# Anti-Lock Brakes - Are they Good or Bad in an EV?



## tj4fa (May 25, 2008)

What's your take?

I have Rear Anti-Lock Brakes (RABS) in my '91 Ford Ranger. I also have about 1400 extra pounds of weight in the rear due to the batteries. The front brakes are disc and the rears are drums.

On wet roads, it can be a littly "hairy" to say the least when braking as the front discs like to lock up and the rear wheels just keep on rolling while pushing the truck forward with the added momentum of built up by the extra weight. I would imagine on snow and ice it would even be worse.

Anyone decided to disconnect ABS? Should they stay or should they go?


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## piotrsko (Dec 9, 2007)

the whole point to RABS in pick-ups was to equalize the tendency for the empty rear to beat the front to the scene of the accident. Good defensive driving with an experienced, well trained driver negates the need, but where does one get that training anymore? 1400 lbs will overcome the rear end's tendency to skid first, but it may shift the front to rear ratio so badly that the point is moot on ice or snow. VW Bugs tend to rear end stuff on icy days. OTOH, traction will be at it's best. don't forget to buy better tires, at least load range "d"


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## 3dplane (Feb 27, 2008)

Hey! When that happens,does the ABS even kick in? ( I don't think it does) Do you feel the brake pedal pulsating? Sounds like you could use a little more weight in the front.


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## tj4fa (May 25, 2008)

3dplane said:


> Hey! When that happens,does the ABS even kick in? ( I don't think it does) Do you feel the brake pedal pulsating? Sounds like you could use a little more weight in the front.


Yes, you can feel the brakes pulsating when the brakes are applied.

I don't think I can put any more weight in the front. It has about the same or maybe a little more than original with the new EV components plus 4 extra 6V batteries.


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## tj4fa (May 25, 2008)

piotrsko said:


> the whole point to RABS in pick-ups was to equalize the tendency for the empty rear to beat the front to the scene of the accident. Good defensive driving with an experienced, well trained driver negates the need, but where does one get that training anymore? 1400 lbs will overcome the rear end's tendency to skid first, but it may shift the front to rear ratio so badly that the point is moot on ice or snow. VW Bugs tend to rear end stuff on icy days. OTOH, traction will be at it's best. don't forget to buy better tires, at least load range "d"


I remember having a '65 VW Bug. I had to add some salt/sandbags to the front-end so that driving on snow/ice/slush the extra weigh to the front end gave some better steering help.


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## Telco (Jun 28, 2008)

It sounds more like the truck is overloaded than anything else, and the front brakes are being overwhelmed. Small truck brakes have never been all that great to begin with.

ABS is a system that should be transparent unless you are in an emergency braking situation. All they do is keep the wheels from locking. Otherwise, there should be no sign that they are there.

What I would suggest doing is visiting a Ford Ranger performance forum like this one. On the Chevy S10 performance forum I normally hang at there is a section dedicated to improving the brakes, and there are several different conversions that help make S10s stop better than they do with the factory system. Their intent is to help the trucks stop better when fitted with a high performance engine, but the same braking system that will slow down a high performance vehicle will also help slow down a heavily loaded vehicle.


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## david85 (Nov 12, 2007)

While I am not a fan of ABS, I would advise against disabling ABS on an originally ABS equipped vehicle. Having more weight on the rear may eliminate the tendancy for the rear wheels to lock up first, but theres no guarantee.

At the very least, don't make any changes perminant just in case it doesn't work.


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## tj4fa (May 25, 2008)

Next time it rains, I plan on unplugging the RABS module and doing a braking tests (normal, hard and panic) on an isolated stretch of road to see what will happen.

I'm not thrilled that the fronts totally lock up and the rears are allowed to "push". During that time, there is no steering control unless you let off the brakes which defeats the purpose of ABS. 

I'm thinking it should be all or nothing.

I guess it's like Piotrsko mentioned earlier, the Rear wheel (only) ABS must have been designed for light trucks to keep the rear end in line and from whipping around.

People can say you need to maintain a safe stopping distance for the road conditions, but those idiots that cut in front of you or jump into your safe stopping zone might as well paint a bullseye on their ass-end.


