New hole in brake pedal

['65 chevy lover]

Is it really necessary to drill another hole ~ 1 1/2" below the existing hole in the brake pedal when changing to disc brakes? Instructions say to do it...just wondering why.


Thanks,
Billy

[KJSR]

It really has more to do with the addition of the booster. The pedal ratio changes when going from a non-boosted to boosted system. Yes its required to have proper braking perfomance.

[slepysal]

X2

['65 chevy lover]

Thanks to all for the reply's!

[Greg63]

I never heard of that.
I switched to power front disc brakes and didn't drill anything in the pedal. Can someone post up some details for me?
Greg.

[markeb01]

It has to do with the specific application. Depending on how the installation was engineered (brackets, booster/master cylinder angles, etc) some aftermarket installations require a different angle attachment to the pedal arm. If a complete factory booster system has been transplanted from another truck, this modification may not be required.

[Trsmotrhed]

Originally Posted by Greg63

I never heard of that.
I switched to power front disc brakes and didn't drill anything in the pedal. Can someone post up some details for me?
Greg.

Same here. This is the 2md truck I've added disk brakes to and just redid the brake rod. My pedal and brakes work fine. Like to see what the reason is.
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[Rich 5150 69]

It has everything to do with pedal ratio, when you add the booster you don`t need the leverage, the stock hole gives the pedal more leverage, if you use the same hole it will tend to make your brakes very touchy plus its also an alighment issue.

[Greg63]

Originally Posted by markeb01

It has to do with the specific application. Depending on how the installation was engineered (brackets, booster/master cylinder angles, etc) some aftermarket installations require a different angle attachment to the pedal arm. If a complete factory booster system has been transplanted from another truck, this modification may not be required.

I have a CaptainFab bracket and an unknown booster. The rod is stock.
Greg.

[Rich 5150 69]

You`ll need to measure the full stroke of the master, your pedal rod will need to move that amount, without going to far ( pedal stop ) to prevent damaging the master, at the same token you will need a half inch to quater inch of pedal freeplay to insure there isn`t any pressure on the booster/master....

[KJSR]

Read this....

http://www.mpbrakes.com/uploads/docu...alratiopdf.pdf

['65 chevy lover]

I did a bit of research on the POL website ( this is where I purchased my brakes and booster ) and discovered this info.



63-66 Chevy C-10 Truck, Power Booster Kit
January 29th, 2009

BB-T6366NOTE: Booster may differ from picture depending on type of booster options you have chosen.

STEPS: Read these instructions carefully!
IMPORTANT: This kit is assembled for shipping purposes only! Be sure to check all nuts and bolts for adequate torque prior to use. Don’t forget!

1.Remove original master cylinder, pedal clevis and hard lines.
2.Remove master cylinder from power booster as you will need to bench bleed it prior to bleeding the system. Inexpensive bleeder kits are available at any auto parts store for minimal cost. We also sell a bleeder kit. Install your pedal clevis onto booster. NOTE: Booster pushrod may need to be trimmed to fit.
3.Install the booster onto the original studs that mounted the original master cylinder to the firewall. You will need to mark and drill the two remaining holes that mount the bracket to the firewall. Some trucks mounting studs are diagonal, this is normal. NOTE: Some firewall studs were course thread and some were fine thread, you will need to supply the appropriate nuts for the installation!
4.You will need to drill a 3/8” hole 1-1/2” lower than the original clevis hole in pedal. Mount the heim joint onto the lower hole with supplied thick washer between the pedal and heim joint. Check for proper adjustment by making sure the brake pedal is all the way up and no pressure is being applied to the booster. Be sure to tighten the clevis jam nut.
5.Mount your bench bled master cylinder to the power booster. Connect all appropriate hard lines and bleed the system. NOTE: ON GM MASTER CYLINDERS, THE FRONT PORT IS FOR THE FRONT BRAKES AND THE REAR PORT IS FOR THE REAR BRAKES.
6.If you are running disc brakes be sure to have the proper proportioning valve kit for your application.
7.Double check all of your work and proceed to check the system for any leaks.
8.Be sure to hook up your vacuum line to the appropriate port on the manifold.
Recommendations:

1.We highly recommend that you perform a vacuum check on your particular engine. Acceptable vacuum numbers would be from 15in/hg to 22in/hg. For those who have lower numbers we offer a vacuum pump. Call for details.
2.We also offer disc brake master cylinders and proportioning valves for those who do not want to run power brakes. Call for details.

[Greg63]

Thanks for the advice.
Greg.

[Trsmotrhed]

Thats for the info. I'll have check mine out now.
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