Brake Shudder For 91 Ls

[vyhanh]

Hi,

I just replaced both front rotors and new brake pads. I checked and greased the caliper pins. Yet, when I brake, there still is shuddering on the pedal. Why?

I also used high temp paint (grey to match the car) on the calipers (my son does not want the calipers to be noticeable Thanks for any tips on the shudders.

VH

03 X5 4.4

99 ML320

91 LS400

92 Preluse 4WS Si

91 Galant

[VBdenny]

vh

You did get the shims on the pads on correctly right? Each pad has two shims and a wishbone spring. If those were not on properly, I'm fairly certain it might cause a shutter.

[vyhanh]

Hi VBDenny,

Thanks for your reply. Yes, there are 2 shims (each facing the other) on each brake pad. I even used anti-squeal brake compound (orange colored) between them and the pad. There are 2 wish-bone-like springs (facing end to end) on each pad as well and they are there. I think that the shudders must come from some other components down there ?

Thanks again

VH

[VMF]

shudder comes from the bent rotors. did you brake hard after you installed new brakes? did you machine new rotors? if not put em on the surfacing machine and first leave a little pitch between the razor and the rotor and they start minimizing the distance and check if razor will touch the rotor only in some areas. if it will be touching only in some areas it means ur rotor is bent. from my experience the brake pedal shuddering comes only from this cause.

[vyhanh]

Thanks for your reply VMF!

I did not brake hard. As a matter of fact, I am trying to 'break' (pardon the pun !) the new brake rotors and pads ! Do I have to turn the NEW rotors even ?

[VMF]

procedure i decribed is not even for turning but for checking if the surface of the rotors is even, they just might be defective.

[UCF3]

It's possible you have something else that is causing the problem. I would also check out your Tire, Tire-Balance, alignment, wheel(s), tie rods, strut tower.

I would suggest, moving the front tires to the back, and while you have the car up in the air look for any leaks in your strut tower, and other places. For the tie rod, try to get underneath the car while it's on the ground, and jiggle tie rods and control arms for movement.

[VMF]

but he has vibration only in the brake pedal, not in the whole car. i had both vibrations once and what UCF told us will help to get rid of the body vibration at certain speeds but brake pedal vibration is related to the rotors. i might be mistaked but warped rotors were the cause for my 96 and my friends 94 LS.

[UCF3]

A bad tire, a bad wheel, and Strut can also be the culprit, depending on the severity of the damage. Even a loose screw can be a problem especailly with the GEn I LS.

vyhanh:

How often does your brake pedal pulsate--rapid, or slow?

[vyhanh]

Thanks to all of you who helped.

My pedal shudders when I brake. The shudder frequency is half a second apart (counting 1001 as 1 second). The shudder decreases as the car slows down to a stop.

[VMF]

well when i had this sympthoms it turned out to be warped rotors. go back to the shop and make em check the surface with the machine.

[vyhanh]

It is raining in the Twin Cities now. I went to Checkers (where I got the rotors) and they would machine the rotors free of charge. I will do that when the sky makes up its mind :cries:

More observations:

1. On the driver side (front), the rotor has 2 screws in the rotor. The passenger side does not. Does it matter?

2. When the brake pedal shudders, the gear shift handle rod also shudders (50% of the time). Maybe something else here?

[UCF3]

Most likely it's your Rotors, but if they check out, you may have another problem. I'd say, feel the rotors and if they don't feel even, you have have another problem and need to consult expert advice from a Toyota/Lexus or independent specialist.

Do you have two screw holes on the Rotors or two screws that are missing from the caliper?

[vyhanh]

Hi,

I just took the rotors to Checkers for machining. The guys there said that they were sure that the rear rotors were the culprits. Beck-Arnley rear rotors will come next week and we will see. After the machining, I cleaned the rotors with brake cleaners, wiped them clear of metal particles. I torqued at 75. The test drive showed some improvement but the shakes are still there.

Each rotor has 2 screw holes. The driver side one has the screws but the passenger side one does not have those screws (missing). All caliper parts are there.

VH

[VMF]

dont u worry bout those 2 screws, they dont really mean anything and only there for ur protection to prevent rotor on fallin on u when u remove the wheel:) did u surface rear rotors as well? front rotors cause more shaking but rear ones might cause some as well.

[vyhanh]

Hello,

Thanks VMF for replying.

Since all of the rotors were under minimum thickness, I am replacing all. The rear ones come next week and I for sure will ask Checkers to machine them before I put them on. I checked what UCF3 said and I think all are tight (at least with my weakling arm )

[ebridges]

Could very well be the rear rotors. Have them checked and/or replaced.

[vyhanh]

Hi,

The rear rotors came in. Checkers machined both before I took delivery.

1. Went home

2. Cleaned new rotors with brake cleaner

3. Jack up rear of car

4. Tackle rear wheel (driver side): custom wheel lock nut could not be undone!

5. Tackle other rear wheel (passenger side): got wheel off

6. Got brake caliper off

7. Got pads out

8. Got caliper brackets off

9. BUT old rotor seemd to have been FUSED to .... COULD NOT GET DARN THING OFF... Using rubber mallet, cheat bar.... Did not want to come off !!!!!!

Did I miss anything?

VH

[CUMan]

Two things come to mind.

First, if your rear brakes are the same as mine (93 LS 400), the parking brake is a drum system inside the rotor. If you have the parking brake on, the pressure of the shoes against the rotor would probably keep it from coming off.

Second, there should be at least two holes in the rotor in which you can insert bolts. Alternate turning these bolts and the rotor will be pushed off. I have not removed a rotor from my LS; however, I did on an Acura Legend I owned, and it worked this way. As I remember, those bolts were about 10 millimeter.

[vyhanh]

Hi,

1. I released the rear brake when I trid to take the rotor off; I even put the trans in neutral. I noticed that I could rotate one rotor and the other one rotated as well. But I could NOT get the darn thing off

2. I also removed the 2 small phillip screws on the rotor.

I forgot to mention that I did also remove the grease cap, removed the cotter pin, the lock ring, but stopped short of the hex nut and thrust washer bcause the hex nut was too big. I believe that this hex nut stopped from removing the old rotor off the stub axle.

[VMF]

try to hit it with big hummer:) it helped in my case.

[vyhanh]

I need help!!!

I checked the workshop manual about rear rotor and it seemed to be straight forward. Any idea since the rotor seems to be stuck as if welded onto the hub!!!!

Thanks

Vh

[CUMan]

Do you feel resistance when you turn the disc? Perhaps the parking brake shoes are tight against the rotor even though you have the parking brake released.

In the 93 LS 400 service manual, they have the following statement: "If the disc cannot be removed easily, return the shoe adjuster until the wheel turns freely."

The diagram shows a plug that can be removed to get to the parking brake adjuster. They show a screwdriver inserted into the hole and backing off the brake shoes by turning the adjuster. The adjuster is at the bottom of the parking brake assembly.

The diagram does not show the holes that some discs have where bolts can be inserted to push the disc off. (I mentioned this in an earlier post.) This obviously would not work with these discs since the parking brake assembly is inside the rotor. There would be no solid surface for the inserted bolts to push against.

[vyhanh]

:o Thanks CUman: I had the same thing in my manual. The reason I did not mention it in my posting was that I was worried I took on more work than I needed to. Thanks for explaining the adjuster (I did not understand what the manual said

[vyhanh]

Finally took 2 hours to change both rear rotors, Using crowbar and lots of wd40, got the darn things off: so rusty around the rims where connected to hub. And what amazing change in the ride and brake the new rotors made.