M886 brake issues

[meg3068]

Have m886 lifted with humvv tires and wheels. Brakes feel soft and doesn't stop as week as it should. New calibers pads rear shoes and wheel cylinders as well as replaced all flex brake limes and master cylinder. Brakes have been bleed twice. Any help or suggestions welcome. Thanks in advance.

 

[NDT]

Did you bench bleed the master cylinder before install?

 

[Bob H]

taller tires take up brake pedal & require more foot pressure.
That being said, I once did the brakes on an ambulance, there wasn't anything wrong with the master cylinder but I figured I should replace it can't hurt. right?
Well after months of beating my head against the wall, I learned it was the "new" master cylinder that was bad!

 

[meg3068]

Yes I did. Pedal still feels spongy it doesn't have the slow bleed down like most I have seen with internal leaks more like low hydraulic pressure in the system.

 

[nattieleather]

You probably still have some air in the lines. Try rebleeding them.

 

[michigandon]

taller tires take up brake pedal & require more foot pressure.
That being said, I once did the brakes on an ambulance, there wasn't anything wrong with the master cylinder but I figured I should replace it can't hurt. right?
Well after months of beating my head against the wall, I learned it was the "new" master cylinder that was bad!

Had this same problem after installing a "rebuilt" master cylinder. Installed a *new* one and all has been well ever since.