Downshifting: when has slipping the clutch gone too far?

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stimpy77
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Downshifting: when has slipping the clutch gone too far?

Post by stimpy77 »

Just learned tonight that downshifting at stoplights and down hills is generally not bad (trade normal wear on drivetrain for wear on brakes), ONLY so long as you rev match and don't slip the clutch.

As I have yet to learn to rev match, I am wondering how slowly I can let up on the clutch before slipping the clutch has become a genuine problem for the maintenance of the clutch? I would never assume that any slipping of the clutch is bad, there has to be some slip in gear transition even if split second, but I'm not racing, I just want a smooth everyday commute in city streets without a lot of rpm noise or thought. For most of my time doing MT driving I was always using slow clutch releases at stop lights but now I know that that's bad, so I am just wondering about opinions, how slow is "just fast enough to not be too concerned"? One second release? Half a second release?

Driving a 20016 Subaru WRX
Last edited by stimpy77 on Wed Jan 20, 2016 1:36 am, edited 2 times in total.
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Re: Downshifting: when has slipping the clutch gone too far?

Post by potownrob »

stimpy77 wrote:n00b MT driver. (Drove MT for years when I was years younger but didn't have access to mechanical friends or the Internet.) Just learned tonight that downshifting at stoplights and down hills is generally not bad (trade normal wear on drivetrain for wear on brakes), so long as you rev match and don't slip the clutch.

As I am learning and have yet to learn to rev match, I am wondering how slowly I can let up on the clutch before slipping the clutch has become a genuine problem for the maintenance of the clutch? I would never assume that any slipping of the clutch is bad, there has to be some slip in gear transition even if split second, but I'm not racing, I just want a smooth everyday commute in city streets without a lot of rpm noise or thought. For most of my time doing MT driving I was always using slow clutch releases at stop lights but now I know that that's bad, so I am just wondering about opinions, how slow is "just fast enough to not be too concerned"? One second release? Half a second release?

Driving a 20016 Subaru WRX
in general, if it takes more than a couple of seconds to fully engage the clutch, you're probably doing it wrong. It will depend on the gap in rpms you have to gain between gears how much wear will be caused by a slow downshift. For rev-matching your goal should be to be able to engage the clutch right away after adding the gas. You will get the rev-matches wrong even with lots of practice (we all do from time to time), but you should still be able to let the clutch out much more quickly. I'm too tired to write more; will let cow explain in more detail. Goodnight.
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Re: Downshifting: when has slipping the clutch gone too far?

Post by tankinbeans »

Quite honestly, many of the people I know who drive a manual have never heard of, nor have any idea how to downshift. Their cars feel no ill effects. Heck, sometimes when wearing bulky shoes which make bastardized heel-towing difficult I do the slow release.

Play it by feel, but don't linger. If you're already slowing then eventually there comes a point where the speed you're driving and the speed of the engine will intersect.

I'd advise strongly against dumping it if you haven't rev-matched, or at least made the attempt.
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Re: Downshifting: when has slipping the clutch gone too far?

Post by potownrob »

tank makes some good points i want to elaborate on:
tankinbeans wrote:Quite honestly, many of the people I know who drive a manual have never heard of, nor have any idea how to downshift. Their cars feel no ill effects. Heck, sometimes when wearing bulky shoes which make bastardized heel-towing difficult I do the slow release.
it seems very few people know how to rev-match on downshifts. many people either learn on their own (usually means bad habits learned), or whoever taught them doesn't know much beyond the basics and also may be self-taught (as in without the help of the SS!! :cry: ). as for no ill effects, i don't think this is true, at least not always. i've known at least one person who lived to ride the clutch, downshifting multiple gears with just the clutch. hearing those downshifts made me cringe. that's what i call braking with the clutch. that is NOT what the clutch is designed for. he had to replace his clutch within 2 years of getting the car, and it was supposedly replaced not long before he got the car (94 altima). that's extreme abuse and an extreme case, but to say you can't ruin a clutch by abusing it is misleading.

