Has anyone ever stalled their car because of locking wheels braking

[oohhh yeah]

I was riding my dirtbike and I came across this phenomenon I never really thought about before. Braked too hard and locked up my rear wheel, so the engine stalled. Was still going pretty fast so it just skidded to a stop. So has anyone ever done this in a car? Cars without ABS can do this because the wheels can lock.

 

[Small_Fryz]

Done it on my dirtbike yes, never in a car though.

Its got to do with the amount of grip + engine braking.
Pretty hard to do in a car unless your on gravel or sand.

 

[MatskiMonk]

Theoretically quite easy to do in a front wheel drive car that doesn't have ABS, but in practice the reflex reaction is to floor the clutch as well during braking manoeuvres that hard.

Having said that, the very first emergency stop I ever made was disasterous, in a corsa, at 30 mph, I just stood on the brakes as hard as I could, locked the wheels instantly and screeched to a halt a long way down the road, EVERYONE turned around to look, and all my instructors stuff on the back seat ended up in the front.... Can't be sure exactly when the engine stalled, but it did, even with dual controls!

 

[DG_Silva]

Your instructor will never dip the clutch on an emergency stop, because the idea is to get you to remember to do it, and not rely on him as a crutch.

 

[lbsf1]

I've done it karting on direct drive karts with only rear wheel braking, however aslong as your still moving when you release the brake then it bump starts the engine again.

 

[poolhaas]

once, was driving 30 - 40 km/h going past a couple with a baby stroller on a narrow road, when suddenly their unleashed dog ran across the street like a madman.
Jammed the brakes but didn't have time for the clutch. They apologised for the dog but I was just glad i didn't swerve into anything.

 

[BobK]

Yeah, I've done it while learning to drive.

 

[Keef]

I did it a few times in my Civic on track, that's one of the reasons I wanted a rear drive car. What a horrible design flaw!

 

[oohhh yeah]

I've done it karting on direct drive karts with only rear wheel braking, however aslong as your still moving when you release the brake then it bump starts the engine again.

It only bumps it back up if you slip the clutch. If you don't touch the clutch the wheels just keep skidding in full lock.

 

[oohhh yeah]

I did it a few times in my Civic on track, that's one of the reasons I wanted a rear drive car. What a horrible design flaw!

I just thought of something, when braking on cars without ABS, the front brake always locks up first. But by how much is different for all cars because of different brake biases right? So it's usually a lot harder to lock the rear wheels and stall a RWD car.

 

[Bones Brigade]

Not the same, but I will occasionally (I'm only 26, and I'm already losing my mind) leave the hand brake on before taking off. That'll do it if I'm in a hurry.

 

[Omnis]

My cars spends 60% of its running time in neutral. Slushbox ftw.

 

[niky]

I just thought of something, when braking on cars without ABS, the front brake always locks up first. But by how much is different for all cars because of different brake biases right? So it's usually a lot harder to lock the rear wheels and stall a RWD car.

If you come to a stop and you're still in gear with the clutch engaged, you will stall, no matter what you're driving.

It's not a design flaw of FWD, mind you... in fact, engine braking on the front axle actually helps you get the rear end to come around in cornering (throttle-lift oversteer) on the right car. The design flaw of FWD is all that weight up front that makes it difficult to tune a good balance into the suspension for track work. Oh, and that out-of-corner traction thing...

Remember: "Car steps out, both feet out, car in spin, both feet in." Same applies to braking in a straight line, keep both feet to the floor to make sure you stop and still have your engine running to get you moving again in case the guy behind you doesn't have the brains to brake.

 

[Alex.]

Coming off the motorway last week the lights went red and the truck in front braked so I stalled it in 3rd whilst braking. Only time I've ever done it though.

 

[oohhh yeah]

My cars spends 60% of its running time in neutral. Slushbox ftw.

What's a slushbox? Automatic?

If you come to a stop and you're still in gear with the clutch engaged, you will stall, no matter what you're driving.

It's not a design flaw of FWD, mind you... in fact, engine braking on the front axle actually helps you get the rear end to come around in cornering (throttle-lift oversteer) on the right car. The design flaw of FWD is all that weight up front that makes it difficult to tune a good balance into the suspension for track work. Oh, and that out-of-corner traction thing...

Remember: "Car steps out, both feet out, car in spin, both feet in." Same applies to braking in a straight line, keep both feet to the floor to make sure you stop and still have your engine running to get you moving again in case the guy behind you doesn't have the brains to brake.

What do you mean by "car steps out"?

And that is the reason for clutch in on braking hard? So the car doesn't stall? But wouldn't it be best to keep the engine engaged for engine braking?

Coming off the motorway last week the lights went red and the truck in front braked so I stalled it in 3rd whilst braking. Only time I've ever done it though.

What's the drivetrain on you car?

 

[Eric.]

Haven't ever stalled from braking, like someone else said, its a reflex to push the clutch in when you brake that hard. I spun the MR2 for the first time at our last big autocross event of the year, and when I look back on it, I have no memory of pushing the clutch in after I knew it was gonna go around. I just came to a stop (backwards), put it in first and continued on.

