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      02-02-2013, 09:44 PM   #1
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Downshifting

Hi guys,

I am newer to manual transmissions. My question is in the winter in order to stop more efficiently I like to downshift occasionally in order to stop better. Do I have to rev match down shift in the winter because even though I do that in the summer in the winter it doesn't help to stop as much as just putting it in the lower gear.

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      02-02-2013, 09:51 PM   #2
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Rev-matching on downshifts preserves your clutch and some wear and tear on the driveline. If you're just letting the clutch out on down shifts, then you're using the clutch as a brake. Sometimes, it's okay, but it's probably best to rev-match as often as possible, at least that's what I do. 108K miles on the original clutch...

Most importantly...Have fun doing it!!
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      02-02-2013, 09:55 PM   #3
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So you're speaking in terms of engine braking?

Also, if you're able to rev-match, why not make it second nature?

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Originally Posted by BMW335icoupe View Post
Hi guys,

I am newer to manual transmissions. My question is in the winter in order to stop more efficiently I like to downshift occasionally in order to stop better. Do I have to rev match down shift in the winter because even though I do that in the summer in the winter it doesn't help to stop as much as just putting it in the lower gear.

Thanks
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      02-02-2013, 10:03 PM   #4
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Use your brakes for stopping. The only time I rev match downshift is to prepare for a turn or when I think the light will turn green soon and I want to prepare to accelerate.
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      02-02-2013, 10:10 PM   #5
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In winter you have to be careful in downshifting especially if you have RWD. If there is snow or ice you could be in for a surprise spin.
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      02-02-2013, 10:26 PM   #6
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If you downshift to slow down without rev matching the car can slow down abruptly and spin. This is called Trailing Clutch Oversteer (TCO). The brakes are for slowing the car down and act on all four wheels.

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      02-02-2013, 10:40 PM   #7
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Yeah, TCO is not fun, here's how I know. It was pouring cats and dogs one night so when I got in my car my shoes were soaked and slipping all over the pedals. Rolling up to a light that was about to change I put it in second and was about to start to rev match and my left foot slipped and I dumped the clutch. The back wheels lost traction and kicked out and I pulled a 180. Thankfully I didn't slide all the way into the guy sitting at the light and the guy behind me was far enough back to stop in time. He had a pretty shocked look on his face with my front end staring him down. Pulled a three point turn and went on my way, narrowly making it out of a situation that could have been far worse.
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      02-04-2013, 10:15 PM   #8
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your brakes are the best bet for smooth deceleration
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      02-04-2013, 11:06 PM   #9
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Quote:
Originally Posted by e90-328i View Post
In winter you have to be careful in downshifting especially if you have RWD. If there is snow or ice you could be in for a surprise spin.
Yep. Do not use downshift to brake, especially not in winter. Brakes are all powerful nowadays, engine braking is unnecessary (except for long downhills).
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      02-04-2013, 11:34 PM   #10
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Quote:
Originally Posted by calicolorado View Post
Rev-matching on downshifts preserves your clutch and some wear and tear on the driveline. If you're just letting the clutch out on down shifts, then you're using the clutch as a brake. Sometimes, it's okay, but it's probably best to rev-match as often as possible, at least that's what I do. 108K miles on the original clutch...

Most importantly...Have fun doing it!!
Quote:
Originally Posted by captainaudio View Post
If you downshift to slow down without rev matching the car can slow down abruptly and spin. This is called Trailing Clutch Oversteer (TCO). The brakes are for slowing the car down and act on all four wheels.
^ solid advice.

http://www.e90post.com/forums/showthread.php?t=112651

http://www.e90post.com/forums/showth...uble+clutching

No, engine braking isn't necessary but I do it all the time. I think it's important is to be in the right gear all the time, but be smooth about it. Why? Because accelerating quickly out of situation may be the better solution than braking.

I've been double clutching a long time and I now have a hard time not doing it. It's fun. Learn it along with heel and toeing after you perfect rev-matching and smooth braking.
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      02-05-2013, 10:32 AM   #11
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Rev matching is fun and useful (when driving agressivelly), but double clutching has been useless since the 60's (since sychro boxes). Nobody does it in Europe, but I keep hearing people doing it in the US, that confuses me.