P.S. If i may teach you one habit not to get into or stick with, it would be riding the clutch. this is when you rest your foot on the clutch or otherwise use the clutch when you don't need to be using it. other than when you are launching, shifting or sitting at a light with the clutch in (if that's your thing), keep that foot off the clutch!! 8) :o
Play it by feel, but don't linger. If you're already slowing then eventually there comes a point where the speed you're driving and the speed of the engine will intersect.
this is true. as i alluded to, it's ok to slip the clutch a little, but it should be brief. if you slow down enough in gear (or in neutral - not the best habit to ride around out of gear, but not the end of the world), you will be at close to the right speed for a lower gear without adding gas.
I'd advise strongly against dumping it if you haven't rev-matched, or at least made the attempt.
what i sometimes do is a test to see how well i rev-matched (or didn't) by letting out the clutch to where it starts grabbing. i then let the clutch out a little more to see if it's reacting smoothly. this is all very quick, mind you, or else i'd lose the advantage of having rev-matched (or not). if i added too much gas, the car may lurch forward a little; if i didn't add enough, it may make the clutch burn sound where the revs go up through the clutch and the car pulls back a little. as long as it's not a major gap in revs, it shouldn't be a big deal either way. this is something you can try doing until you get your rev-matches down (how much to add, ability to add gas and then quickly let out clutch). YOU CAN DO IT!! :o
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Re: Downshifting: when has slipping the clutch gone too far?

Post by stimpy77 »

as i alluded to, it's ok to slip the clutch a little, but it should be brief.

OK. This is what I asked and what I hoped someone more in the know might say. Gives me some relief.

.. found a pattern on my 2016 Subaru WRX that seems to work (in 4th slow to 2k, apply clutch, switch to 3rd, rev to 3k, release clutch, brake to 2k, apply clutch, switch to 2nd, rev to 3k, release clutch, brake to 2k, apply clutch, switch to 1st, rev to about 3300, release clutch, brake to 1k, apply clutch, switch to neutral, release clutch, brake to stop. Now just to memorize the sound and vibrations so I'm not staring at the tachometer so as to work towards second nature
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Re: Downshifting: when has slipping the clutch gone too far?

Post by potownrob »

stimpy77 wrote:
as i alluded to, it's ok to slip the clutch a little, but it should be brief.

OK. This is what I asked and what I hoped someone more in the know might say. Gives me some relief.

.. found a pattern on my 2016 Subaru WRX that seems to work (in 4th slow to 2k, apply clutch, switch to 3rd, rev to 3k, release clutch, brake to 2k, apply clutch, switch to 2nd, rev to 3k, release clutch, brake to 2k, apply clutch, switch to 1st, rev to about 3300, release clutch, brake to 1k, apply clutch, switch to neutral, release clutch, brake to stop. Now just to memorize the sound and vibrations so I'm not staring at the tachometer so as to work towards second nature
your downshifting pattern is good practice for rev-matching, but please do not feel the need to downshift through all the gears to come to a stop. i also recommend tapping the brake pedal periodically (one tap, not multiple; can't think of the right word for that) to let people behind you know if you are slowing down without the brakes. i used to do the downshifting through all the gears routine as a (relatively) younger shifter, before i realized the brakes were there to slow down the car :lol: :evil: :P
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Re: Downshifting: when has slipping the clutch gone too far?

Post by stimpy77 »

Sure, my goal though is to train on downshifting w/ revmatching. I'm fine with being excessive with downshifting on every gear if it means months or years from now when and if I feel ready to just brake in neutral always I'll also have much greater natural command of MT clutching and shifting to support the machinery for long life.
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Re: Downshifting: when has slipping the clutch gone too far?

Post by potownrob »

stimpy77 wrote:Sure, my goal though is to train on downshifting w/ revmatching. I'm fine with being excessive with downshifting on every gear if it means months or years from now when I feel ready to just brake in neutral always I'll also have much greater natural command of MT clutching and shifting to support the machinery for long life.
atta boy!! 8)
next challenge: downshifting right before a turn!! :twisted:
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Re: Downshifting: when has slipping the clutch gone too far?

Post by stimpy77 »

So I'm guessing the technical answer to the question is:

If you "pop" the clutch with an approximate revmatch, you have a teensy little bit of spring action to handle the transition ..

