car talk says double clutching is bad?

[daniel]

Quoted for un-truth. Sure, some cars are more difficult than others to blip into first gear at a roll, but if you can't do it with your E30 via a simple rev-match, then you've probably already beat-up your transmission trying to learn the useless art of double-clutching a synchro'd tranny.

alright, well considering how much easier it is to shift into first gear when DCing, i see no reason why someone should just rev-match to get into first.

i don't see how DCing is useless with a synchro'd tranny when downshifts are much much smoother when executing a DC correctly. if one is going for smoothness, then DC, if you are going for convenience, then rev-match.

[Beach Bum]

Double clutching SAVES synchros; to all of you who thing DC'ing is going to burn them faster, you're simply wrong.

I'm going to make this easy for all of you. Read these.

http://auto.howstuffworks.com/transmission.htm

http://www.mproved.com/dblcltch.htm

"Double-clutching is the proper way to downshift at speed without placing excessive wear on the transmission's synchronizers."

If you examine how a transmission works and understand it, and then take the time to understand how double-clutching manipulates the parts and forces in the drivetrain, you'll see that the above statement is true.

I really can't make this any easier for those of you who believe DC'ing will harm synchros.

[HiTheNameIsBJ]

Not double clutching like you should, not to mention the piston rings you fried now me and the mad scientist gotta rebuilt the block.

[daniel]

I really can't make this any easier for those of you who believe DC'ing will harm synchros.

people aren't saying that. they are saying that it wears out other parts of the drivetrain, instead, like the clutch, and that it is better to put wear on the synchros and just rev-match instead of DC.

[nando]

like I said, unless your Getrag 260 has 500,000 miles on it, synchro wear probably isn't even on the radar yet.

as long as you aren't just putting it in a lower gear and letting out the clutch, whatever method you choose is just fine. heel/toe is likely better if you are braking into a corner, DC may be better for slower driving where entry speeds and corner exit are perhaps not a big priority.

[z31maniac]

^Unless you bought your car from a no driving track monkey who had the trans trashed at 123k miles.

[RangerGress]

that's the common name for it, but since I don't actually use my heel, rev matching is a better term. It's more like pinky toe/ball of foot. ;)

Rev matching isn't a better term because no one will understand that you mean HnT. Most folks don't use their heels with modern pedal systems, but they still understand what the phrase means. Most people HnT by braking with the ball of their big toe and (if necessary) rotating the foot a little such that the outside of the foot can hit the gas. If you pedals are set up well, you don't move your heel hardly at all, you just kind of roll your foot, instead of rotating it.

Which sounds pretty much what you were describing.

When I say rotate I mean around the axis of your shin, whereas by rolling the foot I mean around an axis that goes from toes to heel.

There's a lot of confusion about what HnT and double-clutching means. Most folks that use those terms are really just blipping the gas during downshifting.

Now don't leap on my ass shouting "I KNOW WHAT < > IS". If you know what HnT and double-clutching is, then obviously I wasn't talking about you.

[daniel]

^Unless you bought your car from a no driving track monkey who had the trans trashed at 123k miles.

my zf320 has 95k miles on it, and the clutch has about 15k miles on it w/ a lightweight flywheel.

[nando]

my zf320 has 95k miles on it, and the clutch has about 15k miles on it w/ a lightweight flywheel.

so it's just broken in then. :p

[Wh33lhop]

double-clutch when upshifting anyway, which is presumably what you do during a drag race.

I hope you're joking.

[Wh33lhop]

Quoted for un-truth. Sure, some cars are more difficult than others to blip into first gear at a roll, but if you can't do it with your E30 via a simple rev-match, then you've probably already beat-up your transmission trying to learn the useless art of double-clutching a synchro'd tranny.

Go ahead, try and get into first going 25mph. It's possible and I'm sure it's cool listening to the synchro spool-up whine, but it gives you the distinct impression that you're doing something wrong, and it should, because you are.

[nrubenstein]

I double clutch when my transmissions are very cold. There's no point in doing it at any other time.

[nando]

I hope you're joking.

out of context quote FTL.

he obviously meant you are upshifting during a drag race, and that double clutching would be pointless in that case. ;)

[87e30]

My guess? He's got no idea what he's talking about. Lots of misinformation, even among techs.

But yeah, if you fuck up a double clutch you WILL grind, fortunately that is a very rare occurrence for me, but it does happen. Double clutching is more risky than regular rev matching.



Well, try rev matching into first and come back. ;)



The clutch "spring" you speak of is actually a disc, attached to the pressure plate. You replace it with the pressure plate every time you use the clutch, and no it doesn't really wear out in that way.

There's also usually a little spring on the clutch pedal, but that's a different matter.



That's because the throw-out bearing is used whenever the clutch is depressed. I don't think that's really applicable here.

Interesting information about the TOB and the disc. However, I definitely think my neighbor knows what he's talking about. Considering the amount of people on here saying that double clutching is stupid I'm going to have to stick with that side of the argument.

Why even do it? It's slower and involves more work.

[87e30]

I'm not sure how double clutching is "smoother." If you're driving regularly doing shifts into gears that are next to each other there is nothing unsmooth about rev matching. it just takes an ounce more effort to move the gear lever. The actual motion of the car is still smooth.