Excessive brake pedal effort required

[Vanwill]

On both Monaco Dynasty's I've owned--1993 and presently a 2000--it always seemed to me that the pedal effort required was abnormally high. Although I've never tried it, I always suspected that the effort required to lock up the wheels would be humongous, and beyond the capability of many female drivers.

I realize that there could be a myriad of MECHANICAL issues that might cause high pedal effort, but I'm primarily interested in hearing from someone with technical knowledge of how the brake controller circuit works. It certainly seems reasonable to assume there is an adjustment somewhere to regulate the air pressure going to the brake air chambers based on the force applied to the brake pedal.

I've driven one Monaco (1994 Sig) which had air-powered disk brakes. Although the systems are of course different from mine, the required pedal pressure was very much like a car.

Anyone know how to change this?

[R2Home]

While I do not have the 'technical knowledge' you may be looking for, here is my understanding of the air brake system. When pressing on the brake pedal, it is opening passage ways in the treadle valve, allowing air pressure to supply air to the air chambers on each wheel. If this seem to take too much pressure, I would looking at the adjustment of the slack adjusters or even looking to ensure that the brake pads/shoes are not glazed. I know that several MH's have self adjusting slack adjusters, but that does not mean that they might not to be adjusted once in a while. The slack adjusters also need to be lube, which some forget to do.

[Vanwill]

Originally Posted by R2Home

While I do not have the 'technical knowledge' you may be looking for, here is my understanding of the air brake system. When pressing on the brake pedal, it is opening passage ways in the treadle valve, allowing air pressure to supply air to the air chambers on each wheel. If this seem to take too much pressure, I would looking at the adjustment of the slack adjusters or even looking to ensure that the brake pads/shoes are not glazed. I know that several MH's have self adjusting slack adjusters, but that does not mean that they might not to be adjusted once in a while. The slack adjusters also need to be lube, which some forget to do.

Actually, pressing the brake pedal would not just open a passage, or the air would continue to build in the air cylinders at each wheel. Pressing the pedal is operating some pressure-balanced piston (as in an air compressor's pressure regulator, where the adjustment spring is the equivalent of the brake pedal). I'm hoping someone has experience adjusting the balance pressure on this device, or diagnosing some problem that requires excessive pedal pressure to cause sufficient air pressure to be admitted to the wheel cylinders.

Thanks for your response, though. You are largely right about how things operate. I just need some details about the adjustment, if there is one.

[twinboat]

Nope, no adjustment, I've ever seen.

Do you have floor mounted pedals. I have seen corrison seize the pedal pin and the plunger, thru the floor.

With or without air pressure, the pedal should push, easily to the floor or pedal stop.

[MSHappyCampers]

When we bought the MH in 2012, I had never driven any vehicle with air brakes. I too was surprised at the brake pressure required. I've never driven another MH, so I assume this is normal!

[SpaceNorman]

Originally Posted by MSHappyCampers

When we bought the MH in 2012, I had never driven any vehicle with air brakes. I too was surprised at the brake pressure required. I've never driven another MH, so I assume this is normal!

I could have easily penned the above comment myself. My first experience with air brakes came when we took possession of our coach at couple of months ago (last weekend in March). Without an basis for my expectations, I figured that the brakes would be similar to that of a "power brake" pedal on a passenger vehicle - and had a fleeting moment of panic when I moved my foot over to the brake pedal for the very first time and nothing happened. The amount of "leg" required to actual the coach brakes definitely took me by surprise.

That said - it took all of about 2 seconds to adjust to the "feel" of the brakes. I've now got 1,500 miles of experience with them under my belt and I'm convinced it was just a case unrealistic expectations - and not an issue with how the brakes function, perform and/or are adjusted.

[bamaboy473]

What is your shoe size? If you look at the brake pedal, it's pretty tall, and leveraged at the bottom. That means that the higher up the pedal you push, the stronger the brake pressure.

