Slight vibration after front brake job

I recently replaced my front rotors and pads with the SSBC short stop kit (slotted rotors). I was real easy on the pads for at least 300 miles but have noticed a slight vibration when decelerating from highway speeds.

If I push harder to make a faster stop it seems to lessen the vibration and when stopping in town there is no vibration.

This was my first complete front brake job so what should I go back and check?

As a note I did not bleed the brakes during this time.

Thanks in advance!

Bleeding (or not) the brakes won't cause a vibration. If anything, it would be a softer pedal so I don't think that's your issue.

Typically a vibration during braking or a 'shudder' may be caused by warped rotors. While possible, I don't think that would be your problem. Be absolutely SURE you properly torque your lug nuts down. If you don't, that can easily cause a warped rotor issue.

As far as what to check. Lug torque is #1. After that, just be sure your caliper bolts are in there good and your castle nut (the one that holds the bearings and rotor in place) is where it should be.

HTH!

Did you bed in your brakes?

Required reading for anyone who wants good brakes:

http://www.zeckhausen.com/bedding_in_brakes.htm
Link from above: http://www.stoptech.com/tech_info/wp_bedintheory.shtml
http://www.stoptech.com/tech_info/wp_bedinstock.shtml
http://www.tirerack.com/brakes/tech/techpage.jsp?techid=85

Read all of these and then decide how you will bed in you brakes, but make sure to do SOMETHING.

Short summary:
1. Get brakes hot enough to transfer pad materials to rotor.
2. repeat a few times, NEVER COMING TO A FULL STOP.
3. cool the brakes down to end the diffusion process before parking the car.


Finally,
You really can't say your rotors are warped unless you actually put a dial indicator on them and see what kind of runout you are getting. If you don't measure it, you won't be able to distinguish if you've got a high spot or a hard spot. These are not the same.

sherlock9c1 wrote:

Did you bed in your brakes?

Required reading for anyone who wants good brakes:

http://www.zeckhausen.com/bedding_in_brakes.htm
Link from above: http://www.stoptech.com/tech_info/wp_bedintheory.shtml
http://www.stoptech.com/tech_info/wp_bedinstock.shtml
http://www.tirerack.com/brakes/tech/techpage.jsp?techid=85

Read all of these and then decide how you will bed in you brakes, but make sure to do SOMETHING.

Short summary:
1. Get brakes hot enough to transfer pad materials to rotor.
2. repeat a few times, NEVER COMING TO A FULL STOP.
3. cool the brakes down to end the diffusion process before parking the car.


Finally,
You really can't say your rotors are warped unless you actually put a dial indicator on them and see what kind of runout you are getting. If you don't measure it, you won't be able to distinguish if you've got a high spot or a hard spot. These are not the same.

Joel,
I made 10 stops from 35-40 mph down to 5 mph and then let the car sit. I have also been easy on them, not sitting in traffic with my foot on the brake.

Do I need to bed them in again?

stockfornow wrote:

I made 10 stops from 35-40 mph down to 5 mph and then let the car sit.

Just so we're absolutely clear, did you completely cool the brakes down before letting the car sit? Or did they get put away hot?

I might have only let the brakes cool for a short distance, then put away....

stockfornow wrote:

I might have only let the brakes cool for a short distance, then put away....

Doh. Cooling after bedding usually means 10+ minutes of driving at 65mph. That could be your problem.

Like I said, take a dial indicator to them and see what they are doing. Two of my cars have developed shimmies over the last 12 months; I need to take the wheels off and measure the runout to see what's really going on.

You may be able to get rid of the shimmy by having the rotors turned and re-bedding them. That's probably the cheapest way out at this point.

Joel, why you gotta try and freak him out so bad? :p

Bedding in the brakes is nice, but not completely necessary on regular, stock, street driven pads. I usually drive around the neighborhood and do a couple 35-40mph to almost stopped and then one 50+ to almost stopped and then drive home and park it. Never had a vibration because of that though. How many mechanics you think go out and bed the pads after a brake job?

I'm with Mike. Check your lug torque and the castle nuts if the lugs check out. You may have just gotten a bum rotor.

Thanks for the help guys. I am going to start with the easy stuff (castle nut and lug torque).

What is the torque spec for SS wheels?

Hopefully I can borrow my boss's dial indicator this weekend and check while the wheels are off.

toomanytoyz wrote:

Joel, why you gotta try and freak him out so bad? :p

Bedding in the brakes is nice, but not completely necessary on regular, stock, street driven pads. I usually drive around the neighborhood and do a couple 35-40mph to almost stopped and then one 50+ to almost stopped and then drive home and park it. Never had a vibration because of that though. How many mechanics you think go out and bed the pads after a brake job?

I'm with Mike. Check your lug torque and the castle nuts if the lugs check out. You may have just gotten a bum rotor.

