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Also, after this failed experiment I added the Girodisk Ti shims. Maybe they would have prevented the meltdown...? My main mistake here was trying these pads on an endurance 200TW. And look at that dive/weight transfer. The non Z07 suspension is likely too soft. Z07 or coilovers and a Hoosier or scrub and they'd probably be a good combo.
Oh and forgot to ask, maybe you already stated. Did you run SR front and rear? Does look like a lot of dive.
Also, after this failed experiment I added the Girodisk Ti shims. Maybe they would have prevented the meltdown...? My main mistake here was trying these pads on an endurance 200TW. And look at that dive/weight transfer. The non Z07 suspension is likely too soft. Z07 or coilovers and a Hoosier or scrub and they'd probably be a good combo.
Do those shims exist for cadilac brembo 4 pistons? What about rear C5 Z51 calipers? I know now the rear C5 calipers have the SR pads available which is great.
Do those shims exist for cadilac brembo 4 pistons? What about rear C5 Z51 calipers? I know now the rear C5 calipers have the SR pads available which is great.
does anybody have "long term" experience with shims? be it ti, ss or carbon fibre? whats the thickness? do they have any real world effect? at least a ss shim will reflect heat even if its not isolating much. if they really block off some heat to the caliper this heat stays in the pad/rotor, right? is that a problem?
edit: what are the calipers above, btw? what kind of pistons?
Finally got to try these. Cota. Pirelli slicks. Oem aero and hp, slightly lightened car. They did fine. Comparable to st47s and DTC70s. They definitely are harder non rotors which considering how expensive girodiscs are, I’m not happy with. The one thing odd is that they changed pedal effort mid session with just a small cooldown which to me means they were getting hot . I was being extra cautious with braking 25m early most places.
below pics of brand new pads and rotors after 20 minutes of lapping (2 sessions) at 2:22-2:24 pace at cota
looks similar to mine but they actually lasted longer. Pads leave deposits which look like wear but actually slightly thickens the rotor protecting it. Need to measure them. I had double the pad like of ST43/45 at Laguna which is one of the the hardest tracks there is on brakes. Running same lap times (1:36-1:37)
Also, after this failed experiment I added the Girodisk Ti shims. Maybe they would have prevented the meltdown...? My main mistake here was trying these pads on an endurance 200TW. And look at that dive/weight transfer. The non Z07 suspension is likely too soft. Z07 or coilovers and a Hoosier or scrub and they'd probably be a good combo.
I have the Ti shims on mine and while I don't have temp data, I can say that the boots are still there and flexible. On my prior car, I melted the boots the first track day I used it.
Different topic....Looks like in your pics you don't have the Z07 cooling "ducts" installed (or aftermarket ducts for that matter). I think you can still buy them through GM and they used to be about $100. The first one is a bit of a jigsaw puzzle to install but once you figure it out, the second one only takes a couple minutes after you have the wheel off. I recommend you consider that.
Re: non-Z07 suspension....yes....too soft. The Z06/Z07 gets a stiffer front spring so that will help your nose dive. It's been years but I think it gets a stiffer rear spring as well, plus different sway bar bushings. After that, it's time for coilovers.
I do not have the wheel blockers but I do have all of the OEM plastic brake ducting, deflectors, etc.. it's just not apparent due to the angle of the pics. There are a few different part numbers but I can't find a distinction between Z06 vs Z07. The stock pics aren't very helpful either.
I do not have the wheel blockers but I do have all of the OEM plastic brake ducting, deflectors, etc.. it's just not apparent due to the angle of the pics. There are a few different part numbers but I can't find a distinction between Z06 vs Z07. The stock pics aren't very helpful either.
z07 has a whole duct from below the control arm to the back of the rotor along with just a deflector.
z07 has a whole duct from below the control arm to the back of the rotor along with just a deflector.
I have a channel/duct that runs from the front bumper as well as the airbox below the control arm that dumps to the back of the rotor and the control arm deflector -- is there something else?
Crude pic since I don't have time at the moment to pull a wheel off:
I have a channel/duct that runs from the front bumper as well as the airbox below the control arm that dumps to the back of the rotor and the control arm deflector -- is there something else?
