fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper?
05-27-2004, 07:41 AM
#1
Member
Thread Starter
Join Date: Mar 2004
Location: Birmingham, Al.
Posts: 1,183
Likes: 0
Received 0 Likes
on
0 Posts
fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper?
A friend of mine who does both SCCA IT and Vintage racing has on several occasions discussed brake pads that keep the heat in the rotors as opposed to brake pads that transfer heat into the calipers. He has suggested that the carbotech XPs (1109s) "transfer" heat into the calipers and make for more boiling fluid issues (not after I get the brake ducts hopefully). I have not asked Carbotech or Hawk tech people about this yes. I read "Racecar Engineering" and other tech magazines but have never heard this discussed? Fact or myth? If true which ones do what? Thanks.
Barry H.
Barry H.
05-27-2004, 07:53 AM
#3
Member
Thread Starter
Join Date: Mar 2004
Location: Birmingham, Al.
Posts: 1,183
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
Thanks for the technical response which clears up that issue RJ. LOL. (sitting at computer in a coffee shop at the beach being one big lazy **** until next tuesday-ahhhh).
Barry H.
Barry H.
05-27-2004, 07:57 AM
#4
Senior Member
Join Date: Oct 2001
Location: RIP Craig Jones
Posts: 30,826
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
Heat doesnt care where it goes, as long as its 'downhill' (i.e. to someplace cooler)
05-27-2004, 08:05 AM
#5
Suspetise...
Join Date: Nov 2002
Location: Burninating the peasants yo
Posts: 12,287
Likes: 0
Received 1 Like
on
1 Post
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ »</TD></TR><TR><TD CLASS="quote">Heat doesnt care where it goes, as long as its 'downhill' (i.e. to someplace cooler)</TD></TR></TABLE>
Right. i don't know how a pad would "specify" where the heat goes unless it was touching the caliper vs. not-touching the caliper, though that's clearly an impossibility. Maybe the backing plate materials are different? If one were more heat conductive or something I suppose it'd allow for more heat to transfer to the caliper. RJ?
Right. i don't know how a pad would "specify" where the heat goes unless it was touching the caliper vs. not-touching the caliper, though that's clearly an impossibility. Maybe the backing plate materials are different? If one were more heat conductive or something I suppose it'd allow for more heat to transfer to the caliper. RJ?
05-27-2004, 08:48 AM
#6
Join Date: Aug 2002
Location: 15 percent slip, FL, USA
Posts: 1,125
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
Y'all are aware that different materials transfer heat at different rates, right? That would be why, for example, styrofoam makes a better cooler than aluminum. I could certainly see different pads transferring heat to the calipers at different rates.
My own, completely non-scientific, experience with this is that the Porterfield R4S were more likely to boil the fluid than the Cobalt GT-Sports, and that the Ferodo DS3000 were less likely to boil the fluid than the Cobalt SpecVR I'm currently using. I've only done one event with the SpecVR, though, and on relatively old fluid, so it's really too early to say about that last one. And I've been using ATE fluid the whole time, so that variable is eliminated.
My own, completely non-scientific, experience with this is that the Porterfield R4S were more likely to boil the fluid than the Cobalt GT-Sports, and that the Ferodo DS3000 were less likely to boil the fluid than the Cobalt SpecVR I'm currently using. I've only done one event with the SpecVR, though, and on relatively old fluid, so it's really too early to say about that last one. And I've been using ATE fluid the whole time, so that variable is eliminated.
05-27-2004, 08:56 AM
#7
Honda-Tech Member
Join Date: Jul 2003
Location: Ottawa, Canada
Posts: 1,115
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
There are ways to block the heat transfer. Everybody say it with me...."in-su-la-tors" 
If you look at OEM pads they have a stainless steel shim between the inner pad and the piston. Reduces the amount of heat transfered into the caliper. On heavy vehicles (like the Odditty) there is a stainless shim on both pads. I know many racers that run a factory stainless shim on the inner pad to reduce brake fluid temps. 
