fishpick

2019 Z06 - both right and left front caliper do this - more so on the drivers side - which I have another thread here in the forums about it making noise...

Pull car onto lift - pull wheels - tap out pins and take off clip. Inside pad is “loose” outside pad is really tight on driver side. Tight on passenger side but can move just a little.

Seems to me like the outside pistons on both calipers are not retracting correctly... anyone smarter than me got any information to share

Video of the above ramblings - no login needed.
https://share.icloud.com/photos/013Q...9B3_AzDBw#Home

Bill Dearborn

I am pretty sure the Brembo calipers have some anti knock back features to keep the pads in contact with the rotors so the brakes react quicker when the driver hits the pedal. Not sure how they do it (springs or seal shape) but it seems likely they would use something like that on a track oriented car like the Z06.

Bill

fishpick

Yeah I mean both sides of the car have the same behavior between inside and outside - but the inside is so sloppy by comparison to the outside - it’s just weird!

add to that the fact I can not get rid of the “swish swish swish” from the drivers front - I’m running out of ideas...

also - if you look at the pads - the outside one shows more heat that the inside one. Like it’s in constant contact with the rotor...

2019GSTX

Fish,
2019 GS, 10k miles
i swapped my Powerstops out Saturday and put the stock pads back in for the hot laps this coming Sunday.
All 4 front pads took a bit of wiggling to get them out. When putting the stock pads back in I had to recess the outer pucks a bit with a screwdriver to get them back in. Bear in mind the stock pads only had about 3k miles on them.
‘Didn’t notice any sloppiness at all inboard to outboard or left to right.
‘Didn’t notice any swish but I do need to ruń it around the neighborhood again.

X25

If there were indeed some pad "knockback" issues, you'd feel it immediately during the initial braking, as in no braking with pedal going to the floor, and it would get very scary, very quick. My hunch would be that you don't have any issues.

Edit: Just watched your video. When you remove the wheels, the rotor will become free (especially if you don't have that little guide bolt, and will move a bit out of the hub surface. It might just be caused by that. In any case, if you don't have pad knockback, I don't think there's any issue.

fishpick

Yeah brakes are fine and firm and consistent. I’m really not worried about air or issues there

The issue with the sound is detailed here - https://www.corvetteforum.com/forums...-new-pads.html

It could be the rotor moving but I do have the little screw in the rotor to the hub -

it’s not like I’m looking for a random issue - I’m trying to determine why that front driver side makes noise when the wheel is spinning...

Scoobydoobydoo

You're not the only one experiencing this. I changed my OEM pads to the Powerstop z26's and just noticed a slight noise on the front drivers side wheel. I took the tire off and sure enough the pads are ever so slightly rubbing against the rotor. Even after rebedding them and trying a few hard stops at highway speeds the noise wont go away. I have an appt with the dealer to have the diff fluid changed and told them to look at the noise. Got a feeling the rotors may have to be resurfaced.

fishpick

WTF - that's insane if that's the case - keep me posted - I'm swinging by the service bay at the dealer this afternoon with my video and getting their opinion - I'll report back too.

Scoobydoobydoo

Ok will do.

Bill Dearborn

As I said the calipers more than likely have some anti knock back capabilities (either springs behind the pistons or in the seal design) which means the pads are supposed to be touching the rotors. You will get a swish swish sound when the rotors are turned because you are supposed to get that noise. My issue would be why are the inner pads loose Vs the outer pads being too tight.

As X25 mentioned when the wheel was taken off the rotor may have been pushed in on one side which might have moved it enough to shove the pistons on one side of the caliper in just enough to make the pads loose. With the wheel off start the engine and apply the brakes to see if the pads tighten up and stay tight once the brake is released. If you have enough strength you can push the brake pedal without the engine running.

Bill

fishpick

@Scoobydoobydoo / @Bill Dearborn : back from Corvette tech... this is getting simpler I think. (I'll go update the other thread to point here now)

So - @X25 is a very smart gentleman... apparently these rotors really "move" when the wheel comes off... so - my measured runout w/o the wheel on of 0.003" is pretty great. And the outside pad being TIGHT and the inside pad being loose - - GM apparently gives the dealers special little fittings to slide over the lug bolts to accept the lug nuts - so they can then torque them down like a wheel - THEN they do all their measurements and look at things. Without any pressure like @X25 said - I'm stupid.

He looked at the video and was confident it's normal... so am I honestly since both sides do it... so I'm back to WHY are these damn pads making the swish swish swish sound after 140 miles...

Couple of things to try -
1 - he said the material from the old pads / track pads could have accumulated in the groves (the cut curves) in the rotor and could be getting picked up slowly and making the sound. So - go home - take off rotors and clean out the groves with a pick...
2 - he has seen this before with the 1521 pads - "some batches of compound" - maybe I have a bad batch...
3 - put the stock pads back on and see if there's any noise after 150 miles with those...

Right now - I have reversed sides / pads completely and will see... if I get the sound from the drivers side again after 140 miles - either something is going on there and I'll try #1 and #3... OR - if I get the sound on the passenger side - then it's #2...

At any rate I have been talking with Mike @ Carbotech - and he's friggin AWESOME! Whatever I discover - he wants to know and so does the Vette tech!

