Brakes rubbing on new disc brake system

[bruceb58]

Probably air in the line
Unlike drums that use springs to retract the pads, disc use the push-pull of the actuator cylinder to extend and retract the cylinder.

BTW, the only difference between a drum brake master cylinder and a disc brake master cylinder, is that the drum brake master cylinder has a residual valve to maintain a few PSI of pressure in the lines at all times. The master cylinder does not pull brake fluid.

 

[dingbat]

Suggest you make your comments on the subject at hand instead of insulting me.

Ok, you're miss informed......lol

Every disc brake actuator I've ever worked with was driven by a single acting, spring return piston actuator. This spring is in effect your return spring, unless you have air and or other parasitic losses of a greater volume than the displacement of the actuator.

If you believe this isn't the case, leave the bleeder cracked when you release actuator and see if it doesn't suck air back into the caliper.

 

[dingbat]

If your question was about pressure at the caliper, each caliper will have identical fluid pressure once the pads contact the rotor.

True, assuming you have an insignificant volume of free air trapped in the system, then all bets are off.

 

[bruceb58]

See that single lip seal? That prevents 99.9% of any suction from happening. As a test while you are bleeding your brakes, depress the master cylinder fully with the bleeder screw open and close the bleeder screw as you release the master cylinder. The caliper pistons will not move at all. You can actually hold your finger over the bleed screw the suction pressure is so low. If you have actually pushed a caliper piston back in its bore before, you will realize how much suction pressure would be necessary to do that.

Even with air in a system, the pressure will be identical at each caliper during braking. When there is no braking there will be 0 PSI at the system.

 

[smokeonthewater]

:shakes head in disbelief:

 

[Idlespeedonly]

I have always wondered how some people come up with their screen names..........

 

[98Shabah]

I'll add in here an experience I had on a saturn vue with what I thought was a locked up front right brake caliper. I figure it was a frozen caliper that was keeping the pads squeezed against the rotor, causing the rotor to become blistering hot, but after I let the car sit for a few hours and jacked the front end up the caliper was no longer frozen.. Odd.. Ended up being a bad rubber brake hose on that caliper, it had a metal clip around the hose where it connected to a bracket but whatever was inside the hose to keep that clip from crushing the hose had failed so the hose was essentially acting like a one way valve letting pressure into the caliper but not back out... The pressure took hours to slowly bleed back out of the caliper past the obstruction in the hose. A new brake hose fixed it.

 

[MercGuy]

Ok, you're miss informed......lol

Every disc brake actuator I've ever worked with was driven by a single acting, spring return piston actuator. This spring is in effect your return spring, unless you have air and or other parasitic losses of a greater volume than the displacement of the actuator.

If you believe this isn't the case, leave the bleeder cracked when you release actuator and see if it doesn't suck air back into the caliper.

I think there is a flaw in your logic. See the hole in the top of the MC that opens to the reservoir? When the MC releases it will fill with fluid from the reservoir to make up for the reduction in pad material as the pads wear.

In reality the pads don't retract much, maybe a few thousands from the o-rings. Instead they just stop pushing. Any run out from the disk will tend to push them our just a hair.

Sure, cracking the bleeder screw can introduce some air into the caliper, only because that is the path of least resistance. In fact, it is a common practice to bleed brakes by simply attaching a hose from the bleeder screw to a small jar with some brake fluid in it. The suction created by the retracting MC is so slight that it doesn't even pull the fluid up the hose. If it doesn't pull the fluid up the hose it sure wouldn't retract a brake pad.

Just my $0.02

 

[UncleWillie]

I recently installed a Tie Down 12" vented rotor kit (including actuator) on my Escort Trailer. After bleeding the system, I took the trailer for a test drive. I noticed that the passenger side brakes are rubbing the rotor, while the driver side seem fine. Any thoughts?...

These are Newly Installed Brakes. A "Little" Rubbing is normal.
If you can spin the wheel with one hand and it will coast a half turn once you let go, it is withing reason for a new installation.
Check it again after a few hundred miles, and it will probably be fine.

If it takes anything more than light force to spin the wheel, something is wrong.
Immediately after installation, you should not expect brand new disk brakes to spin like they don't exist.

To the OP...
How much rubbing are we talking about?
Is the rubbing disk getting significantly hotter that the free spinning one?

 

[21BaylinerCC]

The side that is/ was rubbing was definitely hot compared to the driver side (not rubbing). It seems to have dissipated - I think you are right about them just being new... just needed to be "broken in" I guess. Thanks for all the feedback everyone!

 

[NHGuy]

Hey, I just read over your spirited discussion. No one mentioned the possibility that the slides are sticky. Check for that and use some brake grease on them if they, as I suspect, are.
While you have then out work the slides back and forth til they move freely. Assuming it's not a bad bearing allowing the wheel hub to tilt. Or a bad caliper that does not line up with the rotor. After all Tie Down is cheap imported stuff, I have a set and they work fine BTW. :lol:
I went to a trailer shop in my city to get some bearing covers for the Tie Down Super Lube bearing caps and the guy was pretty down on Tie Down stuff, sold me Dexter caps which fit great.

 

[AZSenza]

Great, I just bought 10" Disc System for my trailer from Tie Down...Maybe I should sell it before I attempt an install

 

[NHGuy]

No, don't sell em. just make sure they work. If they don't, explain why and get the right bits. You don't want to pay extra do you?

 

[bruceb58]

Great, I just bought 10" Disc System for my trailer from Tie Down...Maybe I should sell it before I attempt an install

See my post #14