Hello, I have Ford Bronco 1995. I replaced stock front IFS axle to straight Dana 44. All parts from knuckles (incl knuckles) out are 8 lug setup from 4x4 F250 - 1979. I did that to accommodate 37" tires. This setup uses dual piston calipers that are one piece setup from F250 - 1987. I have brand new brake pats, rotors are not brand new but very little used in great shape. I rebuilt both calipers - everything is new - all pistons & seals. I also upgraded to brake booster from F250 that came with master cylinder - all new. Booster is reman from Autozone. I've been driving the truck with this setup for about 500+ miles now. Now with front truck on jack stands (of course I have 4x4 disengaged) front wheels should be spinning rather freely or with ease - with wheels on. I can spin front wheels without a lot of effort but they turn only 1/4 to 1/2 the rotation. There's definitely a drag because when I remove wheels and calipers the rotor spins freely for several rotations. When I compress the caliper pistons with clamp and re-install calipers and wheel - it spins several rotations - as it should be. As soon as turn engine on and use brakes again - at first brakes are soft and then they became hard and firm - resulting in significant increase of drag. Is there any adjustment available to caliper or master cylinder or booster so the pistons are not so tight? The drag seems to be same on both wheels. I need to get rid of or reduce that drag. Thank you.

 

The booster could have an internal leak and causing the brakes to actuate ever so lightly . Or a bad booster check valve . Try this...disconect the booster hose and plug the hose and the fitting. Perform your test again and see if it drags.

 

Hi HIO Silver - thank you for quick response and advice. I'm not sure I fully understand your suggestion. Do you suggest I unplug the booster hose while engine is not running and then plug it back in? The booster and master cylinder are brand new - under warranty from Autozone and on one of the warning labels on the booster was do not unplug the booster hose while engine is running - or it will void warranty. Please explain in more details. Thank you.

 

No not while running . Configure as if the booster is not there...as if it has manual brakes.

Don't be overly confident the new or reman parts are never bad. They can be and have been in more than a few instances in my experience.

 

Oh I see. OK I'll disconnect the hose and rotate the wheels. Not sure how this could help thought? Does the booster release the pressure to the caliper - when the hose is disconnected - and pistons in both calipers retract a bit so wheel will spin easy?

 

Let's start over... configure as if it has manual brakes. Verify the wheel pins freely withe the engine off. Then start the engine, apply the brakes a few times, and the see if the brakes are dragging. Shut off the engine and configure with the booster hooked up. With the engine off, verify the wheel spins freely. Start the engine, apply the brakees a few times and check if the brakes drag . If they do drag then the problem isnwith the booster.

 

Ok got it. Will do that. Thank you for advice.

 

A common cause of brake drag is a problem with sticking calipers. Less common (but I had it once) would be deteriorated flex hoses. They can collapse internally and prevent return flow of fluid. Also less common would be a drum type master with residual pressure valve that keeps some pressure on the discs. If you can check/eliminate any of these problems that would help.

 

And I'll add that what you feel as "slight drag" when turning a tire with the hand quickly becomes "no drag" in use on the roadway. The pads and pistons will ease back off the rotor in real use. If pistons or calipers or a bad line are causing a no release situation, that wheel and tire ain't gonna free roll much. What you are likely feeling is the brakes as they rest after you last applied them just before you jacked the front end up to "rotate the tire testing". If you can easily pry the pads back away from a rotor just a hair using a brake spoon .... so to will real world use push them back.

I tell ya', that "I can spin front wheels without a lot of effort but they turn only 1/4 to 1/2 the rotation." sounds OK to me. I'ld drive her a few miles, just normal like, and then pull over and check for abnormally hot brakes. Some heat is normal. Also take special note of any pull developing.

Chances are you don't have a bad hose or bad caliper on both sides at same time, but it can happen.

 

Thank you all for your inputs and advice. I'm almost 100% sure that brake hoses are fine - they are less then 1 year old premium braided extended lines. What I'm not certain about are calipers because I rebuilt them myself. I'll try - in my quest to get rid of that drag - to resurrect the old original calipers that are two pieces bolt together type and swap them in and do test again. Thx again.

 

Are your caliper slides and caliper mounting points clean free of rust and did you use antiseize grease on them.

 

Hi, yes caliper slides and mounting points are clean - no rust. I did not use grease or anti-seize.