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Brake balance 7/8 vs 13/16 wheel cylinders


Tom1200

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On my 1200 coupe I'm looking for more rear brake. I tend to go with more rear brake than most club racers so I'm looking for simplier ways of doing this before going to the trouble of fitting dual master balance bar etc.

 

The front calipers are the ubiquitous 280ZX and the rear brakes are 510 (H190 Wagon) with Z car alloy drums. The rear wheel cylinders are 13/16ths and I'm contemplating going to 7/8ths. If anyone has tried this I'd like to know the results.

 

Also before anyone says just add Wilwood or Tilton pedal set; to do that properly is more work then most people think it is.

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7/8 is about 15% larger than a 13/16

 

Well assuming a 3/4" master (.441 sq in) and 5 to 1 pedal ratio. If 100 pounds are applied when braking that's 500 x .441 = 220 PSI available on the brake line.

 

A 13/6 wheel cylinder will exert 114.2 pounds and a 7/8 will exert 132.5 pounds. This is also about 15% larger.

 

 

If anyone wants to argue this I am totally willing to fold. Math was something I only endured in school.

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Mike by your calculations that's an 18lb difference, not huge but an incremental change that might be enough of a difference. My next step if the wheel cylinders don't get the balance I want is softer compound brake shoes. I have brand new wheel cylinders in the next two sizes down should the shoes go to far on the balance.

 

Tom

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Well the increase in size is about 15%. No idea if the pressure is actually that amount or not. Also how does brake line pressure relate to actual brake shoe friction against the drums? I guess trial and error. 

 

Larger brake cylinders should apply more brake pressure to the shoes. The brake pedal will travel farther and may 'feel' softer/mushier.

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Right now I'm using a 11/16th master which I may need to change out; right now there isn't a huge amount of pedal travel (about the same as my formula car) but we'll have to see.

 

If money were no object then obviously I'd spend the $600-$700 to get a pedal set with a balance bar.

 

Tom

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