how do you know when to change gears in a manual car?

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how do you know when to change gears in a manual car?

In: Engineering

Practice and experience. Each gear has a range of speeds that it is meant for, though there is some overlap. When you are reaching the top end for one gear, you generally begin the process of shifting to the next one. Watching/feeling your RPMs is a good gauge of when you should shift as well.

if RPM is over 3K, or the engine gets loud, you shift up.
if RPM is getting below 1K or engine hiccups, you shift down.

Or you can go by speed, e.g.:
1st gear for take off, parking, pulling up in traffic jam, etc.
2nd gear up to 20 mph
3d gear is 20-40
4th gear is 40-60
This will be different for 5-gears, or car with bigger engine, or if you are going uphill.

Over time, you learn to do it automatically. But it is still a hassle.

Several ways: engine gives a high pitched whine and your rpm needle is too damn high; car won’t go faster unless you shift up; each car is different but you’ll have regular speeds at which you shift up/down at.

You “feel” when it’s time. The rotation speed of the engine is felt and heard in the car, and once you learn what to feel and listen to, you do it pretty automatically.

EDIT: meh. feel and listen. Feel and listen. Not “hear and listen”, as I typed first.

When the engine gets close to its max rpm. The dial has an indicator on most cars (I guess) you can also tell by sound of the engine, when you get familiar.

Changing gears (along with gas pedal position) is used to control the RPMs of the engine and the speed of the vehicle.

When accelerating, you push on the pedal and RPMs increase.

For casual driving, people usually want to keep the RPMs within a comfortable range. This will differ from engine to engine and people to people, but an example might be between 1000 and 5000 rpm.

So as the RPMs increase, you change to a higher gear. This will reduce engine rpm while maintaining about the same speed.

When slowing down, the RPMs will decrease. You can change to a lower gear which will increase rpm.

So whether accelerating or decelerating, you change gears to keep the RPM in the range that you want.

How do you know when? One way would be to look at the tachometer, which shows engine rpm. However, most people also use the sound of the engine, the speed of the vehicle, and the rate of acceleration. They develop a feel for when to change gears and it becomes very intuitive.

Thanks everyone, I’m thinking about buying manual and I have been practicing so it’s nice to see it’s just a practise and learn thing!

Every time you switch, in order, you move to a bigger gear so the car has more traction per revolution of said gear. When you’re in first gear (the smallest) you need to complete many more revolutions to move X distance, when you switch to second you will accomplish X distance in less revolutions and so on. It’s usual to switch at 3k revolutions/min (RPM) because beyond that point you’d be overstressing the engine. Surely by driving the car and getting to know it, and practicing, it will come naturally to switch gears by feel to make it smooth.

My old motorcycle didn’t have a tachometer, so I had no direct readout of how fast the engine was turning. People who were used to working with tachometers asked me this very same question, so I’ll tell you what I told them:

When it goes “EEEEEEEEE!” I shift up, and when it goes “Putt . . . Putt . . . Putt” I shift down.

There is no time or rpm or speed which to shift. It’s by feel, and hopefully I can give you a bit of insight.

First, you shouldn’t skip gears on a regular basis. It makes sense if you accelerate hard and fast, like you hit 60 mph in 2nd gear but then you want to cruise; instead of bouncing between all the gears, because they’re all the wrong gear, just to get up to top gear, you can just pop it into top gear. You can hear your automatic transmission do exactly this if you accelerate like a banshee and then let off. You shouldn’t be driving like you stole it all the time, though…

So what you should aim to do is, since you know approximately what you’re going to be accelerating up to, try to give each gear equal time. This should be easy on most cars if you’re going >30 mph. Slower speeds, and you end up with a lot of short durations in each gear, and at slower speeds, you might not even get into higher gears.

Aim to make the drive smooth and comfortable, for yourself and your passengers. If nothing else, this is all that matters. If it feels right, if it sounds right, then it is right. The goal isn’t to get to any particular gear, it’s to make your shifts smooth and the ride comfortable. It’s to keep the RPMs low for fuel economy, regardless of what gear accomplishes that for the speed. It’s about not doing anything unexpected, so you don’t surprise the other drivers on the road and insight an accident. Imagine your grandmother is in the car – she is not going to appreciate shift shock, jerkiness, and vibration. Neither will your car’s mechanics.

Going by speed is the easiest but also the most incorrect way. You can go at 20 on a level road in gear 4 but if the road is steep, you might need to go down to 2. What matters is how much load the car is carrying.

All experienced drivers do it by feel. And this feel is an internal assessment of multiple factors such as sound of the engine and rate of acceleration.

An example I haven’t seen yet in here (but plenty of good answers), have you ever rode a bicycle with multiple gears?

You start off in a low gear, it’s easy to get moving but eventually as you speed up you’ll be working too hard to maintain the speed you want. So you switch to a higher gear, pedaling suddenly becomes easier and you can maintain a higher speed until you get going even faster and then it’s time to change gears again.

Once you start slowing down or come to a stop however, those higher gears stop being effective. If you’re in a high enough gear you’ll just be spinning the pedals and getting nowhere. So you need to gear down to an appropriate gear.

It’s essentially the same thing in a manual car, except it’s the engine doing the work. 1st or maybe 2nd gear will get you rolling from a stop, but get going fast enough and that engine will start screaming at you and you won’t be able to go any faster until you shift up. Likewise 5th or 6th gear are what you’ll be using on the highway, but they’ll probably stall the engine out if you try to use them from a stop.

While cars will typically have suggested speeds and/or RPM ranges for gear shifts, eventually you’ll just learn to feel based on the engine and the type of driving you’re doing when it’s time to shift.