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Shelby GT500 brake upgrade problems

I just installed front and rear Shelby GT500 brake upgrade with Brembo 6 piston calipers on my 2011 Mustang GT performance pkg which had 4 piston Brembos. Problem is larger caliper piston area has added pedal travel. Has anyone found a master cylinder with a larger than stock 1.062" bore that will fit factory power booster? Alternatively has anyone found or used a different booster to reduce the pedal travel. I'm also looking at ways to use a vacuum regulator to reduce vacuum to booster from the engine. Still unsure about that one from safety standpoint. Basic question is how are you guys handling pedal travel with bigger brakes on 2011-2014 S197 Mustangs? Not really significant but with new calipers rushing air noise from booster air inlet valve every time I hit brakes is very disconcerting. Anyone solved that problem?
 
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Ended up taking this setup out, as I had massive bleeding problems that turned out to be ABS module related. At that time, I
pulled the larger master and tried a brand new stock master in my troubleshooting. But it fits and should work fine otherwise.


 
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I just installed front and rear Shelby GT500 brake upgrade with Brembo 6 piston calipers on my 2011 Mustang GT performance pkg which had 4 piston Brembos. Problem is larger caliper piston area has added pedal travel. Has anyone found a master cylinder with a larger than stock 1.062" bore that will fit factory power booster? Alternatively has anyone found or used a different booster to reduce the pedal travel. I'm also looking at ways to use a vacuum regulator to reduce vacuum to booster from the engine. Still unsure about that one from safety standpoint. Basic question is how are you guys handling pedal travel with bigger brakes on 2011-2014 S197 Mustangs? Not really significant but with new calipers rushing air noise from booster air inlet valve every time I hit brakes is very disconcerting. Anyone solved that problem?
What year GT500 calipers? If they are the 2013 - 2014 six piston calipers, they do not have more piston area than the four piston Brembos you replaced. The 2013 - 2014 GT500 uses that same master cylinder as the 2010 - 2014 Mustang GT. There is only one master cylinder for all Mustangs from 2010 - 2014.


If you are using 2013 - 2014 GT500 calipers the problem is not an incorrectly sized master cylinder. Most likely the system is not properly bleed and there is air either in the lines, calipers, or the abs block.
 
What year GT500 calipers? If they are the 2013 - 2014 six piston calipers, they do not have more piston area than the four piston Brembos you replaced. The 2013 - 2014 GT500 uses that same master cylinder as the 2010 - 2014 Mustang GT. There is only one master cylinder for all Mustangs from 2010 - 2014.


If you are using 2013 - 2014 GT500 calipers the problem is not an incorrectly sized master cylinder. Most likely the system is not properly bleed and there is air either in the lines, calipers, or the abs block.
Actually I'm using the 2017 red Bullitt Brembo calipers which have (6) 36mm pistons which have about 10% larger piston area than the (4) piston Brembos. Assuming a 6:1 pedal ratio (I haven't measured it yet) and guessing 1mm pf piston travel I calculated .228" of additional pedal travel.
 
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Ok, those are different calipers than the 2013 -2014 GT500 calipers. Those are the S550 performance pack calipers and they do have a larger piston area. The pedal will be lower with those calipers and a stock 2010 - 2014 master cylinder.

Ok, now for the bad news. There is no off the shelf master cylinder with a larger bore you can retrofit to your car. The S550 master will not work with your power brake booster. The S550 booster will not bolt into the S197 - the bolt patter is different. Even if the S550 booster would bolt onto the S197, I am not sure if the pedal boxes are compatible. You also can't get the S550 booster into place - the valve covers create a clearance issue.

If you want to try to install the S550 booster, you need to roll the engine towards the passenger side to gain clearance to drop the booster in place. But, I doubt this will give you enough room to do the necessary firewall modifications to bolt in the booster. You may need to pull the engine to do all the necessary firewall modifications.

So, your easiest options are to get used to the lower pedal, try installing a pedal block, or change brake calipers to something compatible with the stock master.
 
I figured that might be the case based on the homework I did before posting the question. I asked because master cylinder manufacturers will often use the same casting when selling to different manufacturers changing the bore size as required. On the last NC Miata I built I found a bolt on larger bore MC from one of the Korean cars, I forget which one. It was worth a try to ask Thanks.
 
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If you find a substitute from another car, post it up. I tried to do the same thing a couple of years ago but either it doesn't exist or my research skills are lacking.
 

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