Maybe I'm overreacting, but I gotta tell you, pulsing brakes is the #1 complaint I get at work (I'm considered the resident car guy). I'm still wrestling with the real cause. I had one neighbor who went through three different sets of rotors on his car, from three different manufacturers, and had pulsing brakes shortly after on every one. Either rotor metallurgy nowadays is universally bad or there's something else going on. That's why I'm so adamant about putting a dial indicator on the rotors before blaming a particular cause.

Bill, I'm not trying to sound like a smart-alec, but have you read those articles I posted?

stockfornow wrote:

What is the torque spec for SS wheels?

100 foot pounds is the torque spec for our lugs, SS or stock wheels.


Joel, I think part of the problem here (and I'm speculating) is the quality of the metal we're getting now. Most of the new rotors are now made in China. We all know the "quality" of the stuff typically made there and the metal being used is likely no different. Last time I bought rotors, I got AC Delco and one was US made, the other China.

Well, I did some research over on ISSF and I stand by what I said. It is probably NOT warped rotors. I do not think the rotor metallurgy is a problem, especially since SSBC made the rotors. So, please read these threads and the links they contain:

Conversation from Bill Harper and Todd @ TCE with lots of good links and info.

More good reading and links by the same guys.

Discussion of Lugnut torque on page 3.

The downsides of turning rotors on b-bodies.

Read these. Then I'd probably go bed in the brakes a different way again.

Any update on the brake vibration?

Mike

a lot of todays pads are crap,. they leave pad material on the rotor in spots,. giving you a pulsing feeling that goes away when you really hammer the brakes, i,ve had luck taking the rotors off and de-glazing them with a 4" grinder and some fairly fine paper,.
Slotted rotors work well too, the scything action of the slots helps to minmize pad material sticking ,.keeps the pads clean too,.
X 3 on the wheel torque,off shore rotors are so chintzy they warp easy with an air gun,..

Nick

All right, here's an update. My wife's minivan had developed a HORRIBLE vibration since we bought it, and even my 9C1, whose brakes had never pulsated ever (even after being road-raced at Pocono at the Impala SS Nationals in 2005), started to develop a shimmy. (This car has a set of Wagner ThermoQuiet pads that have been on it since 2003 - I am VERY PLEASED with these pads). So, I went out on the interstate late at night and did a series of progressively harder stops until smoke was coming out of the front wheelwells on the last "stop." 60-5, 70-5, 80-5, then 85-5, and each progressively harder on the pedal. Then, drove the car for 10 miles continously at 70mph to cool the brakes down, then took it home. Shimmy was gone.

Then, I took the minivan out:
0. Ensured the rear drums are working properly.
1. warmed up the brakes on the way to the interstate.
2. Got up to 60mph, moderate pressure stop (to 5mph, DO NOT COME TO FULL STOP WHILE DOING THESE).
3. 70mph - full pressure
4. 75mph - full pressure
5. 80mph - full pressure - smoke out of the front wheelwells
6. Drove a mile, moderate pressure stop 75 mph just to make sure I'm getting some pad material on the rotors.
7. Drove 12 miles at 70mph to cool the brakes down; wheels were hot to the touch when I parked it but not super hot. VERY IMPORTANT - DO NOT PARK THE BRAKES HOT!!!

Shimmy is GONE. In fact, the whole brake pedal feel is now very controllable. Very gentle apply, but the van stops in a hurry if you stand on it. No disassembly, no new parts, no nothing; just bed in the rotors or scrape them with the pads (however you want to word it!).

So, if you've got a shimmy, go find at least 10-15 miles of unobstructed highway roads, and take care of the problem.

I can personally attest to what Nick and sherlock9c1 are saying.

The front brakes on my 92 RMW were driving me nuts.... the pulsating and steering wheel shimmy had me thinking "crud the rotors are going to need to be agressively cut or replaced".

This was after about 2 years of around town driving, some interstate...but mostly trips of 10 miles or so on surface roads, traffic lights etc. Not New York City, but stop and go nonetheless.

ANYWAY.....while returning home from our roadtrip summer vacation up and down the east coast of the US I had to panic stop the car about 10 miles from home. A few cars ahead of me had an accident and everyone behind them was jumping on the brakes. Fortunately I was able to not only stop quick , but also had room to dive to the left shoulder thereby ensuring that I did not collect the rear of the Honda I was behind ...... RMW meets Honda at 75 MPH....that would have been ugly!

(LOL over 10 days I drive 3K miles without incident and then nearly get into an accident 10 miles from home ) ).

While driving the remaining 10 miles home I noticed that the pulsating and shimmy were gone. They have yet to return.

Granted I recommend sherlock9c1's method over my accident avoidance panic stop scenario.....but the pad build up points are valid.