Rear disc brakes grabbing too hard

[Bruce and Jenna]

Today, thanks to a warning by a passing RVer, I learned that both my rear disc brakes are grabbing much harder than the front ones. The driver side tire smokes, the curb side tire skids.

I have not changed the setting in the truck brake controller in three years.

No work on the brakes at all. Guy changed my Dexter suspension equalizers coupla weeks ago.

Of course, I have a Dexter electric over hydraulic brake actuator, less than one year old. Wouldn't think this is a factor, since only only one hydraulic line runs out of it for all four brakes.

[Still Working "NOT"]

You may need to adjust the brakes. I don't know if they self adjust like cars did or you manually adjust them

[rockintom]

Originally Posted by Bruce and Jenna

Today, thanks to a warning by a passing RVer, I learned that both my rear disc brakes are grabbing much harder than the front ones. The driver side tire smokes, the curb side tire skids.

I have not changed the setting in the truck brake controller in three years.

No work on the brakes at all. Guy changed my Dexter suspension equalizers coupla weeks ago.

Of course, I have a Dexter electric over hydraulic brake actuator, less than one year old. Wouldn't think this is a factor, since only only one hydraulic line runs out of it for all four brakes.

Based on the little info given.......I would first check the brake pads and rotors for wear. Cheap as it is only a visual. But if you havta replace anything on a Dexter brake you'll learn what expensive is!!! Good luck!

[rockintom]

Originally Posted by Still Working "NOT"

You may need to adjust the brakes. I don't know if they self adjust like cars did or you manually adjust them

Still, If you are gonna be my backup.....get with it. These are disc brakes!!!! SKIA II Smart allick!!!

[Bruce and Jenna]

What would make both brakes on the same axle stop too hard? I can't say if the front brakes are too weak along with the rear ones too strong, but that's a possibility too....

[Still Working "NOT"]

Originally Posted by rockintom

Still, If you are gonna be my backup.....get with it. These are disc brakes!!!! SKIA II Smart allick!!!

Realize that after I went offline. HUA working well tonight

[rockintom]

Originally Posted by Bruce and Jenna

What would make both brakes on the same axle stop too hard?

Both pads and/or rotors worn out on that axle. Take 10 minutes and crawl under with a light and take a look. Easy things things first.

[Workshop]

Sorry Bruce but I have electric, I understand the basics of Hydraulic brakes and after looking on Dexters site wasn't able to find anything that would give any insight to your problem. Here's a link to Dexter's Troubleshooting guide Installation guide.

I agree that having one axle with a hard braking problem being feed by a one line system is puzzling. I also agree to look as the hubs/disc area. I would also look/follow the hydraulic lines back towards the front to insure their condition. Don't know how your lines are run...but the diagram shows each axle saperate and connected to a main line by a 'T'....?

As you had your equalizers changed...I would inspect that area as well. don't know if the lines run through that area and could have been danaged....know it has been several weeks ago.... but if the hydraulic brakes are staying engaged, it means that the fluid that engaged them isn't being released fully or something is hanging them up at the hub/fluid.... Fluid or mechanical?


Sorry couldn't help more.

workhorse

[rockintom]

Originally Posted by Workshop

Sorry Bruce but I have electric, I understand the basics of Hydraulic brakes and after looking on Dexters site wasn't able to find anything that would give any insight to your problem. Here's a link to Dexter's Troubleshooting guide Installation guide.

I agree that having one axle with a hard braking problem being feed by a one line system is puzzling. I also agree to look as the hubs/disc area. I would also look/follow the hydraulic lines back towards the front to insure their condition. Don't know how your lines are run...but the diagram shows each axle seperate and connected to a main line by a 'T'....?

As you had your equalizers changed...I would inspect that area as well. don't know if the lines run through that area and could have been danaged....know it has been several weeks ago.... but if the hydraulic brakes are staying engaged, it means that the fluid that engaged them isn't being released fully or something is hanging them up at the hub/fluid.... Fluid or mechanical?


Sorry couldn't help more.

workhorse

Work,

As usual, fine material you share!! Maybe I can shed just some llght on the subject. Regarding running of the brake lines on trailers with disk brakes, there is only one line coming from the brake actuator mounted in the front bay area. Then it splits in two lines when it meets the axles to feed both brakes on each axle. Unfortuneatly, if you had a major leak anywhere in the hydraulic system on a trailer.......you've lost ALL brakes on the trailer.

Just to give you something else to think about.....The rear brakes on a trailer always lock up before the front in a super hard stop. When you're making an emergency stop the inertia moves or shifts forward and in an trailer that means the brunt of the braking shift to the front axle(s), thus skidding the rear the tires first. Remember, on this system setup, you have equal hydraulic pressure on all brakes. Bruce's issue could be as simple as the controller gone haywire and allowing too much braking on a normal stop (as if the gain was set too high).

