rear brake pressure - PowerStrokeNation : Ford Powerstroke Diesel Forum
 
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post #1 of 5 (permalink) Old 11-17-2011, 05:28 AM Thread Starter
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rear brake pressure

is there a pressure regulator that regulates the pressure applied to the front and rear breaks.
my rear breaks are getting more pressure then the front it feels like, sometimes loocking the rears up in the morning when the road is wet.

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post #2 of 5 (permalink) Old 11-17-2011, 08:32 PM
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Re: rear brake pressure

There is the RABS valve on the frame rail under the driver's side. Is your ABS light illuminated? Cheers!

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post #3 of 5 (permalink) Old 11-17-2011, 09:24 PM
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Re: rear brake pressure

Pull your drums. I would say leaky wheel cyl or axle seal leaking

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post #4 of 5 (permalink) Old 11-17-2011, 10:07 PM Thread Starter
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Re: rear brake pressure

Quote:
Originally Posted by Patrick Feeley View Post
There is the RABS valve on the frame rail under the driver's side. Is your ABS light illuminated? Cheers!
the abs light isn't lit up

97 7.3l cclb 6" lift on 35s
stage 1's
idp fuel
swamps tunes
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post #5 of 5 (permalink) Old 11-18-2011, 01:19 AM
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Re: rear brake pressure

I can offer my understanding, I may be wrong... The surface area of the pistons in your master cylinder have a correlation with the surface area of the wheel cylinders. There are two pistons inside a common bore in the master, one sends fluid to the front section, one to the rear. They are almost always the same diameter as each other. Engineers determine the amount of pressure differential they want supplied between the front and rear friction surfaces, which will vary depending on type of rear brake. Drums don't require as much pressure do to mechanical advantage inherent in their design. You will notice the large pistons that are on your front calipers vs the small cylinders inside your drum assembly. The differential valve often mentioned in brake circuits only senses when there is a change of fluid pressure between the front and rear circuit, it does not control the pressure difference. With different sized pistons at the wheels, the same pressure applied will result in different amounts of clamping force. I have had a few trucks with heavy duty drums in the rear, and grabbing hard for the first few applications in the morning or after parking for a day, are usually exacerbated by damp air causing the drum surface to oxidize slightly, and therefore increase their coefficient of friction. As mentioned in an earlier post, shoe contamination can also have a similar effect. I found that during tire rotations I would check for brake or axle seal leaks and adjust my shoes on the rear a little bit tighter than recommended clearance helped a little. I just got used to the first couple grabs in the morning and they were fine the rest of the day. Now to see if anyone concurs with me or calls me a fool... You can enjoy guessing who may have your answer.
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