Crude pic since I don't have time at the moment to pull a wheel off:
You have the factory options covered
Re: suspension work. Z07 "stuff" probably isn't enough unless you work on a driver mod to change braking style. Looks like you use "count to 3, brake when you see God". The extra 100lbs over the nose on the Z06 is also a factor.
Re: suspension work. Z07 "stuff" probably isn't enough unless you work on a driver mod to change braking style. Looks like you use "count to 3, brake when you see God". The extra 100lbs over the nose on the Z06 is also a factor.
Ha! That's one big-*** assumption based on a single glamour shot with an improper pad.
Ha! That's one big-*** assumption based on a single glamour shot with an improper pad.
I'd say it's highly unusual for someone to change up their braking technique specifically for a glamour shot in a specific spot on track. Based on your calipers and what's happened to the factory powder coating, that too indicates a more aggressive technique. That's not being critical. Everyone has their approach and as in many things, there's more than one way to skin the proverbial cat.
If you have PDR, it's an easy to look at what's going on regarding braking using Pi Toolbox (not to be confused with Cosworth Toolbox). Plot longitudinal acceleration
I can relate to heavy braking and front end dive. Note where the tires are inside the front fender well. Z07 suspension. 570rwhp and obviously aero....
From my PDR, this is snapshot of 3 laps., You can see the repetition. I highlighted "0" to make it easier to read. Of course traffic and other things will affect absolute values at any given point in time but it does allow you to look critically at what's happening.
Here's the TL;DR -- These pads have a hyper aggressive Mu and are essentially a solid block of metal which doesn't isolate heat from the rest of the components like a composite pad. The (over-simplified) result was the extreme dive and glowing rotors which in turn cooked off the calipers in a single session. Coincidentally there happened to be a photographer that got some great shots of this FAFO moment. I've previously never had a single issue with the brakes, nor since; this experience was completely isolated to the SR pad experiment.
Here's the TL;DR -- These pads have a hyper aggressive Mu and are essentially a solid block of metal which doesn't isolate heat from the rest of the components like a composite pad. The (over-simplified) result was the extreme dive and glowing rotors which in turn cooked off the calipers in a single session. Coincidentally there happened to be a photographer that got some great shots of this FAFO moment. I've previously never had a single issue with the brakes, nor since; this experience was completely isolated to the SR pad experiment.
Just to clarify, to your reasoning a semi-met would actually reject more heat into the rotor and make it glow easier. There has been significant testing thinking that caliper and fluid temperatures would rise with the sintered pad (big concern of mine in development), but to my surprise it actually didn't. When you think of how a system reaches equilibrium, its really just a ramp rate that is different. The whole system might get up to temperature faster, but it shouldn't get hotter per say. That would defy the laws of physics. The only way it would get hotter is if you were going faster, or your weight increased.
want to chalk it up to a fluke because I can't explain it, but on many instances peoples systems run cooler. That has been on vehicle and on the dyno. Only thing I can think of is that on certain tracks the heat is transferring into the caliper quicker (not hotter!) so maybe ones on long straights you can utilize the whole system as a heat sink. I don't really know why, its bar talk at that point lol
When you think of the paths of heat dissipation, your biggest one is going to be the rotor. If the heat was high enough to discolor your powdercoat through the pistons and pads alone, I would venture to say you would have fluid boil issues. This was probably caused by radiant heat. Did the inside of the caliper discolor in the same manner? Just curious.
Ultimately, as you said you ran SR front and rear, so why would brake dive increase? That again defys dynamics, your brake bias didn't change unless you ran staggered compounds which it seems like you didn't. Were you braking harder by chance? That would at least change the heat flux and potentially dive degree.
Genuinely not trying to challenge or discredit your info, I just like to get to the bottom of why something happened so we can try to figure it out!
For what its worth, I have seen the calipers do the exact same thing with the OE compound on a GS. So its easy to do.
Last edited by PLapping12; 07-21-2023 at 11:00 AM.