Lay a piece of 2x6 in front of brake and gas pedal and you'll likely notice a big difference in braking ability. press the very top of the pedal and you'll be back to car-like stopping.

[SpaceNorman]

Originally Posted by bamaboy473

...If you look at the brake pedal, it's pretty tall, and leveraged at the bottom...

Not in my coach. The pedals in my coach come down above - such that there's no contact at the bottom (i.e., on or near the floor). Theoretically, the point of best leverage for the pedals in my coach is at the bottom of the pedal.

In practical terms - braking the coach works best when I put the ball of my foot squarely on the pedal - and apply pressure using my leg. It's not a workout to stop the thing ... but, it's also not the "slightly move your ankle, flex your toes" sort of pressure I can get away with when using the power brakes in our car.

[Vanwill]

Originally Posted by bamaboy473

What is your shoe size? If you look at the brake pedal, it's pretty tall, and leveraged at the bottom. That means that the higher up the pedal you push, the stronger the brake pressure.

Lay a piece of 2x6 in front of brake and gas pedal and you'll likely notice a big difference in braking ability. press the very top of the pedal and you'll be back to car-like stopping.

Rick, sounds like there may not be anything that can be changed. My 1993 had the hinged pedal you are referring to. This 2000 has upper-pivot pedals like a car.

[oldguy70]

When pushing on the brake peddle you are pushing on a rod that pushes a diaphragm
and behind a spring. So what you are pushing on is a spring, a heavy spring. It should
be engineered with a lighter spring so it would be easier to push. Some peddles may be
easier to push, but I can't be sure. My peddles pushes fairly easily at first and then get
really hard. Mine is a suspended peddle and all other trucks I have driven were floor mounted and they seem to be more linear

[Dennis_K]

Both Monaco's I have driver had hanging swing petals and both required more foot pressure than they should. The one floor mounted petal MH I had was much easier to operate. I drove a '15 Newmar with swing petals and it was almost too easy.
It could be that the petal to air valve ratio on Monaco's is not enough.

[dieselbeaver]

The "treadle valve" is not engineered from a pedal feel stand point. There are many publications you can research by the different manufacturers and you will almost certainly not find any reference to an effort measurement. Normally the measurement quoted in testing a valve is application pressure as read on a gauge that is sampling the amount of pressure sent to a brake chamber.

As was mentioned there are floor mounted, firewall mounted, and hung valves that are chosen by the OEM. Having driven and worked on trucks I can say that there are differences in the perceived application pressure. Several factors can cause this, such as; pedal ratio, internal pressure ratios, obstructions to the pedal pivot, corrosion of the plunger, and brake adjustment (if your adjustment is way out then it can take more application volume to reach a point of feeling the deceleration).

Monaco's engineers may have selected different p/n valves over the different models and years. Country Coach or Fleetwood may use another manufacturer. Generally coaches don't have application gauges like trucks, so you can see you are appoint 10psi or 40psi to stop. It may be worth a look at installing one as a point of reference. Also find out your valve manufacturer and locate the applicable reference materials for study.

I drive a Dodge with an aftermarket performance clutch that if you jumped out of your identical truck into mine you would wince on the first application. Yet, after just part of a day it would seem normal. So perception also plays a part in how much is too much effort. Furthering this point, there are other valves at play that also can affect braking.... Relay valves separate the treadle valve from a direct connection to your brake chambers. They also can have a ratio percentage or crack
pressure to add to the mix. Heck, sticking s-cams can make you apply more foot pressure to begin slowing down.

Look for information from: Bendix, Wabco, Meritor, Haldex and see what you find. They are all players in the air brake game.

Hope this helps,

Allen - Diesel Mechanic and RV owner

[deSanford]

Van is this going to be the next GREAT innovation from your "can we make it better" attitude? Sanford

[George Crow]

If you have adjustable pedals, then you will have the hung pedals, if not, then the floor mounted pedals -- George Crow