The Physics of Towed-Vehicle Braking

[CoyRhonda]

I have a 22’ Class C Jayco Redhawk 24B and just bought a Jeep Wrangler to flat tow behind it using a Blue Ox Towing System. Also, I purchased a Stay N Play break System to have installed. My mechanic stated the brake system for the Jeep is not necessary. We plan to take a trip cross country in a few months and I wanted to get some expert experience, opinions, or thoughts on whether to add the brake system to the Jeep, or not.

[Lt Dan]

First off, Welcome to IRV2!

Check with a different mechanic and get your brake system installed. The Jeep weighs approximately 1/4-1/3 of what your motor home will and its brakes are not designed for that much weight. In addition, if you travel through a state where a braking system is required, you are in violation of their laws. I have towed Jeeps without and with braking systems and would never tow another one without.

[texasrs]

Originally Posted by Jagob

Great discussion. I was looking seriously at a surge brake type system that mechanically apples the toad brake. I took my Jeep Wrangler down the drive and at about 20 mph, killed the ignition, and started applying the brakes. The first application was pretty effective but after about the 3rd it was just about zero braking. I’m wondering how effective any of these braking products really are if you aren’t using some type of vacuum booster. Based on my simple test, these type systems (with no vacuum boost) are doing very little other than giving you a false sense of security. DISCLAIMER- totally new to MH and toad pulling and just trying to educate myself!!!

Check out M&G Engineering in Athens, TX. (If you have air brakes)
I had that system installed and it is wonderful. Brakes on your toad are applied by connection with your coach air brakes.

https://m-gengineering.com

Ray

[wolfe10]

Originally Posted by texasrs

Check out M&G Engineering in Athens, TX. (If you have air brakes)
I had that system installed and it is wonderful. Brakes on your toad are applied by connection with your coach air brakes.

https://m-gengineering.com

Ray

CoyRonda,


YES, you need a supplemental braking system on your jeep behind a Class C (gasoline) motorhome. It is well heavier than would it be legal to tow it without a supplemental braking system. Sorry, your tech is WRONG! Maybe he just doesn't want to install one.


NO, you don't have air brakes, so, though the M&G is a good system, it is not tailored for your needs.

[NXR]

Originally Posted by CoyRhonda

I have a 22’ Class C Jayco Redhawk 24B and just bought a Jeep Wrangler to flat tow behind it using a Blue Ox Towing System. Also, I purchased a Stay N Play break System to have installed. My mechanic stated the brake system for the Jeep is not necessary. We plan to take a trip cross country in a few months and I wanted to get some expert experience, opinions, or thoughts on whether to add the brake system to the Jeep, or not.

DOT regulations require that the braking system on a vehicle, in this case your Class C, only be able to safely stop the GVWR of the vehicle.

You did not specify your RV's year so I looked up the 2021 specs here: https://www.jayco.com/products/class...1-redhawk/24b/

The GVWR is 14,500 pounds.

For your Class C to be able to safely stop a 5,000 pound Jeep without a braking system on your Jeep, your Class C fully loaded for a trip with water, people, fuel, junk etc. could weigh no more than 9,500 pounds. Probably not anywhere close to possible.

Your GCWR is 22,000 pounds. The formula GCWR minus GVWR tells you how much weight your Class C can safely tow unrestricted without damaging the engine, frame, transmission etc.

That's 7,500 pounds so you can easily and safely tow a fully loaded four-door Jeep Rubicon. With really big tires, a winch, etc.

BUT without a supplemental braking system in the Jeep you cannot safely stop. You can stop but with significantly increased stopping distances (especially going down a hill) and with far more rapid Class C brake wear than otherwise.

So you either pay for a good supplemental braking system in the Jeep or you pay more later for a major brake job on the Class C far earlier than you otherwise would and maybe some body work if you smack into someone.

The Stay-IN-Play DUO is what I have in my Equinox and it is an excellent system with an excellent reputation. Since you already own it, it just needs installed by someone competent.

Make sense?

Ray

[n2zon]

It's not just the braking system one must consider. It's which tires are braked, and which are not. Unbraked load-carrying axles *will* increase the stopping distance because their tires cannot contribute to slowing the rig down.

See post #73 in this thread. I'd independently reached the same conclusions for the same reasons, but I think his writeup is better than mine was.

[Isaac-1]

Originally Posted by CoyRhonda

I have a 22’ Class C Jayco Redhawk 24B and just bought a Jeep Wrangler to flat tow behind it using a Blue Ox Towing System. Also, I purchased a Stay N Play break System to have installed. My mechanic stated the brake system for the Jeep is not necessary. We plan to take a trip cross country in a few months and I wanted to get some expert experience, opinions, or thoughts on whether to add the brake system to the Jeep, or not.

I am not going to say that your mechanic is wrong, but I will say there are only 3 states where at first glance it is legal to tow something as heavy as a Jeep Wrangler without a braking system, those are Texas, Alaska and Massachusetts, and Texas is marginal depending on the exact weight.

[tim myers]

Have the Stay n play installed, the peace of mind will make your travels more stress free.

I jave one and love it.

