: braking problem



CTS-V420
11-21-07, 02:48 AM
Ive been having some braking issues lately.... at highway speeds 65mph+ when i step on the brake the car shakes/vibrates slightly..it doesnt not feel safe. i took it to the dealer and they 'shaved' the rotors..but it still does it? any1 else with the same problem? any ideas what the problem could be? Its not the pads bc i got new ones a 2 or 3 months ago...
hmmmm
thanks in advance

CTSV_Rob
11-21-07, 03:18 AM
When did the problem start?

Naf
11-21-07, 03:58 AM
HAHAHA

I had this before on another vehicle, its a combination of little things...

One of your pads are cracked, look really hard and dump the brake cleaners on them all...
You may also want to take a look at your calipers, the shakin comes because the "floating" system is jammed. Typically your brakin cylinders swish side to side. If this is not possible then your car will shake. Its normal, 2 pistion calipers use a pin for sliding to float.
Lastly shimmin isnt always the best thing to do. I rarely shim, its not good for the coolin of the rotor. The thicker the less prone to brake fade, the thinner the more prone it is...
Best thing to do is feel the rotor, if it feels like there are ribs or is uneven yes you may have to shim, if not leave it alone. You are only wastin money. Uneven is 0.060+ inches or 1.5+mm grooves.

JMBCTSV
11-21-07, 09:00 AM
Did they tighten the Caliper Mounting bolts enough?
Is the rattle clip in place properly?

nikon
11-21-07, 10:25 AM
what shakes....the steering wheel or your ass??? at least that'll narrow it down a bit.

atdeneve
11-21-07, 10:37 AM
I've had the same issue for over 15,000 miles.

Initially, I was beginning to think that it might have just been warped or grooved rotors. I do now have grooves that I can easily feel with my fingers. There's also visible dark spots along the fire path of the pads (hot spots?). Was gonna give my rotors to someone (forget who it was), but since I was thinking that they might be bad, I didn't want to hand off shoddy pieces. But there seems to be not one occurence of warped/cracked stock rotors (they seem to be a good piece). So, I began to wonder if my calipers were causing the vibration.

Now that you make mention of the calipers, it sorta confirms it. Could the problems with the calipers cause grooving of the rotors? Can it cause rotors to have hotspots? Are my rotors done or do they just need to be turned (basically, is it safe for me to send it to someone else)?

As for the calipers, Naf, what do you mean when you say the "floating" system is jammed? I thought the V calipers were fixed. How would you go about un-jamming the calipers?

What are you talking about when you say shimming? And when you talk about thickness and brake fade, are you referring to the thickness of the rotor or the shim?

Can you clarify some of the notes you made. Thanks.

CTS-V420
11-21-07, 01:40 PM
this has been happing for id say 2 weeks..but since i only drive on the highway maybe once a month, its not as noticable-
it is NOT just a steering wheel shake- my ass shakes, the car shakes- it does not feel safe
-what if gatherd from the above posts..it could be a slight crack in my pads, a not smooth rotor, and a floating thing?
-it was not my idea to shave the rotors..the dealer did it when i complaind about the shake- the shaving didnt help-
So my car is at Cadillac now getting an oil change..what shud i tell them to look at/tighten?
thanks again

ZEUSROTTY
11-21-07, 01:46 PM
Who uses there brakes anyway?

nikon
11-21-07, 02:12 PM
we don't have floating calipers....we've got pistons on each side of the rotor, so thats not it.....floating calipers are when the piston is only on one side of the caliper..........and eh, I too get this sometimes, really not sure what it is......

BBV
11-21-07, 02:34 PM
we don't have floating calipers....we've got pistons on each side of the rotor, so thats not it.....floating calipers are when the piston is only on one side of the caliper..........and eh, I too get this sometimes, really not sure what it is......

^^Exactly what nikon said.

I too had this issue and as you and nikon noted it was intermittent.

