When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Just wanted to start a conversation to learn abit more about braking upgrades and how those apply to certain situations. So much talk about brake pad compound and caliper/rotor size that sometimes it gets confusing, so I'm going to start with the basic question and then expand on it after.
What is going to benefit a road course car more, better pad compound or more clamping force?
For example, take 2 identical stock C6 cars with the stock PBR 2 piston calipers. One upgrades the pads to something very aggressive for track use only while keeping the stock calipers and rotor size while the other upgrades to slightly bigger rotors and the C6Z calipers while using a semi-aggresive street friendly pad. Which car would have better stopping distance? Which setup would experiene less brake fade over continous braking around a track?
Now I know you're thinking to yourself, why not do both the bigger calipers and aggressive pads? Well I understand that's the best option but just wanted to get more educated on how pad compound works vs. clamping force in terms of stopping effectiveness.
Just wanted to start a conversation to learn abit more about braking upgrades and how those apply to certain situations. So much talk about brake pad compound and caliper/rotor size that sometimes it gets confusing, so I'm going to start with the basic question and then expand on it after.
What is going to benefit a road course car more, better pad compound or more clamping force?
For example, take 2 identical stock C6 cars with the stock PBR 2 piston calipers. One upgrades the pads to something very aggressive for track use only while keeping the stock calipers and rotor size while the other upgrades to slightly bigger rotors and the C6Z calipers while using a semi-aggresive street friendly pad. Which car would have better stopping distance? Which setup would experiene less brake fade over continous braking around a track?
Now I know you're thinking to yourself, why not do both the bigger calipers and aggressive pads? Well I understand that's the best option but just wanted to get more educated on how pad compound works vs. clamping force in terms of stopping effectiveness.
The brake pad Mu or coefficient of friction and the pad heat rating are of paramount importance for track usage. Vintage (C2/C3) Corvettes use stock 1965 thru 1982 calipers and rotors successfully on cars which ara FAR faster than they were inperiod. Brakes turn kenetic energy into heat which is then disapated thru the air cooled heat sync rotor. There are much more expensive options available for modern race cars, but the good ones use the same engineering principles. Sliding disc or single sided calipers are NOT appropriate for any race vehicle, even a bicycle. Most modern brakes will stop the vehicle ONCE. A race vehicle must have the ability to seamlessly stop the vehicle consistently many times in a row.
Good pads, fluid, and duct cooling are a must and a good start.
Rotor quality is also important (not all rotors are equal, metal quality, # of cooling vanes, drilled versus slotted versus blank).
My street C6 Z51 has stock calipers, stock rotors, Carbotech XP12's, Castrol SRF and spindle ducts. On the track they work well with good bite, modulation, and no appreciable fade. The stock calipers will start to spread and pad wear is not as even as you get with better calipers. Rotors and pads last about 6 days.
Once you start running slicks and r-compounds then you start to run into limitations with the calipers.
My race car has Brembo GT 355mm front with Pagid RS29 pads, spindle ducts, and good fluid. Rotors and pads last more than 12 days but this car has full aero (big splitter, wing, canards, vented hood and fenders, etc.) and so I spend ~40% less time on the brakes (even though it's faster). Pedal feel is awesome - a little less bite than the Carbotech's but modulation is very nice and you can press as hard as you want. That car also has GM race ABS system (non stock) which allows much greater control at threshold.
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13
If you boil it down to the extreme basics there are really only two major factors that effect how well a car can stop.
Friction between the pad and the rotor, and the friction between the tire and the ground.
If the tire can not hold the grip of the pad, it locks up and you can not stop well. If the pad can not apply enough force to the rotor then the car will not stop well either. That is why pad compound is so important on a track car.
Now moving on.....again basics here.
Rotor size does two important things. It gives you mechanical advantage on stopping....just as a longer throw crank increases torque of an engine...same principal. The other thing you have is more surface area to dissipate the heat energy created by the brakes.
Calipers.....these are going to increase clamp force on the pads and also dictate the size of the pad you can have. Thicker pads provide more life and generally more heat protection to the pistons and fluid. A longer and tall pad gives you more grip area. The strength of a caliper is also something to pay important attention to. As you increase the torque to the wheel by going to a stickier tire and a more aggressive compound tire that force is being transmitted to other areas of the car. Think of it just like a big HP car on tiny tires. Big power...little tires...wheel spin. Big tires and big HP..no you start breaking things like your driveshaft, axles, diff, clutch....so on and so forth. Same with your brakes. You put slicks on the car and the most aggressive pads you can you will see calipers spreading, you will see wheel bearings taking more abuse, you will see control arm bushings move, you will see rotors fail sooner. So this is a very important thing to think about as well. Your brakes need that rigidity just like the chassis does to do their job as well.
As you have seen from other companies like StopTech, Wilwood, Brembo, AP...everyone has awesome tech drawings of their calipers, their rotors, their hats to give you an idea of why they do things the way they do. We have all seen great posts from Jeff Ritter and his details of why Essex does their parts the way they do. To some degree this is something you need to do as a buyer to pick the right one for your application.
