Brembo brake upgrade - Master Cylinder.

[Optimum Performance]

"Bigger" outside dimension does not mean larger pistons. In fact, the total displacement might be less than the 4-piston caliper (e.g., 94-98 Cobra = 2x38MM, 13" rotor; 99-04 Cobra = 2x40mm - 13" rotor; 99-04 GT = 2x44mm - 11" rotor). These re not interchangeable without other matching changes for optimal braking - not merely "great" braking. And we haven't even discussed brake torque bias and how the car behaves in dive.

Could you explain what you mean by bigger outside diameter doesn't mean larger pistons?

We have measured every caliper and piston on the S550. Going from the stock 4 piston calipers to the 6 piston Brembo caliper reduces the piston area by 4.7%. The master cylinder used with the 4 piston calipers is the same master cylinder used in the GT350. The GT350 total piston area is a 14% increase from the 4 piston calipers and a 19.4% increase from the 6 piston calipers.

Ford has been selling both the 6 Piston and GT350 kits as bolt ons. You seem to have a good understanding of how all this works together. I understand that a larger piston surface area, due to volume will require less pressure but the original complaint was the car did not stop. That is a different issue. We also have sold many of these kits to our Track Customers who have not had any issues reported back.

Sponsored

 

[BmacIL]

Could you explain what you mean by bigger outside diameter doesn't mean larger pistons?

We have measured every caliper and piston on the S550. Going from the stock 4 piston calipers to the 6 piston Brembo caliper reduces the piston area by 4.7%. The master cylinder used with the 4 piston calipers is the same master cylinder used in the GT350. The GT350 total piston area is a 14% increase from the 4 piston calipers and a 19.4% increase from the 6 piston calipers.

Ford has been selling both the 6 Piston and GT350 kits as bolt ons. You seem to have a good understanding of how all this works together. I understand that a larger piston surface area, due to volume will require less pressure but the original complaint was the car did not stop. That is a different issue. We also have sold many of these kits to our Track Customers who have not had any issues reported back.

Thank you! I knew that the numbers would back up what intuitively made sense.

 

[qtrracer]

Could you explain what you mean by bigger outside diameter doesn't mean larger pistons?

We have measured every caliper and piston on the S550. Going from the stock 4 piston calipers to the 6 piston Brembo caliper reduces the piston area by 4.7%. The master cylinder used with the 4 piston calipers is the same master cylinder used in the GT350. The GT350 total piston area is a 14% increase from the 4 piston calipers and a 19.4% increase from the 6 piston calipers.

Ford has been selling both the 6 Piston and GT350 kits as bolt ons. You seem to have a good understanding of how all this works together. I understand that a larger piston surface area, due to volume will require less pressure but the original complaint was the car did not stop. That is a different issue. We also have sold many of these kits to our Track Customers who have not had any issues reported back.

You need to measure the piston inside the sleeve. But "diameter" is not what I was talking about. The caliper itself needs to fit the rotor being used. When pistons are used on both sides the caliper dimension must increase. But the same caliper dimension can be used with a multitude of pistons sizes. So, when we are talking about brake torque, not only do you need to consider the number of pistons used and their size, but also the rotor diameter and swept area of the pad.

For most mustangs with a weight bias of 60/40 to the front, the brake torque bias is generally 70/30. How we get that torque bias is as discussed above.

For example on my 86 using the SVO single 76mm front caliper and 11" rotors with the TB T/C rear 44 mm caliper with 10.25" rotor I get a torque bias of about 80/20 - way too much front bias. Moving to the sn95 Cobra front 38mm dual piston with 13" rotor and keeping the rear as is, I move to a 74/66 torque bias. If I upgrade the rear to the 11.65" rotor and 38mm caliper, my torque bias is about 70/30. And if I upgrade the front to a Stoptech 4-piston caliper with 14" rotor keeping the rear the same, the torque bias is 68/32. In all the above, the only other change was from a 1-1/8" M/C to a 1' M/C. The brake pedal feel was normal, throughout but stopping distances were dramatically different.

