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NotBrad

NotBrad

Active member
Joined
Apr 19, 2015
Posts
39
Location
Gold Beach Oregon
Hi,

We've got an Class A (06 Discovery 39' DP) and are looking at towing our 89 BW 325i (3,000 lbs. curb weight).  Should we add a braking system or is it small enough relative to the size of the MH to go without?

Thanks,
Brad
 
3000# behind a big DP should barely be a blip on the screen.  I wouldn't think you need extra braking, but I'll let some of the pros chime in.  I towed 3500-4000# cars many times on a tow dolly, behind the 35' Class A gas motorhome we used to own.  I could feel the toad back there a little bit, but not much.  Flat towing (which I assume you will be doing?) may be a different story too, so wait for some more responses before you run off with my advice.  ;)
 
Add a braking system. 

I've had three panic stops where the ABS came into play and I'm glad I had brakes on the toad.

Another issue is if your toad gets detached from your coach a braking system will stop it, hopefully before it kills someone.

 
It is illegal on different weights to tow without auxiliary brakes in all States and all provinces in Canada; as low as 1500 lbs, you'll need brakes on your toad when towing in certain States and don't forget to install the "brakeaway" feature, it is a must  for safety and for all of us.
 
A braking system is always better, even though that Bimmer is a small blip in the total weight of the rig. And if that Discovery is already loaded to near its GVWR, the chassis specs say any towed weight MUST have its own braking. That's because the coach braking system is designed to stop only its own weight, i.e. the coach GVWR. If towing anything that causes the combined weight to exceed the coach GVWR weight, then that thing must have its own braking.

The legal requirement (or not) to have a toad brake is a complex thing. Most states exclude towed cars from the general laws for trailers, so it can be difficult to determine exactly what is legally required in a given state, if anything. It's hardly worth the research or the debate, though, since the combined coach & toad will always stop more quickly (shorter distance) using a toad brake than without one. Always. What's not to like about that?
 
The dynamics of a 3000 lb towed vehicle pushing on the rear of a swerving, braking motorhome during an emergency braking maneuver, are tremendous. Yes, they're fairly expensive but, in my opinion, an auxiliary braking system should be considered mandatory equipment.

Kev
 
It sounds like safety outweighs the physics (and for good reason I'm sure), and aux braking is recommended in most cases.  Please notice that everyone else who has responded has a vehicle listed in their signature, that is their regular "toad" behind their motorhome... i.e. they know what they are talking about.  ;)
 
I admit it.  We towed a CRV for 3 years without a braking system.  I'm now slapping myself in the head because I can absolutly feel the difference every time I have to stop quickly.

 
OK, 8Muddypaws I'm going to take your advice for the reason that we have two goldens as well so that trumps all else... 

That said, going to see what other options exist for braking applications - the Brake Buddy looks like a over-priced redneck engineered contraption (literally like something my dope addled, idiot ex-BIL would come up with) and the others I've seen at $1K+ are over-priced as well.

Seems to me that using a separate master cylinder along with a relay actuated valve (for flipping the "source" master cylinder when the ignition is on although this could be done manually) along with an actuator and fail safe solenoid ought to do the trick for a whole lot less money and work better as well.

In addition to being right up my alley this will be a fun little project as well.

I'll post pics and instructions as I go along.



 
We do love our Goldens.

Virtually all of the towed braking systems work almost the same way.  They actuate the cars original brakes, either by a compressor, a vacuum pump, or the tow vehicles air brake connection.  There's a mechanical system that uses something similar to surge brakes you'd find on a boat trailer.  As far as I know nobody has a system that cracks into the cars hydraulics.  The liability would be very troubling.

Engineering problems you may need to think about:
How much pressure is required on the Beemers brake pedal in the absence of vacuum boost?  (Lots)
How much power is it going to take to generate the required force?
How are you going to isolate the two master cylinders from each other?
Forgetting to switch from one to the other could be disastrous.

I'm thinking the redneck looking device might actually be a safer choice.  Look in the 'for sale' section of this site, Craigslist, Amazon etc.

I just sold an Evenbrake system yesterday for $150.

Or maybe you'll build a better mousetrap and make a bazillion bucks?  ;D
 
As far as I know nobody has a system that cracks into the cars hydraulics.  The liability would be very troubling.
Click to expand...

That's how the M&G brake system works.  It installs in the brake line just after the master cylinder.
 
The other systems have a common design problem and that's that they need to be easily adaptable to a wide variety of cars.

