Brake Question
10-26-2007, 09:19 PM
#11
4th Gear Member
Join Date: Mar 2006
Location: CA
Posts: 1,313
RE: Brake Question
ORIGINAL: F1Fan
Hi UrS4,
The limiting factor in how short a given car can stop is the friction the TIRES can genrate not the brake system. If you kept the same suspension and tires ona car and the brakes were working properly before installing larger calipers with 4, 6 or 8 pistons and larger 14" or 15"2-piece rotors the car will stop in approximatelythe same distance. The reason is the tires cannot generate any more gripthen they could before you installed those monster sized brakes. Also consider the fact that with more rotating mass you not only have more mass to stop you have more mass to accellerate so whilea little bitbigger may be an advantage in terms ofbrakingtoo much bigger brake rotors may actually hurtthe car's accelleration.
Knowing this can you see that adding more swept area and larger pads cannot improve stopping distances?What adding more pad area does is potentially increase pad life. Longer pad life is a nice thing to have but alarger pad area means you need to better support the brake pads to prevent poor pad wear patterns due to the various forces working on the calipers, pads, rotors, hubs etc. This is where multiple pistons with different sizebores comes into play. By varying the piston bores carefullyyou can for a given pad shape, caliper stiffness and mounting style reduce irregular pad wear to a minmumimproving pad life. More pistons doesnothing to improve single stop braking distances just as larger higher friction coefficent pads and larger rotors do nothing to reduce single stop braking distances.
Once the car has stopped two, three, four or more times the brakes will start to heat up and need to cool down or the stopping distances will start to go up with repeated use and inadequate time for the brake system to shed the heat of conversion. This is thereal advantage to larger diameterhigher mass rotors with better ventilated brake rotors, the ability of the larger brake system to absorb and shedheat. If your caris street drivenand only occasionally sees a road course a much more effectivebrake upgrade than a big brake kit would be to optimize your stock brake system by improving the brake pads using pad materials with a higher friction coefficent, reduced brake line compliance, resistance to fluid failure (boiling),and massively improved cooling of the rotors. In return for performing these upgradeson your stock brake system your car will stop just as well as the car with giant brake rotors all aroundAND your car will accellerate faster thanhe other car. Your brake padsand rotors will lastmuch longer and your car willbe able to make repeatedstops from high speeds with much less brake fade AND they will recover much faster! The guy who spent his money ona big brake kit will be able to stop a few more times beforehis brakes start to overheat butoncea big brake kit has overheatedall the extra mass of the larger rotors of abig brake system will be working against him as they willtake longer to cool down before his brakes are back into the normal heat range. Without effective brake coolingbig brakes are no better stopping when overheated than your stock brakes. As you can see cooling the brakes isthe key to effective long lasting brakes.
I used to design and build Porsche and VW race suspension parts for various teams and private parties. Trust me your Audi and Porsche did not stop any faster because of thelarger brakes or higher friction pads you installed. If you had your cars insturmented you would have seen the same peak and averaged stopping forces before and after the brake upgrades IF the stock brakes were working right to begin with and you did not change the tires or suspension settings. What you probably felt was the higher friction and lighter pedal pressure needed to get into the ABS which you may have interpreted to mean that the car was stopping faster. This is a common misinterpretation of pedal travel, pressure and stopping feel.
Does this help answer your questions?
Cheers!
ORIGINAL: UrS4
I understand the tire part but do you agree that switching pads from stock to Hawk or EBC causes you to stop in a shorter distance due to more friction generated by the better pads? With that said wouldn't using bigger pads (greater swept area) create more friction and provided the tires were soft enough to maintain traction slow the car down faster and thus in a shorter distance?
When I had my Audi, I was running a summer tire with stock calipers and rotors but better pads and the car stopped sooner. And when I went to a larger Porsche caliper and rotor and larger pad the car stopped significantly faster.
Can you please explain as I would like to learn more about brake upgrades as I thought the more friction you generate the quicker you can stop.