Image

.. but short of "popping" the clutch, as a clutch is halfway engaged you're literally grinding the clutch, to whatever extent you're unsuccessful in rev matching.

https://www.youtube.com/watch?v=pqF-aBtTBnY
https://www.youtube.com/watch?v=FfjGohWy-OU
https://www.youtube.com/watch?v=zgb8-2Y4A8A
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Re: Downshifting: when has slipping the clutch gone too far?

Post by theholycow »

Image

Don't pop the clutch. (By "pop" I assume you mean an uncontrolled engagement, likely accomplished by sliding your foot off the pedal sideways while it's floored.) The springs in the clutch disc don't absorb enough of that shock to avoid abusing the rest of the drivetrain, not to mention the clutch disc itself.

"Grinding" is inaccurate because the surfaces involved are smooth and sufficiently well-matched in hardness that you really can't call it that any more than you can call regular use of your brakes "grinding" the brake pads. By slipping the clutch (within reason) you are using it the way that it was designed to be used. Wear is far less than you think it is.

I used to have the worst clutch wear paranoia. Then in 2010 I converted my Buick and my potential costs for clutch replacement dropped dramatically. Then just a few months ago I replaced the clutch (and transmission) (after 90,000 miles of abuse on a mismatched clutch set with a clutch disc way too small for my car) and found that it really hadn't worn much but my habits of trying too hard to preserve clutch wear (along with the aforementioned too-small clutch) caused a delamination failure. Instead of wearing it down I shocked it to pieces. Now I get it...the thing doesn't look very thick but it really doesn't wear fast at all, you'd have to be a really severely abusive driver to wear a clutch prematurely.

Image

Now, a bit of counterbalance for all of that: If you do abusively slip it for too long, repeatedly, then excess heat could also contribute to such a failure. Actually I don't doubt that it was a combination of both issues in my case.
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Re: Downshifting: when has slipping the clutch gone too far?

Post by stimpy77 »

theholycow, awesome reply, thanks for the followup
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Re: Downshifting: when has slipping the clutch gone too far?

Post by childoffire »

potownrob wrote: Mon Jan 11, 2016 2:52 am tank makes some good points i want to elaborate on:
tankinbeans wrote:Quite honestly, many of the people I know who drive a manual have never heard of, nor have any idea how to downshift. Their cars feel no ill effects. Heck, sometimes when wearing bulky shoes which make bastardized heel-towing difficult I do the slow release.
it seems very few people know how to rev-match on downshifts. many people either learn on their own (usually means bad habits learned), or whoever taught them doesn't know much beyond the basics and also may be self-taught (as in without the help of the SS!! :cry: ). as for no ill effects, i don't think this is true, at least not always. i've known at least one person who lived to ride the clutch, downshifting multiple gears with just the clutch. hearing those downshifts made me cringe. that's what i call braking with the clutch. that is NOT what the clutch is designed for. he had to replace his clutch within 2 years of getting the car, and it was supposedly replaced not long before he got the car (94 altima). that's extreme abuse and an extreme case, but to say you can't ruin a clutch by abusing it is misleading.

P.S. If i may teach you one habit not to get into or stick with, it would be riding the clutch. this is when you rest your foot on the clutch or otherwise use the clutch when you don't need to be using it. other than when you are launching, shifting or sitting at a light with the clutch in (if that's your thing), keep that foot off the clutch!! 8) :o
Play it by feel, but don't linger. If you're already slowing then eventually there comes a point where the speed you're driving and the speed of the engine will intersect.
this is true. as i alluded to, it's ok to slip the clutch a little, but it should be brief. if you slow down enough in gear (or in neutral - not the best habit to ride around out of gear, but not the end of the world), you will be at close to the right speed for a lower gear without adding gas.
I'd advise strongly against dumping it if you haven't rev-matched, or at least made the attempt.
what i sometimes do is a test to see how well i rev-matched (or didn't) by letting out the clutch to where it starts grabbing. i then let the clutch out a little more to see if it's reacting smoothly. this is all very quick, mind you, or else i'd lose the advantage of having rev-matched (or not). if i added too much gas, the car may lurch forward a little; if i didn't add enough, it may make the clutch burn sound where the revs go up through the clutch and the car pulls back a little. as long as it's not a major gap in revs, it shouldn't be a big deal either way. this is something you can try doing until you get your rev-matches down (how much to add, ability to add gas and then quickly let out clutch). YOU CAN DO IT!! :o
Your comment is chock full of assumptions and personal opinions but few facts.