 

[VTRacing]

Yes, on gravel. Happens all the time in a FWD rally car (4WD and RWD too if you're trying hard enough).

As lbsf1 said above, so long as you're moving when you release the brake it'll bump start the engine again.

 

[niky]

What do you mean by "car steps out"?

When the car starts sliding. Once the rear end starts to come around, STOP all pedal inputs... Don't try to brake or increase/decrease throttle. Catch the slide first, then let off or let on the gas. Of course, this is very generalized... as with a front-wheel drive, as long as you're in the right gear, you can stomp on the gas to try to straighten the car out (fun off-road), but you're better off trying to correct with steering first.

Then, when the car is in an irrecoverable spin, as Eric says, clutch and brake in. Brake to help the car stop, clutch to keep the engine alive so you can move away from the stop.

And that is the reason for clutch in on braking hard? So the car doesn't stall? But wouldn't it be best to keep the engine engaged for engine braking?

Engine braking is a non-issue. In an emergency, nobody has time to shift down two, three, four or five gears while standing on the brakes. You can use engine braking when slowing down gently or going downhill or when your actual brakes fail on the highway... but nothing stops the car as quickly as the regular brakes.

We've done 0-100-0 tests, and clutch-in or clutch-out, there's no difference in stopping distances. The difference is in whether you have to restart the car or not after you've come to a stop.

-----

I like to tell people, the brakes are not for slowing the car down. They're for stopping it. Period. To save on brake wear and fuel while on the highway or between lights, coast or engine-brake down to the speed you want. One of my biggest pet peeves is people who tap their brakes endlessly on the expressway to bring the car back down to whatever target speed they're trying to hit. Great way to heat up the brakes and glaze the pads... A smart and economical driver will only use the brakes sparingly, which keeps them fresh for when he actually needs them.

 

[Grayfox]

What's a slushbox? Automatic?

Slang term for a vehicle equipped with an automatic transmission.

 

[oohhh yeah]

Yes, on gravel. Happens all the time in a FWD rally car (4WD and RWD too if you're trying hard enough).

As lbsf1 said above, so long as you're moving when you release the brake it'll bump start the engine again.

You have to slip the clutch right? Because if the clutch is fully engaged the wheels will just stay at full lock and keep skidding, instead of starting the engine again. Am I right?

When the car starts sliding. Once the rear end starts to come around, STOP all pedal inputs... Don't try to brake or increase/decrease throttle. Catch the slide first, then let off or let on the gas. Of course, this is very generalized... as with a front-wheel drive, as long as you're in the right gear, you can stomp on the gas to try to straighten the car out (fun off-road), but you're better off trying to correct with steering first.

Then, when the car is in an irrecoverable spin, as Eric says, clutch and brake in. Brake to help the car stop, clutch to keep the engine alive so you can move away from the stop.



Engine braking is a non-issue. In an emergency, nobody has time to shift down two, three, four or five gears while standing on the brakes. You can use engine braking when slowing down gently or going downhill or when your actual brakes fail on the highway... but nothing stops the car as quickly as the regular brakes.

We've done 0-100-0 tests, and clutch-in or clutch-out, there's no difference in stopping distances. The difference is in whether you have to restart the car or not after you've come to a stop.

-----

I like to tell people, the brakes are not for slowing the car down. They're for stopping it. Period. To save on brake wear and fuel while on the highway or between lights, coast or engine-brake down to the speed you want. One of my biggest pet peeves is people who tap their brakes endlessly on the expressway to bring the car back down to whatever target speed they're trying to hit. Great way to heat up the brakes and glaze the pads... A smart and economical driver will only use the brakes sparingly, which keeps them fresh for when he actually needs them.

Makes sense. But can you elaborate on your 0-100-0 tests? Are you talking about real life or GT5? And how is it possible that the times are the same? Engine braking HAS to help. Even if it is a tiny bit. Should reduce the time at least. Unless you are talking about the engine already turned off because of locked wheels?

One more thing, what you talk about being economical on the highway, wouldn't using engine brakes use alot of gas? It would be more economical to just use the brakes?

Thanks

 

[Alex.]

What's the drivetrain on you car?

Front drive dude.

 

[Sureboss]

One more thing, what you talk about being economical on the highway, wouldn't using engine brakes use alot of gas? It would be more economical to just use the brakes?

Not at all. Lets have an example.

I'm doing a km of driving, I'm using a constant amount of fuel for the first 500m, up ahead I see traffic pulling to a stop. If I use engine braking I let off the power and let it just slow down nice and easy. If I'm using brakes, I may be using the accelerator for another 300m. Yet you've travelled no further.

That's a rubbish example, but the point is that engine braking is more efficient than using the brakes as you're not using the throttle for that distance difference.

Wait for Famine/Niky to provide a better explanation!

 

[homeforsummer]

Not at all. Lets have an example.