If you look at OEM pads they have a stainless steel shim between the inner pad and the piston. Reduces the amount of heat transfered into the caliper. On heavy vehicles (like the Odditty) there is a stainless shim on both pads. I know many racers that run a factory stainless shim on the inner pad to reduce brake fluid temps.
Trending Topics
05-27-2004, 08:58 AM
#8
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MightyMouseTech »</TD></TR><TR><TD CLASS="quote">There are ways to block the heat transfer. Everybody say it with me...."in-su-la-tors" If you look at OEM pads they have a stainless steel shim between the inner pad and the piston. Reduces the amount of heat transfered into the caliper. On heavy vehicles (like the Odditty) there is a stainless shim on both pads. I know many racers that run a factory stainless shim on the inner pad to reduce brake fluid temps. </TD></TR></TABLE>
LOL
the only reason that shim is there is to prevent squeeling...
nothing to do with heat transfer.
If you look at OEM pads they have a stainless steel shim between the inner pad and the piston. Reduces the amount of heat transfered into the caliper. On heavy vehicles (like the Odditty) there is a stainless shim on both pads. I know many racers that run a factory stainless shim on the inner pad to reduce brake fluid temps. </TD></TR></TABLE>LOL
the only reason that shim is there is to prevent squeeling...
nothing to do with heat transfer.
05-27-2004, 09:04 AM
#9
Honda-Tech Member
Join Date: Jul 2003
Location: Ottawa, Canada
Posts: 1,115
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo »</TD></TR><TR><TD CLASS="quote">
LOL
the only reason that shim is there is to prevent squeeling...
nothing to do with heat transfer.</TD></TR></TABLE>
There are two completly different shims. There is a dark grey one and the stainless one. The dark grey shim (never figured out what it is covered with yet, most likely a synthetic rubber) is for noise cancelling properties. The stainless shims are a heat reflector.
http://essexparts.com/CatalogP...l.pdf
and from:
http://www.ferodo.co.uk/ferodo....html
Thermal Underlayer
FERODO go one step further than the competition in the manufacturing process. All DS3000 brake pads are manufactured with a Thermal Underlayer, a barrier which keeps the heat where it should be. The underlayer also increases the mechanical link between the friction material and the backplate giving added strength to prevent 'edge lifting'
Modified by MightyMouseTech at 1:44 PM 5/27/2004
LOL
the only reason that shim is there is to prevent squeeling...
nothing to do with heat transfer.</TD></TR></TABLE>
There are two completly different shims. There is a dark grey one and the stainless one. The dark grey shim (never figured out what it is covered with yet, most likely a synthetic rubber) is for noise cancelling properties. The stainless shims are a heat reflector.
http://essexparts.com/CatalogP...l.pdf
and from:
http://www.ferodo.co.uk/ferodo....html
Thermal Underlayer
FERODO go one step further than the competition in the manufacturing process. All DS3000 brake pads are manufactured with a Thermal Underlayer, a barrier which keeps the heat where it should be. The underlayer also increases the mechanical link between the friction material and the backplate giving added strength to prevent 'edge lifting'
Modified by MightyMouseTech at 1:44 PM 5/27/2004
05-27-2004, 09:12 AM
#10
Honda-Tech Member
Join Date: Jan 2000
Location: Charlotte, NC, USA
Posts: 1,771
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
The pad material does affect the rate at which heat transfers from the rotor/pad to the caliper. One pad may transfer heat through radiation faster than another pad, yet transfers through radiation slower than the other pad. I'm not sure that this is important since most heat is most likely transferred to the caliper pretty quickly: ie while the pad is still in contact with the rotor.
A thin piece of steel (shim) will pretty much just let the heat pass right on through.
Edit: stupid words
Modified by GSpeedR at 1:40 PM 5/27/2004
A thin piece of steel (shim) will pretty much just let the heat pass right on through.
