New Product: Ultimate Brake Kit for the 928
04-13-2011, 06:19 PM
#76
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Just dont be THIS GUY
As luck would have it, when I came out from my dyno session yesterday (we were measuring back-pressure in the exhaust system of the Bonneville engine) I spied this Corvette in the parking lot.
The boys tell me these are called "caliper covers". In high-school we had another word for them, "Falsies"
The boys tell me these are called "caliper covers". In high-school we had another word for them, "Falsies"
475hp/460lb.ft
04-13-2011, 06:28 PM
#79
Drifting
There is no mystery in this statement from the F1 technical expert website;
"the only way to slow down the car is to convert the kinetic energy into another form. Brakes as we know them both in race cars and road cars convert this movement energy to heat."
Argue with the scientists, I have posted a lot of helpful technical info, that's all I can do. To believe you, I would have to accept that having GT2RS brakes on my car w/o any other change would not slow me down any better than now.
04-13-2011, 06:29 PM
#80
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Years ago I had proposed such "caliper covers" , then last couple years they have been on E-bay....great idea helps hold the heat around the calipers 
Just remember "falsies" worked because by the time you knew for sure....it did not seem to matter much.
Just remember "falsies" worked because by the time you knew for sure....it did not seem to matter much.
04-13-2011, 06:34 PM
#81
Rennlist Member
Dan and to All who say tires are the big deal;
A 1986 Formula 1 car had the widest slick tires ever in F1 and carbon ceramic rotors, yet a 2005 F1 car stops in a much shorter distance and with way more G-force on narrower tires that are grooved.
The reason - even better Carbon Ceramic brake technology that disspates heat even better. It is all kinteic into heat energy transfer. That said as you approach the limits of the heat dissipation, having a wider tire will keep you in control longer before it loses adhesion.
A 1986 Formula 1 car had the widest slick tires ever in F1 and carbon ceramic rotors, yet a 2005 F1 car stops in a much shorter distance and with way more G-force on narrower tires that are grooved.
The reason - even better Carbon Ceramic brake technology that disspates heat even better. It is all kinteic into heat energy transfer. That said as you approach the limits of the heat dissipation, having a wider tire will keep you in control longer before it loses adhesion.
1) Downforces are greater today
2) Tire compounds are faster today grooved, than slicks back then.
04-13-2011, 06:38 PM
#82
Rennlist Member
I give up on the 60-0 versus multiple stopping fade.
Anyway back to Carl's kit...which I am liking.
Do you have Brembo rear calipers so if I get those big front Brembo's I can get rears to so all my calipers will say Brembo?
Anyway back to Carl's kit...which I am liking.
Do you have Brembo rear calipers so if I get those big front Brembo's I can get rears to so all my calipers will say Brembo?
04-13-2011, 06:45 PM
#83
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The first 1 G of decceleration from high speed for an F-1 comes the moment you lift because of the aerodynamic drag before they touch the brake pedal. The very high g forces they can brake is largely due to the downforce which gives the tires more traction allowing the brakes to dissipate more heat. Tires are what sets the upper limit of how quickly a car can brake....just as they limit acceleration and cornering. If a brake system can hold the tires at just before lock up skidding during the entire stop, the system is big enough. If you are doing repeated stops it may need to bigger, better, cooled better, run "better" pads. The larger diameter rotor means more leverage and might make it easier to hold the brakes at the limit just before lockup but the tires still determine the maximum rate of braking that is possible.
04-13-2011, 06:47 PM
#84
Nordschleife Master
You're missing the point. The single largest factor may well be heat dissipation, however it is still only one factor in the equation, and there are many others that will have an effect.
There is no "bottom line".. thats part of the reason manufacturers devote incredible amounts of resource to tweaking and testing their designs - the sum of many tiny gains is significant.
04-13-2011, 06:48 PM
#85
I calculated a 41mm to 43mm 4-piston set of front calipers for the 85 928 without having to jack with the Master Cylinder. But an adjustable Wilwood Bias valve on the rear circut would allow 45mm piston calps. Even so It wouldn't be difficult to mod a different MC to fit the 928 Vac booster.