That being said, the rest of what Alezandr said is correct, you don't want to brake with the clutch, but you still want to downshift so that you can resume acceleration if needed (so, downshift when you are out of the power band, to land in the middle low of the power band on the new gear).
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      02-05-2013, 10:59 AM   #12
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Quote:
Originally Posted by VTECaddict View Post
Use your brakes for stopping. The only time I rev match downshift is to prepare for a turn or when I think the light will turn green soon and I want to prepare to accelerate.
+1, brakes were meant to perform that function. brakes are wear and tear item and replacing those are far cheaper than your engine. and while say these expensive cars are capable of engine braking on a regular basis, the point is why would you want to when you have brakes for that reason. only time i use engine braking is when i go down a steep hill.
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      02-05-2013, 01:10 PM   #13
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Quote:
Originally Posted by Meeni View Post
but double clutching has been useless since the 60's (since sychro boxes).
I believe that sychromesh was invented in the late 1920's and was common in US cars by the mid 1930s.

What happened in the 60's (in the US) was the availablilty of 4 speed transmissions with synchromesh 1st gears, as most domestic MTs were 3 speeds with synchronized 2nd and top gears only.

And (at regular 25k mile intervals) when the clutch cable broke on my 4 speed '65 Corvair , double-clutching became necessary so I added an accessory tachometer.

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      02-05-2013, 02:40 PM   #14
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brakes are cheaper than replacing a clutch and brakes work better as many have said, when i used to drive stick i only downshifted to speed up, never for anything else.. well except to sound cool driving around a parking lot i guess? lol
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      02-05-2013, 05:43 PM   #15
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Rev match to save your tranny, not for braking.

111k on stock clutch no issues and I rev match quite alot. Yes thats what sincros are for but they do wear out over time.
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      02-05-2013, 05:53 PM   #16
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Personally, I would limit the downshifting to periods of "spirited driving". Its saves on the clutch, wear on the engine, and fuel. As suggested by others, rev matching will help make that clutch last longer, and when you get the heel and toe thing going, you will feel and sound like a pro!
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      02-06-2013, 03:18 PM   #17
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Quote:
Originally Posted by junkie90 View Post
So you're speaking in terms of engine braking?

Also, if you're able to rev-match, why not make it second nature?
Yeah I am saying as far as breaking. It is second nature but it helps to slow down the car.

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      02-06-2013, 03:22 PM   #18
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Ok so when coming up to a light you guys would just recommend pressing the clutch and then putting it in neutral.

If the light changes when I am coasting in neutral then I would normally just rev to the correct RPM and then put it in the correct gear. Does it matter if the clutch is depressed or not.

Thanks
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      02-06-2013, 03:38 PM   #19
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Quote:
Originally Posted by BMW335icoupe View Post
Yeah I am saying as far as breaking. It is second nature but it helps to slow down the car.

Thanks
Downshifting solely for the purpose of slowing down isn't as effective as braking.

Quote:
Originally Posted by BMW335icoupe View Post
Ok so when coming up to a light you guys would just recommend pressing the clutch and then putting it in neutral.

If the light changes when I am coasting in neutral then I would normally just rev to the correct RPM and then put it in the correct gear. Does it matter if the clutch is depressed or not.

Thanks
My take is that if your car doesn't need to be in neutral, don't do it. If you pop the car into neutral and let it coast, braking while your engine is not in gear will probably yield less braking power.

Edit: did a quick search for you.

http://www.m5board.com/vbulletin/e39...r-neutral.html
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      02-06-2013, 04:14 PM   #20
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Quote:
Originally Posted by BMW335icoupe View Post
Ok so when coming up to a light you guys would just recommend pressing the clutch and then putting it in neutral.

If the light changes when I am coasting in neutral then I would normally just rev to the correct RPM and then put it in the correct gear. Does it matter if the clutch is depressed or not.

Thanks
My technique is to shift into neutral (using the clutch) only after having slowed to about 5 mph. If the light then changes before I come to a stop, I shift into 1st or 2nd also using the clutch.

I've yet to replace a clutch in 5 Bimmers, so I guess it's working.

Tom
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      02-06-2013, 04:32 PM   #21
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Thanks guys. So you end up downshifting either way correct if you don't put it in neutral.
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      02-06-2013, 07:55 PM   #22
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Quote:
Originally Posted by BMW335icoupe View Post
Ok so when coming up to a light you guys would just recommend pressing the clutch and then putting it in neutral.

If the light changes when I am coasting in neutral then I would normally just rev to the correct RPM and then put it in the correct gear. Does it matter if the clutch is depressed or not.

Thanks
The optimum soltion is to depress the clutch, and just brake. In an auto, bump it into neutral. It unloads the drive train, and prevents the car from overdriving the brakes on snow/ice. Most pro drivers will say popping a manual into neutral is a no no from a safety point of view though.

You don't really need to rev match. Slow clutch release with slight throttle is fine.

Downshifting when coming to a stop is a way to kill and expensive clutch vs cheap brakes.
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