Do you need floating rotors? If so who's is easiest to work with and provides the best support?
Who's rotors offer the best life and cooling?
Who's calipers offer the stiffest design? Do I need to have a quick change pad setup?
Do I need knock back springs?
So your question about two cars using the same setup with stock parts just a pad and tire change....yes the OEM parts can generally hold it together for a short time but the harder you push them the quicker they fail. That is the most important thing about a big brake kit for your car. It is not the ability for it to stop the car any quicker than it would stock (using the same pads and tires) it is the ability for that kit to keep stopping lap after lap after lap after lap.
What is going to benefit a road course car more, better pad compound or more clamping force?
For example, take 2 identical stock C6 cars with the stock PBR 2 piston calipers. One upgrades the pads to something very aggressive for track use only while keeping the stock calipers and rotor size while the other upgrades to slightly bigger rotors and the C6Z calipers while using a semi-aggresive street friendly pad. Which car would have better stopping distance? Which setup would experiene less brake fade over continous braking around a track?
I think that's a very cool question. And one that I'm not certain there is a blanket answer for.
I also think that any of us either in the business or with considerable track experience would first pick "rotor size" vs about any other option. Anthony, myself and the others have explained the basis of that a few times already.
Assuming you put in the hot-rod race pad on the PBR I'd say for a relatively modest time this set up will give you ample stopping power and short distances. The limitation coming with time- smaller pads, higher temps, pad plate deflection, and ultimately a longer pedal from overheating.
On the other hand a slightly larger rotor, the six pot caliper, larger pad and street compound would be acceptable for a few laps and offer modest distance changes. For a bit. But the first to go would be the pad. My money would say this will give up first depending upon track demands, driving style and tire.
End of the day..I think this is pretty much a tit for tat formula. Obviously the worst being the small parts and street pads, the best the larger and track pads. A hybrid of items 'tween seems a recipe for continued frustration.
*I'd like to note too that you reference "clamp force" in the first sentence. That's piston area in my world. Assuming the PBR and the six pot are about the same (we know both to be about 4") there is no clamp force change. The change being (possibly, depending upon the hard data) rotor torque- the mathematical value of clamping (piston force) x Cf (Mu) x Er (effective radius). Swapping one for the other can make the same net result. How well they play together in the real world once hot however is not always the same.
If you boil it down to the extreme basics there are really only two major factors that effect how well a car can stop.
Friction between the pad and the rotor, and the friction between the tire and the ground.
If the tire can not hold the grip of the pad, it locks up and you can not stop well. If the pad can not apply enough force to the rotor then the car will not stop well either. That is why pad compound is so important on a track car.
Now moving on.....again basics here.
Rotor size does two important things. It gives you mechanical advantage on stopping....just as a longer throw crank increases torque of an engine...same principal. The other thing you have is more surface area to dissipate the heat energy created by the brakes.
Calipers.....these are going to increase clamp force on the pads and also dictate the size of the pad you can have. Thicker pads provide more life and generally more heat protection to the pistons and fluid. A longer and tall pad gives you more grip area. The strength of a caliper is also something to pay important attention to. As you increase the torque to the wheel by going to a stickier tire and a more aggressive compound tire that force is being transmitted to other areas of the car. Think of it just like a big HP car on tiny tires. Big power...little tires...wheel spin. Big tires and big HP..no you start breaking things like your driveshaft, axles, diff, clutch....so on and so forth. Same with your brakes. You put slicks on the car and the most aggressive pads you can you will see calipers spreading, you will see wheel bearings taking more abuse, you will see control arm bushings move, you will see rotors fail sooner. So this is a very important thing to think about as well. Your brakes need that rigidity just like the chassis does to do their job as well.
As you have seen from other companies like StopTech, Wilwood, Brembo, AP...everyone has awesome tech drawings of their calipers, their rotors, their hats to give you an idea of why they do things the way they do. We have all seen great posts from Jeff Ritter and his details of why Essex does their parts the way they do. To some degree this is something you need to do as a buyer to pick the right one for your application.
Do you need floating rotors? If so who's is easiest to work with and provides the best support?
Who's rotors offer the best life and cooling?
Who's calipers offer the stiffest design? Do I need to have a quick change pad setup?
Do I need knock back springs?
So your question about two cars using the same setup with stock parts just a pad and tire change....yes the OEM parts can generally hold it together for a short time but the harder you push them the quicker they fail. That is the most important thing about a big brake kit for your car. It is not the ability for it to stop the car any quicker than it would stock (using the same pads and tires) it is the ability for that kit to keep stopping lap after lap after lap after lap.
Again...general explanation.
What a crystal clear explanation. Thank you, Anthony!
08-28-2015, 10:44 AM
Brake upgrade discussion
Most modern brakes will stop the vehicle ONCE. A race vehicle must have the ability to seamlessly stop the vehicle consistently many times in a row.
