Loony - I think that any term involving depressing the clutch twice is double clutching.....you can double clutch upshifting as well, you are 100% correct, however, a good driver shifts so fast, that the difference RPMS you would bring it up to in double clutching and the RPM drop if you shifted as fast as posible is very minimal. Because of only a slight RPM drop, you go for whats fastest, which would be going directly to the next gear w/o pausing in N...... at least thats the way I see it.......

 

LG Motorsports sells an alum pedal (the G2 pedal cover) that bolts on to the FBody rubber gas pedal that widens the pedal and enables you to roll your foot on to the gas while braking. I had one on my old 98 SS, and it helped a bunch.

You don't really "heel and toe", anyway. You brake with your foot to the right side of the pedal, and then while keeping brake pressure, you roll the right side of your foot onto the accel to "blip" or match revs on downshifts. You can blip whether you single or double clutch, although with double clutching, you don't need to blip as hard to match revs--the process of letting out the clutch in neutral has already equalized the speed of the input and output shafts, so all you are doing is matching the diff in revs between the gears when you let out the clutch in the lower gear.

As to why you do it, well, if you engage a lower gear without matching revs, sometimes you'll lock up or break traction with the rear wheels and spin. Not good. It also makes for much less wear and tear on the driveline.

 

Thanks for the info on that
I know, I don't literally mean i have my foor turned 90*, more like 30*
Exactly, it can only help (if you do it right) and does make a difference on driveline durability duration.

 

Double clutching is a technique used by truckers (some times) when they are shifting because they don't have synchronizers in their transmissions. When you upshift or downshift you push in the clutch place the transmission in neutral, release the clutch, bring the engine rpm's to match the speed and gear, press in the clutch and place in desired gear. The reason they do this is to match the input shaft speed with the tailshaft speed for the desired gear. This isn't neccessary on any automotive transmissions because they are synchronized and automatically match the shaft speeds.

 

does anyone make a different pedal that would make heel- toeing easier. not just a pedal cover but a whole new pedal? i just dont like the idea of putting a cover on the current pedal. id rather have a whole new one if possible.

as far as doing it. well im trying to learn myself and the only way i could possibly do it is like most everyone else. left side brake right side gas. but the gas is just a little too far right. i dont feel comfortable at all. which is way i asked the above question. thanks trey

 

thats what I thought... because ive always been into dirt biking and thats what the term has always meant in the dirt biking world. But not in car terms I guess.

 

Down shifting only. Unless your really slow on the up shift.

msw

 

exactly, double clutching involves clutching twice......the term double clutching doesn't necessarily mean upshifting or downshifting...... whatever people are more familiar with, it seems they associate double clutching to either upshifting OR downshifting... I think double clutching is a more general term.....

 

Double clutching dose involve clutching twice and is a term best applied to what an over the road trucker dose when he downshifts. One time to get the transmission out of gear (or gentle application of the throttle and slip it out) and another time to get it back in. A driver with full talent will use the clutch only to start, and slip shift all gear changes up or down after, simply by modulating the throttle. Truck drivers with something less than full talent may choose to double clutch on up shifts also. Particularly in lower gears were ratios are very tight and its easy to miss the "window" for the next gear. A driver with good throttle control and mechanical symphony will be able to get it done with one dip of the clutch. Or none.


msw

 

Well I finally realized what heel/toeing really is....Haha....And Ive been doing it for the longest time. I dont use both heel and toe at the same time but Im gonna try it out. I usually push clutch, tap gas/brake/downshift clutch up. Haha I do the tap gas press brake shift and let up on the clutch just about all at the same time. My one friend was driving with me one time and he said he never saw that. I do it all the time because I just think its less wear on the clutch and it doesnt make you jerk when you downshift.

 

hmmm... interesting thread.

Any dog-leg transmissions require double-clutching... this includes NASCAR, many other race-only manuals (like Jerico), and heavy duty big-rig trannies. The torque or rpms' involved typically make syncros unworkable at those levels... or at least within the weight limits expected.

Here's the concept (the way I understand it at least):
1) The idea is to free the input shaft from speed of the outsput shaft (direct linked to the drive shaft obviously) by disengauging the gear and placing it in neutral,
the 2) having it (the input shaft) match the speed of the engine by releasing the cltuch. If you don't release the clutch while the tranny is in neutral, you NEED syncros or a ton of skill to hit the next gear.

3) Spinning up the engine with a throttle-blip then accelerates the input shaft so that BOTH the engine AND the input shaft are hopefully insynch with the output shaft once the new gear is selected.

