The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

Talk me in to or Talk me out of doing this…

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Alright so here’s the deal, I have everything minus SS brake lines for a 4 piston Brembo swap on my V6 mustang plus the gt500 rear brake upgrade.

I found someone local who has 6 piston brembos from the S550 and is willing to do a straight trade for my 4 piston Brembos.

The rotors and brake pads I have can be returned and exchanged for the correct variants that I need. Here’s where it gets squirrely. My 18” SVE Drifts won’t clear these massive brakes and so I will need to trade my wheels to a size or brand that can fit the calipers. Mainly it comes down to hassle of trading, returning, buying new brake lines. Etc..

What are your thoughts? The calipers are brand new, never been used.
 
899
548
I think the 6-piston S550 setup may be overkill for a V6 platform. You will need different rotors for the S550 calipers (2014 GT500 rotors). The larger rotors and calipers will add a lot of weight. You may not like the pedal feel of the S550 based setup. The S550 caliper is not correctly matched with the S197 master cylinder. The result is a lower, softer pedal compared to a 4-piston caliper configuration.
 

Mad Hatter

Gotta go Faster
5,319
4,332
Santiago, Chile
Dido, the 14" brembos are great and with less weight you should be fine. Would rethink the rear discs, it's really only for looks and again your just adding weight.
 
317
413
CA
The 6 piston setup may be overkill in raw stopping power, but keep in mind that having more brake is better from wear perspective. You are simply managing thermal energy. I am a sub 300rwhp S-197 and get 15+ events out of my s550 6p’s w/G-LOC R16 pads. Nobody I know on 4p brembos can claim the same. Brakes and tires are some of the only consumables costs we have control over. Having to replace $300 pads every 5 events gets old real quick, both from a cost and labor perspective.

The big cons to the 6p s550 imo are the loss in pedal feel, and the increase in unsprung weight. You can go girodisc rotors to combat the weight, but it’s still more than 4p brembos.

With that being said, the pedal feel with the 6p is quite poor. The first (what feels like) 30% of pedal travel does nothing. As the pads and rotors wear down, the feel gets worse and worse.
 
The 6 piston setup may be overkill in raw stopping power, but keep in mind that having more brake is better from wear perspective. You are simply managing thermal energy. I am a sub 300rwhp S-197 and get 15+ events out of my s550 6p’s w/G-LOC R16 pads. Nobody I know on 4p brembos can claim the same. Brakes and tires are some of the only consumables costs we have control over. Having to replace $300 pads every 5 events gets old real quick, both from a cost and labor perspective.

The big cons to the 6p s550 imo are the loss in pedal feel, and the increase in unsprung weight. You can go girodisc rotors to combat the weight, but it’s still more than 4p brembos.

With that being said, the pedal feel with the 6p is quite poor. The first (what feels like) 30% of pedal travel does nothing. As the pads and rotors wear down, the feel gets worse and worse.
Thanks! That’s a perspective I haven’t heard before of how much less they wear. Didn’t consider how long pads would last. Of course, this is a daily and I’m only looking to do my very first track day this year.
When this opportunity came up I figured I would ask those who knew more than me because of course, the mod bug in me says the best for everything. Even when it may not lead to exact performance or in this case, worse pedal feel than the 4 pot and more weight.
 
357
372
Dido, the 14" brembos are great and with less weight you should be fine. Would rethink the rear discs, it's really only for looks and again your just adding weight.
Agree the bigger rear discs won't improve actual braking performance. But imo they do improve heat management and help avoid melting rear axle seals. So there is a purpose to them.
 

TMSBOSS

Spending my pension on car parts and track fees.
7,608
5,369
Exp. Type
HPDE
Exp. Level
10-20 Years
Illinois
The improvement I found with the larger rear rotors was seal life. With the smaller rotors, I cooked seals about once a year. Since I went with the larger rotors and moved the heat outbound, I have not lost a seal.
 
899
548
The car only has about 250 rwhp and is 100 - 200 lbs lighter than the V8 car depending on options. It will have a lot lower MPH at the end of straights due to the decrease in power. The 14" brakes are more than up to the task, especially with some brake cooling. I would much rather have the reduced weight and pedal feel. The car will be faster in a straight line and through corners with the lighter weight brakes and the pedal feel will lend to a higher drivers confidence level. True, you might preplace pads a little more often, but you could also try a good endurance pad like a Pagid RSL1 which has a higher level of friction and lasts for a very long time.

