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Discussion Starter #1
Hi Guys,

I just got this info from Bob at Race Technologies. Race Tech is one of 2 distributors in the USA for genuine Brembo products, and its the source we use b\c they are awesome on stocking parts for the Supra. Anyhow, I wanted to pass this along, I thought you might find it interesting.

Hey Guys!
I just got this information from Brembo.
The Brembo 4-Piston F50 Caliper with the 14" (355mm) dia. Rotor Produces 9.8% more Brake Torque than the equivalent AP system with the AP 6-Piston Caliper!
Brake Torque is based on Piston Size and Effective Radius and is completely un-related (not effected by) to pad size.
Therefore, the Brembo Supra 14" Kit will feel & respond 10% better than the AP 6-Piston Kit.
If you want more technical information related to this let me know & I will try to get it today.
Bob



I'm glad I just put the 14" Brembo on my street car, I can't wait to get it broken in!

Later,

Dusty
 

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If AP (braking division) were not bought by Brembo, I would say that this is just propaganda and ignore. But since Brembo did purchase AP's braking division, I need to question the validity of the statement. According to Bob, the brake torque is based on piston size and effective radius. Brembo F50 kit uses 355x32 disk, caliper with piston sizes 40x2 and 44x2. AP's 6-piston kit uses 356x35 disk, caliper with piston sizes 27x2, 31.8x2, and 38.1x2. 1mm difference in brake disk size is not much difference. Since Bob didn't mention thickness, let's forget about the thickness difference. Doing some calculation one can see that Brembo F50 caliper has piston area of 55.5cm2 and the AP 6-pot caliper has piston area of 50.1cm2. This does show that Brembo has ~9.7% more piston area. So, what Bob said is correct on paper.

However, how does 9.7% more piston area translate into feel and response better? Three sets of differential bored pistons are supposed to allow for better brake force application and even distribution, not to mention better pad wear. He also said that the pad area has nothing to do with brake torque. How so? The pad areas are 62.1cm2 (Brembo) and 76.8cm2 (AP). Note that AP pads are longer and thinner. This allows AP's to run most of its pad area along the outer edge of the disk. We all know that more torque can be applied if the applying force is further away from the center.

I don't claim that I am an expert; I just don't find Bob's argument very convincing. Dusty, if you can pass my notes above to Bob and see what he says, that would be great.

Thanks,

--Joey
 

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Don't suppose anyone has any data on the 13.28 inche Brembo kit? I've searched the net and haven't really been able to find out squat about it.


-Mike


NA2TT said:
If AP (braking division) were not bought by Brembo, I would say that this is just propaganda and ignore. But since Brembo did purchase AP's braking division, I need to question the validity of the statement. According to Bob, the brake torque is based on piston size and effective radius. Brembo F50 kit uses 355x32 disk, caliper with piston sizes 40x2 and 44x2. AP's 6-piston kit uses 356x35 disk, caliper with piston sizes 27x2, 31.8x2, and 38.1x2. 1mm difference in brake disk size is not much difference. Since Bob didn't mention thickness, let's forget about the thickness difference. Doing some calculation one can see that Brembo F50 caliper has piston area of 55.5cm2 and the AP 6-pot caliper has piston area of 50.1cm2. This does show that Brembo has ~9.7% more piston area. So, what Bob said is correct on paper.

However, how does 9.7% more piston area translate into feel and response better? Three sets of differential bored pistons are supposed to allow for better brake force application and even distribution, not to mention better pad wear. He also said that the pad area has nothing to do with brake torque. How so? The pad areas are 62.1cm2 (Brembo) and 76.8cm2 (AP). Note that AP pads are longer and thinner. This allows AP's to run most of its pad area along the outer edge of the disk. We all know that more torque can be applied if the applying force is further away from the center.

I don't claim that I am an expert; I just don't find Bob's argument very convincing. Dusty, if you can pass my notes above to Bob and see what he says, that would be great.

Thanks,

--Joey
 
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V8THIS said:
Don't suppose anyone has any data on the 13.28 inche Brembo kit? I've searched the net and haven't really been able to find out squat about it.


