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I have a 1972 240z that the brakes will not lock up no matter how hard you press them. It has new stock calipers and pads on the front. New shoes and wheel cylinders on rear. new brake lines. Front line pressure is around 1800 lbs. with the car not running. Around 2300 lbs. running. Booster seams good. Stops fair at best but has a very firm peddle. Is this normal for these cars? Any suggestions? 

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Not normal.  What size tires?  What type of pad?  I think that ceramics have a lower coefficient of friction.

 

https://ctbrakes.com/brakeanswers/friction-compounds/

 

On the back I found that typical parts stores shoes are meant to fit a larger diameter drum.  Only the ends contacted the drum when used.  But the back tires still locked up when I was having front brakes bleeding problems.

 

 

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When you say "very firm peddle"....I'm wondering if you are getting power assist from the brake booster.  Why do you say the "booster seems good" -- have you actually tested it, or had someone else test it?

 

It's not uncommon for the check valve to either be installed backwards or to malfunction.  Either condition will result in little/no assist from the booster, so I'd start by checking that first.

 

Also, as @NewZed suggested...harder compound pads won't function properly until they get some heat into them.  It is for this exact reason that I will often run organic, or softer, compound pads in my street cars.  (And vendors like Carbotech and Porterfield both make a wide range of excellent brake pad options for the S30.)

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1972 240Z SBC 350

 

My brake set up:

 

  • Front - Toyota calipers with solid stock rotors
  • Rear - 240SX calipers with 300zx solid rotors.
  • Booster - 280z 8.5in
  • Master Cylinder - 1979 280zx 15/16in
  • Carbotech AX6 compound

 

I have experimented with all of the so called "performance street pads" available over the last 20 years. They all suck for street use. Every one of them lacked good cold bite which is what you want driving in traffic. Some of them were like using wood blocks for pads.

 

About four years ago I replaced the front  and rear pads on my 240Z with Carbotech AX6 pads. They have excellent cold bite which get gets better as they heat up.  I have intentionally heated up the front brakes until smoke was rolling out of the fenders and there was no fade at all.

 

They are expensive, but if you mention that you belong to HybridZ they will give you a 10% discount. You can  buy directly from the company:

 

https://ctbrakes.com/

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hi, guy's, Thanks for the help. I looked up the pads and they are wagner  thermoquiet ceramic #pd161. They do not get any better with heat. Tires are 225-50-16 continental extreme contact sport. Also Old booster was set up with proper gap and new 7/8 master cylinder . additional information- Was a standard transmission but was changed to 4l60e automatic and a LS motor. I changed to a 240z automatic peddle. I'm thinking about trying a new 8.5 inch booster.

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I went with those pads on my 76 and replaced them with Beck Arnley after just a short while.  They didn't have any initial bite when you first pressed the pedal.  Took extra effort to start the stopping process after you felt the pads hit the rotors.  The Beck Arnley pads had great pedal feel, very noticeable.  But they wore faster and dirtied up the rims.  I never tried to lock them up and had 205's on so might not apply to what you're trying to do.  

 

If you still have drums on the back you might pull them and check the actual contact patch.  Mine only contacted at the ends of the shoes.  I could not lock up the back wheels with the parking brake.  Very little stopping power back there.  The lack of quality shoe options is actually a valid reason to swap to disks on the back.  

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Good tips from @NewZed on the rear brakes.  Most of the OTS drum brake shoes from parts stores are so-so at best.  Fortunately, Porterfield produces a nice shoe that fits our rear drum brakes....you can check them out here:

https://www.porterfield-brakes.com/Products/?YearSelected=1972&ModelSelected=240Z&MakeSelected=NISSAN&selectManufacturer=Porterfield Brakes

 

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