Thought I'd change my front rotors
09-15-2008, 08:53 PM
#1
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Thought I'd change my front rotors
They looked pretty bad. (understatement!!!)
Cracks and grooves.....
I'm using Pagid RS19 pads which still have some meat left on the bone
Cracks and grooves.....
I'm using Pagid RS19 pads which still have some meat left on the bone
09-15-2008, 08:58 PM
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My question(s) is(are), will the Pagid pads just groove the new rotors?
After a short ride with maybe 10- 60mph stops.... not panic stops, the rotors are not looking quite right.
Do I just keep going or order new pads too??
After a short ride with maybe 10- 60mph stops.... not panic stops, the rotors are not looking quite right.
Do I just keep going or order new pads too??
09-15-2008, 09:34 PM
#5
Banned
I think the universal recommendation is to always use new pads with new rotors. I've never heard of anyone using old pads with new rotors.
The old pads have the wear pattern of the old, uneven rotors. And that unevenness is what you're seeing on your new rotors from your old pads, no doubt. With new pads you're guaranteed 100% flat surface to flat surface contact.
Your old pads will eventually wear to conform to your new rotors, as pads are softer than rotors. But I wouldn't track the car like that if you're expecting full brake power. If you're comfortable with the amount of braking power you currently have, so as to not compromise your safety, just wear the pads out and then get new ones once those have worn down.
The old pads have the wear pattern of the old, uneven rotors. And that unevenness is what you're seeing on your new rotors from your old pads, no doubt. With new pads you're guaranteed 100% flat surface to flat surface contact.
Your old pads will eventually wear to conform to your new rotors, as pads are softer than rotors. But I wouldn't track the car like that if you're expecting full brake power. If you're comfortable with the amount of braking power you currently have, so as to not compromise your safety, just wear the pads out and then get new ones once those have worn down.
09-15-2008, 09:37 PM
#6
Race Director
I think the universal recommendation is to always use new pads with new rotors. I've never heard of anyone using old pads with new rotors.
The old pads have the wear pattern of the old, uneven rotors. And that unevenness is what you're seeing on your new rotors from your old pads, no doubt. With new pads you're guaranteed 100% flat surface to flat surface contact.
Your old pads will eventually wear to conform to your new rotors, as pads are softer than rotors. But I wouldn't track the car like that if you're expecting full brake power. If you're comfortable with the amount of braking power you currently have so as to not compromise your safety, just wear the pads out and then get new ones once those have worn down.
The old pads have the wear pattern of the old, uneven rotors. And that unevenness is what you're seeing on your new rotors from your old pads, no doubt. With new pads you're guaranteed 100% flat surface to flat surface contact.
Your old pads will eventually wear to conform to your new rotors, as pads are softer than rotors. But I wouldn't track the car like that if you're expecting full brake power. If you're comfortable with the amount of braking power you currently have so as to not compromise your safety, just wear the pads out and then get new ones once those have worn down.
Ben, put a set of Pagid RS19s (yellows) on your car and the stopping power will throw you out of your seat if you are unbelted.
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09-15-2008, 10:36 PM
#8
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I've always changed both rotors and pads along with a quick bleed of the system. No need to bed the old pads to new rotors. Pads are cheap, rotors and the time removing them are not.
I've done moderate pads with new rotors to get a good heat cycle on them and to start wearing the rotor face even so not to groove it, then switch to more agressive pads and follow with full heat cycles and check them right afterwards.
Since I now have PCCB's I do not need to worry abouth this now. But if I ever switch to steels, I'll be using the method listed above.
Pads cheap, rotors $$, do the math!
Deanski
I've done moderate pads with new rotors to get a good heat cycle on them and to start wearing the rotor face even so not to groove it, then switch to more agressive pads and follow with full heat cycles and check them right afterwards.
Since I now have PCCB's I do not need to worry abouth this now. But if I ever switch to steels, I'll be using the method listed above.
Pads cheap, rotors $$, do the math!
Deanski
09-16-2008, 12:10 AM
#9
Race Director
I've always changed both rotors and pads along with a quick bleed of the system. No need to bed the old pads to new rotors. Pads are cheap, rotors and the time removing them are not.
