What causes this? w/PIX

[DrumrBoy]

I changed out the Hawk blue track pads a couple of months ago to street pads.

I've changed them 3-4 times in the past 8 months. The rotors have always been like glass and I bed the pads in right after install using 70mph to 40mph smooth decels.

I went to put the track pads on yesterday and noticed the rotors were all grooved up. Hasn't affected stopping performance (at least what I can feel on the street) but clearly, they weren't like this when I last put the street pads on.

Here's what they look like. Its never happened to me before, what causes this?

 

[Purdue_Boiler_Viper]

Good question. Are you driving the car this winter?

 

[DrumrBoy]

Yes. Not alot but at least once a week, sometimes more. I live in Atlanta (ain't changed the avatar) so its pretty much a 12 month deal. The car sat once for 2 weeks but that's about the longest stretch without braking.

I just looked at the track pads that came off and they're smooth too. Had the rotors been like this during the last sessions on the track, assume the pads would have had the same grooves worn into 'em.

 

[99 R/T 10]

My guess, lots and lots of bite with those new pads

 

[dave6666]

When I put CNC brakes on another vehicle I have the pad and rotor wear was incredible. In a bad way. I contacted CNC and they said they come with an off road racing type pad if you don't ask otherwise. They sent me an HPS - High Performance Street - and the wear went away.

The racing pads stopped great, and my rotors looked like yours. Still do.

 

[RAYSIR]

Sounds like everyones on the right track. The pads have more metal in them than the sets that leave the rotors smooth like glass. The cheaper pads with less metal, the pads wear out first and when they get hot don't stop as good as the higher quality,more metal, pads. The more metal in the pad the worse the rotor wear, like the pics, but they stop better with heat and in wet weather. Usually the high metal content pads are required on trucks that tow trailers. Kind of a toss up. Pads that wear out quick and don't stop hot or pads that wear rotors and stop good the hotter they get.

 

[DrumrBoy]

When I put CNC brakes on another vehicle I have the pad and rotor wear was incredible. In a bad way. I contacted CNC and they said they come with an off road racing type pad if you don't ask otherwise. They sent me an HPS - High Performance Street - and the wear went away.

The racing pads stopped great, and my rotors looked like yours. Still do.

Thanks for the input.

So perhaps the rotors were grooved by the Hawk Blues and I didn't notice it .....and the grooved rotors wore similar grooves in the street pads that are now on there (i.e. the street pads didn't smooth the rotors any).

I'm also getting that this grooved surface isn't necessarily a bad thing once the track pads go back on....that's just the wear pattern for more aggressive hi-temp pads.

Correct?

 

[dave6666]

I'm also getting that this grooved surface isn't necessarily a bad thing once the track pads go back on....that's just the wear pattern for more aggressive hi-temp pads.

Correct?

More surface area actually, as long as the rotors are still flat - not warped - and the grooves don't change radius around the rotor.

 

[Purdue_Boiler_Viper]

I'm not sold that the grooving is not a problem. Regardless of the brake pad composition, why would the harder bits align to produce grooves? Hell, I would guess that it would be a tough engineering task to get the bits to align around the curve of the pad.

I did a little searching, and found grooving associated with hydraulic issues (partially plugged brake line not allowing pressure release), fluid overfill, and worn pads. I did not find any source that indicated that it is a normal function of pad composition.

Of course, all of this could be crap information found on the internet.

Maybe Tom the geek has experience with this?

 

[Tom F&L GoR]

I have experience, but am not any expert here.

On track days, my rotors tend to get those grooves. Seemed to go hand in hand with thinning pads, like those weekends where 8 hours is enough to go through brakes. I've also seen them on street brakes where the pads are nearly worn through. I assumed it was a heat issue, either from higher speed braking or from pads that were close to rivets or backing plates and the heat dissipation was uneven.

Fundamentally the pads and rotors will wear. It doesn't seem too much a stretch that under severe service or abuse that they would wear less than perfectly. I probably thought more about this answer than I have any other time I've seen rotors like this.

 

[JonB]

I changed out the Hawk blue track pads a couple of months ago to street pads. ...
I've changed them 3-4 times in the past 8 months. The rotors have always been like glass and I bed the pads in right after install using 70mph to 40mph smooth decels.


3-4 times swapped in 8 MONTHS? As in Blues-Streets-Blues-Streets-Blues-Streets? All on same rotors, obviously? What are the street pads? Any resurface of rotors? What kind of rotors? Metallurgy varies..... this is the kind of thing that CRYO minimizes a bit.....

Hawk Blue are simply rotor-eaters. I used em twice, years ago, and went back to Brakeman. The metal matrix, even if bedded, simply wont match up when, and after bedding. Im not skeptical as Purdue...the tiny metal bits create the grooves, like an old phonograph needle in wax. The grooves-in-grooves scenario makes for a "toothy" pad, like a sawblade-sideways, that eats rotors even faster, if you dont resurface the rotors! And old pads on new rotors dig channels and eat rotors faster. Even faster with hawk. The rotor and pad life per mile is terrible

 

[Hoop]

I'm not sold that the grooving is not a problem. Regardless of the brake pad composition, why would the harder bits align to produce grooves? Hell, I would guess that it would be a tough engineering task to get the bits to align around the curve of the pad.

You don't have to have "alignment", 10 little pieces of metal anywhere on the pad will cut 10 groves as the rotor moves around them... just picture a little stone between the pad and disk... that'd cut a groove, right?

 

[dave6666]

Isn't an ultimate measure of whether the grooves are a problem or not is does the car appear to stop safely time after time?

 

[DrumrBoy]

Car stops fine. I'll put the Hawk Blues back on this weekend (supposed to be sunny and near 70) and wail on 'em to see if there's any less grip or increased fade.

Jon B - Yes, Blue-Street-Blue-Street etc without resurfacing the rotors....although several sets of blues because they wear much faster than thew streets.

The rotors were cryo treated so they do tend to hold up....no warping that I can tell, stops smoothly with no vibration. Both the street pads and the Blues have plenty of meat on 'em....

I'll report back on the experience. Thanks for the thoughts folks.

 

[FATHERFORD]

My truck rotors look like that. It will still come to a stop just fine time after time. Even pulling a trailer.

 

[JonB]

Car stops fine...... The rotors were cryo treated so they do tend to hold up....no warping that I can tell, stops smoothly with no vibration..

Fact is, a uniformly, lighlty grooved rotor, mated with a bedded, grooved pad, is NOT a bad thing: It actually offers MORE surface area for pad friction than does a brand new pad and rotor, machied-flat to machined flat!

The problem occurs with new pads that dont match the old rotor grooves, or visa versa. Used old rotors AND old pads whoose grooves dont match are the WORST, till bedded in.

 

[DrumrBoy]

Jon B - That makes alot of sense....thanks. I'll spend time both bedding and braking with the Blues this weekend and then remove to see if the grooves end up matching, or close to matching.

Which wears faster, the hawk Blue pads or the rotors? I.e. which is more likely to cause the other to conform?

 

[Bill Pemberton Woodhouse]

Frankly going back and forth from pad to pad is going to cause a myriad of issues, and extensive cleaning should be done between the two. Get a set of Brakemans ( Partsrack and Woodhouse both sell them ) and just leave them on. I can't imagine how you even have any rotors left ,if you have been tracking the car, and resurfacing them may work, but it depends on the thickness left. Getting new rotors and new pads are just part of the track experience and though you see no cracks you may have easily outlived the life on these rotors. Keep in mind that even after the rotors are turned , there may not be enough thickness left for them to dissapate heat properly -- have a tech verify the thickness level is safe from the Viper Service Manual.