The GT500 rear brakes do add more rear brake bias. That is simple math. Larger diameter is a longer lever. When combined with the same pad coefficient of friction and caliper clamping force, you get a higher level of overall brake torque. But, I do not think it is needed in the instance and would stick with the smaller OEM rotor to reduce weight.
 
I’ve decided to stick with my current plan with the 4 piston Brembo calipers. Thanks for all the input!

As for the rear gt500 brake upgrade, before I knew it would help with heat management and the rear seals, I had decided to make that switch purely for aesthetic reasons. (Conflicts with the idea of saving weight up front only to add some in the rear, but I really like the look of wheel barrels filled with rotor) This car is 100% daily at the moment.

Check out my build page to see all the products I’ve gone with on this brake upgrade! Nothing crazy, just fun on my end.
 
Just to comment on the poor pedal feel, I would imagine that when making that big of a change in piston surface area on the caliper side, you'd be expected to change the master cylinder out. There is a formula for that to determine the bore size of the master you need but it has been over a decade since I looked at it. I've not kept up with anything past the S197, can you swap the S550 master into the S197 directly or does this turn into a nightmare?
 

xr7

TMO Addict?
727
855
Exp. Type
Autocross
Exp. Level
10-20 Years
Minnesota
Just to comment on the poor pedal feel, I would imagine that when making that big of a change in piston surface area on the caliper side, you'd be expected to change the master cylinder out. There is a formula for that to determine the bore size of the master you need but it has been over a decade since I looked at it. I've not kept up with anything past the S197, can you swap the S550 master into the S197 directly or does this turn into a nightmare?
Nightmare, I think somebody on here has done it, not a bolt in swap.
 

Mad Hatter

Gotta go Faster
5,319
4,332
Santiago, Chile
Master cylinder swap between the S550 and the S197 is a lot bigger job then I thought it was. In the end left it as is and got used to the longer pedal travel.
 
Master cylinder swap between the S550 and the S197 is a lot bigger job then I thought it was. In the end left it as is and got used to the longer pedal travel.
What was the tipping point on everything involved to swapping an S550 master into your S197 that made you decide not to move forward??
 
I'm looking at some pics on Rockauto. It looks like the flange where it bolts to the booster would be a bolt on but the hard lines connect on the opposite side of the MC so you'd probably just need to fab new hard lines or cut the existing ones, reflair them and build an intermediate hard line to connect to the factory lines. Does that about sum it up? I wonder if you could just get an SN197 MC with the correct bore size? From the pics, the flange mount ears are clocked at a goofy angle but it LOOKS like the same angle between a S197 and a S550. If not, I guess you could swap the brake booster out with it but I'm not sure if a S550 booster would swap cleanly into a S197.
 
7
6
Exp. Type
HPDE
Exp. Level
5-10 Years
Michigan
I did this swap prior to last season, I love it. Brake feel is the same as far as I can tell. The pad size of the 6 piston is huge compare to the 4 piston. I push my speed as deep into the corner as I can so I'm hard on the brakes with no fade now. I do have 5.0 so I'm carrying more weight.
This year I upgraded to the Girodisc 2-piece rotors to drop some weight. Looking forward to see how they perform.

IMG_4372.JPG

IMG_4883.JPG
 
225
177
Exp. Type
Autocross
Exp. Level
Under 3 Years
Colorado Springs
I did this swap prior to last season, I love it. Brake feel is the same as far as I can tell. The pad size of the 6 piston is huge compare to the 4 piston. I push my speed as deep into the corner as I can so I'm hard on the brakes with no fade now. I do have 5.0 so I'm carrying more weight.
This year I upgraded to the Girodisc 2-piece rotors to drop some weight. Looking forward to see how they perform.

View attachment 84837

View attachment 84838


I did the swap mid last season, the size difference is comical. Think I had some semi-related issues that are finally resolved. Let me tell you, with no ABS, the Brembos will lock up the front end with very little effort. With ABS working, they feel very firm. Still haven't had on a full track yet. Those girodiscs look so good, I just can't justify....
 

TMO Supporting Vendors

Latest posts

Buy TMO Apparel

Buy TMO Apparel
Top