Edit: stupid words
Modified by GSpeedR at 1:40 PM 5/27/2004
05-27-2004, 09:16 AM
#11
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSpeedR »</TD></TR><TR><TD CLASS="quote">The pad material does affect the rate at which heat transfers from the rotor/pad to the caliper. One pad may transfer heat through conduction faster than another pad, yet transfers through convection slower than the other pad. I'm not sure that this is important since most heat is most likely transferred to the caliper pretty quickly: ie while the pad is still in contact with the rotor => convection doesn't have a chance to occur.
A thin piece of steel (shim) will pretty much just let the heat pass right on through. </TD></TR></TABLE>
Convection rate has nothing to do with pad properties, other than it's temp...
A thin piece of steel (shim) will pretty much just let the heat pass right on through. </TD></TR></TABLE>
Convection rate has nothing to do with pad properties, other than it's temp...
05-27-2004, 09:21 AM
#12
Honda-Tech Member
Join Date: May 2000
Location: Atlanta, GA, USA
Posts: 2,861
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
The material the pad and backer is made of will certainly effect how well it transfers heat. But the surface area of pad in contact with the rotor is so much bigger then what is in contact with the caliper that I don't see it making too much of a difference.
I also don't think a little shim, unless it is made out of some F1 alien materiel, will do much either.
Maybe one of the Carbotech or Cobalt guys who lurk here might be able to give some input.
I also don't think a little shim, unless it is made out of some F1 alien materiel, will do much either.
Maybe one of the Carbotech or Cobalt guys who lurk here might be able to give some input.
05-27-2004, 09:24 AM
#13
Suspetise...
Join Date: Nov 2002
Location: Burninating the peasants yo
Posts: 12,287
Likes: 0
Received 1 Like
on
1 Post
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SPiFF »</TD></TR><TR><TD CLASS="quote">Maybe one of the Carbotech or Cobalt guys who lurk here might be able to give some input.</TD></TR></TABLE>
That's what we really need, instead of us bunch of brainless goobs throwing theories around.
That's what we really need, instead of us bunch of brainless goobs throwing theories around.
05-27-2004, 09:25 AM
#14
Member
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
a long time ago, in a galaxy far far away, i used Porterfield R-4 race pads. they used to manufacture them with a thin thin layer of ceramic in between the friction material and the steel backing plate. this was to help insulate the caliper from the heat generated in the pads.
don't know if they still make them like that; i haven't used a porterfield pad since about '97.
don't know if they still make them like that; i haven't used a porterfield pad since about '97.
05-27-2004, 09:37 AM
#15
Honda-Tech Member
Join Date: Jan 2000
Location: Charlotte, NC, USA
Posts: 1,771
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo »</TD></TR><TR><TD CLASS="quote">Convection rate has nothing to do with pad properties, other than it's temp...</TD></TR></TABLE>
You are correct. I wrote convection when I should have written radiation. Post is edited sans convection.
You are correct. I wrote convection when I should have written radiation. Post is edited sans convection.
05-27-2004, 09:52 AM
#16
Honda-Tech Member
Join Date: Aug 2001
Location: CA, U.S.A
Posts: 2,198
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
You've got to ask some simple questions:
1. Why do you run high temp race pads at the track?
2. Why do you run high temp brake fluid at the track?
3. Why do you duct your brakes?
4. Why do racing teams do for the largest, thickest brake setups possible?
The answer to all 4 is : to deal with the heat.
If you consider what the braking system does, every component becomes a limiting step. You use high temp pads b/c they maintain sufficent braking torque at high temps ( i.e., no pad fad), but b/c they're designed to run at higher temps, they raise caliper temps.
Moreover, simply because you add a sliver of ceramic (which actually becomes a conductor above 1100 F), or a piece of Tin doesn't mean you've redueced the localized heat inside the caliper -- using higher temp pads means your mean brake temps will increase.
This in turn causes you to run higher temp brake fluid -- to cope with the elevated caliper temps, and the streeses therin.
Once you've got those two components maxed out, then the rotor (or primary heat sink) becomes the limiting factor and so you duct it to artificially elevate it's thermal threshold by adding outside cooling.
