Question regarding the double-clutching topic.

[DainBramaged]

I thought that I knew how to double-clutch. I finally realized what it really was after reading several of the posts and links in the recent thread/poll. Now, I can easily get my Maxima to downshift into 1st gear around 25 mph if I so desired if I rev-match and then shift. I was never able to downshift until about 10-15 and then sometimes it would grind. Now it is smooth and no grinding.

My question is is double-clutching hard on the car in any way? A guy at work was telling me that this is hard on all of the synchros and I don't think that this makes sense, but I thought that I would ask around here. To me, it seems like this should be *easier* on the car. Please give my your thoughts.

 

[Sqube]

What the hell is double-shifting, anyway?

Benefits? Downsides?

 

[CRXican]

why would you ever downshift to 1st at 25mph?

 

[chrisms]

My 4-speed, 86 toyota pickup works just fine without double clutching

 

[DainBramaged]

Originally posted by: Sqube
What the hell is double-shifting, anyway?

Benefits? Downsides?

If you want to know *what* double-clutching is, read this post.

 

[DainBramaged]

Originally posted by: CRXican
why would you ever downshift to 1st at 25mph?

Going around a corner, by the time I am doing about 20, if I wanted to accelerate quickly, I could. Especially since my Maxima has a VTC issue and has very little low-end power, it's nice to be able to accelerate from 15-20 mph no problem.

 

[chrisms]

It's kind of hard to double clutch when I'm frying on acid

 

[StageLeft]

Originally posted by: DainBramaged

Originally posted by: CRXican
why would you ever downshift to 1st at 25mph?

Going around a corner, by the time I am doing about 20, if I wanted to accelerate quickly, I could. Especially since my Maxima has a VTC issue and has very little low-end power, it's nice to be able to accelerate from 15-20 mph no problem.

Yeah the maxima rather sucks until you hit about 3k.

 

[Sqube]

Wow... interesting thread and a lot of subtly different explanations. Which doesn't help for people trying to understand.

 

[StageLeft]

Originally posted by: Sqube
Wow... interesting thread and a lot of subtly different explanations. Which doesn't help for people trying to understand.

If you are at 4k in 2nd gear and want to go into 3rd gear and 3rd gear, at this speed, would be about 3k RPM, normally you just put the clutch in and move from 2nd to 3rd. Double clutching would involve you putting the clutch in, moving to neutral, letting the clutch off, revving the engine to 3k, then putting the clutch in again, then move it to 3rd, then disengage the clutch and you're finally in third.

Other than a few circumstances like if dainbramaged wants to get into 1st, there is never a reason to double clutch on a modern transmission.

 

[DainBramaged]

Originally posted by: Sqube
Wow... interesting thread and a lot of subtly different explanations. Which doesn't help for people trying to understand.

Dude, no way you had time to read the whole thread and read the links in the thread. I had no idea what it was before I read the thread and now I have a pretty good understanding of it. Just spend a little time with it.


Does NOBODY have any idea if it is hard on the car???

 

[TheLonelyPhoenix]

Originally posted by: DainBramaged

Originally posted by: Sqube
Wow... interesting thread and a lot of subtly different explanations. Which doesn't help for people trying to understand.

Dude, no way you had time to read the whole thread and read the links in the thread. I had no idea what it was before I read the thread and now I have a pretty good understanding of it. Just spend a little time with it.


Does NOBODY have any idea if it is hard on the car???

It is *slightly* harder on the synchos (to my understanding), but nothing significant. Of course, it sounds like your using it around 5-6k rpms, so maybe it would be significant.

I think I'd take off the lead shoes in your case and use 2nd gear when at 15 mph. You really shouldn't downshift to 1st unless you're hardly moving and absolutely have to.

 

[gsellis]

It saves wear on the synchronizers, but does more wear on the throwout bearing and the clutch plate (marginal). It also does more wear on the engine at higher revs. But the wear on the synchronizers is the worst of all these, so if you must ... Good synchronizers would not need double clutching.

A really good gearbox needs no clutching at all, just good rev match and better driver. That is where you find left-foot braking coming in.

 

[DainBramaged]

Originally posted by: TheLonelyPhoenix

Originally posted by: DainBramaged

Originally posted by: Sqube
Wow... interesting thread and a lot of subtly different explanations. Which doesn't help for people trying to understand.

Dude, no way you had time to read the whole thread and read the links in the thread. I had no idea what it was before I read the thread and now I have a pretty good understanding of it. Just spend a little time with it.


Does NOBODY have any idea if it is hard on the car???

It is *slightly* harder on the synchos (to my understanding), but nothing significant. Of course, it sounds like your using it around 5-6k rpms, so maybe it would be significant.

I think I'd take off the lead shoes in your case and use 2nd gear when at 15 mph. You really shouldn't downshift to 1st unless you're hardly moving and absolutely have to.

Again, the only reason that I would do it is because the car has almost no power in 2nd gear at 15 mph. It's not something that I would do often, but it's kind of nice to be able to when I want to, especially considering that it shifts so smoothly when doing it.