Last week I turned all four rotors, installed new Hawk pads, and flushed and filled the brake fluid with ATE Super Blue. I have since done about 40-50 laps at the track and have not had any vibrations under braking at any brake pressure.

nikon
11-21-07, 02:42 PM
^^ see what I don't get is I had this issue before I hit the track.....it would happen sometimes under light braking, sometimes under heavy breaking....but you usually had to be doing at least 65mph....now I only felt it on the track once/twice and attributed it too not letting the brakes cool long enough before I stopped the car and having some pad melt on there.....because after a couple hard stops it went away.....the only other thing I can think of is maybe the ABS/Stability system is doing something......and for me the problem was also only felt in the wheel (front brakes).....I flushed my fluid 2 weeks ago and haven't felt anything yet but at the same time I can't remember feeling anything for a couple weeks before that......I just chalk it up to a ghost in the machine, because I've got plenty of pad left, and if the rotors were warped you'd always feel a pulse due to the design of our brakes.....and she never pulls when you get on the brakes either.....so I just kinda forget about it.

ZEUSROTTY
11-21-07, 04:35 PM
get new rotors and pads... easy to do in about 30 minutes. I did my rotors paads and brake lines this weekend in about 4 hours... Its is soooooo easy. After that make sure you bed them in properly, and enjoy... Problem solved.

nikon
11-21-07, 05:45 PM
^^ the labor isn't the hard part....it's forkin over the dough for the pads and rotors..... :p

regardless I've never heard of an intermittent brake pulse...it makes no sense whatsoever.

ZEUSROTTY
11-21-07, 05:59 PM
Then get your rotors turned again... And just get brake pads... If you turned your rotors, and put the same pads on it, you will still get an issue because your pads are garbage. If you have a high spot on any part of your pad you may see a change in feel as you noted. My family has owned brake shops for 20 years... So I do have some good experience with this...

nikon
11-21-07, 06:12 PM
^^ I'm not the OP

I've never gotten my rotors turned and am on stock pads.......I do not get a vibration or pulse everytime I hit the brakes....in fact I can't remember the last time I got the vibration, however it has happened many time before...hence the reason I said it was an intermittent problem....if my rotors were warped I would feel the problem ALL the time. I don't.

Twitch
11-21-07, 06:26 PM
Seems to be a Caddi issue. My 89 eldo had it. Sometimes really bad, then others, you dont notice. We changed pads and rotors,,,same thing. Both my SLSs didnt have it, but my pops 98 STS had it. Highway speeds, but very little.
I thought about the ABS also.

Let us know what you find,,,good luck.

lunarx
11-22-07, 04:38 AM
Do you feel a pulsation in the brake pedal?

If not, it could be shock, ball-joint (or other suspension item) related.
V front lower ball-joints are known to fail.

CTS-V420
12-29-07, 02:39 AM
finally got the car in for the brakes...they replaced front and rear rotors under warrenty! are they usualy covered under warrenty? i have 45k on my V and a 100k warrenty...i thought since they were a wear and tear item they would not be covered BUUT I sure wasn't about to complain about frree brakes!

nikon
12-29-07, 04:16 AM
The big question is did it fix the problem???

bjohnso0
12-29-07, 12:03 PM
Sounds like it could be a sticky piston in the caliper. Have the fluid flushed and replaced. If you have non uniform hot spots, something is hanging up. Multi-piston calipers show odd problems when the pistons stick. With a single piston set up a stuck piston would just cause premature wear on one pad.

thebigjimsho
12-29-07, 02:42 PM
Do you feel a pulsation in the brake pedal?

If not, it could be shock, ball-joint (or other suspension item) related.
V front lower ball-joints are known to fail.Agreed. Some of the worst shimmies are from a loose suspension part.

fredcook
12-31-07, 07:46 AM
get new rotors and pads... easy to do in about 30 minutes. I did my rotors paads and brake lines this weekend in about 4 hours... Its is soooooo easy. After that make sure you bed them in properly, and enjoy... Problem solved.