Then, after all that, you move up to slicks over DOT R compounds, and the whole cycle starts over, and you have to re-optimize the whole systm, again.
Point is, you can attempt to "channel" heat, but the notion that you can direct it, is false -- Heat is something you simply have to attempt to cope with.
1. Why do you run high temp race pads at the track?
2. Why do you run high temp brake fluid at the track?
3. Why do you duct your brakes?
4. Why do racing teams do for the largest, thickest brake setups possible?
The answer to all 4 is : to deal with the heat.
If you consider what the braking system does, every component becomes a limiting step. You use high temp pads b/c they maintain sufficent braking torque at high temps ( i.e., no pad fad), but b/c they're designed to run at higher temps, they raise caliper temps.
Moreover, simply because you add a sliver of ceramic (which actually becomes a conductor above 1100 F), or a piece of Tin doesn't mean you've redueced the localized heat inside the caliper -- using higher temp pads means your mean brake temps will increase.
This in turn causes you to run higher temp brake fluid -- to cope with the elevated caliper temps, and the streeses therin.
Once you've got those two components maxed out, then the rotor (or primary heat sink) becomes the limiting factor and so you duct it to artificially elevate it's thermal threshold by adding outside cooling.
Then, after all that, you move up to slicks over DOT R compounds, and the whole cycle starts over, and you have to re-optimize the whole systm, again.
Point is, you can attempt to "channel" heat, but the notion that you can direct it, is false -- Heat is something you simply have to attempt to cope with.
05-27-2004, 09:53 AM
#17
Join Date: Aug 2002
Location: 15 percent slip, FL, USA
Posts: 1,125
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
Convection vs. Conduction vs. Radiation:
http://www.mansfieldct.org/sch...d.htm
Thermal transfer from pad surface to caliper is primarily by conduction.
http://www.mansfieldct.org/sch...d.htm
Thermal transfer from pad surface to caliper is primarily by conduction.
05-27-2004, 09:57 AM
#18
Senior Member
Join Date: Oct 2001
Location: RIP Craig Jones
Posts: 30,826
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Agent Smith »</TD></TR><TR><TD CLASS="quote">Y'all are aware that different materials transfer heat at different rates, right?
the Porterfield R4S were more likely to boil the fluid than the Cobalt GT-Sports, and that the Ferodo DS3000 were less likely to boil the fluid than the Cobalt SpecVR I'm currently using.</TD></TR></TABLE>
I'm having a hard time with this.
You're dissipating the same amount of energy (KE = 1/2 mv^2) into heat no matter what pad you're using. Is the rate of heat transfer through the pad that different? And even if it is, wont you reach a somewhat stable temperature range of the rotor/pad after a few laps, so it wouldnt matter what the rate of transfer is.... because the heat is still gonna get there even if it does just a bit slower?
Unless i'm wrong
the Porterfield R4S were more likely to boil the fluid than the Cobalt GT-Sports, and that the Ferodo DS3000 were less likely to boil the fluid than the Cobalt SpecVR I'm currently using.</TD></TR></TABLE>
I'm having a hard time with this.
You're dissipating the same amount of energy (KE = 1/2 mv^2) into heat no matter what pad you're using. Is the rate of heat transfer through the pad that different? And even if it is, wont you reach a somewhat stable temperature range of the rotor/pad after a few laps, so it wouldnt matter what the rate of transfer is.... because the heat is still gonna get there even if it does just a bit slower?
Unless i'm wrong
05-27-2004, 10:01 AM
#19
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ »</TD></TR><TR><TD CLASS="quote">
I'm having a hard time with this.
You're dissipating the same amount of energy (KE = 1/2 mv^2) into heat no matter what pad you're using. Is the rate of heat transfer through the pad that different? And even if it is, wont you reach a somewhat stable temperature range of the rotor/pad after a few laps, so it wouldnt matter what the rate of transfer is.... because the heat is still gonna get there even if it does just a bit slower?