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## david85 (Nov 12, 2007)

The idea behing RABS is to have more powerful brakes for when you have a load in the box, but not have the truck swap ends on you when its empty. My 1986 F250 predates ABS but it has a brake line pressure modulator that connects the rear axle to the frame. Basically its a load sensor that does the same thing as the RABS, but without any electronics. I've been in some hairy situations with that truck and not once did I wish for ABS (4wd would have been nice though).

Something else you might try is to check out therangerstation.com for info on the brakes. If nothing else you could swap the older verison of brake system into your truck that has the brake proportioning valve to prevent rear end lockup.

All this probably won't matter with so much lead in the back though and you might be fine to just unplug the ABS.


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## azdeltawye (Dec 30, 2008)

tj4fa said:


> I'm not thrilled that the fronts totally lock up and the rears are allowed to "push".


 
The coefficient of friction between the tire and the road decreases significantly when the tire breaks traction and locks up. This is the advantage of ABS. It keeps the wheels from locking up and maximizes your brake effectiveness. During this scenario when the fronts are locked up and the rears are not, the rear brakes are providing more braking force than if they were allowed to lock up. This is assuming the ABS is working properly…


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## AlterPower (Sep 5, 2008)

Howdy folks. I'm converting a '93 Ranger and the first thing I did was get my broken the RABS system working. Without it, the truck was a real beast to panic stop in wet conditions with the rear wanting to whip right around. With the RABS online it panic stops in a straight line. I can't imagine the tendancy to swap ends is made less by the additional weight bias to the rear. The RABS has a massivly positive effect in my Ranger's wet weather manners, I wouldn't disable mine under any conditions. I would look to shifting some weight forward first to get more performance out of the front end. If that isn't possible, one idea would be to look at an adjustable proportining valve from a racing vendor like Summit and dial the fronts back a bit.

Luck!

JK


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## tj4fa (May 25, 2008)

AlterPower said:


> ...If that isn't possible, one idea would be to look at an adjustable proportining valve from a racing vendor like Summit and dial the fronts back a bit.
> 
> Luck!
> 
> JK


Hmmm...not a bad idea. Thx!


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## david85 (Nov 12, 2007)

Much better idea.


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## Telco (Jun 28, 2008)

Question, you say the rear wheels push, does this mean that your EM is still turning the rear wheels even when you let off the "gas"? If so then this would be a separate problem. I know that on my pickup when the road is slick, if I leave the truck in drive it will not want to slow down enough to take a turn, the front wheels will start sliding, but if I shift to neutral braking action is tons better because the brakes are no longer fighting the engine. Does your EM freewheel when you aren't into the "gas" pedal or will it move the vehicle on level ground?


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## david85 (Nov 12, 2007)

If the rear wheels lock in a hard braking situation, the vehicle has a dendancy to swap ends. Thats true no matter what powers it. Pickups are especually vulnerable to this because of the weight distribution.


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## tj4fa (May 25, 2008)

Telco said:


> Question, you say the rear wheels push, does this mean that your EM is still turning the rear wheels even when you let off the "gas"? If so then this would be a separate problem. I know that on my pickup when the road is slick, if I leave the truck in drive it will not want to slow down enough to take a turn, the front wheels will start sliding, but if I shift to neutral braking action is tons better because the brakes are no longer fighting the engine. Does your EM freewheel when you aren't into the "gas" pedal or will it move the vehicle on level ground?


What is "EM"? 

If I'm off the accelerator pedal braking, the motor and driveline is still spinning, however there is no electricity going to the motor.

If I brake hard or on slick roads, the front disc brakes will lock up and the RABS (rear anti-lock brakes) will not allow the rear drums to lock up.

When this happens, the "payload" of approximately 1400-1500 lbs of lead acid batteries in the rear of the truck, will keep driving the truck forward with all that weight and forward momentum of the vehicle.

The only way to keep the front non-ABS tires from skidding (and resulting loss of steering control) is to let off the brakes and try it again (and again and again if necessary) thereby increasing the stopping distance and likelihood of hitting something.

Other than what is said previously about the possibility of the rear spinning out, half an ABS system (rears only) seems lame IMO.


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## 92 Escort EV (Jul 3, 2008)

david85 said:


> If the rear wheels lock in a hard braking situation, the vehicle has a dendancy to swap ends. Thats true no matter what powers it. Pickups are especually vulnerable to this because of the weight distribution.


david85 has a good point. I once had a vehicle (not an EV), with a rear disk brake conversion that got totaled. I salvaged it and had to get a brake inspection in california, and the inspector made me add an adjustable proportioning valve to make the front wheels lock up before the rears to avoid the possibility of "swapping ends" or spinning rear first in an emergency panic stop. Dosn't sound right at first, but if the rears lock up and the fronts have traction, you can spin around. 