I understand the tire part but do you agree that switching pads from stock to Hawk or EBC causes you to stop in a shorter distance due to more friction generated by the better pads? With that said wouldn't using bigger pads (greater swept area) create more friction and provided the tires were soft enough to maintain traction slow the car down faster and thus in a shorter distance?
When I had my Audi, I was running a summer tire with stock calipers and rotors but better pads and the car stopped sooner. And when I went to a larger Porsche caliper and rotor and larger pad the car stopped significantly faster.
Can you please explain as I would like to learn more about brake upgrades as I thought the more friction you generate the quicker you can stop.
The limiting factor in how short a given car can stop is the friction the TIRES can genrate not the brake system. If you kept the same suspension and tires ona car and the brakes were working properly before installing larger calipers with 4, 6 or 8 pistons and larger 14" or 15"2-piece rotors the car will stop in approximatelythe same distance. The reason is the tires cannot generate any more gripthen they could before you installed those monster sized brakes. Also consider the fact that with more rotating mass you not only have more mass to stop you have more mass to accellerate so whilea little bitbigger may be an advantage in terms ofbrakingtoo much bigger brake rotors may actually hurtthe car's accelleration.
Knowing this can you see that adding more swept area and larger pads cannot improve stopping distances?What adding more pad area does is potentially increase pad life. Longer pad life is a nice thing to have but alarger pad area means you need to better support the brake pads to prevent poor pad wear patterns due to the various forces working on the calipers, pads, rotors, hubs etc. This is where multiple pistons with different sizebores comes into play. By varying the piston bores carefullyyou can for a given pad shape, caliper stiffness and mounting style reduce irregular pad wear to a minmumimproving pad life. More pistons doesnothing to improve single stop braking distances just as larger higher friction coefficent pads and larger rotors do nothing to reduce single stop braking distances.
Once the car has stopped two, three, four or more times the brakes will start to heat up and need to cool down or the stopping distances will start to go up with repeated use and inadequate time for the brake system to shed the heat of conversion. This is thereal advantage to larger diameterhigher mass rotors with better ventilated brake rotors, the ability of the larger brake system to absorb and shedheat. If your caris street drivenand only occasionally sees a road course a much more effectivebrake upgrade than a big brake kit would be to optimize your stock brake system by improving the brake pads using pad materials with a higher friction coefficent, reduced brake line compliance, resistance to fluid failure (boiling),and massively improved cooling of the rotors. In return for performing these upgradeson your stock brake system your car will stop just as well as the car with giant brake rotors all aroundAND your car will accellerate faster thanhe other car. Your brake padsand rotors will lastmuch longer and your car willbe able to make repeatedstops from high speeds with much less brake fade AND they will recover much faster! The guy who spent his money ona big brake kit will be able to stop a few more times beforehis brakes start to overheat butoncea big brake kit has overheatedall the extra mass of the larger rotors of abig brake system will be working against him as they willtake longer to cool down before his brakes are back into the normal heat range. Without effective brake coolingbig brakes are no better stopping when overheated than your stock brakes. As you can see cooling the brakes isthe key to effective long lasting brakes.
I used to design and build Porsche and VW race suspension parts for various teams and private parties. Trust me your Audi and Porsche did not stop any faster because of thelarger brakes or higher friction pads you installed. If you had your cars insturmented you would have seen the same peak and averaged stopping forces before and after the brake upgrades IF the stock brakes were working right to begin with and you did not change the tires or suspension settings. What you probably felt was the higher friction and lighter pedal pressure needed to get into the ABS which you may have interpreted to mean that the car was stopping faster. This is a common misinterpretation of pedal travel, pressure and stopping feel.
Does this help answer your questions?
Cheers!
I understand now and it makes good sense. I think that I was assuming I was stopping in shorter distances because I didn't encounter as much brake fade with the porsche turbo brake kit on my Audi. I guess I didn't stop any shorter than my first stop with my stock setup, it was just the lack of fade and repeated fade free stops that made me think I was stopping shorter with the bigger kit.
Have you heard of any good quality brake cooling kits/ducting for the front brakes on the S197? I have seen some peolpes home grown kits using flexible tubing and zip ties but are there any quality kits?
