73mm caliper upgrade on 89,5.0L Mustang with drum brakes

8950HO · Aug 14, 2005

To those who have done the 73mm front caliper upgrade on a 87-93,5.0L Mustang with the rear drum brakes in place,did you have any problems with a soft longer travel brake pedal afterwards?

I would be using the following parts;1991 Lincoln Mark 7-73mm calipers,94-95 master cylinder,Maximum Motorsports 3>2 port master cylinder conversion kit.

The reason I ask is because Maximum Motorsports told me that I would most likely experience a soft/long travel brake pedal because the rear wheel cylinders don`t have the ability to flow enough brake fluid and I wouldn`t get enough brake fluid going to the rear of the car.

,are they whacked,or is this a possibility with the rear drums?

I find it hard to believe that there would be a problem with the 73mm upgrade with the rear drums.

ram360 · Aug 14, 2005

Done the upgrade on my 88gt w/ rear drums and it still has a good pedal feel. If it did change I really didn't take notice.

ratrapp2 · Aug 15, 2005

mine got real soft also.you may have to adjust your pedal rod out alittle to tack up the extra travel.probably only 1 turn or so.i couldn't adjust mine because it was a 4 cyl. car and the boosters are non adjustable.i swapped in a 94-95gt booster and m/c assembly.

OL' WHITEY · Aug 15, 2005

You should probably go with the '93 cobra MC and do Matt's conversion. This will bring your pedal back to normal and allow you to upgrade to rear discs in the future. Gutting the factory proportioning valve and puting an adjustable prop valve in line may help as well. If I were you, I'd do both.

8950HO · Aug 15, 2005

ram360 said:
Done the upgrade on my 88gt w/ rear drums and it still has a good pedal feel. If it did change I really didn't take notice.

Sounds like you didn`t have any problems.

Can you list the parts you used,eg,calipers,MC,3>2 port conversion kit,stock or different brake booster and how much you adjusted the brake booster rod out?

gt90stang · Aug 15, 2005

On my 90GT I'm running a 93 Cobra booster, Sn94 MC, 3-2 port conversion, stainless steel flexable brake lines, MM rear pads & 73mm calipers and added an adjustable PV in series with the stock PV and combo valve. This works great with good adjustment to prevent rear wheel lock up due to more fluid needed for the larger calipers. Don't feel the need to go rear discs.

Good Luck, Don

ram360 · Aug 15, 2005

8950HO said:
Sounds like you didn`t have any problems.

Can you list the parts you used,eg,calipers,MC,3>2 port conversion kit,stock or different brake booster and how much you adjusted the brake booster rod out?

88 crown vic calipers
95 gt mc
My 3-2 conversion was a little different b/c I have a line lock on my car.
I also have braided stainless lines.
I think I adjusted to rod out around one turn ( but It's been awhile so I could be wrong on that.)

speedytang · Aug 16, 2005

Installed 73mm on my '89 and changed nothing else and the pedal is fine. Been installed for 7 years. Just a note on the 73mm install. Stock rotors lost nothing in stop distance. Slotted and Drilled rotors gained 2 feet in length. Installed slotted rotors lost 7 feet. Was curious about the 7 feet, installed the stock calipers back on and lost 6.5 feet. 73mm calipers do nothing but cause clearance problems with Weld wheels of 15x3 or 15x5. I have both sizes and you must grind the metal of the pads to get clearance or the brake pad will dig into the rim. All measurements done with a G-Tech and a Laser Temperature gun to make sure the rotors started at the same temperature and stops started at 50 mph. MidOhio track day at 92 degrees air temperature and track temperature at 148 degrees. Tires used for test 91 16" GT wheels with stock size rubber using Nitto 555 Roadrace tires.
Now the Short Version.
Waste of Money and don't look any better than the stock Mustang Calipers.

92BlackGT · Aug 16, 2005

speedytang said:
Installed 73mm on my '89 and changed nothing else and the pedal is fine. Been installed for 7 years. Just a note on the 73mm install. Stock rotors lost nothing in stop distance. Slotted and Drilled rotors gained 2 feet in length. Installed slotted rotors lost 7 feet. Was curious about the 7 feet, installed the stock calipers back on and lost 6.5 feet. 73mm calipers do nothing but cause clearance problems with Weld wheels of 15x3 or 15x5. I have both sizes and you must grind the metal of the pads to get clearance or the brake pad will dig into the rim. All measurements done with a G-Tech and a Laser Temperature gun to make sure the rotors started at the same temperature and stops started at 50 mph. MidOhio track day at 92 degrees air temperature and track temperature at 148 degrees. Tires used for test 91 16" GT wheels with stock size rubber using Nitto 555 Roadrace tires.
Now the Short Version.
Waste of Money and don't look any better than the stock Mustang Calipers.

That's why you go 5 lug and convert to Cobra brakes and rear disc....big difference from stock when trying to stop from 80+ mph.

73mm caliper upgrade on 89,5.0L Mustang with drum brakes

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