Drive axle brakes

Topic: Drive axle brakes (Read 1577 times) previous topic - next topic

Drive axle brakes

August 07, 2018, 06:32:27 pm

Went into Les Schwab and had my drive tires replaced. And I was horrified at the condition of the passenger side brake rotor. It needs to be replaced. Anyone know if FT used off the rack Rockwell parts. And Does anyone know the model or a good source for those parts?

The coach never gave an inkling that the rotors were toast. Stops straight and true. No lack of braking power either. The inboard rotor faces are smooth which is why I was surprised at the condition of the outer face upon wheel removal. Lesson learned.

Re: Drive axle brakes

Reply #1 – August 07, 2018, 06:52:52 pm

The outers are the "lazy" side, with retraction requiring that the caliper slide WORKS.

If outers are bad, suggest a complete brake service by someone familiar with air disk brakes. And, install the Meritor helper springs.

Re: Drive axle brakes

Reply #2 – August 07, 2018, 07:10:01 pm

Quote from: bigdog – August 07, 2018, 06:32:27 pm

Anyone know if FT used off the rack Rockwell parts.
And Does anyone know the model or a good source for those parts?

bigdog,

Those parts are Meritor parts and they are "off the shelf" parts.
Here is what should work but YOU need to double check
4M brake manual
http://www.meritorwabco.com/MeritorWABCO_document/mm4m.pdf
rear rotor Kit 3218K167
slide pin Kit15016
pads Kit15625 PM
helper springs Kit 15018
There are other parts, but what you need will depend on damage found. This is just the basic stuff not anything to do with the actual calipers. If you need caliper rebuild kits they are also avalible.

Mike

Re: Drive axle brakes

Reply #3 – August 07, 2018, 07:23:55 pm

Quote from: wolfe10 – August 07, 2018, 06:52:52 pm

The outers are the "lazy" side, with retraction requiring that the caliper slide WORKS.

If outers are bad, suggest a complete brake service by someone familiar with air disk brakes. And, install the Meritor helper springs.

I'm not going anywhere near those myself. This is a job for an experienced pro. The shop I use mentioned that slide pins are a known issue on air disc brakes. I was just looking to get ahead on what parts I might need before they get to it on the week of the 20th of August.

Thanks for the info Brett. That goes for you to Mike.

Re: Drive axle brakes

Reply #4 – August 07, 2018, 07:26:01 pm

Quote from: bigdog – August 07, 2018, 07:23:55 pm

I'm not going anywhere near those myself. This is a job for an experienced pro. The shop I use mentioned that slide pins are a known issue on air disc brakes.

Totally agree-- both on having a pro do it and that pitted or seized slide pins can cause this issue.

Re: Drive axle brakes

Reply #5 – August 07, 2018, 07:35:47 pm

bigdog,

If the slide pins are bad I always put in new slide pin bushings in the calipers. That is KIT 15010

The thing about any disc brake caliper it has to have some type of slide for them to operate. No matter whether they are Ford, Chevy, Dodge, or ___________ (fill in the make) the calipers have to be able to move. Just because they are on air brakes makes no difference in issues. If any slide pin gets stuck due to dirt, mud, or what ever they will not let the caliper move.

Mike

Re: Drive axle brakes

Reply #6 – August 07, 2018, 08:00:09 pm

the caliper has to move on most systems unless you have the rotor on a floating bracket and pistons on both sides.
bigdog did you have the motorhome greased some where since your safety inspection when you purchased it? incorrect greasing will cause residual pressure behind the piston and drag the brakes

Re: Drive axle brakes

Reply #7 – August 07, 2018, 08:27:48 pm

My calipers needed the mentioned bushings.

Re: Drive axle brakes

Reply #8 – August 07, 2018, 08:32:09 pm

I will have all the brakes gone through.
I know the basics of brakes.
It's just that mine gave no indication via pulling to one side, Hot brake smell, Grinding, Squealing, Diminished braking power. Nothing that indicated anything was amiss.

It will all be sorted out shortly though.

Thanks for the help guys.

Re: Drive axle brakes

Reply #9 – August 07, 2018, 10:10:53 pm

OK, TWO, repeat two kinds of disk brake systems:

Fixed caliper: caliper does not move-- pistons on both sides of the caliper. More expensive/more complex. Have not seen them in air brakes. More expensive cars and very few motorhomes.

Sliding caliper: piston(s) on only one side so the "lazy side" has to be free to move toward the disk when applied and retract when released. Used on most vehicles as they are less expensive-- both hydraulic and air.

Re: Drive axle brakes

Reply #10 – August 08, 2018, 09:19:29 am

Won't help on a stuck pin but before every drive exercise your brakes by pressing the brake pedal to the floor after you hear your air pop off before you leave the campground. If the coach has been sitting a while I pump them a few times.

I do it while testing the turn signal, brake lights, and flashers after we hook up the toad. Helps keep the pins clean.

see ya
ken

Re: Drive axle brakes

Reply #11 – August 08, 2018, 09:30:25 am

Don't know if I would push the brake pedal all the way to the floor or not puts a lot of unnecessary pressure on things. A couple of light applications should be ok. But as always do what works for you.

Re: Drive axle brakes

Reply #12 – August 08, 2018, 11:02:45 am

And release the brake switch before you do any pedal pushing or you will be COMPOUNDING the brake pressure and that can lead to problems.
JohnH

Re: Drive axle brakes

Reply #13 – August 08, 2018, 11:23:59 am

The resistance you feel when you step on the brake pedal is caused by a spring in the pedal assembly. The brake pedal assembly may be ordered with a lighter spring that makes it easier to apply more brake pressure. Many vehicles with air brakes have a hand valve on the steering column to apply the brakes while stopped on an incline. These hand valves either have no spring or a very light spring that allows the hand valve to return to the normal driving position. Most of the hand valves are on vehicles with manual transmissions.