If executed correctly, a double-clutch preforms a gear change (and engine/input shaft rpm adjustment) without any interuption. Obviously this can still be performed with a syncro-mesh tranny (either ring or cone style), but there is a trade-off:
time.

Syncromesh permits the driver to either:
a) be a few more RPM's off of a perfect match when throttle-matching a downshift. (pointless gains when youy consider the weight gains and durablity lost with syncros)
or b) to elliminate the time-consuming neutral-gear pause, and double-pump of the clutch leg.

For drag racers there is an obvious advantage to syncro-enabled manuals, although most serious drag-only guys go with automatics anyway. For enthusiast road racers, sycros finally allow people to pump through gears like a pro of yester-year, granted, at the risk of burning out syncros (instead of clutches or bogging engines).

Even with Syncro's, you really should try to throttle-match to save your clutch/flywheel (which is the point of the modern heal-tow downshift)... but taking the time to hit a double-clutch just isn't worth it IMO.

Looking at this speed-matching issue, it's clear that double-clutching on a upshift is mostly pointless. While you're expecting the engine RPM to drop, and the input shaft WILL be slowing down on it's own, that's where you WANT it to be on an upshift... slightly slower that when it was at shift point. Double clutching the input shaft to engine speed, then pressing the clutch allows it to slow BELOW the engine speed, while trying to match it to output shaft/gear speed. This is why double-clutching is typically considered a down-shift only technique... because the time/effort it takes up is useful on a downshift (when the input/engine NEED to be throttle-matched to higher rpms), but not really worth it when the drag/resistance in the tranny is already helping out with matching speeds.




BTW, I'd wager Tony Stewart would kick Scheumacher's @ss in a heal-toe competition (if any such thing really existed )... those sissy F1 guys use paddle shifters, and computer-controlled throttle blips to artifically throttle-match.

My money goes on his *** in heal-toe technique by far.

 

Yep... that sounds right to me. That jerk you describe is the same chasis-unsettling stuff that causes tires to break free when at the limit of adhesion on a fast corner. This is why us amature drivers are told to downshift before the corner, instead of during a corner... it's just safer that way. Mastering heal-toe is on my list of "to do" ... everytime I've tried it at speed (ummm... ok I admit it... cloverleaf on ramps ) it's either an outstanding success, or an scared-stiff near miss.

Driving school will be fun once I get everything squared away on the car.

 

Are you guys sure you are double clutching? I do not see the point at all. It appears that some of you may be referring to general rev-matching. When you downshift, you push the clutch in, blip throttle quickly and move shifter to desired gear. Are you actually letting out the clutch with the shifter in neutral, and then pushing it in again? If so, WHY? I do not see ANY benefit to this. Am I missing something on it? On a side note, its funny as hell if you don't match revs and drop it from 5th to 3rd, and then floor it. It makes the tires slow down a second, and chirps them. Rough as hell on the drivetrain I'm sure, but still makes people think the car is fast as nuts. My buddy used to do it in his 14 second mustang all the time.

 

No I dont double clutch but I do rev match.

 

Steve, I think for the most part you are right. You went into allot of the detail I was trying to avoid.
On the Jerico which I think is mandated for road courses by NASCAR, Ive seen many in car shots of drivers downshifting without H-T. What am I missing? IE syncros. Even if it has syncros You'd think they would still H-T.

"3) Spinning up the engine with a throttle-blip then accelerates the input shaft so that BOTH the engine AND the input shaft are hopefully in synch with the output shaft once the new gear is selected."
In a pure racing gearbox (crash box) you need not perfectly match the speeds of the associated components when shifting up and down thru the gears. H pattern and sequensal included. A Champcar would be an example. You only need to be close, and have good timing. The trick is to make sure the dogs on the end of the gears are not overlapped. One of the characteristics of this form of shifting done properly is a quick jerk ahead as the new gear is selected, pulling the engine revs down slightly. The skilled drivers do this well and make time. The less skilled tear up the dogs on the gears and are the ones you often hear about late in a race with a car "jumping out of gear". By necessity, if you are a left foot braker in one of these cars you don't use the clutch and consequently must be good in the above technique. If you are good on the downshifts the up shifts would not be that tuff to master.

On the Schumacher deal, your probably right. His rep in F1 has been that of pure speed, car control, set up, *****, etc... Strangely, he also had the ability to go thru transmissions at a rate higher than the norm. He was saved by the paddle shifter in 93 or 94. For a circle tracker turned road racer Stewart is a VERY quick study and could very well be better on the 3 pedal dance. Once the turns began I'm afraid Smoke would get smoked though. Schumacher is that fast.

msw