FAQ: Vibration under braking: warped rotors? NO!

[D.J.]

The top of the Kia pad has a bit of a different contour as well where the anti-rattle hardware pushes down. We've had 1 issue with that.

-Ken

Please forgive my re-use of your image - but for clarity, are you saying there was 1 issue where someone had a fitment issue related to around here (red arrow)?

do you know what the resolution was? (I have seen people put the anti-rattle hardware on upside down)

 

[laynevans]

that definitely could be the issue but not guaranteed. If your car has high mileage its always worth having the hubs checked for run out. It would be worth getting that checked when/if you get the rotors turned

Do you mean test run out just with a dial gauge kind of thing? How much runout should show up in a hub? Where would be the best spot to measure from? I checked runout on some of my discs while on the car that were making vibrations and they were all under 0.04mm which is pretty low. (Just double checked the gauge and def just .04mm runout, not 0.4)
Swapped them all out for some freshly machined discs and it was buttery smooth again, no vibrations. Either my measurements weren't acurate enough or 0.4mm is still too much and is enough to cause vibrations.

 

[D.J.]

Do you mean test run out just with a dial gauge kind of thing? How much runout should show up in a hub? Where would be the best spot to measure from? I checked runout on some of my discs while on the car that were making vibrations and they were all under 0.4mm which is pretty low. Swapped them all out for some freshly machined discs and it was buttery smooth again, no vibrations. Either my measurements weren't acurate enough or 0.4mm is still too much and is enough to cause vibrations.

The runout you measured is 10x the limit specification. Unless you forgot a zero

That's 1000%

 

[laynevans]

The runout you measured is 10x the limit specification. Unless you forgot a zero

That's 1000%


View attachment 66252

So the 0.04mm runout I saw is actually quite a bit. I really need to find a brakes solution that doesn't warp discs... or be a lot less agressive at the track which is not easy to do.

 

[D.J.]

So the 0.04mm runout I saw is actually quite a bit. I really need to find a brakes solution that doesn't warp discs... or be a lot less agressive at the track which is not easy to do.

Did you measure 0.04mm or 0.4mm?

I am no expert in this matter, but I have read about how important it is to have equally torqued lugnuts (per wheel) if you are getting the discs very hot.


I do not think there is such a thing as a brake pad that heats the disk less, for the same amount of deceleration. The energy has to go somewhere..



Could the high spots on your rotors be brake pad deposits?

 

[laynevans]

Did you measure 0.04mm or 0.4mm?

I am no expert in this matter, but I have read about how important it is to have equally torqued lugnuts (per wheel) if you are getting the discs very hot.


I do not think there is such a thing as a brake pad that heats the disk less, for the same amount of deceleration. The energy has to go somewhere..



Could the high spots on your rotors be brake pad deposits?

It was definitely .04, not .4. But that's still at the high end of how much run out should be there. I thought it would be more than that before it would cause a problem.

I definitely torque the wheel nuts.

I'm looking at maybe going for some 2 piece race pieces which can handle the track temps but it's just my work car and I'm not really supposed to spending too much money on it. Supposed to be spending money on my project car.

 

[RedCal]

Yup, it's not heat that warps them

 

[laynevans]

Yup, it's not heat that warps them

Um... Ok.... What is it then?

 

[D.J.]

Um... Ok.... What is it then?

Could be this

Attached

 

[MerlintheMad]

Could be this

Attached

Yes, I have that bookmarked for years, only here: Myths of the Braking System | Brakes-shop.com

 

[laynevans]

It was definitely .04, not .4. But that's still at the high end of how much run out should be there. I thought it would be more than that before it would cause a problem.

I definitely torque the wheel nuts.

I'm looking at maybe going for some 2 piece race pieces which can handle the track temps but it's just my work car and I'm not really supposed to spending too much money on it. Supposed to be spending money on my project car.

Could be this

Attached

Interesting. Still doesn't really help me unfortunately. I've tried about 4 different brake pads now and 2 different discs and 1 set of pads has been better and 'almost good', in that the vibrations became basically unbearable after 2 race meets whereas as most others lasted less than 1 session. OEM pads didn't even last 4 laps before fade/poor pedal was too much to continue racing with and I had to come off to let things cool down.
I actually just think maybe the brakes are not big enough for such a heavy car... on a race track anyway. They probably need to be 6 piston.

 

[D.J.]

Interesting. Still doesn't really help me unfortunately. I've tried about 4 different brake pads now and 2 different discs and 1 set of pads has been better and 'almost good', in that the vibrations became basically unbearable after 2 race meets whereas as most others lasted less than 1 session. OEM pads didn't even last 4 laps before fade/poor pedal was too much to continue racing with and I had to come off to let things cool down.
I actually just think maybe the brakes are not big enough for such a heavy car... on a race track anyway. They probably need to be 6 piston.

