Air Brake - How free should front wheel spin in park?

[dansawyer]

The vehicle is a 2002 National Tradewinds on a Spartan chassis. While parked and leveling I inadvertently lifted a front wheel of the ground. Mostly out of curiosity I tried to rotate the wheel, to my surprise it did not move. I tried with 50 lb or so force.

The parking brake was on. The front brake has standard single chamber actuators, no spring brake.

[Jzack]

That is curious, it should spin freely. More investigation is needed. Try adjusting the slack adjuster would be the first thing I'd do.

[Dunrollin]

I have the same brake setup you do on 22.5 wheels with oil lubericating the bearings and when jacked up it is easy to rotate the wheel with your hand.

[Argosy]

That's too tight. At the least you need to adjust them, but as it's 20 years old pulling the drum and checking for heat cracks would be a good idea. That also gives you a chance to change the bearing lube, check the bearings, brakes and hardware. Doing the other side is also a good idea.

[BillJinOR]

The air E brake / park brake only applies the rear brakes , not the front.

[Rob_M]

It should spin freely. Sometimes a little brake drag is normal but you need to figure out whats up. Do you lube your brake mechanisms? It’s either brake drag of a tight or failing bearing… either will create extra heat.

When I’m on the road almost every time I fuel, I walk around and grab every hub to see if one is hotter than the rest. I would venture to say if you had done that you would have noticed that one being hotter than the rest either from brake drag or a tight or failing bearing.

[dansawyer]

Thank you. I thought it should spin way more freely then it did. Another issue to chase down.

Will pressing the brake to the floor loosen as well as tighten the adjusters? Or do I need to actually loosen the adjustor with a wrench?

I watched a video on wrench adjusting, I will have to identify where the adjustment is on these.

[Domo]

Originally Posted by Rob_M

It should spin freely. Sometimes a little brake drag is normal but you need to figure out whats up. Do you lube your brake mechanisms? It’s either brake drag of a tight or failing bearing… either will create extra heat.

When I’m on the road almost every time I fuel, I walk around and grab every hub to see if one is hotter than the rest. I would venture to say if you had done that you would have noticed that one being hotter than the rest either from brake drag or a tight or failing bearing.

Rob_M - excellent advice and don't forget the Toad hubs!

[FIRE UP]

Originally Posted by dansawyer

Thank you. I thought it should spin way more freely then it did. Another issue to chase down.

Will pressing the brake to the floor loosen as well as tighten the adjusters? Or do I need to actually loosen the adjustor with a wrench?

I watched a video on wrench adjusting, I will have to identify where the adjustment is on these.

Well Sir,
First, BEFORE you go adjusting ANYTHING in terms of "Slack adjusters" etc., there's a thing or two you need to do first. Second, an air brake pedal should NEVER go to the floor! The treadle valve shouldn't allow for that much travel.

As has been stated, yes, your emergency/parking brake only applies the rear brakes and has absolutely nothing to do with the front. So, obviously, when parked, the rears are the ones holding the coach in place. That means obviously that the fronts are free to spin. Slack adjusters pretty much NEVER self-adjust to a point they're TOO TIGHT!

Adjusting slack adjusters on an air braked coach is not rocket science. However, if you've NEVER done it before, or you've not witnessed it being done, you better make darn sure you find out through videos/books etc. on the procedure. Adjusting them too loose will cause excessive brake pedal travel and on an air braked coach, that does affect stopping distance acutely. Adjusting them too tight, causes excessive heat build up due to drag which, obviously is not good on both the shoes or drums, (if you have drums).

Now, again, BEFORE you adjust anything, the smart thing to do would be to get under there, in a safe manor, and with a full air tank, have someone press on the brake pedal while you witness the brake arm (the part that attaches to the slack adjuster) travel distance. There is a specific distance that brake arm is supposed to travel, based on brake can size. And the slack adjuster's adjustment, is what determines the distance.

IF you've been under there and observed that there is absolutely nothing in contact with the wheel/tire to prohibit it from free spinning, then it's quite obvious that something's amiss with the brakes. Is it possible the wheel bearing is too tight, not really. Can it happen? Well, if so, I highly suspect there's bearing damage already if that was/is the case.

Have you smelled any hot brakes, observed any smoking or haseing from around those front wheels after stopping and parking?
Scott

[dansawyer]

Thank you all. This turns out to be an actual problem. I took a quick trip out to the RV over lunch and used the front levelers to lift the wheel in question just clear of the ground.

It was not moving at all.

