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#1 |
Registered User
Join Date: Sep 2014
Location: USA
Posts: 2,249
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Brake Pedal Travel?
I'll post this here since I have a '68 GM 12-bolt rear in my truck.
7" POL dual chamber power booster, Mustang II front discs, GM rear drums. With the engine off I have just 1 inch of pedal travel. With the engine running I have about 3 inches - about half way to the floor. This seems like excessive pedal travel - is it? I have bled the MC, bled all four brakes, adjusted the rear drum brakes, and adjusted my booster pushrod. Brakes work great, had to lock 'em up recently when a deer jumped out in front of me. Since there's a big difference in running/not running pedal travel I suspect the issue lies in the booster? I did lengthen the pedal arm a couple of inches, but I wouldn't think that would account for that much difference. What am I missing here? __________________ 1951 Chevy Panel Truck
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1951 Chevy Panel Truck |
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#2 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,621
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Re: Brake Pedal Travel?
How did You lengthened the pedal arm?
Did you change the pedal ratio? |
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#3 | ||
Registered User
Join Date: Sep 2014
Location: USA
Posts: 2,249
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Re: Brake Pedal Travel?
Quote:
Quote:
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1951 Chevy Panel Truck |
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#4 | |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,621
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Re: Brake Pedal Travel?
Quote:
An easy test is to drill a new pushrod hole in the pedal about 1 1/2 inches further from the pivot point. |
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#5 |
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![]() Join Date: Oct 2018
Location: Tiffin Ohio
Posts: 74
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Re: Brake Pedal Travel?
Not to steal the thread, but how do you figure out pedal ratio? And which way would the op move the pivot point? I may need to do this on my 51 3100 and thought I would ask. Maybe it will help someone else too.
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#6 |
Registered User
Join Date: Feb 2013
Location: Upland, Calif
Posts: 698
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Re: Brake Pedal Travel?
obviously your booster is working. It's the master bore diameter that determines the pedal travel, well technically the bore diameter in relation to the caliper bore sizes. I would guess you might have a 1" bore master, changing to an 1 1/8" master will bring the pedal up an inch or maybe a little more. The smaller the bore of the master the higher the pressure BUT less fluid is moved. The larger the bore the pressure is lower but the pedal doesn't have to travel as far to move the same amount of fluid. The only time you use a small bore master is if the caliper pistons are really small. Since you have Mustang II I would bet you have S10 calipers which have 2.5" pistons. That size is borerline between the two master sizes. Since you don't like the way it is now change to a 1 1/8" master and it will come up and will be a little firmer feel also.
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1957 CHEVY 1/2 TON SHORT BED 1940 FORD 1/2 TON SHORT BED |
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#7 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,621
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Re: Brake Pedal Travel?
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#8 | |
Registered User
Join Date: Sep 2014
Location: USA
Posts: 2,249
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Re: Brake Pedal Travel?
Quote:
Plus I found about 3/4" of free play in the pedal that I could adjust out. I was looking for zebras when in fact it was just horses.
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1951 Chevy Panel Truck Last edited by MiraclePieCo; 09-27-2019 at 09:21 PM. |
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#9 |
Registered User
Join Date: Jan 2007
Location: Puyallup, WA
Posts: 1,662
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Re: Brake Pedal Travel?
Stock bore size
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72 C10 lwb fleetside -stock 350/350 combo |
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