I made this image when I first got my car in 2018....

Seems relavent here.

 

[laynevans]

I made this image when I first got my car in 2018....

Seems relavent here.

View attachment 66258

I'm pretty familiar with how discs/calipers/pads work so the reality of the pad sizes is also my expectation. I had no unrealistic expectations about that. Just didn't think they'd suffer as bad as they have doing track work. The same package is pretty common on other cars but much lighter than the stinger.

 

[StingertimeNC]

Did you upgrade your fluid? Have you tried GLoc pads? Just for the track of course. Run Hawks or ebc red stuff for daily. Kobe at KNS brakes recommended Motul RBF 660 fluid and GLoc R10 pads me. I’ll be trying them in a couple of months. Got them, just not heading to track until March.

 

[RM7]

Again...it's a caliper/pad/rotor vibration/resonance issue...not a pad deposit issue. That's just the cop-out Kia is telling you to avoid having to deal with this on a larger scale. This is a well-documented issue with many cars over many years, this is not unprecedented. Some of my mountain bikes do it. People need to make Kia buy back the damn car to solve this.

 

[D.J.]

Again...it's a caliper/pad/rotor vibration/resonance issue...not a pad deposit issue. That's just the cop-out Kia is telling you to avoid having to deal with this on a larger scale. This is a well-documented issue with many cars over many years, this is not unprecedented. Some of my mountain bikes do it. People need to make Kia buy back the damn car to solve this.

Pretty sure mine was a deposit issue, also well documented. Resolved 100% by swapping the pads.

Kia ain't buying no cars back. That isnt happening.


Kia definitely should have a solution by now, which they don't

 

[RM7]

Pretty sure mine was a deposit issue, also well documented. Resolved 100% by swapping the pads.

Kia ain't buying no cars back. That isnt happening.


Kia definitely should have a solution by now, which they don't

If the problem is reoccurring, more than twice, they have to buy back the car. I threatened GM with this and they promptly fixed my car, but if you are within the legal allowances of your state for lemon buy back...they HAVE to.

Changing pads can totally solve a vibration issue, because that changes the natural frequency of of the system, so the resonance doesn't propagate. It's the reason that pads have weights, no weights, different backing weights, etc.

 

[D.J.]

If the problem is reoccurring, more than twice, they have to buy back the car.

Not in my country.

And nobody, literally zero people, have been able to return a Kia Stinger to Kia for pulsating brakes.

Are you sure they have to "buy the car back"?

Has it occurred since the car was realeased nearly 5 years ago?

 

[laynevans]

Did you upgrade your fluid? Have you tried GLoc pads? Just for the track of course. Run Hawks or ebc red stuff for daily. Kobe at KNS brakes recommended Motul RBF 660 fluid and GLoc R10 pads me. I’ll be trying them in a couple of months. Got them, just not heading to track until March.

Haven't done fluid. If there was pedal fade I'd more inclined to go for better fluid but there isn't.
Haven't tried GLoc pads. Will add them to the list of recommendations. I've tried EBC yellow stuff but am hearing Red might be better. I had best success with some Project Mu pads.

 

[SRV]

Interesting. Still doesn't really help me unfortunately. I've tried about 4 different brake pads now and 2 different discs and 1 set of pads has been better and 'almost good', in that the vibrations became basically unbearable after 2 race meets whereas as most others lasted less than 1 session. OEM pads didn't even last 4 laps before fade/poor pedal was too much to continue racing with and I had to come off to let things cool down.
I actually just think maybe the brakes are not big enough for such a heavy car... on a race track anyway. They probably need to be 6 piston.

Using OEM pads on a roadracing track will never work with any car, let alone one which weighs 4000+ lbs.

You need to be using dedicated roadracing pads at the track, which by the way, will not work on the street since you'll never get enough heat in them, plus, they'll squeal like crazy.

For our Porsches at Road America we choose to run Pagid Orange and are very happy with them. The OEM Textars wouldn't last 1 lap where one is braking from 150 mph going into Turn 1, Turn 5, and Canada Corner.

Therefore, install track pads first and then determine your braking needs.

With all that said, a 4000 lb car is not a very good choice for tracking. You will/should be burning thru tires, rotors and pads like crazy unless you drive like a grandpa.

Finally, I would strongly encourage you to buy a book on car prep for roadracing. The basics include proper brake fluid, bleed intervals, brake pads/rotors, dedicated set of track rims/tires, pressures, etc.