Intermittent vibration from brakes

[DeleriousZ]

Been having an interesting issue on and off for the last little while with the s4.

Running slotted rotors with Hawk HPS pads.

When the car is cold, there's zero vibration under braking, more pedal pressure required, but I think that might have something to do with the pad compound.

After a long highway drive, the first few stops the brakes vibrate like the rotors are warped. After getting on the brakes a couple times, the vibration tends to go away. I've narrowed this down to the front rotors (doesn't happen when applying the e-brake at speed)

Anyone have insight on this? I'd think if the rotors were warped, the vibration would be constant.

Thanks!

[airjawed]

Been having an interesting issue on and off for the last little while with the s4.

Running slotted rotors with Hawk HPS pads.

When the car is cold, there's zero vibration under braking, more pedal pressure required, but I think that might have something to do with the pad compound.

After a long highway drive, the first few stops the brakes vibrate like the rotors are warped. After getting on the brakes a couple times, the vibration tends to go away. I've narrowed this down to the front rotors (doesn't happen when applying the e-brake at speed)

Anyone have insight on this? I'd think if the rotors were warped, the vibration would be constant.

Thanks!

I'm having a similar problem. I have slotted rotors up front and unknown pads from previous owner. When it is cold it brakes perfectly. When heated it vibrates like crazy. I'm getting ceramic pads tomorrow and will change them in a few days. Sometimes when a pad and rotor heat up it will change its braking characteristics...sometimes for the better and sometimes for worse. In my case I think the pads are organic and are becoming like rubber.

Another thing that happens is embedding....pads get hot and leave pad material on the disc...this can also make for rotor vibrations.

[killerkali]

Vibrating when braking from high speeds is almost always the sign of warped rotors

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[AUDI_S4_ATL]

Vibrating when braking from high speeds is almost always the sign of warped rotors

Sent from my Inspire 4G using Tapatalk

You're not serious are you?

[AUDI_S4_ATL]

OP you may need to re-bed your pads. There are quite a few sites that have directions for this process but I think most people still use the Stasis method



http://stasisengineering.com/sites/d...0Procedure.pdf

[killerkali]

You're not serious are you?

? Are you not being serious? Either his rotors are warped or pads aren't bedded.
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[AUDI_S4_ATL]

No such thing as "warped rotors".

[ChinookS4]

Or you could have bad inner CV joint(s) or the wheel bearings getting ready to let go or the least likely a bent or unbalanced half shaft. The vibration could only be most obvious when applying brakes. CV joint and bearings typically "click" & "hum" but if they have not quite let go they could be noticed as a shake/ vibration when applying brakes. I experienced the same type of vibration when applying brakes and immediately jumped to the rotors. While new pads and rotors reduced the vibration while braking they did not eliminate it. I had two bad front bearings (replacing them helped but still did not eliminate the vibration) I also discovered a bad inner CV joint. If you are almost due for new disks and pads then id say try to replace them first since it will be the cheapest and easiest. Just don't be surprised if the problem persists.

[DeleriousZ]

Thanks for the help guys, both front wheel bearings have been done in the last couple years so I hope they're not going again. I will try re-bedding the pads when I get the noisy water pump fixed with. Looks like I'm finally experiencing the real s4 experience lol.

[ECS Tuning-Audi]

It's your slotted rotors.

In the past we had issues where the machining of the slots was off with our slotted rotors which created an undesireable lip. When pressure was applied to the brakes they would shutter.

The fix was to have them turned.

Once they were turned customers said the vibration/shutter was no longer present.

Jason

[DeleriousZ]

Killer, I'll look into that. Thanks Jason!

[Timtheguru]

No such thing as "warped rotors".

Yes there is... really? I've warped rotors on shitty cars and have driven cars with warped rotors.

[ECS Tuning-Audi]

Killer, I'll look into that. Thanks Jason!

Definitely! If you don't mind me asking what rotors are you using?

