Backing down launch ramp with surge disc brakes

[bruceb58]

That is not necessarily true. A study by Car & Driver a number of years ago showed that locked wheels stop a tiny bit sooner than those at the threshold of lock-up. You just can't control where you are going. I supposed this might not hold with some tires, though.

Back off topic...If that was true, they wouldn't put ABS on cars.

 

[Lou C]

The primary benefit of ABS is the ability to steer around obstacles because you are not locking your front brakes.
I'm still betting on the rear drums being way out of adjustment and not contributing to any braking effort in reverse . The front tires are doing all the braking and to get it to stop he has to brake so hard they are locking up and exceeding the traction available to those 2 tires. Keep in mind the brake torque needed to stop a combined weight of close to 9,000 lbs all being on 2 tires braking and traction. Not gonna work.

 

[wrench 3]

Just to note, the Bronco rear drum brakes self energize when used in a forward rotation. So they are less efficient when backing up.

 

[GA_Boater]

Dear Mother Nature,

Will you please hasten the arrival of Spring?

Signed,

Tired of Winter!

---

Every weekend thousand and thousands of boaters launch and retrieve trouble free. Front, rear, all wheel and four wheel drives. We have no idea if the OP's Bronco is a mini-monster truck or has functional brakes, let alone ABS. Why all the speculation and talk about ABS?

It would be nice if w2much would give us some answers and until he does, stay on topic. And stay on topic after he does answer back.

Thank you.

 

[Outsider]

For the OP, once the vehicle goes over 'the break', put in in forward gear and inch down the ramp. And I do mean inches at a time, momentum is not your friend. If you're still being pulled down or locking up your brakes, have your brakes seriously checked. I have pulled some serious weight with an F-150 2wd, some ramps warranted serious caution, but never once 'slid' ...

 

[MercGuy]

If you are just using the brakes, it makes no difference if you are in 2WD or 4WD. You could be in freaking neutral! The number of DRIVEN wheels has absolutely NOTHING to do with braking.

Went to his claim that putting a vehicle in 4WD backing down a ramp helps which it will do absolutely nothing.

I'm going to have to disagree with that.

I pull my 18 foot SeaRay with a 1995 Jeep Cherokee. Usually my wife backs the Jeep/Trailer down the ramp while I'm in the boat.

When we first started doing this we had a lot of trouble with the boat pulling the Jeep backwards in an uncontrollable slide, which freaked my wife out !!

Eventually I noticed that while the Jeep was sliding the front wheels were locked up tight and skidding, while the rears where still turning. The Jeep has front disk brakes and rear drums.

So, what was happening was that while backing down the ramp the tongue weight from the trailer unloaded the front wheels which allowed them to lock up and slide, The rear drums, much like our boat trailer brakes, do not brake effectively in reverse and no amount of pedal pressure would fix that.

My solution ? Put it in 4WD. The Jeep 4WD system has a locked center differential, meaning that the front and rear wheels must turn together, otherwise something will break.

The end result is that by locking the front and rear axles together the front disk brakes effectively stop the rear wheels from turning.

Since we started putting the Jeep in 4WD during launches were have never had any skidding or sliding while launching the boat.

Interestingly enough my wife puts it in 4WD to go DOWN the ramp, then takes it out of 4WD to drive to the parking spot and rarely puts it in 4WD to go UP the ramp !!

 

[bruceb58]

MercGuy

What your saying makes sense if the back brakes are not working effectively.

I think I have said that as well as some other people in previous posts. Still waiting for OP to come back and tell us what his situation is.

 

[Fed]

I can't say I've tried it but if I had a car that couldn't lock the rear wheels while going backwards I'd say there's something wrong with the rear brakes.

We're not talking aqua-planing or car control (steering) here & I think the best braking is in fact with all wheels locked up, I mean you're either slipping the tyres on the ramp or slipping the shoes on the drums and the last thing to slip is the tyres when enough braking is applied.

Push that pedal harder, don't ease off trying to regain grip on the front (reflex action).

 

[bruceb58]

Anyone who has taken high school or college physics knows that a skidding tire will not stop as fast as one that doesn't. Static coef of friction will almost always be higher than dynamic coef of friction. That's why you don't want to lock up the brakes.

If you have ever tried to slide a heavy box across a floor, it takes way more force to get the box sliding than the force required to keep the box sliding. Same goes for tires.

 

[Blind Date]

The comments about putting the truck into 4WD for better braking are dead on. Go back to the original post, full-size Bronco means he's got disks in front and drums in back. That's a big part of the problem.

 

[bruceb58]

The comments about putting the truck into 4WD for better braking are dead on. Go back to the original post, full-size Bronco means he's got disks in front and drums in back. That's a big part of the problem.

My friend has a 2012 Chevy Silverado with drum brakes in the back. He tows a 24' boat and has no issue with steep ramps. Of course his drum brakes work properly.

 

[Fed]

Anyone who has taken high school or college physics knows that a skidding tire will not stop as fast as one that doesn't.

Sure Bruce, stiction does play a part but it all goes out the window if the driver is not braking hard enough because the front is already locked up.

 

[bruceb58]

Sure Bruce, stiction does play a part but it all goes out the window if the driver is not braking hard enough because the front is already locked up.

We have no idea which wheels are sliding since the OP hasn't told us.

 

[Fed]

Yeah I guess we shouldn't assume anything other than the front will lock up before the back.

Edit: Maybe...LOL

 

[David Young]

Well, its probably a pretty old Bronco, to be full size. My 1991 F150 rear brakes lock up all the time and the rear brakes are anti-lock. So it says in the owners manual. I say 'something is wrong with the original posters brakes'. Ford has never had good brakes and i have 3 Fords.

 

[w2much]

1992 Ford Bronco full size. Rear drum front disk .10.5 x 15 tires.Boat loaded probably about 3800 lbs(just a guess) Fairly steep ramp with lots of algae on low tide high tide thin layer of sand.Corrugated concrete surface. Once the rears hit the algae she starts to slide pulling the front wheels over the light sand then to the algae if I let it go that far ,I try not to.
Correct once the boat is in the water I would stop sliding but backing down in a skid you lose control of the placement of the boat and trailer in regards to the dock or others users who tend to freak out seeing a boat skidding down the ramp perhaps toward them or the dock. I use 4wd to avoid giving the secret evil wishers a chance to get their hopes up that today will be the day they saw a boat and truck disappear below the water at the launch ramp.
I'll just keep using the 4wd.