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Discussion Starter · #1 ·
To increase the caliper pressure with the same pedal effort, should you increase or decrease the bore size?

I'm thinking increase. For the same pedal pressure, a 1" bore will provide greater pressure than a 3/4".

The reason I'm asking is, I want more rear brake action. Everyuthing works good, but I want more. I used a more agressive pad in the rear, and that gets it pretty close. If I increase the rear caliper pressure, then I can run a more agressive pad in the front.

I have the CNC dial MC with balance bar, and two 3/4" bore MC's. The simple answer is replace the rear MC with a differant size.
 

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increasing the fluid pressure with the same pedal effort would require a reduction in bore size. The trade-off is a longer throw at the pedal/pushrod since the piston has to move further now to displace the same amount of fluid.
 

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Like Wade stated it is a trade off, bore for stroke. Smaller bore is more pressure but needs more stroke. The problem is the really small bore will run out of stroke on some of the larger calipers. HTH, Cheers Richard.
 

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BoB,

So does that mean you need a 5/8" bore MC for the rear, or will this be insufficient volume for your T-bird rear calipers?

What about Cobra rear calipers? Don't they use a larger rotor but a smaller caliper? Maybe this would work in conjunction with the smaller rear MC bore?

Sean
 

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Discussion Starter · #5 ·
I'm thinking that the 5/8" bore will provide the additional pressure I'm looking for. I can live with a longer stroke.

I considered switching to Cobra brakes in the rear. Kind of expensive, but might be worth it. But then I discovered that the Cobra piston is smaller. With a larger rotor, it's a wash.

Also, can't use a T-bird caliper with a larger Cobra rotor because the Cobra rotor is thinner. The caliper piston falls out when the pads get thin. I'm not sure, but I think that's a bad thing. ;)

Also considering a Wilwood caliper on the back. Again, kinda expensive.

Economically speaking, sounds like a differant MC is the best answer. I think I may try that in the next few months. Too busy right now.
 

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boB,

I'm clearly no expert, just trying to understand the theory myself.

So I think as Wade explained, the longer stroke is required (when switching to a smaller MC bore) to make up for the volume of fluid required to move the caliper piston?

And Richard suggests that smaller bore MC's may not move enough volume (insufficient stoke) for 'larger calipers'? Is he referring to T-bird calipers? I think (?) they a slightly larger (volume) than the Cobra calipers.

So if the 5/8" bore MC does not have sufficient stroke to match your calipers fluid volume, can you get longer MC's or do you need to find smaller (volume) calipers? Wouldn't the larger Cobra rotor help compensate for having to use a smaller caliper?

Just trying to think outside of my (very small) box.

:D

Sean
 

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Ideally you need 3/4" for the front brakes and 5/8" for the rear, i.e. CNC dual master cylinder. It also has a adjuster bar for more rear bias.

Dick
 

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Discussion Starter · #8 ·
Originally posted by canuck1:
boB,

And Richard suggests that smaller bore MC's may not move enough volume (insufficient stoke) for 'larger calipers'? Is he referring to T-bird calipers? I think (?) they a slightly larger (volume) than the Cobra calipers.

So if the 5/8" bore MC does not have sufficient stroke to match your calipers fluid volume, can you get longer MC's or do you need to find smaller (volume) calipers? Wouldn't the larger Cobra rotor help compensate for having to use a smaller caliper?

Changing to a 5/8" bore would increase pressure, and increase stroke length. But by how much? I don't know.

The t-bird caliper is a little larger, and would require a slightly larger volume. But going to a smaller Mustang/Cobra caliper is a step backwards. Small caliper+large rotor=large caliper+small rotor. What I want is large caliper+large rotor.

I think I'm at an impass here. The brakes are very good; but always looking for more. I don't see any reasonable ($$) upgrades available. I could spend $2,500-3,000 for a Wilwood set up. But I think that's overkill.

[ January 09, 2007, 10:34 AM: Message edited by: boB ]
 

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On my Wilwood setup (Fortes) I have 3/4" for the front, 5/8" for the rear, and 1" for the clutch. The balance bar can handle the front/rear bias adjustment.
 

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Originally posted by boB:
Changing to a 5/8" bore would increase pressure, and increase stroke length. But by how much? I don't know. [/QB]
Going strictly by bore size, the 5/8" piston would have to travel about 44% further than the 3/4" piston to move the same volume of fluid. Additionally, with a given pedal effort, the 5/8" piston will develop about 44% more hydraulic pressure than the 3/4" piston.
 

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boB,
I'm not seeing what type of brake calipers you have.
I have the dual CNC 3/4 front bore and 5/8 rear with bias bar setup & Richard Oben's Turbo rear calipers. I put Carbotech Panther pads front and rear but still wasn't happy with my stopping power. Probably because I had to dial the bias a little too far rearward for my liking. I solved this by adding a 2# residual valve on the rear line only. I now have better stopping power and the car seems to be balanced front-to-rear.
Take care,
Ron
 
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