lexus RX300 has been making a very strange vibration that is worst between 35 and 55 mph. It seems to be coming from the left rear wheel and only started after I mounted the snow tires in December. At first I thought it might be a stuck caliper but now I'm leaning towards an out of round tire as the culprit.

Any other ideas?

 

Can you have them rebalanced?

 

I can sure try. I'm going to call my favorite independent shop tomorrow.

 

I agree. Many tires out of balance are only noticeable at certain speeds.





Terry

 

If in fact it is out of round, it will need to be trued or replaced.

 

I'm starting to go back to a stuck caliper even though the Lexus dealer didn't find anything wrong. I left the car in the driveway to show my mom how clean it was and when I pulled it back into the garage, I had to step on the gas to get it to move. It never used to do this, would always inch forward on its own in drive. If I just gave it a touch of throttle, I could feel something resisting and grabbing. Then there was a grinding noise coming from the left rear wheel.

There is something wrong with this car....again.

 

Could be a stuck caliper or the parking brake is sticking/out of adjustment and causing the wheel to lock up. Check the rotor surface for blueing and the outer edge for a bright orange rust color. These are signs of a frozen caliper.

I would start by having the wheels and tires road force balanced. If one wheel has excessive road force, that can cause the vibration.

 

Very similar thing happened to my mom's car. It ended up being uneven wear on the front tires. The car shook violently anything above 60mph. Uneven wear on the front tire was due to worn out shocks. Her car is 13 years old afterall...

Sounds like something else on your mom's car.

 

I am taking the car in tomorrow (or today, whatever you prefer) because this problem has gotten worse. I left the car parked on a grade with the parking brake set for just under two hours. Upon leaving, I released the parking brake, shifted into drive and when I let off the brake, the car just stayed there. I literally had to give it gas to make it move downhill. The car started vibrating so violently I thought the left rear wheel was going to fall off the car. I pulled over as soon as I could and could smell the rear brake disc roasting. I could feel the heat with my hand a good eight inches from the rotor. I was able to make it slightly better by pumping the brake pedal several times but I still had to literally floor it so the car would make it up the next hill.

What usually causes a caliper to get stuck like this?

 

Couple stuck caliper incidents

I had a stuck rear caliper on a 86 Prelude Si, rust had formed on the bore outside the piston seal and caused the calipe to drag. Not as bad as your's, but the brake pads on that caliper would wear through in ~5K miles.

I also had a stuck rear calipers on our 89 Legend. Honda used to have a mechanical mechanism on the rear calipers for the parking brake. The mechanical mechanism was some jack screws, cams , and levers which were actuated with the parking brake lever. It was also prone to freezing up due to water in the brake fluid. Honda went away from that caliper design and I doubt your Lexus has one (most use small parking brake drums on the rear rotors.

My gut feeling is probably the rear parking brake had a locked shoe or the caliper has a stuck piston due to corrosion. Both get corroded if the vehicle goes through deep water occasionally.

 

Does the parking brake use a hub-style setup or the same pad/rotors as the regular brakes?

 

rust forming inside the caliper or around it due to a lack of brake fluid changes can cause issues over time. The MAX interval between fluid changes should be 3 years, a good idea is every 2 years, and if you have the money and need the performance, once a year.