 

[TwoBills]

Originally posted by: Skoorb

Originally posted by: Sqube
Wow... interesting thread and a lot of subtly different explanations. Which doesn't help for people trying to understand.

If you are at 4k in 2nd gear and want to go into 3rd gear and 3rd gear, at this speed, would be about 3k RPM, normally you just put the clutch in and move from 2nd to 3rd. Double clutching would involve you putting the clutch in, moving to neutral, letting the clutch off, revving the engine to 3k, then putting the clutch in again, then move it to 3rd, then disengage the clutch and you're finally in third.

Other than a few circumstances like if dainbramaged wants to get into 1st, there is never a reason to double clutch on a modern transmission.

Skoorb, your talking about upshifting using a double clutch. Totally unnecessary w/todays trannies. Grabbing that 1st gear, as mentioned by the OP, well, I can't remember the last time I dropped down to 1st, double clutching or not. It's just totally unnecessary.

On the other hand, a double clutch downshift can be quite handy, but you've got to be a rather assertive driver to make it benificial. The thing everybody is missing on this subject is the use of the brakes. Without proper use of the brakes (I like to call it the control petal when I'm in front of a judge), before the double clutch, well, you'd be just putting undue stress on all driveline components, not to mention the connecting rod bearings.

Here's a classic example of where double clutching comes in handy: Leaving an 80mph highway and entering a 360 degree uphill ramp. Blip it from 5th to 4th (no dc) on the approach, brake hard going in to burn off the speed, dc into 3rd, accelerate into the apex, back off a little to let the ass kick, dc into 2nd and hit it. At this point your hitting the entrance ramp at speed, shift into 3rd and merge. Without the dc this would be a jerky, non fluid event.

If you're a good, fast driver, you need to double. If you're just an adverage, daily, "get the hell out of the fast lane!" driver, well, forget double clutching. It's just going to cost you vast amounts of money in extra repairs, until you learn how, and when, to do it properly.

 

[jlee]

I sometimes DC just..because..but revmatching works just as well, since my synchros work fine..

Run it 'till it breaks and fix it faster.

:thumbsup:

 

[Zenmervolt]

Originally posted by: DainBramaged
I thought that I knew how to double-clutch. I finally realized what it really was after reading several of the posts and links in the recent thread/poll. Now, I can easily get my Maxima to downshift into 1st gear around 25 mph if I so desired if I rev-match and then shift. I was never able to downshift until about 10-15 and then sometimes it would grind. Now it is smooth and no grinding.

My question is is double-clutching hard on the car in any way? A guy at work was telling me that this is hard on all of the synchros and I don't think that this makes sense, but I thought that I would ask around here. To me, it seems like this should be *easier* on the car. Please give my your thoughts.

The guy at work is an idiot.

Double-clutching saves wear on the synchros. That's why you can downshift at higher speeds when double-clutching, it synchronizes the transmission without using the synchros.

Double-clutching wears the clutch slightly more (nothing significant), and it wears the associated clutch componants (master and slave cylinder, bearings, clutch arm) a very tiny bit more since you're cycling the clutch twice instead of once, but it's not significant enough to make any kind of difference.

ZV

 

[Zenmervolt]

Originally posted by: TwoBills

Originally posted by: Skoorb

Originally posted by: Sqube
Wow... interesting thread and a lot of subtly different explanations. Which doesn't help for people trying to understand.

If you are at 4k in 2nd gear and want to go into 3rd gear and 3rd gear, at this speed, would be about 3k RPM, normally you just put the clutch in and move from 2nd to 3rd. Double clutching would involve you putting the clutch in, moving to neutral, letting the clutch off, revving the engine to 3k, then putting the clutch in again, then move it to 3rd, then disengage the clutch and you're finally in third.

Other than a few circumstances like if dainbramaged wants to get into 1st, there is never a reason to double clutch on a modern transmission.

Skoorb, your talking about upshifting using a double clutch. Totally unnecessary w/todays trannies. Grabbing that 1st gear, as mentioned by the OP, well, I can't remember the last time I dropped down to 1st, double clutching or not. It's just totally unnecessary.

On the other hand, a double clutch downshift can be quite handy, but you've got to be a rather assertive driver to make it benificial. The thing everybody is missing on this subject is the use of the brakes. Without proper use of the brakes (I like to call it the control petal when I'm in front of a judge), before the double clutch, well, you'd be just putting undue stress on all driveline components, not to mention the connecting rod bearings.

Here's a classic example of where double clutching comes in handy: Leaving an 80mph highway and entering a 360 degree uphill ramp. Blip it from 5th to 4th (no dc) on the approach, brake hard going in to burn off the speed, dc into 3rd, accelerate into the apex, back off a little to let the ass kick, dc into 2nd and hit it. At this point your hitting the entrance ramp at speed, shift into 3rd and merge. Without the dc this would be a jerky, non fluid event.