What did you torque your rotors to? I am replacing my rotors, and am getting conflicting torque specs...

lunarx
12-31-07, 12:59 PM
What did you torque your rotors to? I am replacing my rotors, and am getting conflicting torque specs...

Do you meen the wheel lugs or the rotor to hub retaining bolts?

Those retaining bolts should not be very tight (just snug) or you will never get them off next time around.
Don't put a torque wrench on those or you most likely will overtighten them.

As for wheel lugs I only go 65lb.
It's all that's needed, just retorque after your first drive.
Shops go ape-shit on wheel lug torque because they don't get a second chance to retorque.
I personally hate broken wheel studs, so I don't over do it.

If you want the torque for the caliper to the hub, then someone needs to look that up.
I will say only that the spec for that is also needlessly high.
But no harm there, since those bolts are strong.

OldRoadDawg
12-31-07, 03:10 PM
As for wheel lugs I only go 65lb.
It's all that's needed, just retorque after your first drive.

FWIW: Owners manual says for 100 ft lb

50 4Ever
12-31-07, 05:54 PM
Do you meen the wheel lugs or the rotor to hub retaining bolts?

Those retaining bolts should not be very tight (just snug) or you will never get them off next time around.
Don't put a torque wrench on those or you most likely will overtighten them.

As for wheel lugs I only go 65lb.
It's all that's needed, just retorque after your first drive.
Shops go ape-shit on wheel lug torque because they don't get a second chance to retorque.
I personally hate broken wheel studs, so I don't over do it.

If you want the torque for the caliper to the hub, then someone needs to look that up.
I will say only that the spec for that is also needlessly high.
But no harm there, since those bolts are strong.

If you are running stock wheels you need to torque to 100 lbs. If you have a good torque wrench and set it at 100 lbs you will never break a stud. After torquing set the wrench to less than 20 lbs to keep it accurate.

The problem with the shaking sounds to me like a warped rotor. I never have my rotors turned when they get too thin, or warped, because shaving a warped rotor causes thin spots which can lead to hot spots which causes warping again.

Hope you find out what it is...

lunarx
12-31-07, 06:17 PM
Ok Guys,

I don't really expect anyone to use 65lb as their wheel lug torque, if they feel safer with 100lb.

My experience has been that at 65lb, I never had a lug loosen after a retorque.

My only point is really to put anyones mind at rest, should you think you might want to torque above 100lb (to be even safer).
100lb is already much higher than needed.

I swap wheels alot, so I apreciate the reduced stress on the studs.

fredcook
12-31-07, 07:55 PM
Do you meen the wheel lugs or the rotor to hub retaining bolts?

Rotor to hub... the FAQ says...

"The torque specs for the caliper to knucle bolts are: 96 ft lbs.(front) 88 ft lbs (rear)- Rotor mounting screw is 124 LB in (you must convert this to ft lbs if using a standard torque wrench)"

rdjiv
12-23-08, 03:20 AM
Ok here's the deal:

Installed UUC stainless steel brake lines and then got new brake pads about 2 months ago. Brake pedal was spongy and began to notice some fluid weeping near the caliper rubber bleeder valve cover intermittently on all four calipers. Went back to dealer who re-flushed the brake system and conducted a proper bleed, eliminating the pedal issue. Conducted a 1000 mile trip and about halfway in, got shaking in the steering wheel and brake pedal when braking. Vibration is worse when braking hard, shaking most of the car. Looked at the left rear rotor and there are some black marks, almost looks like scoring of some kind. Now vibration is noticable at very low speed braking and still have a fluid leak on the calipers.

Concern: Its sounds to me that the cause is a warped rotor...but how many? What would cause the fluid to leak out of the caliper? I'm not 100% confident in the install of my brake lines and if that is questionable, would a poor pad installation be the overall culprit?

50 4Ever
12-23-08, 01:27 PM
Shaking through the steering wheel is indicitive of something from the front two tires. Just a thought, you might check for tread seperation (bump in the tread). I had this happen in my pickup and under heavy braking it would almost yank the wheel out of my hands.

Don't know about the leaks.