I didn’t claim I did double clutch.
I don’t get it.
My father used to own a Civic with a manual transmission. He drove that car almost daily for nine years and over 200,000 miles. He never once double-clutched or rev-matched, and yet we NEVER had to replace a clutch. He was simply very smooth and used the clutch only as often as necessary.
Seems to me that simple good driving habits will make a considerably greater difference to the life of your transmission than rev-matching or double-clutching.
Double declutching is simply not necessary on a modern manual transmission. Unless you’re doing some serious racing, why bother? The amount of wear and tear you save is negligible for the average driver. The whole point of synchro mesh is to do without this nonsense.
That said, it’s kind of fun. I do it to keep myself entertained on long drives. Try out some heel-and-toeing for fun (if your pedals layout allows it.) It also feels kinda cool–I like it.
As for popping the car into neutral while slowing down, personally, I like to do it. I’ve heard that it’s a big no-no for driving tests in Europe, but if I’m going from 60 mph to 20 mph (let’s say), I’d rather have the car in neutral and ready to throw it into the correct gear for maximum performance than risk having it at 30 mph in 5th and slowly lurching forward when I hit the throttle. Of course, this also means that when I’m slowing down, I usually have one hand on the wheel, and one on the stick. Given the tradeoff (two hands driving, much too high of a gear vs. one-handed driving and the ability to throw it into the correct gear in a split second), I prefer the latter. YMMV and all that.
No, no, no! What he said was “to blave”.
I haven’t driven manual for 14 years now, but I don’t recall downshifting much at all. I have no clue how to “blip the throttle” [sub] are we sure that’s not a euphemism for something else?[/sub]. I drove manual for 16 years before that. I was taught by my dad who would never let me do something that would harm the car. (I thought those veins in his head would burst when I ground the gears while learning to drive.) As best as I can remember, if I downshifted I did so by Method A. My last manual transmission vehicle I owned for 9 years and never had problems with the clutch, never had to have it replaced and it probably would have lasted even longer but I just had to have a new car with air conditioning.
Blip Throttle would make a great screen name or porn name.
I don’t use method B as my feet are too big to heel and toe properly, putting more revs on than necessary when re-engaging the clutch doesn’t seem a very hot idea for normal driving IMHO.
Besdies, I’m normally covering the brake when changing down, the only time I’m not is when I’m changing down for more power and it’s not like my Civic has a light flywheel that drops the revs quickly anyway.
I thought I read (maybe here) that double clutching gets the “lay shaft” or whatever it’s called up to speed, whereas normal “blipping” doesn’t.
That is, even though you have sychros, there is still something that isn’t up to speed when you just “blip” instead of “double clutch”.
FWIW, I’ve found I don’t need to be as accurate with the revs when I double-clutch as compared to blipping for a smooth transition. That’s just my feeling though.
I’ll do ‘A’ sometimes when the overall revs are low, I guess, but not too often.
I’ve never “rev matched” on any car I’ve ever owned. I’ve also never had to replace a clutch due to excessive wear. I did replace a clutch on my old 1971 Super Beetle once, but it was necessary due to an engine upgrade.
I will note that the owner’s manual on the 2002 Corvette I just sold recommends against using the transmission to slow the car down, saying the brakes alone should be just fine.
I dunno, but this rev matching thing sounds to me like an invitation for disaster. I’d rather replace an inexpensive clutch than some more expensive component of the tranny. Then again, since I’ve somehow managed to not wear out a clutch, I must be doing something right.
The main reason to double-clutch/rev-match/whatever is not to save the clutch, and not to save the synchros in a modern manual tranny.
The real reason is that, as the multiple parts of a transmission come together for a downshift, there is some drivetrain shock. This drivetrain shock will, when driving at the limit, cause inbalance in the car, which can cause it to do some unpredictable things, like lose traction. This is especially true of downshifting in a turn, when your tires are nearing their limit of grip. You don’t want to be sending a sudden shock through the system, and moving the weight of the car around in unpredicatable ways.
But, I’ve also found that, since most people aren’t race car drivers, there is some real world benefit as well. If you ever drive in snowy or low traction situations, you may be driving closer to the limit of grip than you think, and accompanying drivertrain shock can make your car behave in undesirable ways.