#1: "Riding the clutch damages it"
How do you know your friend had to get his clutch replaced BECAUSE he was riding the clutch? Could it not have been something else? Had you been with him on every drive he ever went on?
I doubt that!

I've been driving the same car for the past 10 years now and I always press the clutch when braking. And I still haven't replaced my clutch, nor do I see any replacements coming up any time soon!

If you'd ask any mechanic, the most common reason for clutch damage is engine lugging, i.e, forcing the engine to pick the car up at low speeds in higher gears. Other reasons include (but aren't limited to): not fully pressing the clutch during shifts, not letting off the gas during upshifts, incorrect rev matching during downshifts, or simply an excessively tight clutch cable.

And this makes sense, because the clutch will be damaged only when there is friction between it and the flywheel (or between the clutch plates in the case of motorcycles), not by pressing the clutch pedal that can only put strain on the clutch springs and nothing else.

So no, riding the clutch can NEVER damage it.

#2: "Slow downshifts damage the clutch"
That's just ridiculous.

If you had two disks rotating at different speeds and you were asked to bring them in contact, what will you do?
Would you just slam them against each other? Or would you allow them to slowly come into contact so that they can match speeds?

Which technique will cause more damage to the disks? The slower one? Seriously?

#3: "Incorrect rev matching is not a big deal!"
I really feel like explaining this to a kid at this point.

How can you even think that slow downshifts cause clutch damage but incorrect rev matches are "not a big deal"?

Going back to the disk analogy again (it's actually not even an analogy... that's exactly how the clutch works!), suppose you were asked to bring the rotating disks in contact but now you were asked to slam them against each other, what will you do to reduce the damage?

Simple. You'll TRY to eliminate the speed difference between the two.

How will you do that?

You'll try to slow the faster one down and speed the slower one up before slamming them against each other.

This is exactly what you're doing when you blip the gas and apply brakes at the same time.

But is it okay if you do it incorrectly?

NOT A CHANCE.

An incorrect blip would not be much better than no blip at all. So it's better if you just eased the clutch out slowly.

And if you still think the attitude your car shows when you blip too high or too low is just quirky behavior, then trust me, you're the one who's soon going to need a new clutch!!!
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Re: Downshifting: when has slipping the clutch gone too far?

Post by ClutchFork »

potownrob wrote: Tue Jan 12, 2016 3:25 am. i also recommend tapping the brake pedal periodically (one tap, not multiple; can't think of the right word for that) to let people behind you know if you are slowing down without the brakes. i used to do the downshifting through all the gears routine as a (relatively) younger shifter, before i realized the brakes were there to slow down the car :lol: :evil: :P
Good idea in case someone is riding your bumper. Oh, I think I read somewhere (maybe here) about some new cars having a brake light go in during downshifting. But all these safety features take a lof of the fun out of things.

Ok the other thing about down shifting is go gently in wet conditions and perhaps DON'T DO IT IN THE SNOW. I once downshifted gently on road that had a half inch of snow (I-96 in morning rush) and my Ranger instantly turned sideways. Thankfully, nobody was in the next lane by me because my tail end went into the next lane.
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Re: Downshifting: when has slipping the clutch gone too far?

Post by ClutchFork »

Here ya go. Auto-rev-match-downshifting on the 2019 Mustang. (No thanks, I'll keep my 1992 Mustang)

https://www.youtube.com/watch?v=rh_7N3j ... e=youtu.be
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theholycow wrote:Why in the world would you even want to be as smooth as an automatic? Might as well just drive an automatic...
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Re: Downshifting: when has slipping the clutch gone too far?

Post by potownrob »

childoffire wrote: Sat Oct 06, 2018 3:27 pm
potownrob wrote: Mon Jan 11, 2016 2:52 am tank makes some good points i want to elaborate on:
tankinbeans wrote:Quite honestly, many of the people I know who drive a manual have never heard of, nor have any idea how to downshift. Their cars feel no ill effects. Heck, sometimes when wearing bulky shoes which make bastardized heel-towing difficult I do the slow release.
it seems very few people know how to rev-match on downshifts. many people either learn on their own (usually means bad habits learned), or whoever taught them doesn't know much beyond the basics and also may be self-taught (as in without the help of the SS!! :cry: ). as for no ill effects, i don't think this is true, at least not always. i've known at least one person who lived to ride the clutch, downshifting multiple gears with just the clutch. hearing those downshifts made me cringe. that's what i call braking with the clutch. that is NOT what the clutch is designed for. he had to replace his clutch within 2 years of getting the car, and it was supposedly replaced not long before he got the car (94 altima). that's extreme abuse and an extreme case, but to say you can't ruin a clutch by abusing it is misleading.