Jason

[AUDI_S4_ATL]

Yes there is... really? I've warped rotors on shitty cars and have driven cars with warped rotors.

Did someone tell you they were warped? A rotor would crack and break before it physically warped.

[ECS Tuning-Audi]

Yes there is... really? I've warped rotors on shitty cars and have driven cars with warped rotors.

There's really not. In order to actually warp a rotor it needs to get extremely hot - I'm talking practically glowing. Which under normal every day braking would never occur.

The vibrations or shutter that you get from whats commonly called "warped rotors" is inconsistencies of pad material across the face of the rotor. These inconsistencies are caused by improper brake bedding.

Having the rotors turned and new pads will 99.9% of the time cure this.

Jason

[Timtheguru]

Did someone tell you they were warped? A rotor would crack and break before it physically warped.

Read the stasis bedding process again.. it even mentions warped rotors.

ECS, there actually is. Geez...

[AUDI_S4_ATL]

Read the stasis bedding process again.. it even mentions warped rotors.

ECS, there actually is. Geez...

Well, according to stoptech and many other reliable sources it is a myth.

http://www.stoptech.com/technical-su...nd-other-myths

[Timtheguru]

Well, according to stoptech and many other reliable sources it is a myth.

http://www.stoptech.com/technical-su...nd-other-myths

It's ok, we can agree to disagree.

[DeleriousZ]

Solution to the argument? Take some 'warped' rotors, throw them on some inspection centers and measure the runout!!

Jason, I'm not sure, they were on the car when I purchased it.

[somebody5788]

I've experienced plenty of warped rotors.... it is far from myth. When you put the rotor on the lathe and it's only taking material off half of it even though it's mounted flush it's pretty damn obvious that it's warped. AKA you can see the run out vs measuring it.

[ECS Tuning-Audi]

Solution to the argument? Take some 'warped' rotors, throw them on some inspection centers and measure the runout!!

Jason, I'm not sure, they were on the car when I purchased it.

Oh OK.

Either way shops usually change >$20 bucks to have them turned. It's definitely worth a shot over spending a few hundred on a new pair of slotted rotors.

Jason

[AUDI_S4_ATL]

It's ok, we can agree to disagree.

Agreed.
My comment reads more serious than I really meant it to be.

[AudiNFS]

You can certainly have warped rotors. I was worried about a warped rotor when my brake piston got seized and my pads were stuck on my rotor for about a 10 mile drive. I didn't realize this happened until I got home. Warped rotors exist

[AUDI_S4_ATL]

I've experienced plenty of warped rotors.... it is far from myth. When you put the rotor on the lathe and it's only taking material off half of it even though it's mounted flush it's pretty damn obvious that it's warped. AKA you can see the run out vs measuring it.

It still could have been build up pad material from a bad bed-in process.

[somebody5788]

It still could have been build up pad material from a bad bed-in process.

Pads were 100% out of the picture when the rotor is on a lathe. So NO it could not be.

[AUDI_S4_ATL]

Pads were 100% out of the picture when the rotor is on a lathe. So NO it could not be.

Were the rotors brand new never used? If not then the pads do play a role.

[quattro_silver]

I'm having this SAME EXACT issue. I'm running Adam's slotted rotors + Hawk HPS pads. I get a terrible shutter only when braking and it's gotten worse and worse
over the last couple of months. Originally I was thinking it was warped rotors but I'm still not 100% certain it is. I'm very curious to see what you guys find out!

I think I may have my rotors turned to identify if it's actually the rotors and see if the shop will do a runout test on them to validate that theory. Otherwise I agree with everyone
here that it 'could' be the front bearings or inner CV joint. Originally I thought the rotors warped fast but we'll find out soon enough. I do not think this is a bedding problem since
I've tried to bed them a couple times and the problem continues to get worse.

* on a side note when I remove my wheel my rotors move a lot, meaning I can move them back and forth. I assume this is normal and I also assume when you tighten the wheel down the
rotor is locked to the hub and will not move but it did occur to me maybe the rotors are moving around..