I'm doing a km of driving, I'm using a constant amount of fuel for the first 500m, up ahead I see traffic pulling to a stop. If I use engine braking I let off the power and let it just slow down nice and easy. If I'm using brakes, I may be using the accelerator for another 300m. Yet you've travelled no further.

This, and that when you lift off the gas on a modern car, it essentially uses no fuel whatsoever. The second you aren't on the gas, it's the road that's driving the engine, rather than the other way around.

The other benefit to what you mention of course is that if you scream up to traffic lights and brake at the last minute, then chances are you'll have to wait in the queue with everyone else for the light to go green. If you lift off earlier then chances are that the lights will already be green as you get to them, so you'll have used less power accelerating too.

Incidentally, ignore anyone who tells you that coasting downhill in neutral uses less fuel than coasting down in a high gear. As long as you've not got engine braking physically slowing you down (which in a high gear shouldn't be the case) then cruising down in gear uses less fuel. Knocking it into neutral means the engine is using some fuel to keep itself running.

As for the 0-100-0 tests Niky is describing, they'll be real, not GT5. The friction brakes on a car are far stronger than engine braking could be so whether you stop in gear or in neutral won't make a bit of difference to the times as it's the friction brakes doing all the work.

 

[niky]

Basically, if you HAVE to use the brakes to slow down, you've wasted too much gas gaining speed that you have to shed, anyway.

Using engine braking is effective because fuel-injected cars use very little (a tiny, tiny trickle) to no gas under engine braking. Much less than when you're coasting in neutral.

You have to slip the clutch right? Because if the clutch is fully engaged the wheels will just stay at full lock and keep skidding, instead of starting the engine again. Am I right?

Nope. A stopped engine will not offer enough resistance to keep the tires locked once you get off the brakes. That's why it's possible to push-start a manual transmission car.

Makes sense. But can you elaborate on your 0-100-0 tests? Are you talking about real life or GT5? And how is it possible that the times are the same? Engine braking HAS to help. Even if it is a tiny bit. Should reduce the time at least. Unless you are talking about the engine already turned off because of locked wheels?

We did this in real life via V-Box for our local Car-of-the-Year tests. I've been one of four test drivers and the assigned data recorder for the last two years and I've recorded over three hundred 0-100-0 (km/h) tests on the racetrack.

The four of us use slightly different techniques. Initially, when we started out, one or two of us would use engine-braking (keeping our feet off the clutch), resulting in a dead engine by the end of the test. The numbers didn't improve. The only technique that improves distance is how aggressive your initial tip-in is. (Threshold and cadence braking are difficult to pull off when you're testing dozens of different models over the course of a day).

With old cars with drum brakes and master cylinders too small to lock the brakes on a bicycle, engine-braking had a measurable effect... but braking at 1G, standing on the pedal, hanging from your seatbelt and with all four tires locked and/or the ABS chattering away, any incremental effects of engine braking will be un-noticeable. If you take the time to downshift and rev-match while slowing down, you're slowing down too slow. Can you downshift and rev-match down through every gear from 5th at 60 mph in just four seconds? Neither can I.

As long as your brakes are strong enough to lock your tires or activate ABS (basically the same thing... ABS activates once you lock your tires), then you have more than enough braking power. Unless your brakes are absolutely, completely shot, you should never need engine braking.

 

[VTRacing]

You have to slip the clutch right? Because if the clutch is fully engaged the wheels will just stay at full lock and keep skidding, instead of starting the engine again. Am I right?


Makes sense. But can you elaborate on your 0-100-0 tests? Are you talking about real life or GT5? And how is it possible that the times are the same? Engine braking HAS to help. Even if it is a tiny bit. Should reduce the time at least. Unless you are talking about the engine already turned off because of locked wheels?

One more thing, what you talk about being economical on the highway, wouldn't using engine brakes use alot of gas? It would be more economical to just use the brakes?

Nope, no need to touch the clutch, the wheels will start rotating once you come off the brakes which will kick the engine in. Of course you need to have some momentum - if you've slowed to walking pace then you may not have enough momentum. Dipping the clutch will keep the engine dead.

Take a manual car and park it on a steep incline facing down a hill with the engine off. Put the car in 1st, release the clutch and brakes and the car will have enough momentum to kick the engine over. Bump start, roll start it's all the same.

And I agree with niky, the effect of engine braking in an emergency stop is negligible. You waste more concentration trying to mess around with the gears that could be put to better use with your actual braking.

 

[Keef]

I just thought of something, when braking on cars without ABS, the front brake always locks up first. But by how much is different for all cars because of different brake biases right? So it's usually a lot harder to lock the rear wheels and stall a RWD car.

Most street cars are designed with conservative (heavy) front brake bias for safety's sake. The front wheels lock first, sliding straight, as oppose to the rear wheels locking and the car spinning out of control. The front brakes don't necessarily need to be that strong. The rear brakes could be strengthened quite a bit and improve straight-line braking distances, but at the sacrifice of corner braking stability.

And then there's the obvious fact that most of the weight is on the front under braking and therefore those brakes need to be stronger.