You have to calculate the torque bias split using something like a factory set-up as a base to gain some appreciation of what goes into the system design. Ford, like all other companies, does not upgrade brakes in isolation of other components. If we do that, the outcome will be less than optimal.

 

[Bahndvr]

So should we try and get more braking in the back, say 60/40?

 

[Optimum Performance]

So should we try and get more braking in the back, say 60/40?

With very few exceptions Mustangs (Modern ones with ABS) do not respond well to a lot of rear brake. This entire recent m/c discussion is based on no real data and the claims of changing m/c and boosters on the S550 to accommodate a swap from the stock S550 4 piston caliper to the S550 6 Piston Brembo or the GT350 calipers has been run through very complicated simulation software that looks at everything from wheelbase, tire contact patch, CG, piston sizes, m/c sizes and proven to be false. In fact the 'data' provided should have had the opposite effect. Again Ford Performance would not release a brake kit that needed a M/C and not include one. This was all related to incorrect selection of brake compounds and the installation of components.

:repost:

 

[Bahndvr]

Did mean to beat a dead horse. The conversation seemed to go back to the fact that these Mustangs are nose heavy and braking is ~70/30 so to keep it from nose diving I would think brake more to the rear but I am not very knowledgeable on this, thus the question.

 

[Optimum Performance]

Did mean to beat a dead horse. The conversation seemed to go back to the fact that these Mustangs are nose heavy and braking is ~70/30 so to keep it from nose diving I would think brake more to the rear but I am not very knowledgeable on this, thus the question.

A majority of braking happens up front, if you add more brake than the car wants or can use you can decrease braking performance. If the ABS system sees the rear tires decel at a faster rate than the fronts it will bleed off pressure to the rear effectively making the fronts do all the braking. GT350's with track rubber and the correct driver can make a higher rear compound pad work. We always recommend staggering the compound towards front bias. This keeps most people out of trouble. On a lot of other platforms we end up running a GS1 street pad in the back with a very aggressive front compound so the car will stop due to no rear grip under braking, most developed FWD cars have this issue on track. Basically more is not always better.

 

[re-rx7]

Could you explain what you mean by bigger outside diameter doesn't mean larger pistons?

We have measured every caliper and piston on the S550. Going from the stock 4 piston calipers to the 6 piston Brembo caliper reduces the piston area by 4.7%. The master cylinder used with the 4 piston calipers is the same master cylinder used in the GT350. The GT350 total piston area is a 14% increase from the 4 piston calipers and a 19.4% increase from the 6 piston calipers.

Ford has been selling both the 6 Piston and GT350 kits as bolt ons. You seem to have a good understanding of how all this works together. I understand that a larger piston surface area, due to volume will require less pressure but the original complaint was the car did not stop. That is a different issue. We also have sold many of these kits to our Track Customers who have not had any issues reported back.

So does this mean that the base brakes are actually better than the brembos if they had a gd rotor? Im looking at the 2piece rotor design from baer.

 

[Optimum Performance]

So does this mean that the base brakes are actually better than the brembos if they had a gd rotor? Im looking at the 2piece rotor design from baer.

No, but for most of the population they are more than effective. A conventionally vented rotor would extend the range of performance.

 

[BmacIL]

So does this mean that the base brakes are actually better than the brembos if they had a gd rotor? Im looking at the 2piece rotor design from baer.

No, as they still wouldn't generate as much brake torque due to the smaller rotor, and have less thermal mass. However as @Optimum Performance said, fixing the rotor design could make it work pretty well.

 

[qtrracer]

So does this mean that the base brakes are actually better than the brembos if they had a gd rotor? Im looking at the 2piece rotor design from baer.