[BITRBO]

I just recently installed Power Slot rotors, Hawk HPS pads, and StopTech SS lines at all four corners, and I noticed the same thing the other day braking hard from highway speeds... We're talking less than 1000 miles since install, and the vibration definitely seems to be coming from the front. Doesn't do it at normal or even moderately hard stops, and not when it's cold either.

Just to be clear I bedded the pads in exactly to Hawk's specification (and even added a few higher speed stops just for good measure), allowed for proper cool down, and didn't apply the e-brake as directed. About 1000 miles prior to the new brakes I had both the front pass-side CV joint and wheel bearing replaced, which leaves the driver-side if it's one of those two items. I do not have any wheel bearing "howl" yet, but I do have a strange knocking noise coming from the driver-front right when I back up and then roll forward (typically while having the wheel turning too). I suppose it could be one of these items, but IDK

I really hope it's not the slotted rotors, cause this is my track setup and I expect these things to perform decent (sans vibration) for at least 20-25min of heavy stopping. We'll see what happens next weekend though and I'll be sure to report back...

[quattro_silver]

Here's how to test the rotors (to check if they are warped):

http://www.youtube.com/watch?v=arQTPeUD4QY

[airjawed]

Just installed new pads on car. Still have to break them in/bed them. Using my old slotted rotors. Will report back later with results. I initially ordered wearever ceramics by the way but the package was put together wrong. They had only 2 sets of outer pads(4 are required) and instead gave me 6 inners... probably just packaged wrong. So I picked up some duralast gold(suppose to be ceramic) since they were available. Not the most expensive pads at all but we'll see what happens. Cheapest way to see if pads were the culprit.

[BITRBO]

Well, I finished my track event this past weekend w/o any problems... No vibration noticed, aside from the slight "ticking" feeling/noise you get from slotted rotors. Granted, I switched my front pads (HPS) to Hawk Blues, so that may have made the difference... But the brakes performed [surprisingly] well for 25-min of WOT and hard stops.

I will switch back the HPS pads this weekend (these Blue squeeeeeel like crazy!!!) and try a few hard stops on the highway to see if it was the pads, but so far so good (*knocks on wood*)

[airjawed]

Update: Duralast gold are not ceramic so I returned them. I reordered the wearever ceramics and they came correctly packaged this time. The brake shudder is still there...I tried to bed them once and it changed the vibes but they did not disappear.

Seems the shudder is worse on warm days. I read somewhere that a lot of city driving can also create shudders and to rebed the brakes once in a while. I'm going to rebed my brakes once more since I mostly do city driving now. If that doesn't work then I'll get new rotors or get the rotors resurfaced.

[ECS Tuning-Audi]

Anytime you install new pads you should get new rotors or at least have the old ones turned so they have a fresh clean surface to bed to.

Jason

[BITRBO]

Anytime you install new pads you should get new rotors or at least have the old ones turned so they have a fresh clean surface to bed to.

Jason

And what about changing back & forth between street and race pads on the same set of rotors? Not advisable?

[ECS Tuning-Audi]

And what about changing back & forth between street and race pads on the same set of rotors? Not advisable?

Actually, if you run a dedicated race pad then switch to a street pad it will be OK due to how abrasive the race pads are.

Jason

[BITRBO]

Actually, if you run a dedicated race pad then switch to a street pad it will be OK due to how abrasive the race pads are.

Jason

Thanks, that confirms my understanding too After the second or third lap at the track, it's basically the equivalent of having the rotors turned on a lath

[ECS Tuning-Audi]

Thanks, that confirms my understanding too After the second or third lap at the track, it's basically the equivalent of having the rotors turned on a lath

Yup! I've known people who just buy a set of race pads to use for resurfacing their rotors. This way you can get the max life out of rotors and make brake jobs timeless since all you need to do is swap in new pads!

Jason