-Mike


Mike,
I run the 13" Brembo's infront... they work great, even on road course events. When I bought my Brembo's I researched the 14" kit and couldnt justify spending more on it.... Brembo didnt prove to me that the 14" kit worked so much better than the 13" kit. My brakes BITE hard, I am very pleased with them. I also talked to several tuners who had installed/tested both kits and they agreed with me that for the dollar it isnt worth going with 14" unless you got dough to throw around like a pimp.

just my 2 cents......

take care,
nils
 

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Nils ,
How would you compare your present Brembo to the stock set-up.I would appreciate your comments. Is it a worth upgrade for 80%street20%autocross/track use , how is the initial bite, pedal travel, fade resistance and stopping distances compared to the stockers.
 
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Just a thought to note: on street tires especially from 60 to 0 your tires are probably going to make more of a difference. Just something to remember as you look for that edge.
 

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Discussion Starter #8
Since I'm not yet a brake expert, I again am using info I got from Brembo directly. This is their response:

The Brembo system has a 9.8% advantage in braking torque, not just piston area. This is assuming an equivalent brake pad coefficient of friction between systems as well. True, this is a result of increased piston area, but your assumption of the AP Racing caliper “concentrating pad area along the outer edge of the disc” is mostly false. The effective radius (the radius at which the braking force acts) is 150.2mm for the Brembo caliper and 151.7mm for the AP Racing 6-piston caliper. As you can see, this is only a 1% increase in effective radius which is more than overcome by the increased piston area.
Braking torque is a measure of the power of the braking system. Obviously the braking system has to have sufficient power to provide maximum possible deceleration. Increase braking torque will increase the speed at which the braking system is still able to provide the maximum deceleration. However, the braking torque has to be balanced between the front and rear of the vehicle as well. This is an area where Brembo pays close attention. Brake feel is a result of a huge number of factors. When limiting the scope to the disc, caliper, and their interface, some of these factors are caliper stiffness, seal design within the caliper, and the brake pad itself.
Pad surface area has no impact on braking torque. Increased pad area generally only manifests itself in better wear rates. However, this comes at the sacrifice of initial brake “bite”.



Dusty
 

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Great info Dusty! Thanks doing the legwork and talking to Brembo for us!!.


-Mike


V8 Killer said:
Since I'm not yet a brake expert, I again am using info I got from Brembo directly. This is their response:

The Brembo system has a 9.8% advantage in braking torque, not just piston area. This is assuming an equivalent brake pad coefficient of friction between systems as well. True, this is a result of increased piston area, but your assumption of the AP Racing caliper “concentrating pad area along the outer edge of the disc” is mostly false. The effective radius (the radius at which the braking force acts) is 150.2mm for the Brembo caliper and 151.7mm for the AP Racing 6-piston caliper. As you can see, this is only a 1% increase in effective radius which is more than overcome by the increased piston area.
Braking torque is a measure of the power of the braking system. Obviously the braking system has to have sufficient power to provide maximum possible deceleration. Increase braking torque will increase the speed at which the braking system is still able to provide the maximum deceleration. However, the braking torque has to be balanced between the front and rear of the vehicle as well. This is an area where Brembo pays close attention. Brake feel is a result of a huge number of factors. When limiting the scope to the disc, caliper, and their interface, some of these factors are caliper stiffness, seal design within the caliper, and the brake pad itself.
Pad surface area has no impact on braking torque. Increased pad area generally only manifests itself in better wear rates. However, this comes at the sacrifice of initial brake “bite”.



Dusty
 

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Just a quick glimpse, but it seems like 50.1 is about 90% of 55.5. Bob's calculation doesn't seem that far off. And as I recall brake pad area isn't nearly as important as material of the pad and rotor.
If you ever work on Mercedes or BMW you'll notice that their pads are unusually small, even on their largest models, compared to lesser cars. But their brakes tend to bit really hard and slow a lot of weight down really fast.
The reason is the pad and even the disk material. The metal used in most newer BMW discs is very soft, and wears out substantially with the pad. That's why the standard BMW brake job is so pricey, since the rotors need to be replaced everytime as well.
You can also see this in clutch design as well, same basic principle as a disk brake. Those four puck disks of certain material tend to engage pretty abruptly with a lot of force for how small the surface area of the pucks contacting the flywheel are.

