A few questions on car mechanisms and driving habits

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Wrichik Basu
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I have a Toyota Etios Liva, about three and a half years old. It is a petrol variant, with manual transmission. I am quite interested in the mechanisms of a car and good driving habits. Sadly, none in my family knows driving. My knowledge of driving habits extend to the manual given with the car (which I have read from the first to the last page). As you can understand, the car is driven by drivers, who do not have good driving habits most of the time. Hence, it has become necessary to take some advice regarding the proper habits of driving. If you know driving, please join and help me out.

Question 1:

I know that pressing the clutch separates the engine from the wheels, and it is used during changing of gears. But what is the difference between pressing the clutch and keeping the gear in neutral?

Question 2:

Say I am on a highway, with speeds around 100km/h. In this condition, I decide to let my car move under inertia (say for the sake of experiment). I have two options: 1. Change the gear to neutral but I do not keep the clutch pressed, or 2. Keep the clutch fully pressed throughout the period, without changing the gear. Which of these is a better method in terms of wearing away of car parts?

Question 3:

When a car has to halt (say because of a traffic signal), I have seen drivers press the clutch while braking. Why is that done? If I change the gear to neutral and do not keep the clutch pressed, what will happen?
 

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  • #2
Borg
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A manual transmission is connected to the engine by the clutch plate. When you press the clutch in, you are separating the engine from the transmission. When the transmission is in neutral, it is connected to the engine but the gears in the transmission are not aligned to provide torque to the wheels. There isn't a lot of difference between these two other than the strain of holding the clutch in for the first option.

For question 2, it's best to just leave it in a higher gear. An idling engine will allow a car to move at a pretty good pace depending on the gear. If you disengage the transmission, you lose that benefit.

Pressing the clutch while braking is done so that the car doesn't fight your braking efforts. Otherwise, you either wouldn't come to a complete stop or the engine wouldn't be able to turn and would quit.

As you can see in the diagram below, when a transmission is "in gear", the engine torque makes it all the way to the set of gears on the top right which provide power to the wheels. When it's in neutral, those gears never get engaged. The clutch in these diagrams would be located to the left of each picture.
manualTrans.jpg
 

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  • #3
russ_watters
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Question 2:

Say I am on a highway, with speeds around 100km/h. In this condition, I decide to let my car move under inertia (say for the sake of experiment). I have two options: 1. Change the gear to neutral but I do not keep the clutch pressed, or 2. Keep the clutch fully pressed throughout the period, without changing the gear. Which of these is a better method in terms of wearing away of car parts?
I'm not sure this is a useful question as asked; since you are doing an experiment, the results don't necessarily mean anything in terms of good driving practice. In general each time you press or release the clutch there is some wear on it. So for normal coasting you want to leave the car in gear. However, most of the wear is when you are using the clutch when accelerating since that is when there is a lot of torque/friction on it.

And as far as I know, it isn't really that important whether you keep the clutch in or release it with the car shifted to neutral.
Pressing the clutch while braking is done so that the car doesn't fight your braking efforts. Otherwise, you either wouldn't come to a complete stop or the engine wouldn't be able to turn and would quit.
I'm not sure if this is specific enough so I'm not sure to what extent I agree/disagree....

You need to press in the clutch just before you come to a complete stop to prevent stalling. Otherwise you can and probably should remain in gear or even downshift to save gas and so the engine can assist in braking (as your brakes wear out faster than your clutch).

It's been a while since I drove stick, but my recollection is that I would just pull the shifter to neutral right before I stopped, without using the clutch. I found that after experience with a car I understood the shift points well enough that I didn't need to use the clutch for several of the situations where it was proscribed.
 
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Borg
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You need to press in the clutch just before you come to a complete stop to prevent stalling. Otherwise you can and probably should remain in gear or even downshift to save gas and so the engine can assist in braking (as your brakes wear out faster than your clutch).
Yes, stalling is what I meant. I've also seen people have difficulty to the point where they couldn't stop and the engine just kept pushing them down the road in a lurching fashion (usually with larger horsepower cars). Pretty funny to watch.
It's been a while since I drove stick, but my recollection is that I would just pull the shifter to neutral right before I stopped, without using the clutch. I found that after experience with a car I understood the shift points well enough that I didn't need to use the clutch for several of the situations where it was proscribed.
I used to always switch to neutral for a stop. The only time that I downshifted was when I wanted to dramatically slow the car but that was hard on the engine as I worked my way into the lower gears.
 
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Wrichik Basu
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I'm not sure this is a useful question as asked; since you are doing an experiment, the results don't necessarily mean anything in terms of good driving practice.
I read on some sites that coasting is not a good practice. What I wanted to say was, "Even though I know coasting is not good, I want to compare the effects on the car with clutch pressed or in neutral gear".
 
  • #6
ChemAir
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I read on some sites that coasting is not a good practice. What I wanted to say was, "Even though I know coasting is not good, I want to compare the effects on the car with clutch pressed or in neutral gear".
When the clutch is disengaged, the pressure plate spring fingers push against a throwout bearing (or something of similar design), rather than seating the clutch. The throwout bearing isn't really meant for continuous use (non greasable, not maintainable). I would expect a throwout bearing to not last as long if overused. That said, the throwout bearing is probably the cheapest part of a clutch/transmission, and sealed bearings are fairly reliable these days.

throwout-bearing-800x800.jpg
 

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