Just to clarify, to your reasoning a semi-met would actually reject more heat into the rotor and make it glow easier. There has been significant testing thinking that caliper and fluid temperatures would rise with the sintered pad (big concern of mine in development), but to my surprise it actually didn't. When you think of how a system reaches equilibrium, its really just a ramp rate that is different. The whole system might get up to temperature faster, but it shouldn't get hotter per say. That would defy the laws of physics. The only way it would get hotter is if you were going faster, or your weight increased.
want to chalk it up to a fluke because I can't explain it, but on many instances peoples systems run cooler. That has been on vehicle and on the dyno. Only thing I can think of is that on certain tracks the heat is transferring into the caliper quicker (not hotter!) so maybe ones on long straights you can utilize the whole system as a heat sink. I don't really know why, its bar talk at that point lol
When you think of the paths of heat dissipation, your biggest one is going to be the rotor. If the heat was high enough to discolor your powdercoat through the pistons and pads alone, I would venture to say you would have fluid boil issues. This was probably caused by radiant heat. Did the inside of the caliper discolor in the same manner? Just curious.
Ultimately, as you said you ran SR front and rear, so why would brake dive increase? That again defys dynamics, your brake bias didn't change unless you ran staggered compounds which it seems like you didn't. Were you braking harder by chance? That would at least change the heat flux and potentially dive degree.
Genuinely not trying to challenge or discredit your info, I just like to get to the bottom of why something happened so we can try to figure it out!
For what its worth, I have seen the calipers do the exact same thing with the OE compound on a GS. So its easy to do.
First, these are not my words RE: SR-21 but instead of paraphrasing I'll just copypasta since I feel it's germane:
One thing to keep in mind with sintered pads is that they're solid metal. Composite pads don't transmit heat very well, blocking it from getting back through the pad to the pistons, although that capability fades as the pads wear. Solid metal sintered pads are the same temperature right through from the first moment they're used to worn out. They're like a pipeline for heat back to the caliper pistons and body. It is worthwhile running insulation plates like titanium, although a little known fact is that stainless actually works better.
I've successfully been through at least 6-7 sets of brake pads on this car since December. Until (and after) the SR-21 I have never discolored the caliper, lost pedal pressure and/or boiled the fluid and burned out the rubber dust shields throughout a 20 min session. This was at Carolina Motorsports Park which is notoriously hard on brakes -- harder in my experience than VIR Full where despite the higher speeds there's really only 2 heavy braking zones; CMP has four with little cooldown between. I didn't get more than 5 laps (less than half a session) before the meltdown. I didn't notice anything was amiss on-track until I rapidly lost almost all pedal pressure. I had to drive off straight off track and cruise down the highway for several miles before I regained mostly normal pressure. I didn't find out about the glowing rotors until the photographer showed up at my bay with a preview, while I was admiring my smoking calipers.... The calipers are cooked on the outside so I don't believe it was radiant heat from the rotor, but rather heat transfer into the caliper. The wheel well side is not discolored, I assume because of the air through the ducting.
As for the dive, without the ride height telemetry I don't have, all I can do is speculate. My guess is because of the aggressive bite the weight transfer was so abrupt the magride was not able to compensate or get ahead of it so the nose is on the ground and the front brakes end up doing 99% of the work -- more heat, vicious cycle. The rear brakes were not overheated and pads have virtually zero wear. I didn't get enough time/wear on these pads to really assess, but my experience with other pads is front to rear wear is relatively even. In this case it's like the rears weren't even there. And FWIW I do a bleed (SRF) with every pad change. As for braking harder than perhaps before, if anything I was having to use less pedal pressure to mitigate hitting ABS or ice mode. I was braking at the same markers as before.
I mark my rotors with temperature paint and my rotor temperatures decreased with SR21 vs ST47. I was skeptical and thought it was BS when I heard that claim.
I do not measure caliper temperature so can't comment other than my brake fluid (ATE) didn't boil or pedal get spongy. My calipers are anodized rather than painted.
"Just to clarify, to your reasoning a semi-met would actually reject more heat into the rotor and make it glow easier. There has been significant testing thinking that caliper and fluid temperatures would rise with the sintered pad (big concern of mine in development), but to my surprise it actually didn't. When you think of how a system reaches equilibrium, its really just a ramp rate that is different. The whole system might get up to temperature faster, but it shouldn't get hotter per say. That would defy the laws of physics. The only way it would get hotter is if you were going faster, or your weight increased."
heat (thermal enegry) is created at the friction surface of the pad and travels through the components to the paint layer on the calipers where it dissipates (simple equilibrium model). the easier/faster it travels the higher the temp of the paint becomes to dissipate it. hight thermal conductivity of the friction material enhances the flow. no? its like an orifice in a water pipe.
