Going to run manual brakes - 15/16" or 7/8" MC recommendation

[davidk68]

Hey Guys,
I'm going to run manual brakes on my car because I'm running Weber 48 mm downdraft carbs and there is no vacuum provision. I am not really interested in running a vacuum pump or hydraboost. My calibers are 13" C5 corvette front and 12" Wilwood D154 floating rear. If I understand correctly, the 7/8" MC would apply more pressure to the calipers and therefore let me run a less agressive pad at the expense of a little lower pedal. Are there other factors to consider? I know I can tune stopping power with brake pad coefficient of friction. The car is more of a resto-mod with occaisional autocross - track days doubtful. 68 Camaro, 383 SBC, 450 hp, T56, triangulated 4-link rear, chicane coil over stock SF front. Thanks in advance for any advice.

David

[19,69camaro]

I have c5 fronts and 4th gen camaro rears on mine with a 7/8" master and Hawks HP+ pads and really like the feel and stopping power. I don't think the travel is too long either.

The downside is tons of brake dust

[Apogee]

The D154 calipers you're running on the rear presumably have the 1.98 effective piston area (2X 1.125" pistons), which is effectively 20% smaller than a corresponding C5/C6 rear kit, so I would run the 7/8" over the 15/16" bore unit without a doubt. That said, there's only a 12% difference between them with respect to pressure/volume, so either should work.

Tobin
KORE3

[davidk68]

Thanks guys.

Aldin - approximately how far does your pedal travel before your brakes start to engage?

Tobin - is it true that I would need a more aggressive pad with a 15/16" bore than with a 7/8" bore. If that is the case then it sounds like the 7/8" would be my choice.

Thanks,
David

[19,69camaro]

I would say about a half inch before there is any real bite

[Apogee]

Tobin - is it true that I would need a more aggressive pad with a 15/16" bore than with a 7/8" bore. If that is the case then it sounds like the 7/8" would be my choice.

Yes, in general we would suggest running a more aggressive compound pad (higher CoF) with manual brakes, however there are a lot of guys running decent "FF" rated pads in manual configurations with good results. I prefer a "GG" friction rated pad, but as noted, that typically comes with more brake dust, noise and rotor wear. Hawk HP Plus, EBC Yellowstuff, Carbotech AX6, etc., are all good choices IMHO, however even the slightly less aggressive compounds still work well, but just require more pedal effort to achieve comparable decel rates.

Tobin
KORE3

[rustomatic]

I would second Aldin's comment above--I had a 7/8 master on my last brake setup (four piston front/single piston rear Ford-type calipers) for manual-only actuation. There was about 1/2 inch of travel before authority, and they felt great, on the road and on the track (until boiling point). Just don't be a dork like me and try doing Laguna Seca with low-quality brake fluid . . .

[davidk68]

Wow, only a 1/2 inch - that's great! I thought it would be at least a couple inches. I can certainly live with that. Looks like I'm going with a Wilwood tandem MC and I'll experiment a little with brake pads when I get the car going, Thanks for the help guys, it is greatly appreciated

David