04-13-2011, 06:52 PM
#87
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So Jeff-
Based on your experience now on-track with your '88, what would be your pad choice(s) for on-track 928 use? I think the rebuilding part of my 928 life is hopefully going to give way to the HPDE part of my 928 life.
FWIW my car had drilled Zimmermans with no appreciable wear on them at all when I got it, yet the holes have tons of spider cracks around them. I'm using Mintex pads for street use. It had Pagid Oranges on it when I got it which gave great pedal feel but squealed like stuck pigs.
Based on your experience now on-track with your '88, what would be your pad choice(s) for on-track 928 use? I think the rebuilding part of my 928 life is hopefully going to give way to the HPDE part of my 928 life.
FWIW my car had drilled Zimmermans with no appreciable wear on them at all when I got it, yet the holes have tons of spider cracks around them. I'm using Mintex pads for street use. It had Pagid Oranges on it when I got it which gave great pedal feel but squealed like stuck pigs.
Recommendations generally come from past experiences...what you liked in past compounds and what you didnt like..etc.
Track only use..Id start..knowing how -I- like to drive, Raybestos ST41 front, and ST42 rear.
If rear still felt stable..up to ST43 in the rear. The ST42's carry a linear friction coefficient across the entire temp range for the most part..so theyre a good all temp, all weather pad..and the 43s ramp up and down in parallel with the 41's..but those would be a bad choice for platforms that experience axle hop under heavy braking.
I would also be on a track tire..if a street tire fronts would be ST43. They carry a lower Mu, at about .68 peak, where the ST41s carry up to a .71..and quicker. They can overtake street tires if not used carefully.
I would not slot or drill either, the Raybestos pads have not needed those with anyone ive sold em to over the last 5yrs since they came out public with these compounds. Some softer pads may appreciate slotting, to prevent glazing.
Hawks new DTCs are nice..they were a late answer to the Raybestos materials, and they're CLOSE..but not quite the same, IMHO. PFC, same old same old, but some people are religion with em, Porterfield..doesnt have a solid race pad for big heavy cars, but smaller spec racers, they have some good choices.
If you wanted a really interesting street setup, you can use the R4-S pads up front, and get the R4-1 specially cut for the rear. Those are a HIGH friction COLD pad, and they're trick for racers that want more rear bite at low temps, but bias valves are illegal to use. They'll dust more than the fronts, but are _anchors_ out back. I would put them up against a prop-valve upgrade..but they would cost more than a $100 valve upgrade.
At that point, its just getting a rear pad that peaks in Mu at the temperatures that you run at..Porterfield R4S or Hawk HP+ would work pretty well, with the HP+ making more dust and being more abrasive to the rotor.
But..on stock sized hardware, this would not be a high speed track day solution..id just say screw it, and swap in race pads up front and tear it up.
The Raybestos ST3x pads can be used as aggressive street compounds as well, and those are typically the re-packaged solutions that Wilwood sells as name-brand pads with their kits.
My S4 has the R4-S pads all around, and im happy, but theres only 2 -fast- laps in them..or a handful of moderately fast ones..heavy car.
My RX8 has Raybestos ST43 up front, and will put your passenger into the windscreen..awesome..and I get about 35k out of a set on the street with daily aggressive mountain road driving..but noiiiisy. I use R4-1 in the rear.
I would love to help an established vendor pipeline some/any of these if they dont carry them already...I wanna play by the rules and all.
04-13-2011, 06:57 PM
#88
Rennlist Member
As to heat dissipation Carbon better, cross-drilled and Vented BETTER;
3 different sources
Carbon ceramic rotors and pads were first utilized on Formula 1 car brake systems, because of the performance requirements involved with racing 200+ mph on the track. Using rotors and pads that are made from carbon fibers ceramically bonded with silicon carbide, “carbon brakes” are very heat-resistant and thus much more durable than conventional steel or iron-based brake components.
In fact, carbon brakes provide three key advantages over conventional brakes of a similar size:
1) They can create more frictional force/stopping power and thus stop the car more quickly;
2) They can shed or dissipate heat buildup much more easily and thus wear much less rapidly;
3) The components usually weigh much less, thus allowing the vehicle to handle more responsively.
