New pads with stock rotor grabby behavior

[Redvoodoo55]

A few months ago I changed out the crappy stock brake pads for the K8SS Elite pads but decided not to replace the rotors since the stock ones had no lip and still had plenty of thickness to them. After bedding properly and driving them for a while I noticed that when braking light to medium steady pressure and as I increase pressure as I approach my stop the brakes exhibit a grabby, almost jerky feel and I back off on the pressure to avoid it. The braking becomes not smooth and steady. Has anyone else noticed this behavior?

I am now wondering if I should have just replaced the rotors at the same time and if it would be ok to do it now with the pads having a couple thousand miles on them or if I would be better off buying everything new and starting over. Thoughts?

 

[NS_Stinger]

Do you mean its vibrating while braking? Thats a huge issue with the Stinger so Im betting thats whats going on. Yes its usually recommended to resurface or replace the rotors when you change out the pads on the Stinger.

 

[socalvn]

Should have had your rotors turned

 

[Thomby]

Is it constant jerkiness, or a couple of individual lurches as you decelerate, with accompanying rise in rpm? If the latter, it may be the transmission being too aggressive with the downshifts, discussed further here:

Hard downshift transmission

I just bought a '22, and the down shifts when coming to a stop are rougher than any car i've ever owned. It is not smooth at all for me. Strange. Do you have videos demonstrating the issue?

stingerforum.org

 

[Redvoodoo55]

Is it constant jerkiness, or a couple of individual lurches as you decelerate, with accompanying rise in rpm? If the latter, it may be the transmission being too aggressive with the downshifts, discussed further here:

Hard downshift transmission

I just bought a '22, and the down shifts when coming to a stop are rougher than any car i've ever owned. It is not smooth at all for me. Strange. Do you have videos demonstrating the issue?

stingerforum.org

It is a 1 or 2 individual lurches (or anti-lurches, meaning momentary more aggressive decelerations) as I maintain the same pedal pressure. I don't think there is any rpm movement and do not think it is transmission related as this behavior coincided with my brake pad change.

As someone else mentioned, I should have had the rotors turned. I wonder if I could do that now to eliminate this condition.

 

[Redvoodoo55]

Do you mean its vibrating while braking? Thats a huge issue with the Stinger so Im betting thats whats going on. Yes its usually recommended to resurface or replace the rotors when you change out the pads on the Stinger.

No not vibration, that is the reason I changed pads to get rid of that, which the new pads took care of.

 

[Thomby]

It is a 1 or 2 individual lurches (or anti-lurches, meaning momentary more aggressive decelerations) as I maintain the same pedal pressure.

Watch your tach next time and see if they coincide with a rise in rpm. It'll be subtle because our 8 gears are pretty close, but should be clear. If so the other thread I linked has the A30D scanners that can reset your adaptive shift pattern to eliminate it.

 

[Volfy]

I'm not familiar with that brake pad, but some performance bake pads - particularly high-performance organic compound - can have very high coefficient of friction even at low temp, the point where the driver needs to very much more gingerly with feathering the brake pedal pressure when slowing down to a stop. This is the case with the EBC Bluestuff and Yellowstuff we're running. It takes a bit of getting used to at first, but just about any driver should be able to adapt to it. My second son just started driving and that was the first thing he noticed about the Stinger - how sensitive the brakes were at crawling speeds. He got used to it fairly quickly and now actually likes the extra braking power.

Other than than, one other possibility is the new brake pads and rotors were not cleaned completely after install. That could lead to glazed pads surfaces, which can then act grabby.

 

[michaelpw97]

I have the same pads from K8SS on the stock rotors as well. rears rotors are new, fronts are relatively new (under 10k miles). I also find that ESPECIALLY when the pads are still cold, they can be grabby, but consistent, not stuttery. at soon as the material is warm they are very linear. I don't think its a huge issue, but I could see it being annoying to others.

 

[Snicklefritz]

Brakes can be very different. When we got the Premium, I had to adjust to the "grabby" feel at low speed. The Brembo brakes on the GT1 have never grabbed. I have to be lighter on the pedal with the Premium's brakes to avoid jerking to a sudden stop.

 

[Volfy]

In my past experience, brake pad materials that change properties with temperature did the opposite. Semi metallics quite often have very low coefficient of friction when cold but great performance when warmed up. Can be kinda dangerous. Back then, that was the only way to get great brakes when pushed hard, so you learned to get used to it.

This "grabbed when cold" behavior sounds rather odd. I can imagine it being annoying.

The EBCs I have behave practically the same regardless of temp, so it's easy to used to.