10-27-2007, 12:03 AM
#12
4th Gear Member
Join Date: Mar 2005
Location: California
Posts: 1,471
RE: Brake Question
ORIGINAL: UrS4
Thanks F1Fan,
I understand now and it makes good sense. I think that I was assuming I was stopping in shorter distances because I didn't encounter as much brake fade with the porsche turbo brake kit on my Audi. I guess I didn't stop any shorter than my first stop with my stock setup, it was just the lack of fade and repeated fade free stops that made me think I was stopping shorter with the bigger kit.
Have you heard of any good quality brake cooling kits/ducting for the front brakes on the S197? I have seen some peolpes home grown kits using flexible tubing and zip ties but are there any quality kits?
ORIGINAL: F1Fan
Hi UrS4,
The limiting factor in how short a given car can stop is the friction the TIRES can genrate not the brake system. If you kept the same suspension and tires ona car and the brakes were working properly before installing larger calipers with 4, 6 or 8 pistons and larger 14" or 15"2-piece rotors the car will stop in approximatelythe same distance. The reason is the tires cannot generate any more gripthen they could before you installed those monster sized brakes. Also consider the fact that with more rotating mass you not only have more mass to stop you have more mass to accellerate so whilea little bitbigger may be an advantage in terms ofbrakingtoo much bigger brake rotors may actually hurtthe car's accelleration.
Knowing this can you see that adding more swept area and larger pads cannot improve stopping distances?What adding more pad area does is potentially increase pad life. Longer pad life is a nice thing to have but alarger pad area means you need to better support the brake pads to prevent poor pad wear patterns due to the various forces working on the calipers, pads, rotors, hubs etc. This is where multiple pistons with different sizebores comes into play. By varying the piston bores carefullyyou can for a given pad shape, caliper stiffness and mounting style reduce irregular pad wear to a minmumimproving pad life. More pistons doesnothing to improve single stop braking distances just as larger higher friction coefficent pads and larger rotors do nothing to reduce single stop braking distances.
Once the car has stopped two, three, four or more times the brakes will start to heat up and need to cool down or the stopping distances will start to go up with repeated use and inadequate time for the brake system to shed the heat of conversion. This is thereal advantage to larger diameterhigher mass rotors with better ventilated brake rotors, the ability of the larger brake system to absorb and shedheat. If your caris street drivenand only occasionally sees a road course a much more effectivebrake upgrade than a big brake kit would be to optimize your stock brake system by improving the brake pads using pad materials with a higher friction coefficent, reduced brake line compliance, resistance to fluid failure (boiling),and massively improved cooling of the rotors. In return for performing these upgradeson your stock brake system your car will stop just as well as the car with giant brake rotors all aroundAND your car will accellerate faster thanhe other car. Your brake padsand rotors will lastmuch longer and your car willbe able to make repeatedstops from high speeds with much less brake fade AND they will recover much faster! The guy who spent his money ona big brake kit will be able to stop a few more times beforehis brakes start to overheat butoncea big brake kit has overheatedall the extra mass of the larger rotors of abig brake system will be working against him as they willtake longer to cool down before his brakes are back into the normal heat range. Without effective brake coolingbig brakes are no better stopping when overheated than your stock brakes. As you can see cooling the brakes isthe key to effective long lasting brakes.
I used to design and build Porsche and VW race suspension parts for various teams and private parties. Trust me your Audi and Porsche did not stop any faster because of thelarger brakes or higher friction pads you installed. If you had your cars insturmented you would have seen the same peak and averaged stopping forces before and after the brake upgrades IF the stock brakes were working right to begin with and you did not change the tires or suspension settings. What you probably felt was the higher friction and lighter pedal pressure needed to get into the ABS which you may have interpreted to mean that the car was stopping faster. This is a common misinterpretation of pedal travel, pressure and stopping feel.
Does this help answer your questions?
Cheers!
ORIGINAL: UrS4
I understand the tire part but do you agree that switching pads from stock to Hawk or EBC causes you to stop in a shorter distance due to more friction generated by the better pads? With that said wouldn't using bigger pads (greater swept area) create more friction and provided the tires were soft enough to maintain traction slow the car down faster and thus in a shorter distance?