So, the spring in the pedal simulates the effort if you were stepping on your car brakes.

Leaving our house and heading down the steep driveway (817 feet plus a 120 degree downhill turn), I actually have to shift to neutral as the torque at idle overcomes the cold brakes and I get going too fast even with the pedal all the way down.

Some owners turn up the valve on the air compressor to gain a little braking ability. This is why it's important to check air pressure before heading down twisty steep downgrades. The parking brake is not going to do anything much to stop the coach in case of an air pressure failure on a downgrade.

Pierce

Re: Drive axle brakes

Reply #14 – August 08, 2018, 11:47:01 am

Quote from: Pierce & Gaylie Stewart – August 08, 2018, 11:23:59 am

Leaving our house and heading down the steep driveway (817 feet plus a 120 degree downhill turn), I actually have to shift to neutral as the torque at idle overcomes the cold brakes and I get going too fast even with the pedal all the way down.
Pierce

Also could be a symptom of your brakes being out of adjustment.

Re: Drive axle brakes

Reply #15 – August 08, 2018, 11:54:09 am

Quote from: Doug W. – August 08, 2018, 11:47:01 am

Also could be a symptom of your brakes being out of adjustment.

No, they work great once I have made a stop or two. I can lock up all six if I have to. You have to see how steep the driveway is. Bill Chaplin has driven up it. Too steep to go up in first so I have to back up where I have a good ratio.

Pierce

Re: Drive axle brakes

Reply #16 – August 08, 2018, 12:57:26 pm

Quote from: bigdog – August 07, 2018, 07:23:55 pm

I'm not going anywhere near those myself. This is a job for an experienced pro.

An excellent choice. The hub has to come off in order to get to the nuts and studs that fasten the rotor to the hub. The nuts are self locking and have to be wrenched off and on. No doubt they are rusty too which makes it even more difficult. I watched this being done and was glad it wasn't me doing it.

Re: Drive axle brakes

Reply #17 – August 08, 2018, 01:00:40 pm

Jerry,do you know or does anyone else know if these same brake parts are the ones that fit the U270?Looks like the pins and
springs are the same,not sure about the other parts.

Re: Drive axle brakes

Reply #18 – August 08, 2018, 01:20:35 pm

Quote from: John44 – August 08, 2018, 01:00:40 pm

Jerry,do you know or does anyone else know if these same brake parts are the ones that fit the U270?Looks like the pins and
springs are the same,not sure about the other parts.

I don't know John. I'm sure someone here will be along shortly that does know. But logic tells me that with the small weight diff between the U coaches and parts logistics in a small firm like FT. It would make sense to have the same braking system across the Uni-coach models. But coaches and their makers aren't always using logic when they make these toys.

Re: Drive axle brakes

Reply #19 – August 08, 2018, 01:28:30 pm

Quote from: John44 – August 08, 2018, 01:00:40 pm

Jerry,do you know or does anyone else know if these same brake parts are the ones that fit the U270?Looks like the pins and
springs are the same,not sure about the other parts.

I don't know if FT used different brakes on the unicoach bus style coach according to model number, but guessing they are the same. I know the front and rear rotors, pads, and calipers are the same on my coach. The slack adjusters and brake cans are different front to back. The rear brakes do more work so everything wears faster back there.

Re: Drive axle brakes

Reply #20 – August 08, 2018, 01:28:49 pm

The slide pins can pit after wearing through their chrome coatings. They can stick. The helper springs help them retract. No lube. Dry silicone. Rotor is heavy. Seals are tender, 2 guys to carefully reinstall them.

We changed our d2 valve to 110-130 for stronger brakes. Adjustable on the valve.

Full depression of the pedal actuates the self adjustment part of the caliper as far as I have read.

Fully depressing the pedal has unstuck my dragging calipers several times before I fixed them.

Not a job for the faint hearted. You need a press to replace the caliper bushings

Re: Drive axle brakes

Reply #21 – August 08, 2018, 01:33:21 pm

All this brake talk is just another example of how sitting around is tough on coaches.
I have owned and operated three 10 ton tractors over the course of ten years. In that ten years the average mileage on my trucks when sold was 400,000-450,000 miles. None of those trucks ever needed new brakes. They still had plenty of lining left and worked great and I hauled around and had to stop a lot more weight than our coaches ever have to deal with.

Re: Drive axle brakes

Reply #22 – August 08, 2018, 01:36:17 pm

S cam drum brakes?

Re: Drive axle brakes

Reply #23 – August 08, 2018, 02:11:36 pm

Quote from: Caflashbob – August 08, 2018, 01:36:17 pm

S cam drum brakes?

Yep. And they have worked extremely well on big trucks for many decades. The lining thickness was easy to see. Very little maint. needed. Just check that the auto slack adjustment was working.

Any way. We are likely dangerously close to going too far off topic for the tech section. General braking might be a good discussion for around the fire ring.

Thanks for the info, advice and part numbers.

Re: Drive axle brakes

Reply #24 – August 08, 2018, 03:09:25 pm

The disadvantage to Foretravel was the s cams brakes lack of a backing plate.

Use on a gravel road could have the front tires throw up rocks that could get in the rear brakes.

That's why OREDS had wedge brakes with a backing plate.

The disks make it hard to get stuff in them also.

I had truckers shatter drum brakes driving on logging roads hard then through a cold stream while hot.

The drums and shoes glazed as the rv'er s never got them hot enough

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