Thor Forums

[Chance]

Originally Posted by Beacher

No. Not quite.

The net effect of the toad load to the coach occurs at the hitch ball.

The hitch ball does not know or care how many wheels behind it have braking force or stopping power. Only the dolly knows! The hitch ball certainly does not only give 50% to 66% credit for stopping the toad due to only two wheels with brakes. The dolly applies a 100% braking contribution for the toad's rolling mass using it's two wheels. As far as the hitch ball is concerned, it doesn't know if there is a dolly or 4-down toad connected, as long as it stops properly.

In order for a tow dolly's two wheels to stop the weight of the toad, (regardless of it's size), it has to apply enough braking force. With hydraulic surge brakes, if you load a small vehicle on the dolly, it applies a small braking force, and with a large vehicle it applies sufficiently more, all automatically. Electric brakes require an electronic brake controller which can be preset to anticipate the mass of the toad, based on inertia.

If you have ever made an emergency stop while pulling a properly configured tow dolly, TT, 5er, or boat you know that the stopping distance is just as good as the coach by itself, (if not better, due to the rolling resistance helping to slow down, like an anchor or drag chute).

In a panic stop it has to make a difference. And I'm not talking about controls -- I'm simply stating that if brakes have enough power to lock up wheels, then any weight that rolls without being braked will add to stopping distance.

In any panic stop the maximum braking force can not exceed what the tires can grip on road, so it pays to have the entire mass to be stopped providing vertical force towards increasing that grip. That's the main reason to add brakes to a toad in the first place.

In trailers of all types it is "typical" to have 100% of trailer weight contributing towards tires getting a better grip (because all wheels are braked). In a tandem-axle trailer if you only had brakes on one of the two axles, then locking up the two braked wheels would not stop as fast as if all four wheels are braked. The same happens with a dolly. Weight on toad's unbraked axle adds to mass that wants to keep going forward during a panic stop but it doesn't contribute as much to braking. This means that a dolly's ultimate braking (the point at which tires lock up) can't be as good as a trailer's or flat-towed vehicles' (assuming great brakes on all).

When an RVer tows a 3,000-pound car behind a 20,000-pound motorhome, these differences in performance that we are discussing are pretty small. I'm not sure it's even worth debating.