See summit racing for the proportioning valve.


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## david85 (Nov 12, 2007)

Its actually really wierd when you think about it. You would expect the end thats dragging to stay behind, but its actually the opposite. The wheels that lock try to turn the vehicle around and get in front. If you are already in a turn, on slippery terrain, or on lateral incline, the effect can be far worse. Front wheels locking might seem like a nusance, but those are the wheels you want to lock over the rear. At least front locking up keeps you pointing strait forward and recovery is a little easier.

I'll be performing a rear disk conversion on my saturn, but the rear of the car could end up gaining close to 500 lbs so I'm hoping that rear locking won't be happen. If rear locking proves to be a problem, then a proportioning valve will go in.


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## Telco (Jun 28, 2008)

tj4fa - EM is electric motor. If the motor is still spinning, is there any chance that the motor might be putting a flywheel effect on the rear wheels, which would force them to keep trying to move the vehicle forward? This is the question I was trying to ask. If this is the case, then the front tires will be fighting both vehicle inertia and the rear wheels trying to move the vehicle forward. It doesn't take much input from the rear wheels to do this either, as being off the gas on an ICE will do it as well. A quick test of this would be to put the vehicle in neutral when in one of these emergency stop instances and see if vehicle braking improves. If this does work, next step would be to determine why the EM is flywheeling the drive wheels, but that's where my ability to help comes to an end.


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## tj4fa (May 25, 2008)

Telco - EM = Electric Motor... I should have thought of that but I was thinking something ICE or brake related like "Engine Management". 

On my (clutchless) truck, the electric motor is "turned off" when you release the accelerator pedal to hit the brake so the EM just spins free-wheeling under no load/power (coasting). In essence it would be like having the vehicle in neutral so I don't think there would be any appreciable flywheel effect.

I missed my chance yesterday during the wet weather to do some controlled braking events but will likely get another chance this weekend.


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## Telco (Jun 28, 2008)

Cool. May not be that, but it's something I know is a problem on some ICE vehicles. In theory they are freewheeling as in neutral when you are rolling down the road off the gas, but sometimes the engine is still pushing the rear wheels. I figured it would be worth checking out.


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## Wirecutter (Jul 26, 2007)

azdeltawye said:


> The coefficient of friction between the tire and the road decreases significantly when the tire breaks traction and locks up. This is the advantage of ABS. It keeps the wheels from locking up and maximizes your brake effectiveness. During this scenario when the fronts are locked up and the rears are not, the rear brakes are providing more braking force than if they were allowed to lock up. This is assuming the ABS is working properly…


This is also exactly why the vehicle would want to swap ends in a panic stop if the rear wheels lock before the front. (If the vehicle is not going in an exactly straight line with exactly equal brake force on each front wheel, etc.)

I had an 81 Jetta once. I replaced the rear axle after a slight mishap, and in the process, messed up the adjustment of the brake proportioning valve. (It was coupled to the rear suspension so the lower the rear rode, the more rear braking you got) Sure enough, some idiot wench going the other direction turned left very close in front of me, and the resulting "panic braking" caused the car to spin around. Scared the crap out of me, but no wreck, luckily for all.

When I got home, I did a bunch of research (pre-Internet), learned about brake proportioning valves, and fixed my little problem. What an education!


Anyway, back on-topic: what about putting ABS on the *front* of the truck? Is this prohibitively difficult or expensive? Other than that, I'd go with an adjustable proportioning valve.

-M


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## piotrsko (Dec 9, 2007)

converting the front will require at least a couple of trips to a wrecking yard, unless he can get a donor vehicle for the parts swap, including the abs module itself. if it were FWD or 4wd, the sensor rotors would already be there.

Don't recall if a lot of rangers came with front ABS, probably the STX or the XLT's, but the later ones might have it. Ford tended to stabilize the body style for perhaps 6 years.

OH yeah, don't forget to look at mazda p/u's, same manufacturer, different trim levels.

I myself would use F150 rear brakes (disc), which interchange on my '88 rangers and get an adjustable proportioning valve.


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