Brake pedal travel with 4wheel disc

Blackdog

Blackdog

Hillbilly Deluxe
Joined
Jan 31, 2008
Messages
801
That is my question. Since my truck now has a 80 disc in the rear I am curious how far the brake pedal goes for you guys that have ran full discs for a while? I have done an old school brake bleed all the way around and the pedal wasn't far from the floor using it decently to stop. Next I did a bleed with a new bleeder kit and on a hard stop the pedal would go half to the floor and I could feel the ABS kicking in.

Now before when I had drums in the rear I just barely had to push the pedal and that was all the braking I needed. Just curious if 4wheel disc should act the same as drums in the rear or is my brake pedal about where it should be or do I need to do more bleeding?
 
Im not 100% sure but I think that the master cylinders are different for disc and drum brakes.
 
01 smoke said:
Im not 100% sure but I think that the master cylinders are different for disc and drum brakes.
Click to expand...

Well, If that is the case I am pretty sure I have the master cylinder on the parts truck the axle came from.
 
i probably move my pedal 1 full inch for a panic stop.....normal stopping is VERY little pedal.
 
With drums, you have a residual pressure check valve that keeps pressure on the shoes even when the brakes are not applied. This is not needed with discs. I'm not sure if this valve is located in the master cylinder or if it is located in the combination valve, etc. (I don't think this is related to your problem, as you would just burn through pads much quicker than typical.)

It does sound like you have way too much travel...I barely push my pedal down to stop. $.02
 
Not 100% sure but I would assume that either the Master or Proportioning Valve (or maybe both) are different on the 4 wheel disc trucks. Just generally speaking from years of doing this type of swap on various vehicles, you usually need a different master cylinder or prop valve (or both) to get the most out of the swap.
 
I have the same axle swap on my 99 & it does not take much pedal at all to get it to stop. I did not change any parts but the axle.
 
Well, I did check the numbers on the master cylinder and they were the same but I don't have the prop valve on the parts truck to check those numbers. I did old school bleed all the brakes six times each and found alot of air in the front lines and after that the brakes act and the pedal travels about the same as my Excursion which is the only other 4 wheel disc I got to compare it to.

If I don't like how it is acting I will look into the prop valve but right now I think it is good. Just need more seat time.
 
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