I dont know how to explain this.

I have an AWD Rx330 04, and around 40mph area, give and take 5 mph each way, the car steering wheel trembles like i need a rotation/balance. however, this has been happening since i can remember and after many times at the lexus dealership for regular maintenance, the car still has this problem. Does anybody else know what im talking about or have experienced this? Also, it is kinda noticeable through the brake pedal.

 

The first thing I would do is to rotate the tires, front to rear, and see if it still happens. I suspect you have either a separated tread on one tire or tire that is out of round and not evenly worn. If rotating the tires doesn't do the trick, take your car to your local tire store and see if they will check it for out of round wear.

Gary

 

If this is happening only under braking, you may have warped rotors. There is a TSB on this your dealer should be aware of. They will replace front rotors and pads under warranty.

 

Has the dealer said that they can't duplicate this or that they can't find the fault? I'd consider trying a new dealer.

 

I have to agree with Lil4X.

Warpred rotors can cause that type of vibration and it does get pronounced at 40 mph (I know from experience with my RX300).

One other thing, right at about 40 mph, there is a gear change more or less at this mph if you floor it from the light.

Also make sure that you haven't lost any weights on the tires (installed after doing a tire balance).

 

well its not while braking, though that has happened to me.

mainly, it has to do with just holding my foot on the brake pedal so that there is contact and i can feel it trembling. the steering wheel is the most noticable part. it just shakes...i dont know how to describe it

about my service department, i havent exactly told them about the problem because its an on going one, and im about to have my tires changed in the next oil change (60K miles). it feels like my car is going over bumps in the road.

 

Tell them what you have told us and I suspect they may replace your possibly warped rotors or at least test drive the vehicle and find the problem. You have 60k on the vehicle so I expect you have changed the brake pads once already, right?

DO you feel this vibration when you don't have your foot on the brake?

 

alright, im sorry im confusing everybody

it does NOT happen when im braking
only when im traveling at 40ish mph and my hands and toes can feel the car trembling at that speed, not at lesser speeds not at more speeds. when my foot is on the brake pedal, im not actually pressing on it, my foot is just resting on it.

i have had my brake pads changed like 4 times, cause i live in san francisco with a lot of hills. rotors have been unwarped maybe twice. i think it has to do with the tires, so perhaps it will all be solved once they have been changed. those damn goodyears

 

my thoughts........

 

OK, so technically you're not "braking" but "resting your foot on the pedal" WILL extend the wheel pistons and lightly engage the rotors with the pads. Going through four sets of pads in 60K is WAY excessive for normal brake service - even for a taxicab. From this alone, you would seem to be constantly dragging your brakes as you drive. This overheats the rotors and warps them.

Have your rotors checked for lateral run-out and replaced as necessary. Then, take your foot off of the brake pedal and put it on the floor.

 

I agree, you have to keep your foot completely off the brake pedal. Use only the right foot for gas and brake pedals.

 

Sounds like they haven't driven in San Francisco. In that city you hardly ever take your foot completely off the brake. It's like riding a roller coaster. You either have your foot on the brake to keep from rolling down hill or your are stopped. Then you can't take your foot off the brake without gassing the car to get started or you will roll into the guy behind you. And don't get me going on parking. Fortunately, mass transit is good in the city.

Damn good thing it never snows there.

It's pretty hard to get up to 40 mph most places there unless you are on the freeway and even then during rush hour 40 mph is optimistic.

 

Well, you can double your brake life if you take your foot off the brake at least when going uphill . . .

 

It might be the engine mounts (the rubberized isolators used to mount the engine to the frame of the car to prevent vibration transfer from the engine to the frame). When it deteriorates, the car might vibrate at a certain frequency (characterized in your car at 40( +/-5) MPH.

 

A more methodical approach needs to be taken.

1. Replace and balance the new tires. 60K is more than decent milage. This would also eliminate one of the most probable source.

2. Rotors. These can be inspected once the wheels are off. A simple gauge based measurement will tell you if the rotor is warped. [If you have had them turned twice and they are warped now, I would suggest replacing them.] Techs can measure thickness to see if it is in specs.

3. Mounts etc can be the cuplrit but the proabability is less.

When you get the vibrations, (if the source is wheel), the wheel itself is wobbling. This shake is transferred through suspension and brake system all over the vehicle. Seat dampens it a bit and so does the carpet. Human senses the shake by tactile feeling via hand and toes. I almost forgot the ears which pick up the vibration sound.

Summary: Get the tires repalced and have the rotors checked. With a bit of care and caution, the rotor change is within DIY capability.

Salim