Unless i'm wrong</TD></TR></TABLE>
You're wrong...nothing stable about it...
BTW, even if there is a difference in heat conduction rates between pads and pistons/calipers I doubt it will be high enough to warrant changing pads....the materials used in pad compounds aren't THAT different, are they?
I'm having a hard time with this.
You're dissipating the same amount of energy (KE = 1/2 mv^2) into heat no matter what pad you're using. Is the rate of heat transfer through the pad that different? And even if it is, wont you reach a somewhat stable temperature range of the rotor/pad after a few laps, so it wouldnt matter what the rate of transfer is.... because the heat is still gonna get there even if it does just a bit slower?
Unless i'm wrong
</TD></TR></TABLE>You're wrong...nothing stable about it...
BTW, even if there is a difference in heat conduction rates between pads and pistons/calipers I doubt it will be high enough to warrant changing pads....the materials used in pad compounds aren't THAT different, are they?
05-27-2004, 10:04 AM
#20
Senior Member
Join Date: Oct 2001
Location: RIP Craig Jones
Posts: 30,826
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo »</TD></TR><TR><TD CLASS="quote">You're wrong...nothing stable about it...</TD></TR></TABLE>
Maybe poor choice of words
what i meant was that you'll see a relatively consistent range of temps (say 600 down the front straight and 1000 deg after you've burninated them in T1) - right? wrong? stupid?
Maybe poor choice of words
what i meant was that you'll see a relatively consistent range of temps (say 600 down the front straight and 1000 deg after you've burninated them in T1) - right? wrong? stupid?
05-27-2004, 10:06 AM
#21
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ »</TD></TR><TR><TD CLASS="quote">
Maybe poor choice of words
what i meant was that you'll see a relatively consistent range of temps (say 600 down the front straight and 1000 deg after you've burninated them in T1) - right? wrong? stupid?</TD></TR></TABLE>
Temps of what?
Maybe poor choice of words
what i meant was that you'll see a relatively consistent range of temps (say 600 down the front straight and 1000 deg after you've burninated them in T1) - right? wrong? stupid?
</TD></TR></TABLE>Temps of what?
05-27-2004, 10:07 AM
#22
Senior Member
Join Date: Oct 2001
Location: RIP Craig Jones
Posts: 30,826
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo »</TD></TR><TR><TD CLASS="quote">Temps of what? </TD></TR></TABLE>
Rotor?
RJ - fishing...
Rotor?
RJ - fishing...
05-27-2004, 10:07 AM
#23
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ »</TD></TR><TR><TD CLASS="quote">
Rotor?
RJ - fishing...
</TD></TR></TABLE>
I thought we were talking about caliper/fluid temps....
Friction from braking generates heat, that goes into rotors + pads...pads then transfer said heat either to air, back to rotors, and some to the caliper...
Rotor?
RJ - fishing...
</TD></TR></TABLE>
I thought we were talking about caliper/fluid temps....
Friction from braking generates heat, that goes into rotors + pads...pads then transfer said heat either to air, back to rotors, and some to the caliper...
05-27-2004, 10:11 AM
#24
Senior Member
Join Date: Oct 2001
Location: RIP Craig Jones
Posts: 30,826
Likes: 0
Received 0 Likes
on
0 Posts
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by El Pollo Diablo »</TD></TR><TR><TD CLASS="quote">I thought we were talking about caliper/fluid temps....
</TD></TR></TABLE>
Wouldnt that be related to the heat sink (rotor) temps though?
</TD></TR></TABLE>
Wouldnt that be related to the heat sink (rotor) temps though?
05-27-2004, 10:11 AM
#25
Re: fact or myth? brake pads that hold heat at the rotor v brake pads that transfer to caliper? (ape
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ »</TD></TR><TR><TD CLASS="quote">
Wouldnt that be related to the heat sink (rotor) temps though?</TD></TR></TABLE>
It'a ALL related
Wouldnt that be related to the heat sink (rotor) temps though?</TD></TR></TABLE>
It'a ALL related