Just thought I'd throw a little more in there to think about. But I'd say if you're into competition, the driver skill will definitely make up the minute difference in these upgraded brake setups. This kind of info just may help some split decisions get pushed to a deciding point for potential buyers... It's still good info to have, but nothing is absolute.
 
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les said:
Nils ,
How would you compare your present Brembo to the stock set-up.I would appreciate your comments. Is it a worth upgrade for 80%street20%autocross/track use , how is the initial bite, pedal travel, fade resistance and stopping distances compared to the stockers.
Les,
to be honest with you I cant remember what the stockers felt like. I do remember being very impressed with the brake kit after installing it on the car. I felt a significant difference in performance. I think it is worth it eventhough Brembo's are very expensive. Always remember that the stock Supra brakes are awsome. I am so pleased with the Brembo's that I am planning on getting them for my 240 aswell.

If you have the money go for it =)

nils
 

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I am confused by the claim of 9.8% advantage in braking torque. Where does the 9.8% come from? The piston area (calculated to be 9.8% larger), or caliper design? I honestly don’t see a relationship between piston area and braking torque.

Without going into Newtonian physics too deeply, the area of an object is not found in any equation in calculating torque (a rotational force) or angular momentum. The radius, however, plays a important role in calculating torque. The radius has a ‘squared’ effect on the resulting torque/angular momentum. This means that if the same ‘force’ is applied 2 measuring units (cm, inches…) further out from the center, the resulting torque is 4 times as much. The pad area has a lot to do with braking power because the placement of the pad (distance form the center) determines where the force is applied on the disk. Looking at the two pads by AP and Brembo, and discarding the overlapping pad areas, one will note that AP pad has the non-overlapping area further out. Wouldn’t AP provide more brake torque? This is assuming same coefficient of friction. Also, doesn’t more pad are give more contact area for the friction material to do its work?

If you say that Brembo calipers can retain more force coming form the brake booster and the force is better distributed to the pistons via superior brake fluid management or whatever, that would make more sense (and harder to proof) than saying that larger piston area provides a braking torque advantage of 9.8%.

AP and Brembo both make excellent and quality products. I am not here to argue that AP is better than Brembo. I just find that the logic used to justify the statement ‘Brembo provides 9.8% more braking torque’ is flawed. Anyway, whatever happened to that rear Supra kit that Brembo was going to make? Someone at Brembo USA told me during spring 2001 that a supra rear kit will be released sometime during the summer of 2001.

--Joey
 

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It seems to me that they are refering to the fluid having a larger surface area to push against (the larger piston). I may be mistaken, but this should apply more total pressure to the pads (or greater braking torque).

Later, Steve
 

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Another question I have besides just the pure braking power -- Dusty, maybe you can bounce this off your contacts at Brembo:

I've heard reviews from different people about the reliabilty of aftermarket calipers. Mainly that some aftermarket calipers do not have seals around the piston that are adaquate for daily use. Or they are designed to be rebuilt frequently.

I've heard this pointed out about the 6 piston AP calipers. Is there any truth to this being the case for the 2 kits we're comparing here? I'm sure the Brembos don't have this issue since there are many street cars running these, but what about the AP?

Thanks for the info!
 

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Both companies offer race/street calipers. Both sets offered for the MKIV are street calipers with sealed caliper pistons and anti rattle clips.

Later, Steve
 

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All this techno babble is a little too much, I can understand piston area is important, along with torque radius, but i was wondering how clamping force comes into play. Even though Brembo supposedly has a 10% larger piston area, how does their clamping force compare to AP's. Would they both be resistant to fade as equally?
 

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My guess is you would never feel the difference "seat of the pants" between these two kits. Assuming you get the 14" diameter kit.

Let me warn that the AP Racing kit has less clearance than the Brembo kit. The 14" AP Racing kit won't fit in my wheels, but the 14" Brembo's will.

Later, Steve
 

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Steve Jarvis said:
My guess is you would never feel the difference "seat of the pants" between these two kits. Assuming you get the 14" diameter kit.

Let me warn that the AP Racing kit has less clearance than the Brembo kit. The 14" AP Racing kit won't fit in my wheels, but the 14" Brembo's will.

Later, Steve
What size wheels you have? And what kind. This of course makes a difference if someone would like to put on race wheels and tires.

Thanks,
 
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