So here's my initial thoughts

Engineering problems you may need to think about:
How much pressure is required on the Beemers brake pedal in the absence of vacuum boost?  (Lots)
- It's a matter of two things 1) the diameter of the piston in the master cylinder and 2) is the actuator levered in such a way as to provide optimum pressure to the aux master cylinder

IOW, if I use the MH air system to power the actuator then I'll have the same, or close to it, assist as what the vacuum provides

How much power is it going to take to generate the required force?
-If the existing air pressure can provide enough for the MH brakes it ought to be able to do the same for the tow brakes especially with the proper leverage

How are you going to isolate the two master cylinders from each other?
Switchable valve prior to the lines entering the ABS actuator (which is conveniently at the left front of the engine compartment in an e30 bmw). I can actually take a single line master and plumb in a proportioning valve prior to the ABS

Forgetting to switch from one to the other could be disastrous.
Push/Pull relay and a default just like airbrakes (i.e. no pressure == brakes applied) which I'd need for the fail safe in case of disconnect anyways.

Car running -> relay switches to normal brakes, car turned off -> relay switches to aux brakes.

Or maybe you'll build a better mousetrap and make a bazillion bucks?  ;D
LOL, doubtful since it'd only be for BMW e30's

Will check out the M&G system...

8Muddypaws said:
We do love our Goldens.

Virtually all of the towed braking systems work almost the same way.  They actuate the cars original brakes, either by a compressor, a vacuum pump, or the tow vehicles air brake connection.  There's a mechanical system that uses something similar to surge brakes you'd find on a boat trailer.  As far as I know nobody has a system that cracks into the cars hydraulics.  The liability would be very troubling.

Engineering problems you may need to think about:
How much pressure is required on the Beemers brake pedal in the absence of vacuum boost?  (Lots)
How much power is it going to take to generate the required force?
How are you going to isolate the two master cylinders from each other?
Forgetting to switch from one to the other could be disastrous.

I'm thinking the redneck looking device might actually be a safer choice.  Look in the 'for sale' section of this site, Craigslist, Amazon etc.

I just sold an Evenbrake system yesterday for $150.

Or maybe you'll build a better mousetrap and make a bazillion bucks?  ;D
Click to expand...
 
It appears that what the M&G system does is to insert a air powered "plunger" between the brake pedal and the vacuum booster and then actuate it via air pressure from the MH brakes.

I could probably build something pretty similar without too much effort.
 
Here's a description of the M&G system (with pictures) in this article in our forum library. The article also discusses several other toad braking systems.
 
Ned said:
That's how the M&G brake system works.  It installs in the brake line just after the master cylinder.
Click to expand...

I've never heard of them until today, I probably would have bought one instead of the SMI!
 
Doing some research and found air brake actuators run on anywhere from 90 to 130 PSI (what our systems in a MH use) and it looks like they're priced $40 - $140 each

Master Cylinder for e30 ~$60, although I could use one from anything I guess.

Now just to find the valves, hoses, etc....

 
I've owned 2 M&G systems. Both are air actuated cylinders with plunger, that goes between the brake booster and the master cylinder. Neither required any intrusion or disconnection of any hydraulic line during installation or operation. IMHO they are a neat and clean braking system. At $700 or so, they are priced about even with the other options. There are many vehicles they don't fit though. There needs to be room in front of the M/C to move it forward and some cars just don't have that room.

I like that the way to hook it up is simply take off the rain cap and push on the quick connect air line fitting. The break away is just another cable to a loop on the switch plug. Fast, easy and nothing to store or move at your destination.

Ken
 
I have had a Brake Buddy type of system that never operated unless a panic stop.  I looked at the M&G and the Air Force One and finally ended up with the Ready Brake (Ready Brute Tow Bar).  Pretty simple in operation, it's a surge brake.  When the towed pushes more than about 300 pounds on the RV the brake is activated by pulling a cable that is attached to the brake peddle of the the towed.  I have a brake light from the towed on the dash of the RV and see that most normal stops that the brakes on the towed are activated.  Much better than when I had the Brake Buddy (Blue Ox Apollo) type system.  It is easy to hook up when connecting the towed and has a break-away built in.  Just another inexpensive brake system to consider.
 
yolo said:
I have had a Brake Buddy type of system that never operated unless a panic stop.  I looked at the M&G and the Air Force One and finally ended up with the Ready Brake (Ready Brute Tow Bar).  Pretty simple in operation, it's a surge brake.  When the towed pushes more than about 300 pounds on the RV the brake is activated by pulling a cable that is attached to the brake peddle of the the towed.  I have a brake light from the towed on the dash of the RV and see that most normal stops that the brakes on the towed are activated.  Much better than when I had the Brake Buddy (Blue Ox Apollo) type system.  It is easy to hook up when connecting the towed and has a break-away built in.  Just another inexpensive brake system to consider.
Click to expand...

That's a good point.  In addition to being a KISS solution it seems like it would work well when the engine brake activates as well.
 
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