Thanks for all the input here guys - excellent resources - as always! I'll keep this thread updated for people to know what happens now... and for the next guy too!

Scoobydoobydoo

I wouldn't bother cleaning out the slots in the rotors. I already tried that and didnt make a difference. I'm beginning to believe Bill and think it's normal. However, I will have the tech at the dealership give it the once over just to confirm. The appt isn't till Friday so I'll keep an eye on this thread in the meantime.

Thanks guys

fishpick

@Scoobydoobydoo - Bill is a genius - I know he knows... what I don’t know / don’t like - is after my last HPDE and switching to the 1521 road pads - the swish sound appeared...

so either the stock pads and the track rack pads don’t do that and these do... or there is something else going on.
Since so many people love the 1521s - I’m just flipping over every rock i can.

(Also - Bill may just be trying to make me buy the AP kit like he has on his car... so he might be messing with me... I can’t tell with him . He’s a dangerous genius...

X25

When you switch back and forth between different pad materials, you can run into issues where the uneven pad deposits create vibration, and sometimes noise, etc. In these cases, cleaning the rotors would work. Alternatively, if you have race pads, you can use them at the street (cold) for a while. Race pads are usually very hard when cold, and they would eventually clean up (scrub) all the deposits.

I honestly just use the race pads all season, so don't run into such issues. They are dusty, though (and some race pads like HAWK race pads have very corrosive dust), and are also a bit noisy. They provide excellent braking, and I like the feel, so they always stay on (again, some racer pads need higher temps to work right; the pads I use work in cold, too).

fishpick

I have scrubbed the rotors with ScotchBrite pads until they looked almost new! If the sound returns after flipping sides and is on the other side - it’s gotta be those pads... if it comes back on the drivers side - I might try the race pads again for a while... but... and this but leads into your second comment about leaving them on...

they sound like a multi ton dump truck stopping... the squeal is BAD... now, as a manly man I could maybe tell myself those disgusted looks you get from people are envious jealousy of “racecar”... but - I have a wife who lets me race the car... and there is no way in gods green earth or blue skies she’s ok with the sounds those cold race pads make...

so in support of her and her support of me doing HPDE- I need a quieter pad

X25

Which pads do you have? I've been very happy with ST43s. Very little noise, if at all, but I should also mention I do track events every once in a while, which 're-beds' the pads, effectively quieting them down.

Since we had our babies, one of us needs to be with them while I drive the Corvette, which meant my wife comes with me, or drives my car, perhaps once or twice a year. I understand, though, you can't expect her to tough it up : ))

In short, if you can somehow do the switches less often (e.g. race pads in track season, OEM or similar in the rest of the year), I'm sure it would help.

fishpick

I ran the Carbotech XP12's at the last event... loved their bite and behavior - but I'm not married to any one pad. This choice was more out of "oops - I ate my stock ones - what can I get overnighted so I can keep doing this event"... Might try the ST43's next time - I have about 1/2 the thickness of the XP12's left - the seemed to go "faster" than other folks track pads...

"season" is one an the same here in western NY... Track events this year were April, May and then I have 2 in September and that's probably it with the car going back into hibernation in October or November... salty roads I do not do with this car. So - either I find a silent on the street high performing track pad (and a unicorn as a pet) or I guess I struggle like this or find a track / street combo that don't HATE each other...

One thing I will say that seems "weird" about these 1521's is they EXPLICITLY say to NOT bed them... like no repeated fast hard stop / start cycle... which is like the opposite of every other pad in the universe... Given my frustration with them - I'm wondering if it's just a compound that hates me...

JMII

You running ST43 on the street? I run them on the track but they are way too noisy on the street.

Additional note: my brother runs ST43 on two different cars - a Boxster GTS and a Golf R, both street and track. On one car (can't remember which) these pads are nearly silent but on the other they screech like crazy so explain that. Both cars have upgraded brake kits and G-Lock two piece rotors.

Once again using my brother's data as he tracks more and way harder then me - the ST43 are the longest lasting track pads he has found.

I gave up on the mixed use pads after several years of tracking my previous car (a Nissan 350Z). Nothing I tired would last long, stay quite and yet still survive track duty. Not to mention the horrible dust levels. When I sold that car I had just switched to Carbotechs so never got enough track days to really learn that much about them.

X25

My take:
When you slam the brakes at the street, the pads usually don't squeak (but they scrub the surface, and make it easier to squeak). It is when you apply soft pressure that they find that "resonance", and start squeaking. In other words, it usually squeaks when you apply very light pressure, and for that reason, it usually happens at the rear brakes. Since these pressures applied are dependent on piston sizes, etc., your experience can vary quite a bit. On my C6 Z06, these pads were obnoxiously loud with horribly designed OEM brakes (and its 20 padlets), but they were almost completely quiet on the same car with the StopTech BBKs front and rear. In a way, it's a gamble : ) With C7 Z06 iron brakes on both my Z51 and Z06, I've had good results.

JMII

That has been my experience as well. Thus way too noisy on the street leading to constantly swapping pads.

One nice thing is the C7's pads are very easy to change. Honestly the only challenge is the last few taps required to fully seat the pins. I have often wondered why the pins aren't threaded on the very end which would allow you to lock them in place (or remove them) with a few twists of a screw driver. My Nissan used cotter pins which was a terrible system... oh how I hated those things.