Why big brakes?
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,638
Likes: 3
Why big brakes?
Ok guys,
forgive my ignorance and inquisitiveness. Lets talk about brakes - and putting bigger brakes on the vettes.
Why?
I doubt that it stops the car faster - because you can lock up the brakes instantaneously with stock brakes (or activate ABS - which is lock up) - anytime you want to. and once the wheels lock up - braking distance increases - correct?
so ideal braking distance is achieved by having wheels rolling - just shy of locking up (ignoring automatic braking systems) correct?
so if the stock brakes are capable of locking up the tires - they must be able to achieve enough grab to stop you in the least distance - correct?
So why the big brakes? the only benefit I see is that a bigger rotor and brake surface will spread the heat around more and dissipate it quicker - so it would be really important in repeated braking situations - like on a road race track car - but I can't seem to find a reason why they are better for the over the road cruising vettes!
anyone want to enlighten an ignoramus?
Carl Johansson
forgive my ignorance and inquisitiveness. Lets talk about brakes - and putting bigger brakes on the vettes.
Why?
I doubt that it stops the car faster - because you can lock up the brakes instantaneously with stock brakes (or activate ABS - which is lock up) - anytime you want to. and once the wheels lock up - braking distance increases - correct?
so ideal braking distance is achieved by having wheels rolling - just shy of locking up (ignoring automatic braking systems) correct?
so if the stock brakes are capable of locking up the tires - they must be able to achieve enough grab to stop you in the least distance - correct?
So why the big brakes? the only benefit I see is that a bigger rotor and brake surface will spread the heat around more and dissipate it quicker - so it would be really important in repeated braking situations - like on a road race track car - but I can't seem to find a reason why they are better for the over the road cruising vettes!
anyone want to enlighten an ignoramus?
Carl Johansson
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
You've got the idea. You don't need bigger rotors/pads on a daily driver or road cruiser...all brakes will stop ~ the same when cool. Bigger,drilled, vented rotors shed the heat generated from the pads faster...so there is less fade with heavy brake use.
Melting Slicks
Joined: May 2006
Posts: 3,385
Likes: 4
From: King George VA
Well you are correct on most of your points but for the autocross members on here big brakes are a must. The brakes stock are good enough for the average vette guy. But some do it for looks, brand name, why not, or performance on the track.
Like you said easing into a corner with 6 piston setup is alot easier and easier to control. You don't wanna slam on the brakes and go into a skid its all about controlled braking. When you watch the 100-0 test they dont slam the brakes they use firm pressure to do their tests.
A increase in performance such as a 1000 hp vette needs alittle more help stopping when your doing a 140-150 mph pass down the track. (My mph is probly off just making a point
)
Just my two cents. Im going to be probly converting to baer system cause I will be seeing alittle track use.
Like you said easing into a corner with 6 piston setup is alot easier and easier to control. You don't wanna slam on the brakes and go into a skid its all about controlled braking. When you watch the 100-0 test they dont slam the brakes they use firm pressure to do their tests.
A increase in performance such as a 1000 hp vette needs alittle more help stopping when your doing a 140-150 mph pass down the track. (My mph is probly off just making a point
)Just my two cents. Im going to be probly converting to baer system cause I will be seeing alittle track use.
Le Mans Master
Joined: Feb 1999
Posts: 9,931
Likes: 38
From: South Carolina
St. Jude Donor '03 & '05
Because chix dig'm.
Seriously, larger brakes makes it easier for the brakes system to stop, more leverage is applied.
Rarely, if any, magazines have done a back to back.
I tried to have a magazine do a C4 base, to J55 to C5.
I was asking for same tires, same material pads, new calipers etc etc so as the car wouldnt have old brakes, old pads. Every test needed to be done on the up and up. But, no takers. I think the faster you go and the more you use them the better a larger brake system works., But it is a system, from the brake pedal, to the fluid, master cylinder, booster, biasing, pad material etc etc.
Seriously, larger brakes makes it easier for the brakes system to stop, more leverage is applied.
Rarely, if any, magazines have done a back to back.
I tried to have a magazine do a C4 base, to J55 to C5.
I was asking for same tires, same material pads, new calipers etc etc so as the car wouldnt have old brakes, old pads. Every test needed to be done on the up and up. But, no takers. I think the faster you go and the more you use them the better a larger brake system works., But it is a system, from the brake pedal, to the fluid, master cylinder, booster, biasing, pad material etc etc.
Safety Car
Joined: Dec 2006
Posts: 4,290
Likes: 6
From: St Marys GA
From what I understand, the purpose of larger-diameter brake rotors is 2-fold.