If you're a good, fast driver, you need to double. If you're just an adverage, daily, "get the hell out of the fast lane!" driver, well, forget double clutching. It's just going to cost you vast amounts of money in extra repairs, until you learn how, and when, to do it properly.

You're wrong about the brakes. Properly executed, a double-clutch downshift is rev-matched perfectly and there is _ZERO_ drivetrain shock since all rotating componants are synchronized through double-clutching and rev-matching even without using the brakes.

ZV

 

[LS20]

Originally posted by: Skoorb
If you are at 4k in 2nd gear and want to go into 3rd gear and 3rd gear, at this speed, would be about 3k RPM, normally you just put the clutch in and move from 2nd to 3rd. Double clutching would involve you putting the clutch in, moving to neutral, letting the clutch off, revving the engine to 3k, then putting the clutch in again, then move it to 3rd, then disengage the clutch and you're finally in third.

Other than a few circumstances like if dainbramaged wants to get into 1st, there is never a reason to double clutch on a modern transmission.

good job skoorb. this is the first time, in 10+ double-clutching threads ive read on anandtech, that someone actually described the technique correctly.

my car's pretty old, and i feel resistance trying to move the gear levers down shifting. doubleclutching makes it butterysmooth. i think 90% of my downshifts are double clutch and turns are heel/clutch. its 2nd nature to me

 

[skyking]

double clutching is clutching into nuetral, then out of nuetral into another gear. That can be either up or down. The only big wear item there is the throwout bearing.
The classical usage is for regular upshifts in square cut gear non-snycro truck transmissions back in the way back days. An example was the '52 corn binder my brother in law had. If you did not double clutch that beast, you were referred to as "grinding a pound for dinner". It also had the nice characteristic of needing to be "unturned". If you went around a right turn, <picture much arm over arm motion>, you had to repeat the process after the corner or run into the ditch. The other trucks I drove would more or less straighten themselves out if you let go of the wheel.
If you ride the clutch at lights and stops, you'll do considerably more damage to the throwout bearing than any amount of double clutching will do.

 

[LS20]

Originally posted by: TwoBills
Skoorb, your talking about upshifting using a double clutch. Totally unnecessary w/todays trannies. Grabbing that 1st gear, as mentioned by the OP, well, I can't remember the last time I dropped down to 1st, double clutching or not. It's just totally unnecessary.

On the other hand, a double clutch downshift can be quite handy, but you've got to be a rather assertive driver to make it benificial. The thing everybody is missing on this subject is the use of the brakes. Without proper use of the brakes (I like to call it the control petal when I'm in front of a judge), before the double clutch, well, you'd be just putting undue stress on all driveline components, not to mention the connecting rod bearings.

Here's a classic example of where double clutching comes in handy: Leaving an 80mph highway and entering a 360 degree uphill ramp. Blip it from 5th to 4th (no dc) on the approach, brake hard going in to burn off the speed, dc into 3rd, accelerate into the apex, back off a little to let the ass kick, dc into 2nd and hit it. At this point your hitting the entrance ramp at speed, shift into 3rd and merge. Without the dc this would be a jerky, non fluid event.

If you're a good, fast driver, you need to double. If you're just an adverage, daily, "get the hell out of the fast lane!" driver, well, forget double clutching. It's just going to cost you vast amounts of money in extra repairs, until you learn how, and when, to do it properly.

double clutching saves wear.. it does not add any stress. forcing the shifter through the gates before the synchros can do their job is worse. your description, while vivid and imaginative, is completely unecessary and irrelevant

 

[TwoBills]

Originally posted by: Zenmervolt
properly.

You're wrong about the brakes. Properly executed, a double-clutch downshift is rev-matched perfectly and there is _ZERO_ drivetrain shock since all rotating componants are synchronized through double-clutching and rev-matching even without using the brakes.

ZV[/quote]

That's true, but if you're double clutching as part of your normal slowing down routine, then I think it's more economical, in the long run, to use the brakes more. I prefer burning off the speed with the brakes, and then execute a 5-3 or a 4-2 dc. I never gear down to slow down, that's what the brakes are for, with some exceptions.

 

[TheLonelyPhoenix]

Hmm, I thought the syncho actually took more wear from being spun down when going into neutral and back up when getting into gear.

Then again, I'm probably wrong. I'm very drunk right now, and this post took roughly 5 minutes to type.

 

[jagec]

Originally posted by: TheLonelyPhoenix
Hmm, I thought the syncho actually took more wear from being spun down when going into neutral and back up when getting into gear.

Then again, I'm probably wrong. I'm very drunk right now, and this post took roughly 5 minutes to type.

If all your drivetrain components are spinning at the appropriate speeds when you shift (which is the case when you double-clutch), there is ZERO wear on the synchros.

I don't know WHERE the theory that double-clutching wears the synchros came from, but it's completely backwards.

 

[thomsbrain]

the guy at work is wrong. it is NOT double-clutching that is "hard" on the syncros (though this is what they are built for, so no worries). double clutching is easy on the syncros, because it makes the syncro redundant.