I then carefully examined both actuator rods. The stuck rod was extended further. I then took a short bar and used it as a lever and carefully, slowly move it in the direction of the position of the other arm. It felt stiff to move. It was not frozen, but stiff. The amount of force required was consitatant, it did not get easier as it went.

The wheel turned with very little force.

First: I believe the brake rod that rotates is called the 'S' rod. It is obviously in need of care. I will start with grease.

Second: Is the only mechanism to retract the actuator rod the internal spring? Once the S rod turns smoothly I can assess the condition of the spring.
Third: Now the potentailly bad part, the bearing oil looks dark. I suspect at a minimum it has been over heated. I will change the bearing oil.

(The wheel turned smoothly. I did not think to assess it for runout. )
What have I missed? I am planning a 5000 mile trip in 2 weeks. I am glad I thought to follow up on this. I could imagine a bad wheel bearing in the middle of South West no where at 6 PM.

[twinboat]

If you can get the clevis pin out, and back off the adjusters, you can rotate the S cam shaft more then you can now, while you grease it.

The more you can rotate it the better it will spread the grease.

Your backing plates should be removable so you can visually check the springs on the shoes.

Once ready to readjust the brakes. Turn the adjuster until you have about 1 inch of travel on the chamber rod. The self adjuster will handle it from there.

Stepping on the brake does not adjust the brakes. IF they stroke to far when stepping on the pedal, the adjuster only tightens them when you let off the pedal. If not out of adjustment, nothing happens, no matter what you do.

[nehog]

Originally Posted by dansawyer

It was not moving at all.

I then carefully examined both actuator rods. The stuck rod was extended further. I then took a short bar and used it as a lever and carefully, slowly move it in the direction of the position of the other arm. It felt stiff to move. It was not frozen, but stiff. The amount of force required was consitatant, it did not get easier as it went.

Does sound like a sticking S-cam shaft. When was the last time they were greased? If not recently (last six months...) then grease them, or have them serviced.

Originally Posted by dansawyer

The wheel turned with very little force.

First: I believe the brake rod that rotates is called the 'S' rod. It is obviously in need of care. I will start with grease.

S-cam and S-cam shaft is the correct term.

Originally Posted by dansawyer

Second: Is the only mechanism to retract the actuator rod the internal spring? Once the S rod turns smoothly I can assess the condition of the spring.

Yes, an internal spring in most.

Originally Posted by dansawyer

Third: Now the potentailly bad part, the bearing oil looks dark. I suspect at a minimum it has been over heated. I will change the bearing oil.

(The wheel turned smoothly. I did not think to assess it for runout. )
What have I missed? I am planning a 5000 mile trip in 2 weeks. I am glad I thought to follow up on this. I could imagine a bad wheel bearing in the middle of South West no where at 6 PM.

Personally I'd do a complete chassis lubrication (grease job!) which is something that I do in my shop. It is not difficult. My Holiday Rambler has a grease point chart, maybe yours does as well. But bottom line: brakes (two fittings on the S-Cam shaft and one on the slack adjuster) drive shaft (U-joints and slip joints) and front suspension (king pins if there are any, or ball joints) and the steering system (don't forget to grease the steering shaft u-joints between the steering wheel and the steering box...

Takes me about 30 minutes to do a grease job, and I recommend Lucas Red-n-tacky grease.

[RichardE]

So,,,,,,,,,,run a small magnet in the bottom of the hub cap that holds the oil. If no steel particles, you should be pretty safe in just changing the oil. If you pick up bits of steel, then you should replace the bearings and races.

When you take the tire off, you will have a lot more sensitivity to anything unusual going on in the hub. If it feels rough or growly when turning, then replace the bearings and races.

If you replace the bearings and races, replace the inner seal at the same time. Or you can come back in a month and replace it.

[dansawyer]

I greased the S cam arm and tested the action with the brake released. It was smooth and operated as expected. I then operated the brake as normal and it stuck again. I then slowly levered the arm back into the release position. I noticed a significant scraping sound. It sounded as though the actuator arm threads were binding on the actuator case.

I then inspected the base position of the actuator that is binding and compared it with the gap on the other wheel. The darker image, left shows a greater gap between the cast and the yoke then the lighter image on the right. I am now suspecting the alignment / positioning of the actual actuator.
I am not sure how to proceed from here. It is a bit over the top suspect the actuator, however the differenct in gaps leads me to go there next. I plan to remove the yoke pin to get a reading on exactly where the neutral actuator position is.

Are there other paths to perform first?