so material with high conductivity (=high metal content*) will heat up the paint more while it dissipates heat from the disc. in case of low conductivity the paint is cooler but more heat stays in the disc. in case of very low contuctivity (probably <10), where the pad friction surface can be several hundred° higher than the disk surface there is no dissipation from disk to pad. so either the disk get hotter or the pain gets hotter, not both, if looking at the influence of thermal conductivity. if both get hotter there is something else at play.
thermal conductivity of friction materials generally ranges from 0,1 to 200 w/mk° (an a-type gray cast iron disk will be around 60 w/mk°). does anybody know in what range it might be for the pads in question?
*carbon content is tricky, i have no idea if its a good or bad conductor, e.g. diamond is 3000 w/mk° while carbon fibre can be <1 w/mk°, it depends on the structure. does anybody know?
"Just to clarify, to your reasoning a semi-met would actually reject more heat into the rotor and make it glow easier. There has been significant testing thinking that caliper and fluid temperatures would rise with the sintered pad (big concern of mine in development), but to my surprise it actually didn't. When you think of how a system reaches equilibrium, its really just a ramp rate that is different. The whole system might get up to temperature faster, but it shouldn't get hotter per say. That would defy the laws of physics. The only way it would get hotter is if you were going faster, or your weight increased."
heat (thermal enegry) is created at the friction surface of the pad and travels through the components to the paint layer on the calipers where it dissipates (simple equilibrium model). the easier/faster it travels the higher the temp of the paint becomes to dissipate it. hight thermal conductivity of the friction material enhances the flow. no? its like an orifice in a water pipe.
so material with high conductivity (=high metal content*) will heat up the paint more while it dissipates heat from the disc. in case of low conductivity the paint is cooler but more heat stays in the disc. in case of very low contuctivity (probably <10), where the pad friction surface can be several hundred° higher than the disk surface there is no dissipation from disk to pad. so either the disk get hotter or the pain gets hotter, not both, if looking at the influence of thermal conductivity. if both get hotter there is something else at play.
thermal conductivity of friction materials generally ranges from 0,1 to 200 w/mk° (an a-type gray cast iron disk will be around 60 w/mk°). does anybody know in what range it might be for the pads in question?
*carbon content is tricky, i have no idea if its a good or bad conductor, e.g. diamond is 3000 w/mk° while carbon fibre can be <1 w/mk°, it depends on the structure. does anybody know?
Yes definitely, it is more conductive than a resin based pad by nature. But the testing shows that it is negligible or even better in both field and dyno testing, I know it doesn't make sense and baffles me too, and it does sound like you may have experienced fluid boil if the pedal went to the floor (if I read that right). Odd that the pedal returned to normal though? Air wouldn't just disappear you'd think.
Not to get into too much of this because it is all proprietary, but the idea of sintered pads being very conductive is based off old knowledge and technology. These thoughts are based on the premise of the metal matrix being Copper, which SR pads are not. I cannot reveal what it actually is, but the thermal conductivity is substantially less than Copper. Also, SR pads are pretty highly filled, so the metal matrix isn't the only contributing factor.
To your other question, graphite is the carbon allotrope commonly used in brake pads. It has high thermal conductivity and resin based pads are highly filled with it.
Either way, bummer you weren't happy with the SR pads but there does seem to be some people out there they don't seem to agree with. Happens though! Hard to make a magic bullet pad, especially for these C7 Z06's, its a lot of car!
Edit: Forgot to address the shim thing, SOME grades of stainless are better than titanium. Just depends, and there is more to it as thermal conductivity values change as temperatures climb. Titanium is pretty consistent in it's thermal conductivity at around 16 W/mK through a typical brake's operating temperature. I assume most are using austenitic SS like 304 due to its price and availability (around 16-17 W/mK), which has a linear climb of thermal conductivity and is actually higher where it matters (21 W/mK at only 500C).
Last edited by PLapping12; 07-24-2023 at 11:04 AM.
sintered: its just a way of producing a pad, right? it doesnt say what gets "sintered" into it, so if you have a mixture of metals and ceramics (of whatever morphology) you can easily get a conductivity of less than 5 w/mk. what is it for the sr11/21 material?
07-19-2023, 12:08 PM
