Help with a Lexus

[Von Hayek]

My father was experiencing vibrations under braking so he bought two new front rotors and I helped him install them on Friday but the problem remains. I drove it for him afterwards, and though there is definitely a noticeable vibration under braking, it appears to be coming from the rear and there is no pulsation in the pedal. So,

- will warped rear rotors cause vibrations that cannot be felt in the pedal?

- if not, what to check? Loose caliper bracket? Frozen shock?

 

[macattack_ga]

RWD Lexus sedan? or LX450?

Had an E46 with similar symptoms (RWD sedan) it was the control arm bushings.

 

[Stumpalama]

Hopefully Ryan or Vince will chime in here, but I will throw out my unqualified opinion.

• Does it happen at all speeds?
• Is the frequency speed or pedal pressure dependent?
  
• Does it happen when you brake hard from moderate speed to stop?
  
• Is there a sound associated with it?
• So, you feel it in the seat, not the steering wheel?

I would check the things you mentioned as well as the ABS (though no light comes on, right?), control arm bushings and rotors and pads. An inspection of the pads may show uneven braking pressure, grooving or waves indicative of caliper or rotor issues.

 

[Stumpalama]

RWD Lexus sedan? or LX450?

Had an E46 with similar symptoms (RWD sedan) it was the control arm bushings.

Hey, I thought of that too! I think it is an LX450.

 

[Von Hayek]

It's an LX450. Good idea on the bushings.

In the seat, no sound, not pedal pressure dependent.

 

[Stumpalama]

Frequency change in relation to speed?

Does it occur right as you touch the pedal or is it as you get deeper into the braking?

 

[Von Hayek]

Really don't remember.

 

[macattack_ga]

How old are the tires?

 

[H2o]

I know it is in rear, but did you replace the pads with the rotors? If you are running the old pads, could take a while to wear in.

 

[Von Hayek]

How old are the tires?

Don't know -- he purchased it used with 114k. I think Firestones.

I know it is in rear, but did you replace the pads with the rotors? If you are running the old pads, could take a while to wear in.

Yes, we replaced the pads as well.

 

[H2o]

You could take the old rotors to a machine shop and check to see if they were warped. could also be the rear that are warped.

If in tires, you could rotate tires and see if there is a difference. I had a noticeable shake in steering on my truck, moved tires to rear, and it was gone. Need to get tires balanced, but those tires are shot anyway.

 

[Skrewball]

you won't always feel rear rotors in the pedal. it is very likely the rear rotors.

If the rear rotors are anything like the rear 80 rotors, they have the e brake in the "hat" of the rotor and the rotor slips on and is retained by the wheel/caliper. that portion of the rotor is quite thin and is easy to warp if the wheel isn't torqued properly.

 

[Jakes40]

Da!
Quit hitting the brakes!
Sorry that's all I got!

 

[Von Hayek]

you won't always feel rear rotors in the pedal. it is very likely the rear rotors.

If the rear rotors are anything like the rear 80 rotors, they have the e brake in the "hat" of the rotor and the rotor slips on and is retained by the wheel/caliper. that portion of the rotor is quite thin and is easy to warp if the wheel isn't torqued properly.

Yes, the rotors have the same exact design and I had to stand on the wrench to get the wheel lug nuts off. A tad over-torqued. Good advice.

Da!
Quit hitting the brakes!
Sorry that's all I got!

That's the Miata dude.