Pulsating Brake pedal. HELP!

[jbres]

I have a 2003 Tahoe. About 30,000 miles ago, I replaced front brake pads and rotors, and rear pads only. NOW, I am getting some SLIGHT pulsating when applying the brakes gently. When applying them hard, don't really feel anything.
I have no ABS light on, and when I visually look at my rear rotors they do have some "grooves" or "streaks" going through them. They are not in perfect flush shape.
Is my rear rotors the problem?
Thanks!

[rockhillmanor]

Brake Lines.

Very often overlooked by inexperienced mechanics because they show no wear on the 'outside'. They collapse on the 'inside'. And it can be intermittent than bamm no brakes.

Brake lines should automatically be replaced after you have gone thru a couple of sets of pads. Not that expensive. Small price for piece of mind that you WILL be able stop.

Happened on my MH, SAME symptoms you are having and then no brakes.
Almost got me killed coming off a ramp.

[jbres]

No, more just like a very slight pulsating feeling

[DanB-ON]

Does the pedal feel like it pushes back at you at all when your braking?
My '02 Duramax has had to have an ABS sensor replaced twice.

[jbres]

Almost seems easier to just buy new rotors valued at $70 bucks, than to leave the Tahoe out of commission while I drop the existing rotors off to get repaired.

[wandering1]

If you are talking out the tahoe take it to the dealer.

[hondapro]

Have the rotors cut on the car.find a shop that uses the pro-cut lathe.the machine compensates for the stacked runout of the spindle,bearing,and hub and resurfaces the rotor true.

[YamaDooed]

I would have the front rotors turned and new pads installed and also at the least inspect the rears.

[BenK]

Am dealing with pulsating front rotors on my Odyssey...that goes away each time
I nail it HARD on the freeway and keep rolling till they cool & stop out gassing

Issue is that these are proto-types from buddy who is a researcher supplying
IP to brake companies....these are supposed to be performance that also has good
cold/slow speed performance

So there is mud hen level stuff (OEM) in there that is very good cold and slow
speeds...that out gases like crazy on the high end

About half gone and still bakes on high spots...even at lower temps (for me)
while driving around town

So, repeat...take it out on the freeway with no traffic (nite is best) and NAIL
them HARD to scrub off the baked on high spots. Keep rolling till they cool
off and stop out gasing.

If that solves it, then it is baked on high spots...if not...then most likely
wrapped rotors

[mabynack]

A good brake shop can use a dial indicator to check for run out or warping on brake rotors. It's not difficult to do and the rotors can be machined if they aren't too worn. It's generally cheaper to turn a rotor than to replace it.

[BenK]

Sounds like improper bedding in of the new pads....they need to cure
and during that process they out gas friction material that deposits
on the rotor.

That is the best braking...when they are properly bedded in...but if
you stopped rolling while they were still out gasing...they will bake
on a high spot.

This also happens all during it's life, but the most out gassing is
during the curing process

See below




Below quote from: Brake Question - 2005 Dodge 2500 2x4, 2014.6.16

BenK wrote:
Rebed them...

Here is a good thread about curing new friction materials...or do a
search using: brake, bedding in

Most all say about the same thing, though there is a slight difference
on HOW2 between regular vs performance vs race

Brake Pads page4

BenK wrote:
Don...didn't want to say it before, but now that you've indicated that
you have glycol 5.1...it is a very good thing.

ABS modules cost in the thousands of bucks and they have the same seal
problems with silicone as normal OEM braking systems

As for the other poster who said new pads had the warped rotor feel...it
most likely is NOT warped rotors but a need to cure and bed in the new
friction materials (pads)

All friction materials need curing and when on vehicle brakes..the term
is bedding in.

The softer materials need more curing than harder materials

What is most likely in your case is that you stopped moving when the
friction material was still curing. Hot and outgassing to create a
high spot on the rotor surface.

Only takes a few ten thousandths of an inch to be noticeable on the
brake pedal

Do a search here and/or on the internet using: "brake bedding in" and
you will find many methods. Most are generic, but there are differences
between mud hen freebies that come with rebuilt calipers all the way
up to pure track/race pads.

This is one of the better explanations and is also my opinion on the
matter. I also bed in my brakes differently, but won't list it here
and best to use these folks. Hot link below

Pad and Rotor Bed-In Theory, Definitions and Procedures
StopTech's Recommended Procedure for Beddin...



This is also a good one:
Zeckhausen Racing

[B_O__Plenty]

If you bought aftermarket rotors rather than original equipment, they may be thinner and more apt to warp.

B.O.

[Bird_Freak]

Turn your rotors. We charge $12.00 each for carry ins.

[Terryallan]

jbres wrote:
terryallan- how do you have them turned? Would it be cheaper to just buy new?

No it is not cheaper to buy new. Turning rotors is VERY inexpensive. You simply take off the rotors, and take them to a mechanic. He puts them on a lathe, and skims off the high spots. Turning them "true"
Some garages can turn them while still on the vehicle. Now IF the rotors are warped badly enough, or very worn, They can turn a hole in them. Then you would have to replace them

Many things can cause the rotors to warp. The main culprit is cold water. Cold water on a hot rotor is almost a guaranteed warped rotor. That is why when I hit a puddle, and see the steam come off the brakes, I gently apply the brakes just enough to dry them.

[powderman426]

Be very careful when putting on a new rotor. All it takes is a tiny piece of rust or dirt where it makes contact on the back side to cause one to think there is a problem with the rotor that doesn't exist. I like to hold the rotor in.place with a couple of the nuts so I can put a dial indicator on it. Takes a few more minutes, but may save some grief.