Brakes pulsating after front rotor/new pad replacement

[TCBRacer77]

Perhaps a moderator will move this thread from the "Engine" section to the "Axles + Brakes" section.


WHAT VEHICLE???

Apparently you have a new enough truck to have 3-channel ABS. Connect a scan tool, see what the ABS module is trying to tell you.


4. Caliper pistons sticking in the bore due to hardened seals, contamination on the seals, flaking chrome on the pistons, and/or contaminated brake fluid. Caliper pistons can seize in the bores, I'm talking more about them just being "stiff" but not yet totally seized.

5. Calipers not "floating" on the O-rings and pins/sleeves. Seized due to worn/rusted parts, or lack of lube.

6. Uneven tension on the lug-studs due to rusted lug nut threads, and/or previously overtightened wheels, and/or rust on the wheels where they contact the rotor.

1997 c1500 4.3, I noticed the pins/sleeves slide but not easily. I’m new to this so I didn’t really think much of it until now

I do have all new front steering components and ball joints, moog

 

[454cid]

Modern pads don't need to be bedded or whatever name you want to call it. It was to heat them up so they could off-gas. I've never seriously done these bedding procuders and I don't get pulating brakes. Maybe in a racing situation you'll get the surfaces to wear perfectly to each other giving optimum contact, but otherwise I think it's just something for the enthusiast to to, to make him feel like he's doing something special for his vehicle. I'm sure the rebuttals will arrive shortly...

 

[Caman96]

I noticed the pins/sleeves slide but not easily.

That would be the first thing I’d replace knowing this. That will definitely cause pulsation.

 

[GoToGuy]

Setup a dial indicator and do a " run out " check. The allowance is in the service manual. If there really way out may need new rotors. But check and verify first.
Good luck.

 

[TCBRacer77]

Thank you for the help everyone, serious! It’s my only way to work lol. I’ll keep the thread updated

 

[Supercharged111]

rotor must be turned

Not true. I've only ever had rotor deposits on my race car and only with a single compound. Race pads can be hard enough cold to clean their own deposits off. Granted their deposits are harder than street pads, but deposits don't automatically mean you need to cut the rotors. Since we're not talking about $600 rotor rings here, the easy answer is to cut or get new rotors. Either are cheaper than getting a hard enough pad to cut the deposits off. That said, I'm leaning more toward @Schurkey's answer now. More likely a caliper pin or piston was sticky, got one or both sides hot, and warped the new rotor(s). That or a sticky caliper got the new pads hot enough to leave deposits before they were fully bedded. Pads need to be hot to leave deposits.

 

[tayto]

Not true. I've only ever had rotor deposits on my race car and only with a single compound. Race pads can be hard enough cold to clean their own deposits off. Granted their deposits are harder than street pads, but deposits don't automatically mean you need to cut the rotors. Since we're not talking about $600 rotor rings here, the easy answer is to cut or get new rotors. Either are cheaper than getting a hard enough pad to cut the deposits off. That said, I'm leaning more toward @Schurkey's answer now. More likely a caliper pin or piston was sticky, got one or both sides hot, and warped the new rotor(s). That or a sticky caliper got the new pads hot enough to leave deposits before they were fully bedded. Pads need to be hot to leave deposits.

the ones i have dealt with (about 10 years ago) i tried sanding with 80 grit and then bedding in again and same thing. getting the rotors turned and then bedding in the brakes fixed it. this was a friend with a express work van that was getting a pulsating pedal about 20,000km after a brake job. my brake job went 80,000+km no pulsating brakes. nowadays rotors are cheap and finding someone with a brake lathe is hard, so everybrake job i do gets new rotors. if the compound is the same and no pulsation, i will deglaze The rotor with 80 grit and do a quick bed in. however i have found with the semi metallic compound i use the rotors are usually pretty groovy after a set of pads so i just replace them

 

[Supercharged111]

the ones i have dealt with (about 10 years ago) i tried sanding with 80 grit and then bedding in again and same thing. getting the rotors turned and then bedding in the brakes fixed it. this was a friend with a express work van that was getting a pulsating pedal about 20,000km after a brake job. my brake job went 80,000+km no pulsating brakes. nowadays rotors are cheap and finding someone with a brake lathe is hard, so everybrake job i do gets new rotors. if the compound is the same and no pulsation, i will deglaze The rotor with 80 grit and do a quick bed in. however i have found with the semi metallic compound i use the rotors are usually pretty groovy after a set of pads so i just replace them

Did you get deposits with new pads on a new rotor or new pad on a rotor bedded with a dissimilar compound?

 

[tayto]

i was going to add if you switch compounds you must turn the rotor. i put hawk LTS on his van, so maybe that was the issue. i have just dealt with this issue so much my recipe is just get the rotors turned or replace them and the brake jobs don't pulsate.

 

[tayto]

I would hate to tell someone to just sand their rotors and the pulsating will be gone after bed in. turning does two things 1. gets rid of uneven pad transfer and 2. trues the rotor (if the operator is competent) . maybe sanding will work in some cases but i personally would never do it or tell someone to do it.