What does "better" mean? In a race environment, the brakes must shed a lot of heat especially where big, sticky rubber is involved. Those brakes must also apply pad pressure as evenly as possible across the rotor's face for optimal contact and wear. BBKs are meant to address both issues with a larger rotor (thermal mass) and multipiston calipers (more evenly spread pressure). Look at a NASCAR brake system. The rotors are not only large diameter but very thick. The calipers are huge too.

Now, if the brake system is unlikely to see the extreme stress of a race environment, then thermal mass and optimal pad application are not primary concerns. Moreover, replacing the pads and rotors are a bunch cheaper for the consumer. For example, the rings for my StopTech 14" two-piece are more than $200 each whereas the one-piece 13" Cobra rotors are $50ish each. Pad prices jump too when going to larger multipiston calipers.

But all of this doesn't address what stops the car - the tires. Put NASCAR brakes on the front with skinnies and I can assure you, braking will suffer. From my
own experience running Fox chassis cars, the stock 11" rotor single piston cast iron caliper accompanied by rear drum brakes do an excellent job of brining the car down from speed IF there is big, good rubber on the ground, the pads/shoes are designed for the job and the driver knows the limits of the system (heat).

I've been running the S550 with the same pads as delivered from the factory doing open track, auto cross and daily driving. Changed the rubber and got better performance with less pad wear. I'm sure the base brakes would perform fine for what I do. Of course the big Brembos look better as do the larger rotors. So, cosmetically the big Brembos/rotors are "better". But I'm not looking forward to the cost of replacement pads and rotors.

 

[zirfj312]

No, but for most of the population they are more than effective. A conventionally vented rotor would extend the range of performance.

Great discussion. I've recently been looking into this topic since I melted the dust boots on my 2018 Base GT 4 piston calipers during a track day at Sebring (due to what I suspect is driver stupidity - not allowing sufficient cool down laps) so, I did look into 'upgrading' to the PP 15" brembos and rotors particularly due to the fact that the inverted hat rotor design can't or won't disperse the heat generated during track days. Would you agree that just by the fact that the design is flawed for that rotor it would be worth the dime to move up to the 15" setup? I have not been able to find 'normal' rotors for the s550 in 14"

 

[Optimum Performance]

Great discussion. I've recently been looking into this topic since I melted the dust boots on my 2018 Base GT 4 piston calipers during a track day at Sebring (due to what I suspect is driver stupidity - not allowing sufficient cool down laps) so, I did look into 'upgrading' to the PP 15" brembos and rotors particularly due to the fact that the inverted hat rotor design can't or won't disperse the heat generated during track days. Would you agree that just by the fact that the design is flawed for that rotor it would be worth the dime to move up to the 15" setup? I have not been able to find 'normal' rotors for the s550 in 14"

If you plan on tracking your car on a regular basis better brakes are the only way to go. One thing left out of every discussion about the base brakes at track days and how they seem to melt down is what pad is being used with them. If you take the stock pads on the base brakes to a track day they will melt. Changing the fluid and running the stock pads isn't going to do much. The fact that Ford is now offering the Base brakes with a better pad on the 2020? Mustang says that for someone taking this car to the track for a track day..actual HPDE the stock brakes will perform fine with a decent pad. Also the number of track pads we sell for these base brakes that do not work on track tells us they are not horrible, planning and driving ability seem to be the larger problem with them. I have very easily faded the 15" Brembo's on a 340 street tire with a track pad and brake cooling, play stupid games, win stupid prizes, don't blame the equipment.

 

[shogun32]

So, Ferodo DS2500 up front be they for the 4-pot or 6-pot caliper variety. What to use on the rear?

 

[mikeD4V]

Just adding a little more info about the master cylinders. Grenaded friction material from my last clutch worked its way up to the brake fluid reservoir and finally made it through my non-PP master cylinder ending its useful life. I ordered the PP master two weeks ago and installed it. The car had 19 track days with the non-PP master and PP brembos so it seemed like a good candidate for this comparison. On track last weekend with the PP master and the only noticeable difference I felt was a slightly shorter pedal throw.

Sponsored