M&G Tow Brake Installation

Installing an Auxiliary Braking system on a 2005 Jeep Wrangler
Article Date: May, 2006

Article and Photography by Mark Quasius

After having the M&G tow brake on our Grand Cherokee for a while now it was time to add one to the Wrangler.

The M&G Tow Brake is a great setup. It utilizes the existing air brake system of any coach with air brakes to proportionately actuate the toad's brakes. For RVs without air brakes they do offer an air compressor setup, but this does add to the cost. The beauty of this system is that there are no electrical connections and no decelerometers. When descending a grade the Jake brake will not engage the toad's brakes. The only time the toad's brakes work are when the coach's brakes are being applied. Being totally proportional the amount of braking depends upon how hard you step on the brake pedal so the toad and coach are always in sync. I've detailed my installation on this page in case any fellow RVers are interested in installing this system on their coach.

The Installation

Installation on the coach is very simple. You simply tap into one of the brake service lines at the rear axle with a tee fitting, then run the extra nylon line to the rear of the coach where you install a quick disconnect coupling. Tapping into this line is no different than feeding a tag axle. In the event of a failure the brake system's isolating valves would still give you 3 wheels worth of braking and the air pressure loss by a severed line would be very minimal because it's the service line, not the "hot" supply line.

On the towed vehicle end you first have to install the M&G adaptor.

This adaptor fits between the master cylinder and the vacuum booster. It consists of a housing with an internal split shaft. Where the shaft is split the piston on the frontmost half is acted upon by the air pressure input. Whenever you are not towing, this system acts as a large pushrod allowing the brakes to function normally. This is a fail-safe design so even if the M&G module was to fail you would still have manual braking. However, when towing, there is nothing pushing on the pedal. Instead, the air pressure from the coach is applied to the M&G module which works the front half of the split shaft to apply the brakes evenly and in direct proportion to the coach.

The RV connects to the front of the Jeep with a short nylon hose with a male and female quick disconnect fitting. I find that running it inside the coiled trailer light umbilical makes it nice and simple. There is nothing to hook up or install inside the towed vehicle and once installed it's totally invisible. You simply plug in the hose and go.

I also ordered the optional breakaway kit. This kit consists of a small air reservoir tank that will supply air to the M&G module should the toad come loose from the RV. This tank is charged up after 3 good pushes on the brake pedal once you connect the toad to the RV.

This tank is connected to a 3 way solenoid valve. This valve allows the tank to charge up while driving and directs normal braking air pressure to the M&G module. Upon breakaway, the valve dumps the contents into the M&G module and locks it up to keep the toad from going ballistic. This solenoid valve has two wires going to it. One wire goes to ground and one goes to a "hot" source that gets energized when the towed vehicle breaks away from the RV.

This requires installing a breakaway switch at the front of the towed vehicle. I mounted both the breakaway switch and the air inlet fitting on the front bumper of the Wrangler. M&G recommends that you just leave the hose loosely coiled up under the hood of the towed vehicle, then hang it out the hood when towing. I wanted something more permanent so I mounted everything in the bumper. Besides, it's a Wrangler, not a Ferrari.

The only drawback to this is that you can get dirt into the fitting. M&G states that the end of this hose should not be capped off or else air pressure could increase within this hose as things warm up under the hood and you might find your brakes dragging while driving. To rectify I took a right angle spark plug boot and inserted a short whip of the nylon brake tubing into it. This gave me a vented dust cap which keeps dirt out, yet allows venting of the system.

Summary

After having a Brake Buddy and US Gear unit previously I am very happy with the M&G system. It's the most foolproof system out there and reacts just as you'd expect, when you expect. For further information contact M&G Engineering.

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