[joshjack]

This thread is why I come here! We’re about to pick up a 42’ Class A and I already have a 20’ car hauler trailer for our toad. I’ve been going back and forth on installing a brake controller and this sealed it for me. In 20+ years of towing with pickups I’ve always been very careful to have working brakes on anything I pull except the occasional piece of farm equipment, but the clear explanation and data in the OP have taken away any illusions of just relying on the Class A to handle the weight.

[Dragpipes3]

Originally Posted by hoosierrun

I have the SMI Stay-In-Play Duo system that appeared to be doing fine until yesterday. I lost the Toad brake indicator about 20 miles from home and wasn't sure what was going on. There was no place to pull over on these highways with Sunday traffic and a narrow shoulder so I had to drive home. As it ended up, I did loose the supplemental braking system because the Toad battery discharged on the trip. Apparently when that happens your Toad brake system won't work.

At home, I charged the battery for about 15 minutes and all is fine again. Perhaps I should look for a new battery, even though the one in there is only 2 1/2 years old.

So, how long will the Sta-In-Play Duo system work on the Toad vehicle before running down the battery? Yesterday's drive did require a lot of braking due to heavy traffic and vehicles always cutting into my safe distance area. My trip time was 2 hours from when the Toad was last driven.

Run 12 volt hot wire from motorhome to the toad battery with a 20 amp fuse protection in line works well

[Shall36]

A couple of observations…

Some of the posts explore legal arguments around wether or not toad braking is required by law. There is no law saying I must clean myself after going to the restroom, but seems like good practice to me. Even if the law is gray here (and I don’t think it is), having the toad help stop itself seems to make good common sense.

Why do people who tow a toad skip the brakes? Expense? Complexity? A belief that the brakes won’t/don’t help or aren’t needed?

How many RV owners would spend $1,000 to improve their RV’s braking by 5% or 10%? That upgrade seems like a no brainer. It would be interesting to do a study measuring the effect of toad braking on coach braking performance. For example, maximum effort stops from different speeds with and without toad braking for different weight coaches and toads. I imagine physics says that toad braking would reduce distance to stop…but by how much? It’s probably substantial for many coach/toad combinations.

[Onyrlef]

Originally Posted by BryanL

I am not happy having problems with the 'lecture' after so many positive reviews. But it does grate on my understanding of physics and my distaste for hyperbolic fear mongering.

The weight does not change no matter how fast you try to change the speed of the rig. Weight is defined as the force due to gravity, not any change in inertia.

The mass also does not change.

The whole argument is much simpler than presented. Stopping quicker means you need more force than stopping slower. Stopping more mass, which has a greater weight, requires more force than stopping less mass. That's all.

As far as I know, any towed vehicle over 1500 to 3000 lb, depending upon state of registration, is required to have braking. This makes me wonder about the scare story used in this presentation and whether it is really appropriate to an honest message.

The limiting factor on stopping force is almost always the tire friction on the road surface. If you slam on the brakes, both your towing vehicle and the towed vehicle should be laying down rubber.

Without the FUD, the lessons I see are these:

1) if you are towing any significant weight without proper brakes, you are probably towing illegally.

2) you must compensate in your driving for the size and weight of the rig you are driving.

3) your RV does not handle like a sports car and should not be expected to.

4) rig your RV and maintain it properly so that it is dependable and is safe if driven properly.

5) safe driving depends upon a confident attitude based on experience and training. Trepidation and fear are indications that this experience and training is insufficient for safe driving.

I note that RV's are generally the safest vehicles on the road and that the primary cause of accidents (after DUI) is not paying attention. Stay awake and alert, take care, and drive safe.

Perhaps you didn't notice he translated those Principia points directly from the latin, ergo, the rest of it must be true.

[wolfe10]

Originally Posted by Dragpipes3

Run 12 volt hot wire from motorhome to the toad battery with a 20 amp fuse protection in line works well

Actually a fuse at BOTH coach and toad batteries.


And, if you want it to only charge when the coach engine is running, easy to wire through a RELAY with ignition hot as the trigger to close the relay.

[n2zon]

Originally Posted by Shall36

A couple of observations…

<snip>

How many RV owners would spend $1,000 to improve their RV’s braking by 5% or 10%? That upgrade seems like a no brainer. It would be interesting to do a study measuring the effect of toad braking on coach braking performance. For example, maximum effort stops from different speeds with and without toad braking for different weight coaches and toads. I imagine physics says that toad braking would reduce distance to stop…but by how much? It’s probably substantial for many coach/toad combinations.

How much is predictable. Divide the weight of the toad by the weight of the coach. In our case, that's 3500#/34000#, or .1029, a bit over 10%. Add one, to get 1.1029. Multiply the stopping distance without the toad by that number to see what it would be with the toad. So if we can stop the coach in 200' from a given speed, for example, it will take about 21' farther to stop with an unbraked toad attached.

The smaller the difference between the weight of the coach and the weight of the toad, the greater the improvement, and vice versa.

Somewhere in this discussion or a similar one is a great post explaining the physics. Elsewhere is another post I wrote that explains the same things but is perhaps a bit harder to follow.