When I had my Audi, I was running a summer tire with stock calipers and rotors but better pads and the car stopped sooner. And when I went to a larger Porsche caliper and rotor and larger pad the car stopped significantly faster.
Can you please explain as I would like to learn more about brake upgrades as I thought the more friction you generate the quicker you can stop.
I understand the tire part but do you agree that switching pads from stock to Hawk or EBC causes you to stop in a shorter distance due to more friction generated by the better pads? With that said wouldn't using bigger pads (greater swept area) create more friction and provided the tires were soft enough to maintain traction slow the car down faster and thus in a shorter distance?
When I had my Audi, I was running a summer tire with stock calipers and rotors but better pads and the car stopped sooner. And when I went to a larger Porsche caliper and rotor and larger pad the car stopped significantly faster.
Can you please explain as I would like to learn more about brake upgrades as I thought the more friction you generate the quicker you can stop.
The limiting factor in how short a given car can stop is the friction the TIRES can genrate not the brake system. If you kept the same suspension and tires ona car and the brakes were working properly before installing larger calipers with 4, 6 or 8 pistons and larger 14" or 15"2-piece rotors the car will stop in approximatelythe same distance. The reason is the tires cannot generate any more gripthen they could before you installed those monster sized brakes. Also consider the fact that with more rotating mass you not only have more mass to stop you have more mass to accellerate so whilea little bitbigger may be an advantage in terms ofbrakingtoo much bigger brake rotors may actually hurtthe car's accelleration.
Knowing this can you see that adding more swept area and larger pads cannot improve stopping distances?What adding more pad area does is potentially increase pad life. Longer pad life is a nice thing to have but alarger pad area means you need to better support the brake pads to prevent poor pad wear patterns due to the various forces working on the calipers, pads, rotors, hubs etc. This is where multiple pistons with different sizebores comes into play. By varying the piston bores carefullyyou can for a given pad shape, caliper stiffness and mounting style reduce irregular pad wear to a minmumimproving pad life. More pistons doesnothing to improve single stop braking distances just as larger higher friction coefficent pads and larger rotors do nothing to reduce single stop braking distances.
Once the car has stopped two, three, four or more times the brakes will start to heat up and need to cool down or the stopping distances will start to go up with repeated use and inadequate time for the brake system to shed the heat of conversion. This is thereal advantage to larger diameterhigher mass rotors with better ventilated brake rotors, the ability of the larger brake system to absorb and shedheat. If your caris street drivenand only occasionally sees a road course a much more effectivebrake upgrade than a big brake kit would be to optimize your stock brake system by improving the brake pads using pad materials with a higher friction coefficent, reduced brake line compliance, resistance to fluid failure (boiling),and massively improved cooling of the rotors. In return for performing these upgradeson your stock brake system your car will stop just as well as the car with giant brake rotors all aroundAND your car will accellerate faster thanhe other car. Your brake padsand rotors will lastmuch longer and your car willbe able to make repeatedstops from high speeds with much less brake fade AND they will recover much faster! The guy who spent his money ona big brake kit will be able to stop a few more times beforehis brakes start to overheat butoncea big brake kit has overheatedall the extra mass of the larger rotors of abig brake system will be working against him as they willtake longer to cool down before his brakes are back into the normal heat range. Without effective brake coolingbig brakes are no better stopping when overheated than your stock brakes. As you can see cooling the brakes isthe key to effective long lasting brakes.
I used to design and build Porsche and VW race suspension parts for various teams and private parties. Trust me your Audi and Porsche did not stop any faster because of thelarger brakes or higher friction pads you installed. If you had your cars insturmented you would have seen the same peak and averaged stopping forces before and after the brake upgrades IF the stock brakes were working right to begin with and you did not change the tires or suspension settings. What you probably felt was the higher friction and lighter pedal pressure needed to get into the ABS which you may have interpreted to mean that the car was stopping faster. This is a common misinterpretation of pedal travel, pressure and stopping feel.