P.S. If i may teach you one habit not to get into or stick with, it would be riding the clutch. this is when you rest your foot on the clutch or otherwise use the clutch when you don't need to be using it. other than when you are launching, shifting or sitting at a light with the clutch in (if that's your thing), keep that foot off the clutch!! 8) :o
Play it by feel, but don't linger. If you're already slowing then eventually there comes a point where the speed you're driving and the speed of the engine will intersect.
this is true. as i alluded to, it's ok to slip the clutch a little, but it should be brief. if you slow down enough in gear (or in neutral - not the best habit to ride around out of gear, but not the end of the world), you will be at close to the right speed for a lower gear without adding gas.
I'd advise strongly against dumping it if you haven't rev-matched, or at least made the attempt.
what i sometimes do is a test to see how well i rev-matched (or didn't) by letting out the clutch to where it starts grabbing. i then let the clutch out a little more to see if it's reacting smoothly. this is all very quick, mind you, or else i'd lose the advantage of having rev-matched (or not). if i added too much gas, the car may lurch forward a little; if i didn't add enough, it may make the clutch burn sound where the revs go up through the clutch and the car pulls back a little. as long as it's not a major gap in revs, it shouldn't be a big deal either way. this is something you can try doing until you get your rev-matches down (how much to add, ability to add gas and then quickly let out clutch). YOU CAN DO IT!! :o
Your comment is chock full of assumptions and personal opinions but few facts.

#1: "Riding the clutch damages it"
How do you know your friend had to get his clutch replaced BECAUSE he was riding the clutch? Could it not have been something else? Had you been with him on every drive he ever went on?
I doubt that!

I've been driving the same car for the past 10 years now and I always press the clutch when braking. And I still haven't replaced my clutch, nor do I see any replacements coming up any time soon!

If you'd ask any mechanic, the most common reason for clutch damage is engine lugging, i.e, forcing the engine to pick the car up at low speeds in higher gears. Other reasons include (but aren't limited to): not fully pressing the clutch during shifts, not letting off the gas during upshifts, incorrect rev matching during downshifts, or simply an excessively tight clutch cable.

And this makes sense, because the clutch will be damaged only when there is friction between it and the flywheel (or between the clutch plates in the case of motorcycles), not by pressing the clutch pedal that can only put strain on the clutch springs and nothing else.

So no, riding the clutch can NEVER damage it.

#2: "Slow downshifts damage the clutch"
That's just ridiculous.

If you had two disks rotating at different speeds and you were asked to bring them in contact, what will you do?
Would you just slam them against each other? Or would you allow them to slowly come into contact so that they can match speeds?

Which technique will cause more damage to the disks? The slower one? Seriously?

#3: "Incorrect rev matching is not a big deal!"
I really feel like explaining this to a kid at this point.

How can you even think that slow downshifts cause clutch damage but incorrect rev matches are "not a big deal"?

Going back to the disk analogy again (it's actually not even an analogy... that's exactly how the clutch works!), suppose you were asked to bring the rotating disks in contact but now you were asked to slam them against each other, what will you do to reduce the damage?

Simple. You'll TRY to eliminate the speed difference between the two.

How will you do that?

You'll try to slow the faster one down and speed the slower one up before slamming them against each other.

This is exactly what you're doing when you blip the gas and apply brakes at the same time.

But is it okay if you do it incorrectly?

NOT A CHANCE.

An incorrect blip would not be much better than no blip at all. So it's better if you just eased the clutch out slowly.

And if you still think the attitude your car shows when you blip too high or too low is just quirky behavior, then trust me, you're the one who's soon going to need a new clutch!!!
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ClutchFork wrote:...So I started carrying a stick of firewood with me and that became my parking brake.
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