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Old 06-21-2007, 06:08 AM
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Brake Pedal ratio: manual-to-power conversion

Shopping for a manual-drum-to-power-disc brake conversion for my '64 Mercury Monterey, I stumbled across a tech article at mpbrakes.com talking about pedal ratio (basically the amount of leverage your pedal is capable of exerting on the master cylinder).

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

My factory-stock manual drum set-up has a pedal ratio of 6:1 (12" long pedal, 2" from pedal bushing to push rod).

Looks to me like Mercury used the same brake pedal and pedal bracket regardless of manual or power brake systems. I've checked the Lincoln-Mercury parts manual, and I've studied the shop manual... there is not a different pedal setup or part for power brakes. (What I haven't done is find an old Merc or Ford with power brakes and compare - I don't have a parts car!)

Here's my question: is pedal ratio a big deal or not? if this is important, then my options are (help me out here!) - stick with a manual disc conversion, or find a different pedal / pedal bracket setup to reduce my pedal ratio down near 4:1.

HELP!!!!!

Thanks
Walt

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Old 06-21-2007, 08:11 AM
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Many times Ford used the same pedal. As a general rule, 6:1 is on the outside edge of the range of pedal ratios for power brakes, but you could go up a size on your master cylinder to make it feel better.

Depending on the size of your calipers, if you set up your new power brake system with a 11" booster and 1" bore master and bleed it properly and you still have a low soft pedal, put an 1 1/16 or 1 1/8" bore master cylinder . If you are using a 7" or a 9" booster you probably can use the 1" and be ok.

Some of the manufacturers of retrofit power brake kits will supply an angled booster bracket that enables you to drill a new pushrod hole lower on the pedal, so you can get the ratio closer to 5:1 (drill your pushrod hole 1/2" lower), or if you really want to be at 4:1 drill it 1" lower.

As your Mercury is a somewhat rare car to be converted to power brakes, be ready to do some fine tuning on the system if you use aftermarket conversions.

Masterpower is a good company, but you still have to mess with their products sometimes.

I have started dealing with a company called Brake Tech Solutions, Anwar, (the owner), is very knowlegeable and helpful. I have found that if he could not help me with a weird application, he will give me the name of a source that may be able to help.

That's a true hotrodder

Later, mikey
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Old 06-21-2007, 06:12 PM
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Anwar at BTS

Quote:
Originally Posted by powerrodsmike
I have started dealing with a company called Brake Tech Solutions, Anwar, (the owner), is very knowlegeable and helpful. I have found that if he could not help me with a weird application, he will give me the name of a source that may be able to help.

Later, mikey
I've heard good things about BTS from a local custom builder. I shot a quick email to Anwar and he's been very helpful. I plan to give him a call tomorrow to finish chasing down some final details about his conversion kit. I'll let you know how the conversion goes.
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