1) More rotor mass means it takes more heat to increase the temperature of the rotor, which transfers to the pad, which transfers to the brake fluid. So, you can brake harder with lower brake fluid temperatures. Also, the larger surface area means that they have a higher heat disappation rate when compared to smaller-diameter rotors.
2) Moving the piston further away from the center of the wheel increases the moment that it can generate of braking force (think torque on the rotor). This means that it needs to apply less force to get the same amount of stopping power. Not only do the pads have to work less, but this allows better control of the braking, since it is further away from the limit.
I might be off on a few of the obscurities, but I think I got the general jist of it down.
1) More rotor mass means it takes more heat to increase the temperature of the rotor, which transfers to the pad, which transfers to the brake fluid. So, you can brake harder with lower brake fluid temperatures. Also, the larger surface area means that they have a higher heat disappation rate when compared to smaller-diameter rotors.
2) Moving the piston further away from the center of the wheel increases the moment that it can generate of braking force (think torque on the rotor). This means that it needs to apply less force to get the same amount of stopping power. Not only do the pads have to work less, but this allows better control of the braking, since it is further away from the limit.
I might be off on a few of the obscurities, but I think I got the general jist of it down.
Last edited by StealthLT4; Mar 10, 2009 at 10:04 PM.
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Team Owner
Joined: Feb 2006
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From: sw Ohio
I can tell you from personal experience that the stock brakes are EXTREMELY INADEQUATE for drag racing. Those puppies overheat very fast and its hard to stop. But yes for everyday driving they work just fine.
Le Mans Master
Joined: Dec 2002
Posts: 5,270
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From: Seattle Area WA
First: Let me declare my conflicting interests: I have C5 brakes on my car. 
Also, I'm regurgitating what I have learned and I'm always learning.
On the street, no real reason besides cosmetics.
If people really wanted to stop faster, they'd be running gumballs all the time (albeit not fiscally reasonable.)
I disagree, a lot of autox guys keep the stock single pistons from the early cars instead of say, J55s, and some try to get the smallest brakes they can going in the opposite direction. You just go to better pads, the weight difference in unsprung mass is not worth it. Additionally you don't need the heat dissipation for 60-90sec runs with cooling periods in-between. The only time I have ever had brakes get really hot on auto-x was doing an enduro and they still don't have the heat/stress checking and spider cracking you consistently get with road racing.
I disagree a 6 piston setup with the wrong master cylinder set up could be much harder to control. It depends more on the system. Now if the volume displaced in the 6 piston setup is different and the master stayed the same, that could be true, but I would be careful before carrying out a swap yourself.
Also, I'm regurgitating what I have learned and I'm always learning. On the street, no real reason besides cosmetics.
If people really wanted to stop faster, they'd be running gumballs all the time (albeit not fiscally reasonable.)
I disagree a 6 piston setup with the wrong master cylinder set up could be much harder to control. It depends more on the system. Now if the volume displaced in the 6 piston setup is different and the master stayed the same, that could be true, but I would be careful before carrying out a swap yourself.
Le Mans Master
Joined: Apr 2005
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From: The Old Dominion
I also might guess they don't do a lot of braking on an oval track...
Le Mans Master
Joined: Feb 1999
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From: South Carolina
St. Jude Donor '03 & '05
Autos. NASCAR is still a heavy *** car, and when road racing, those brakes go through hell, so they must be pretty darn good to haul them down over and over from the speeds they run.My point is bigger brakes may not always be feasible, so make do with whats feasible. 13 inch brakes are still large brakes and can doa n impressive job for joebagodonuts.
Race Director
Joined: Jun 2004
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From: WI
Carl, many people put on large brake kits just for looks.
Melting Slicks
Joined: Feb 2006
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From: backwoods upstate ny
can't base anything on Nastycar, Goodieyar only brings 15" 'tares' and them's the only 'thang' allowed, 15" wheels are thus reqd and small brakes are all that will fit inside those...brake useage is minimal on the 'stupor-speedways', almost nil when the 'show' uses engine intake block-off plates, 'small brakes' suffice... but on 'short tracks' and road courses, the brakes do get used heavily and failures are common, sometimes with catastrophic results, most often just 'action' (crashes) that the 'beer-cans' (nastycar fans) come to see.
back to 'our' world...for a one-time 'panic stop', the stock c4 brakes are satisfactory but used REPEATEDLY, as in a long descent, simply to keep speed below posted limits, extreme pedal pressure becomes necessary (my observations, NOT 'theory')...since replacing my c4 front brakes with c5 brakes, the pedal pressure problem has not recurred...in 'theory', the heavier c5 brakes will reduce acceleration, a burden that is acceptable, imho.
back to 'our' world...for a one-time 'panic stop', the stock c4 brakes are satisfactory but used REPEATEDLY, as in a long descent, simply to keep speed below posted limits, extreme pedal pressure becomes necessary (my observations, NOT 'theory')...since replacing my c4 front brakes with c5 brakes, the pedal pressure problem has not recurred...in 'theory', the heavier c5 brakes will reduce acceleration, a burden that is acceptable, imho.