Per Italian supercar tradition, the 2012 Pagani Huayra rides a 4-wheel independent suspension with classic double wishbones and coil springs at each corner, plus front and rear antiroll bars. The wishbones are forged from aviation-grade aluminum for high strength with low weight, and work through racecar-style pushrod shock absorbers with automatic front-height adjustment. Brakes are the expected jumbo 4-wheel discs--15-inch diameter all around--with ABS and an integrated traction-control system, but with rotors made of advanced carbon-ceramic material instead of steel to provide better heat dissipation and durability in repeated high-speed stops.
Cross-drilled and Ventilated Rotors
Cross-drilled and ventilated rotors are brake rotors that have vents on the edge of the rotor cast into it during the manufacturing process. The vents serve the same function as cross-drilling, which is to help dissipate heat build-up more quickly. To see if a rotor is vented, look at the outer edge of it to see if there have been vents hollowed into the metal that extend into the rotor. Frequently, rotors are only vented and not cross-drilled as well, though there are rotors that are vented as well as cross-drilled.
3 different sources
Carbon ceramic rotors and pads were first utilized on Formula 1 car brake systems, because of the performance requirements involved with racing 200+ mph on the track. Using rotors and pads that are made from carbon fibers ceramically bonded with silicon carbide, “carbon brakes” are very heat-resistant and thus much more durable than conventional steel or iron-based brake components.
In fact, carbon brakes provide three key advantages over conventional brakes of a similar size:
1) They can create more frictional force/stopping power and thus stop the car more quickly;
2) They can shed or dissipate heat buildup much more easily and thus wear much less rapidly;
3) The components usually weigh much less, thus allowing the vehicle to handle more responsively.
Per Italian supercar tradition, the 2012 Pagani Huayra rides a 4-wheel independent suspension with classic double wishbones and coil springs at each corner, plus front and rear antiroll bars. The wishbones are forged from aviation-grade aluminum for high strength with low weight, and work through racecar-style pushrod shock absorbers with automatic front-height adjustment. Brakes are the expected jumbo 4-wheel discs--15-inch diameter all around--with ABS and an integrated traction-control system, but with rotors made of advanced carbon-ceramic material instead of steel to provide better heat dissipation and durability in repeated high-speed stops.
Cross-drilled and Ventilated Rotors
Cross-drilled and ventilated rotors are brake rotors that have vents on the edge of the rotor cast into it during the manufacturing process. The vents serve the same function as cross-drilling, which is to help dissipate heat build-up more quickly. To see if a rotor is vented, look at the outer edge of it to see if there have been vents hollowed into the metal that extend into the rotor. Frequently, rotors are only vented and not cross-drilled as well, though there are rotors that are vented as well as cross-drilled.
The holes ppl cast/drill into a rotor face, dont move any air at all, and actually lower the efficiency of the pump built into the rotor.
They cost friction space, ive measured some rotors at over a 12% LOSS of braking area on the rotor face.
Cross drilling is a weight savings game, but ONLY if your budget allowed for the additional braking force required to overcome the loss of area, and heat generated from it as a heat sink.
Im cool to disagree, I wont go biblical on this, and start shooting infidels or anything.
04-13-2011, 07:00 PM
#89
Rennlist Member
In fact, thats a crappy pattern to drill at ALL, since it concentrates the uneven heating & cooling, and eventual pad & rotor wear into those places.
Cooling takes forever compared to heating up, drilling is NOT worth the losses in braking, the cooling just doesnt happen fast enough to worry about it.
04-13-2011, 07:46 PM
#90
Drifting
I already posted linked info FROM F1 saying tires were NOT grippier, faster, or better in 2005 than in 85. It was on purpose by F1.
Sometimes experts know what they are talking about.
From an F1 site
They say ----------- "Braking distances in F1 have got smaller and smaller over the years due to brakes getting better and better. By reducing the performance of brakes, some have suggested using steel brakes, the braking distances would increase significantly and this would increase overtaking."
Brakes are doing the braking and of course all things help, but brakes have gotten really good in F1. It is heat dissipation!