Does this help answer your questions?
Cheers!
I understand now and it makes good sense. I think that I was assuming I was stopping in shorter distances because I didn't encounter as much brake fade with the porsche turbo brake kit on my Audi. I guess I didn't stop any shorter than my first stop with my stock setup, it was just the lack of fade and repeated fade free stops that made me think I was stopping shorter with the bigger kit.
Have you heard of any good quality brake cooling kits/ducting for the front brakes on the S197? I have seen some peolpes home grown kits using flexible tubing and zip ties but are there any quality kits?
Agent47 and FRPPboth make excellentvery complete kits complete with large front scoops, 3" brake hose and spindle mounted brake ducts. These are thebest, most effective, highestqualitycompletekits on the market. V8 Power makes a really good spindle mounted brake duct that Quantum Motorsports has basically copied for their "race" kit at a slightlylowerprice but the Quantum "kit" lacks a front duct which of course you can buy for an extra wad of cash but it is a small flat plate with a 3" hole in in it.
HTH!
10-27-2007, 11:58 AM
#13
4th Gear Member
Join Date: Jun 2006
Location: CA
Posts: 1,700
RE: Brake Question
FWIW guys I run Hawk 9012 ("blue") pads on factory takeoff rotors at the track and they work awesomely (is that a word?). When back on the street I run Hawk HPS with takeoff rotors as well. Those, in addition to a quality duct kit, braided lines, and Motul 600 fluid, make my car stop just fine - and Iabuse it at the track on a regular basis.
If you look at NASA American Iron cars you will see that they are restricted to a 17" wheel - no room for big 14" rotors. The guys running fancy calipers are doing so for brake life and lighter weight. I can guarantee they have much higher braking requirements than most anybody in here.
F1Fan explained it perfectly. A bigger brake kit is only extending the time before they overheat. Guys have the same belief about radiators. They think a bigger one makes the car run cooler. In reality all it does is buy a little more time before it gets hot.
Of course in the end I can't help but admit that big Brembo calipers sure do look sexy
If you look at NASA American Iron cars you will see that they are restricted to a 17" wheel - no room for big 14" rotors. The guys running fancy calipers are doing so for brake life and lighter weight. I can guarantee they have much higher braking requirements than most anybody in here.
F1Fan explained it perfectly. A bigger brake kit is only extending the time before they overheat. Guys have the same belief about radiators. They think a bigger one makes the car run cooler. In reality all it does is buy a little more time before it gets hot.
Of course in the end I can't help but admit that big Brembo calipers sure do look sexy
10-27-2007, 03:15 PM
#14
1st Gear Member
Thread Starter
Join Date: Jan 2007
Posts: 116
RE: Brake Question
So the bottom line is that I should not need to get a big brake kit when I install my 20" wheels? I to admit that big brake kits do look very good, but I thought they served a purpose too. So do a lot of car manufacturers put on bigger brakes specifically for looks and not for necessity?
By the way, what is a really good tire to get? I am looking for an all season tire since I sometimes have to drive in snow, or in the cold. My price limit is $250 per tire. I was looking at the Bridgestone Pontenza RE90AS or the Nitto NT555's.
By the way, what is a really good tire to get? I am looking for an all season tire since I sometimes have to drive in snow, or in the cold. My price limit is $250 per tire. I was looking at the Bridgestone Pontenza RE90AS or the Nitto NT555's.
10-27-2007, 04:48 PM
#16
2nd Gear Member
Join Date: Nov 2006
Location: Caracas, Venezuela
Posts: 401
RE: Brake Question
I assume the photo in the FRPP site is wrong, a carbon fiber kit for 300$?
I'll make my own as in other cars, I already have the 3" silicone hose, just have to find adecuate plastic container (I think 4 quart oil platic container will do) as a base to do de front nozzles and work on the current dust shields on how to fix the end of the hose.
I'll make my own as in other cars, I already have the 3" silicone hose, just have to find adecuate plastic container (I think 4 quart oil platic container will do) as a base to do de front nozzles and work on the current dust shields on how to fix the end of the hose.
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