 

[michaelpw97]

Brakes can be very different. When we got the Premium, I had to adjust to the "grabby" feel at low speed. The Brembo brakes on the GT1 have never grabbed. I have to be lighter on the pedal with the Premium's brakes to avoid jerking to a sudden stop.

I’m referring to the brembos btw

 

[michaelpw97]

In my past experience, brake pad materials that change properties with temperature did the opposite. Semi metallics quite often have very low coefficient of friction when cold but great performance when warmed up. Can be kinda dangerous. Back then, that was the only way to get great brakes when pushed hard, so you learned to get used to it.

This "grabbed when cold" behavior sounds rather odd. I can imagine it being annoying.

The EBCs I have behave practically the same regardless of temp, so it's easy to used to.

K8ss pads are ceramic

 

[Redvoodoo55]

I have the same pads from K8SS on the stock rotors as well. rears rotors are new, fronts are relatively new (under 10k miles). I also find that ESPECIALLY when the pads are still cold, they can be grabby, but consistent, not stuttery. at soon as the material is warm they are very linear. I don't think its a huge issue, but I could see it being annoying to others

I also mainly notice this grabbiness at lower speeds (City driving, under 50mph) and when first driving (So the brakes are cold). So this may be completely normal then based on what you are saying.

 

[michaelpw97]

I also mainly notice this grabbiness at lower speeds (City driving, under 50mph) and when first driving (So the brakes are cold). So this may be completely normal then based on what you are saying.

Yup. That’s been my experience. Your also referí g to the stock brembos with k8ss pads yeah?

 

[Redvoodoo55]

Yup. That’s been my experience. Your also referí g to the stock brembos with k8ss pads yeah?

Yes, I am referring to the stock brembo calipers and rotors with the K8SS pads. All I chose to do was change out the pads since the rotors had plenty of material thickness on them.

 

[michaelpw97]

Yup, so sounds like our experience has been the same then

 

[NS_Stinger]

I'm not familiar with that brake pad, but some performance bake pads - particularly high-performance organic compound - can have very high coefficient of friction even at low temp, the point where the driver needs to very much more gingerly with feathering the brake pedal pressure when slowing down to a stop. This is the case with the EBC Bluestuff and Yellowstuff we're running. It takes a bit of getting used to at first, but just about any driver should be able to adapt to it. My second son just started driving and that was the first thing he noticed about the Stinger - how sensitive the brakes were at crawling speeds. He got used to it fairly quickly and now actually likes the extra braking power.

Other than than, one other possibility is the new brake pads and rotors were not cleaned completely after install. That could lead to glazed pads surfaces, which can then act grabby.

Are you running bluestuff up front? I have a set of those but never put them on the car are they noisey?

 

[Volfy]

Are you running bluestuff up front? I have a set of those but never put them on the car are they noisey?

Yes, on both our Stingers. For a track-ready brake compound Bluestuff is actually pretty quiet. They don't squeal or hiss. The only time they make any sort of noise is at crawling speed just before coming to a stop. Because Bluestuff has such excellent friction coefficient even when stone cold, I have to be extra careful feathering the brake pedal coming to stop, or else the pads will groan and come to an abrupt stop. It does this regardless of temp, so it's pretty consistent and easy to get used to. I much prefer this to the semi-metallic track pads we used to run back in the days. Those will glide right through the first couple of stop sign on a cold Winter morning. Scared the bejesus out of me the first time I experienced that.

I have no problem using it on a daily driver and occasional weekend track bunny. To me, the only downside is the prodigious amount of brake dust. It's not bad when I run them at the track. The high temp and heavy braking forms a micro layer of brake pad compound material transfer on the brake rotor surface. Since that micro layer is what the brake pad actually wears against, brake dust is actually quite a bit less when run at track paces. For daily driving though, that nice micro layer gets worn out or rusted out fairly quickly, and so brake dust production becomes quite prodigious. I expected this and am fine with it. I run wheels that are easy to clean, which helps.

 

[Redvoodoo55]

Watch your tach next time and see if they coincide with a rise in rpm. It'll be subtle because our 8 gears are pretty close, but should be clear. If so the other thread I linked has the A30D scanners that can reset your adaptive shift pattern to eliminate it.

So, this weekend I spend some time analyzing this "lurching" behavior in more detail. So I did a lot of stopping tests both in manual transmission mode and in full auto. So I am noticing a harsher transition both in and out of 2nd gear which explains what I was experiencing. I will likely take my car to the dealer to address this since my car is still under warranty.