Last edited by redrose; Mar 11, 2009 at 11:24 AM.
Le Mans Master
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From: Akron Ohio
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St. Jude Donor '09-'10-'11
Like some have stated, faster you go the harder it becomes to stop. The stock brakes might be fine for street driving, or hauling the car down from highway speeds, but if your going 140 MPH down a straightaway with a 60MPH turn at the end of it, the stock brakes will have to work way too hard to slow the car down enough. Granted the bigger brakes make it easier to lock the tires up at lower speeds, but at high speeds is where you need them. This along with the cooling benefits.
Le Mans Master
Joined: Feb 1999
Posts: 9,931
Likes: 38
From: South Carolina
St. Jude Donor '03 & '05
can't base anything on Nastycar, Goodieyar only brings 15" 'tares' and them's the only 'thang' allowed, 15" wheels are thus reqd and small brakes are all that will fit inside those...brake useage is minimal on the 'stupor-speedways', almost nil when the 'show' uses engine intake block-off plates, 'small brakes' suffice... but on 'short tracks' and road courses, the brakes do get used heavily and failures are common, sometimes with catastrophic results, most often just 'action' (crashes) that the 'beer-cans' (nastycar fans) come to see.
back to 'our' world...for a one-time 'panic stop', the stock c4 brakes are satisfactory but used REPEATEDLY, as in a long descent, simply to keep speed below posted limits, extreme pedal pressure becomes necessary (my observations, NOT 'theory')...since replacing my c4 front brakes with c5 brakes, the pedal pressure problem has not recurred...in 'theory', the heavier c5 brakes will reduce acceleration, a burden that is acceptable, imho.
back to 'our' world...for a one-time 'panic stop', the stock c4 brakes are satisfactory but used REPEATEDLY, as in a long descent, simply to keep speed below posted limits, extreme pedal pressure becomes necessary (my observations, NOT 'theory')...since replacing my c4 front brakes with c5 brakes, the pedal pressure problem has not recurred...in 'theory', the heavier c5 brakes will reduce acceleration, a burden that is acceptable, imho.
And, I have blue a set up C5 rotors on Hawk pads with my C4 at an autocross. I use synthetic fluid, SS lines, Hawk pads, and C5 calipers, and GM rotors.
Anyways, I hope you see my point, that you can brake sufficiently at tracks with 13 inch brakes, as long as the brake system is matched well.
Melting Slicks
Joined: Jul 2004
Posts: 2,295
Likes: 14
From: Grand Sport #82
The stock 13" HD brakes on my Grand Sport will overheat i 2-3 laps on a normal road track. Also the fluid will boil pretty fast...
Weather the ABS is activatet or not, is not a real meassure on your brakes performance, since it is very dependat on your tires and shocks.
On the street only, the stock brakes will do. On the track
When driving on the german autobahn at HIGH speeds, the stock brakes would also cook after a couple of HARD brakes from 120 mph.
Combinde the right pads and tires with this setup I have, and you dont have to think about that anymore...I love my DRM brakes
Weather the ABS is activatet or not, is not a real meassure on your brakes performance, since it is very dependat on your tires and shocks.
On the street only, the stock brakes will do. On the track
When driving on the german autobahn at HIGH speeds, the stock brakes would also cook after a couple of HARD brakes from 120 mph.
Combinde the right pads and tires with this setup I have, and you dont have to think about that anymore...I love my DRM brakes
Safety Car
Joined: Sep 2001
Posts: 4,157
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From: Glenbeulah Wi
Carl,
My stock brakes on my 1986 work just fine in street driving and 120 MPH drag strip passes. When there is enough time to cool the stock brakes between runs the stock work well. If I was road racing the stock brakes would not be good enough for hard driving but for everyday use and drag strip passes they work fine.
My stock brakes on my 1986 work just fine in street driving and 120 MPH drag strip passes. When there is enough time to cool the stock brakes between runs the stock work well. If I was road racing the stock brakes would not be good enough for hard driving but for everyday use and drag strip passes they work fine.