Brake Pulsation

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Crafty93

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Hey all, I'm new here and new to doing my own servicing. I went and changed my rotors and brakes Friday night because last Sunday, I lost control and went over a side walk ass end first and when I went to the dealership they said my front rotors and brakes needed to be replaced. Which I knew because the pulsation in the brake was unbearable at any speeds and braking. My normal mechanic was out so I opted to save money and do it myself(due to dealership markup). Anyways, now I feel a slight pulsation in the brakes at only a constant light braking. What could this be from? I will admit I didn't use a torque wrench for bolting the caliper and boot on, or my rims/wheels. Any advice would be appreciated. And I mean it may even be something other than my rotors and brakes, I don't know.
 

CunningStunt

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Did you grease the brake pad clips?
Recheck all the bolts that hold brake pads and caliper onto the hub and try to check torque per specs if possible.

Where do you feel the pulsation from? The whole truck, the steering wheel, seat, floor pans?

Check that the disc is properly secured to the hub

Calipers sticking may be part of the cause. Maybe even bleed the brakes again.

Also, do not rule out the fact that you may just need your wheels balanced and/or aligned after going over a sidewalk


In seeking out my own vibration issues I discovered there are so very many causes for vibrating, and I have yet to completely fix my own however, I had my rotors turned and my vibration issues got better but not gone so I am considering getting all new brakes and rotors and swapping when I put my bilsteins on. I hit 90k this week and I am pretty sure my ride quality is poor due to the suspension components normal wear n tear and am replacing all ball joints and TRE's as well

The suspension and wheel assemblies can be very touchy and hard to narrow down vibration issues sometimes, but I hope your issue is as simple as a loose screw or greasing the clips
 

Jeepwalker

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Here are a couple tips:

1) Always clean any and all corrosion and debris off the hub (around the wheel studs) with a file ...right down so you can see the original machining marks. Make sure to knock any rust above the area away so none will fall in when you go to install the rotor later on. Also, inspect the back of the rim and chase the mounting surface with a file as well. Coat the hub, both sides of the rotor mounting areas ...and the wheel mating surfaces with anti-sieze.

2) Always use a dial indicator to check the rotor for 'true-ness'. Never accept that a new rotor is going to be perfect. For a while there, I'd say 1/2 the rotors I bought just weren't true and Napa or whoever would then tell me they've gotten a lot back. Lately I haven't had too many problems, but for a while it was epidemic. The last set for my Ram I got at Oreilies, ceramic coated (the less expensive set), were great! Be sure to get a dozen large nuts for like 5/8" bolts to fit over the wheel studs so you can tighten the rotor to the hub w/o your wheel on. Install the rotor, get the wheel lug nuts tight ..they don't need to be super-tight, then check. An inexpensive Harbor Freight dial indicator with a magnetic base is all you need. You can take the old rotor lay it on a 5 gal bucket and use the bucket to raise things to achieve the right height (if you're working with the vehicle on jackstands). Fill the bucket 1/2 full of water and make sure it doesn't 'rock' so your indicator provides a trustworthy reading.

You may need to remove the rotor, mark it, then rotate it one stud clockwise, check again, Move another stud and so on until you get it right. You might even swap side to side or it's even acceptable to shim with a semicircle of paper underneath if need be. That would be required if you swapped side to side and it didn't make a difference and you needed to compensate for a hub or axle flange that wasn't 'true'.

How good should they be? Well, how about 0.000 thousandths of an inch?? A good set-up guy should be able to get rotor run-out dead nuts right on. This is something brake shops aren't going to take the time to do. 99% are going to take the rotors out of the box and slap them right on. If they don't hear from you, who cares? Truth be told, most people can't even feel minor rotor deflection or know what it is. I've ridden with people and first time they hit their brakes I detect it. Sometimes I've had buddies say, "yeah I just had the brakes done ...don't they feel good?". But you can achieve better than that. Anyway, you can live with .003 which is what most vehicles' specs are. I wouldn't go any more than that. I strive for 0.000 all the time and usually get there or damn close. Don't remove the rotor hold down bolts until you are ready to install the wheel. Leave at least 2 hold-down nuts on.

The next thing ...actually you should do this before installing the rotor, is to clean off the caliper and brake pad mating surfaces with a file. The idea is to ensure nothing is binding and the calipers slide in/out freely. Remove all corrosion and debris with a file right down to the original machining marks. Rust can build up UNDER the stainless sleeves and cause them to essentially 'squeeze' on the ends of the pads and the brake pads don't move in/out freely (and can heat and re-warp new rotors right away). So clean up the mating surfaces and apply some silicone grease or I use anti-sieze. Then fit your pads. The way pad backing plates are stamped, there is often a sharp edge on the top and bottom this can cause binding. I file this down because over time it cuts into the cast iron surfaces ...or if there is a stainless sleeve, it can distort it. In either case it can lead to pads hanging up. Again, ensure the caliper sliding pins are well lubricated and the boots not torn. Often the lower one gets wet and can become frozen or at least sticky. I run my caliper pistons in and out several times using a c-clamp. It helps keep the piston loose inside the bore.

Rotors can come pre 'out of parallel' as well. I don't usually check for it, but if you know the outside was dead nuts on and you still have pedal pulsation, then a guy would want to position the dial indicator to the inside of the rotor and check that. Make sure your tires aren't out of round either (like a broken belt).

In your case there is a good chance if you really whacked the sidewalk curb you bent a rim or even an axle or hub. That's another reason to check things. You might want to put the dial indicator on the outer face of each axle and hub. Remember that a rear axle can have some in/out movement so you'll need to somehow hold it in as you turn it ..or remove the axles and bench test on V-blocks.
 
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Docpaulo

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Did you break in your pads... very important.. there's a specific procedure to burnish the rotors
 
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