I've done moderate pads with new rotors to get a good heat cycle on them and to start wearing the rotor face even so not to groove it, then switch to more agressive pads and follow with full heat cycles and check them right afterwards.
Since I now have PCCB's I do not need to worry abouth this now. But if I ever switch to steels, I'll be using the method listed above.
Pads cheap, rotors $$, do the math!
Deanski
I've done moderate pads with new rotors to get a good heat cycle on them and to start wearing the rotor face even so not to groove it, then switch to more agressive pads and follow with full heat cycles and check them right afterwards.
Since I now have PCCB's I do not need to worry abouth this now. But if I ever switch to steels, I'll be using the method listed above.
Pads cheap, rotors $$, do the math!
Deanski
09-16-2008, 12:30 AM
#10
Still plays with cars.
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[QUOTE=OCBen;5810814]I think the universal recommendation is to always use new pads with new rotors. I've never heard of anyone using old pads with new rotors.
/[QUOTE]
NO NO NO. ALWAYS bed in new rotors with used pads. Always bed new pads with used rotors if at all possible. If you doubt this go check out the FAQs on the Stoptech website.
best,
/[QUOTE]
NO NO NO. ALWAYS bed in new rotors with used pads. Always bed new pads with used rotors if at all possible. If you doubt this go check out the FAQs on the Stoptech website.
best,
09-16-2008, 01:17 AM
#11
Banned
But for street cars and street use only, always use new pads with new rotors. As was mentioned, pads are cheap.
Also, for machinable rotors, it's best to turn them before using the new pads to ensure even wear of the pads and to eliminate any warpage that can lead to shimming of the wheels during brake application.
I just recently replaced my front pads for the first time and I didn't turn the rotors, as there hasn't been any vibration at all. But I'll probably turn them next time I replace the pads.
09-16-2008, 09:13 AM
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Any concern switching the used pads from rear of the rotor to the front and vise versa?
I did this also on each wheel......
Geez Ben, you actually have enough miles on that car to NEED to replace your front pads??
Actually I've put maybe 7 track days on since noticing the cracking starting. Was VERY concerned at first but guys like Bob put my mind at ease. Only when the cracks got as long as you see here after 2 days of track time this past weekend, was it time to swap.... so they were due.... not overdue.
Actually per side Pagid pads are ~$50.00 than OEM rotors......
Last edited by NVRANUF; 09-16-2008 at 10:03 AM.
09-16-2008, 09:55 AM
#14
Banned
What's interesting about your photos, Peter, is that it clearly demonstrates that rotors during braking action are subjected to circumferential tensile stresses. The radial stress cracks at the holes clearly illustrate that.
I still can't see the value in using old pads on new rotors for tracking purposes, from a mechanical engineering perspective. It's like taking brand new cars off the assembly line and before you can run one on the track you need to pull it aside and take off the new pads and replace with old worn pads. Just doesn't make any sense to me. But oh well.
09-16-2008, 10:07 AM
#15
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I was referring to my daily driver, the Mini Cooper. I changed the pads at 42k miles. My 911 won't be needing pads for a long, long time. Just barely turned 5k miles on the clock with it.
What's interesting about your photos, Peter, is that it clearly demonstrates that rotors during braking action are subjected to circumferential tensile stresses. The radial stress cracks at the holes clearly illustrate that.
I still can't see the value in using old pads on new rotors for tracking purposes, from a mechanical engineering perspective. It's like taking brand new cars off the assembly line and before you can run one on the track you need to pull it aside and take off the new pads and replace with old worn pads. Just doesn't make any sense to me. But oh well.
What's interesting about your photos, Peter, is that it clearly demonstrates that rotors during braking action are subjected to circumferential tensile stresses. The radial stress cracks at the holes clearly illustrate that.
I still can't see the value in using old pads on new rotors for tracking purposes, from a mechanical engineering perspective. It's like taking brand new cars off the assembly line and before you can run one on the track you need to pull it aside and take off the new pads and replace with old worn pads. Just doesn't make any sense to me. But oh well.
If experienced track guys like Bob R. say it's OK to use, then I'm good with it. Still probably half the pad material is left... and... your analogy is slightly askew...... my car isn't brand new, only the front rotors are...
