Author Topic: rear brake settings on a 230- 113 euro (drums)  (Read 3923 times)

gatorjaws

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rear brake settings on a 230- 113 euro (drums)
« on: March 30, 2011, 18:44:24 »
I went through my rear brakes a few months ago. New bearings, wheel cylinders,seals, shoes and gaskets. What I was wondering was where do most of you 230 owners set the shoes for  good balanced braking? When I put everything back together I set the brakes so that there was just a little drag when I spun the tire. Everything worked fine but I was just wondering if a little tighter is better or if I was running too tight. I just don't the front brakes doing all the work or locking up the back before the front even start to grab. I don't hotrod my car but I do drive kind of fast so I use a lot of brake.

ja17

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Re: rear brake settings on a 230- 113 euro (drums)
« Reply #1 on: March 31, 2011, 13:22:16 »
Hello Gatorjaws,

The adjustment of the rear brakes only effects pedal travel when braking. The hydraulics and configuration of the master cylinder, the diameters of the hydraulic in the system, is what determines the woking brake pressure in the brake system. You should be fine as long as everything is working and your brake pedal travel and height are ok.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

gatorjaws

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Re: rear brake settings on a 230- 113 euro (drums)
« Reply #2 on: March 31, 2011, 23:23:53 »
Thanks, I was thinking that the closer the shoe was to the drum the sooner it would grab. If it grabs too soon then the rears would be braking before the front. Is this not true?

ja17

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Re: rear brake settings on a 230- 113 euro (drums)
« Reply #3 on: April 01, 2011, 00:14:06 »
Hello Gatorjaws,

On most modern passenger  cars the rear brakes  activate before the fronts, then the fronts kick in and do most of the braking.
The sequence is...............initial pedal travel fills all cylinders, front and rear, moving the rear shoes to the drums and the brake pads to the front discs. As pedal pressure increases, slight  rear braking occurs, next the front brakes kick in and do most of the braking. The rear brakes will lock up eventually only under the most severe braking and usuallyafter the front brakes have locked up.

 If  the rear brake adjustment is loose, it take more initial pedal travel to move the shoes into position. Braking by front and rears remains functionally the same. No real breaking occurs until all the friction pads are next to their drums or their  rotors.

The internals of the master cylinder are designed with two sequential stages. The master cylinder controls when each axle does its braking.  Some cars have  different bore diameters in the master cylinder to vary pressure in the front and rear circuits . Most master cylinders are designed  to lightly pressurize the rear axle first then the front axle. Different diameters of the pistons in the front calipers and the rear brake cylinders also regulate the amount of braking force at each axle. In addition the square inch area of the brake friction surfaces, front and rear,  also determines which axle does more or less braking.

On the later W113 cars a rear proportioning valve was added to tweek braking characteristics.

On race cars a main proportioning valve or dual master cylinders can be adjusted to change braking characteristics for variable road surfaces.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

gatorjaws

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Re: rear brake settings on a 230- 113 euro (drums)
« Reply #4 on: April 03, 2011, 04:52:04 »
So by adjusting the cams on the rear brakes to bring the shoes closer to the drum the brakes would make contact sooner, right. But you don't want them to engage too soon or they would lock up before the fronts were really working.

ja17

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Re: rear brake settings on a 230- 113 euro (drums)
« Reply #5 on: April 03, 2011, 13:01:54 »
Hello Gatorjaws,

Tighter adjusted rear brakes would "pressurize the system sooner"  (rear and front) and it would  minimize brake pedal travel. The time  intervals between front and rear braking is not changed and is not adjustable no mater what you do with the rear brake adjustment. 

Adjust the rear brakes as per BBB. You cannot change the sequence of front and rear braking it is controlled by the design of the master cylinder.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

gatorjaws

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Re: rear brake settings on a 230- 113 euro (drums)
« Reply #6 on: April 03, 2011, 19:03:07 »
OK, thanks for the discussion & the info!