In a basic automotive braking system we use a dual hydraulic system so if you have a hydraulic failure in one system, you've got the other as a back up.......chances are very slight both system fail at once. Regarding the braking front to rear we use a porportioning valve arrangement to control front to rear braking to reduce excessive braking in the rear to reduce the chance of skidding.

I know someone gonna come back and give more advanced systems used on today's car and trucks.....but I'm just giving the very basics so folks can understand that trailer brakes, even disk brakes, are still crude in comparison to automotive. That said, I would never tow a trailer again (that I own) without disk brakes. Disk brakes are the best brakes we have in the trailer world. End of sermon!!! Should I pass the hat??? rockin'

[Jim & Bona]

Originally Posted by rockintom

...... Disk brakes are the best brakes we have in the trailer world. End of sermon!!! Should I pass the hat??? rockin'

Ditto on Tom's comment regarding disk brakes. I first had hydraulic disk brakes on a '76 Airstream and would never again be without them.

Jim

[Bruce and Jenna]

Thanks as always for your ideas and help.

The rear brakes only lock up when I apply them. Not dragging otherwise as far as I know. I haven't seen them myself. But DW says that the curb side rear locked and skidded as I passed by and hit the brakes. Street side brakes emitted smoke and rubber smell as I applied them past her.

I inspected the brake lines and see no damage at all. Likewise the rotors. No apparent difference between the front and rear, no real difference among the four at all. I cannot see the surface of the pads and don't want to try to remove them.


The equalizers look OK, as far as I can tell. Pretty simple gizmo bolted onto the hanger and the springs.



I like Tom's idea that the truck brake controller is sending an outsized signal to the brake actuator. It certainly makes the most sense, in light of his explanation that the rear brakes grab harder than the front ones. Guess I could test the theory by backing up at 30mph and applying the brakes, to see if the front ones skid instead?

Or maybe the actuator is working too hard? It's a factory rebuild, just three months old.

It's Labor Day, when no one does. I think I will test it again on Wed, when I leave. Back off the controller setting and see if I can stop the problem. If this works, I'll tow down to the dealer in Eugene, OR, who I hope can look at my problem slide again. Ask him to gaze at the brakes and equalizers. If OK, I'll take the truck to Ford to test the controller. Assuming they know how to test such a thing. If I can't stop the skidding with the controller, I'll find someone locally to look at the trailer.

Unless anyone else has other suggestions.

PS I just added this pics to show SKIA that I can crawl under the trailer.

[Bruce and Jenna]

I backed off the setting on my Ford integrated brake controller one click. From 6.5 to 6.0. No more skidding. Of course it’s hard to judge when you’re moving. But I don’t see any smoke emitting from the tires when I brake. And DW says it looks fine.

On the other hand, here is the text of two emails from Dexter. Note Duane says that the “leaf spring suspension with an equalizer the dynamic forces during stopping will generally cause the front axle to skid first.” So why would the rear axle skid?

====================================
First email
I cannot readily explain why the back axle would lock up and slide the tires and the front axle does not.
Any modifications that we do to actuators shipped from here at DEXTER AXLE Headquarters are only to improve reliability and durability. There are no performance upgrades. Occasionally some actuators have more pressure output potential than others but this is just due to manufacturing tolerances.
The actuator (pump) produces the same pressure for the entire brake hydraulic system. i.e. all brakes will always see the same pressure as long as there are no restrictions in the hydraulic lines.
If the back axle is carrying less weight then it would be more likely to lock up and slide the tires. If you have Torflex suspension and the trailer is lower in the front than the rear, then the back axle will be carrying less weight.
You may have to adjust the “Gain” setting on the Ford Integrated Brake Controller (IBC). This not unusual and is frequently done to compensate for changing loads or changing weather or road conditions.

Second email
Weight transfer during stopping definitely can be a factor, especially if you have the Torflex suspension. If you have leaf spring suspension with an equalizer the dynamic forces during stopping will generally cause the front axle to skid first.

[rockintom]

Thanks for the update....I surely wouldn't want to debate Dexter's email, but guess what? When my gain is set too high, it skids the rear tires first.......and when your gain is too high......guess what.......it skids the rear tires first....Hmmmm.....I'm sticking to "what is" and not what theory says it should do.

I wouldn't be scared to run the controller back to 5.5 and see how it works. Based on my experience with the brakes on my last rig or this rig....the brakes have more stopping power when they are warmed up.

Glad it's working out for ya. Every once in a while 'ol SKIA gets one right. My lucky day. rockin'

[Bruce and Jenna]

Originally Posted by rockintom

Glad it's working out for ya. Every once in a while 'ol SKIA gets one right. My lucky day. rockin'

And my lucky day! Thanks again!