So, beyond the clutch wear issue, double-clutching is a safer, smoother, faster way to drive.
At one point is it “riding the clutch”? If I’m at a stop, with the car in first, but the clutch fully depressed, am I still “riding the clutch”? Nothing is in contact at that point, right? What if I depress the clutch while the car is not in gear at all?
Riding the clutch is not associated with using the clutch. Riding the clutch is resting one’s foot on the clutch pedal when not using it. The problem with doing this is that it tends to allow a slight amount of slippage, which over time can significantly shorten the life of the clutch mechanism.
Weird. I’ve always heard “riding the clutch” as coasting with the clutch fully depressed. It would never occur to me to simply rest your foot atop the clutch pedal. Seems rather tiring. A quick Googling, though, seems to show that both uses are fairly common.
Driving with the clutch held down puts stress on the throwout bearing, and can lead to premature failure of that part, but as long as the clutch disk surface isn’t subject to friction, it’s not bad for the clutch itself.
The problem with prolonged idling with the clutch in is that while the clutch pedal is depressed, you are putting a great deal of sustained axial load on two bearings:
-The clutch throwout bearing
-The thrust bearing inside the engine.
The clutch linkage weather mechanical or hydraulic typically provides around a 25:1 or more, mechanical advantage to your leg. So if it takes ~10# of force to hold your clutch in, you are putting a ~250# axial load on those bearings.
The throwout bearing is typically on the nosepiece of the transmission. It is lubricated prior to installation with grease, and the transmission has to be removed to add any lubrication. Thus, it never gets any attention until it fails or something else fails that also requires removal of the transmission. This bearing is not an expensive part, (lots of labor though) so is normally just replaced rather than serviced.Ideally the grease, and thus the bearing, will outlast the clutch, at which time both can be replaced. Time and heat, though, will eventually use up the grease in this bearing so they do sometimes fail well before the clutch.
Prolonged clutch-in time causes this bearing to heat. The good news is that you are ideling, so the bearing isn’t seeing high load and speed simultainiously. Still, it
is taking wear that would be avoided if you put the transmission in neutral until, say, the cross traffic gets a yellow light. Reving your engine with the clutch in IS pretty hard on this bearing.
The thrust bearing in the engine is possibly a greater issue over time. This is a plain, oil film bearing. It depends on engine oil pressure, and hydrodynamic forces to keep the two metal parts seperated. (think water skier). At idle, both the oil pressure and hydrodynamic forces are at a minimum. As the engine wears, oil pressure typically decreases, so what may have been sufficient when the engine was new may no longer work the same. Hydrodynamic force varies with oil viscosity, which depends on rating, condition, and temperature.
An old hot engine due, or overdue, for an oil change may permit direct metal-metal contact in the thrust bearing when presented with clutch throwout loads.
Conversly, ideling in neutral spins transmission bearings which are under essentially zero load, and are literally dripping with relativly cool gear lube.
Kevbo, thanks for the explanation. I have replaced clutches, and trannies, and wasn’t even fully aware of what a thrust bearing did. I appreciate the time you put into that post.
Has anyone here had a vehicle that had to be double clutched? Two of my last 3 vehicles required it, one was a bottom loader that would throw linkage if you missed matching the revs. I got real good real quick at both double clutching and squaring away the linkage. The other was just old with no synchros. It’s such a habit now that I do it without thinking.
I noticed another oddity to my driving style, most likely learned with my first sportscar…it had a weak or dying synchro going into first gear, so if I was slowing down and would need first gear (e.g. slowing down, but not stopping completely), I’d have the clutch in, select SECOND, then select first.
This would allow me to get first gear without grinding. In retrospect, it was keeping the input shaft spinning, rather than forcing the synchro to get the input assembly rotating all by it’s lonesome.
In my advancing age, I may have done it in mom’s car too, she had an AMC Eagle that didn’t like engaging first gear above 15 mph. (yeah, selecting 1st gear at 20 mph in a four door AWD station wagon is not exactly expected by anyone other than a wet behind the ears teenager.)
Smoked its clutch pretty good too, but that’s another story.
Yep, that’s what I do. Why? Because brakes are lot easier and a lot cheaper to replace than a clutch.