Can someone explain why "heel & toe"

[mickey356]

Originally Posted by darrin

Exactly -- My VERY MINIMAL track driving education taught me that the only real reason to downshift is to be in the sweet spot, power-wise, when coming back on throttle out of a turn. Braking in the track environment is seldom done gradually, as 1) gradual braking scrubs speed and 2) sharp braking provides effective weight transfer (loads up the front end going into a turn). Or -- put another way, since a clutch replacement is more $$ than new brake pads, it makes little economic sense to preserve brakes at the expense of your clutch when slowing down.

^^^^^^This.
Unless you drive on track, and your pedals are set up properly, or you're ridiculously seasoned at performance driving, you really don't ever have a need for heel toe shifting on the road. It's pretty hard to drive a car aggressively in most places, legally and safely, to the point you'd benefit from heel toe.

[Bill Verburg]

Originally Posted by Neilnaz

Bill, I said going from 4th to 3rd to 2nd wouldn't be useful. I would advocate going from 4th to 2nd with a bigger blip as you say....

well everyone has a reason, the trans guys like you to hit each gear on the way down even if you don't spend time in them to reduce the shock load on the syncros, the Instructors like it because it reduces the chance of a goof and spin w/ them in the car

[kent olsen]

Ok my opinion. Heel/toeing is easier on clutch engagement and transmission scyncros. I heel/toe all the time. Both engines I have installed in my 72 (230,000 miles, 2.4L to 2.7L to 3.0L) the clutch disc looked as good as the new one I put in. Also it's much easier on the transmission. There will come a day when the transmission needs to be rebuilt and guess what is the main part replaced, yep the 2nd and 3rd gear scyncros.

On the track or fast track autox, you what that gear to give you max torque pulling out of the turn. If you just pull it down into the gear you what when you let out the clutch you may find yourself looking back the way you came. Also I have found that in some situations, a high speed straight coming down to a much slower turn I can concentrate more on my braking and then heel/toe down from say 5th to 3rd with out sometimes getting a little unstable downshifting 2 gears.

Just my opinion.

[scarceller]

Mechanically heel toe isn't really any easier on the syncros, only double clutching really reduces syncro wear. The syncro bands are to get the tranny main shaft and intermediate shaft at the same speed only double clutching will do this. Bliping just the motor revs will not.

[gliding_serpent]

I rev match all downshifts on the street. I will often heel-toe and brake a bit later and harder on the street if no one is around. Practice for the track. Once I get to the track it becomes subconscious after a lap or two. It makes everything smooth like butter.

Shifting down two gears is slow with the 915 if you hit the gear between. Our track only has one area that requires me to double downshift in my 911, and I have done both (skip a gear, or hit the gear in between). For my situation, I am going from one downhill right sweeper to a left hairpin, and the double shift is rushed. Easy place to spin out (and lots do) with a bad shift as you are never really going straight. I have begun to just go 4th to 2nd, skipping 3rd. If it was in a straight line, I might hit 3rd then second.

With my 2002Tii there was an area where I would need to drop two gears (in a straight line, 4th to 2nd). I tried skipping 3rd, but my 40 year old synchros whispered to me that they did not much like it. I opted to hit 3rd on my way down and never had another issue.

[winders]

Wow. So much misinformation here.

Racers heel/toe when they need to be in a lower gear after braking for a corner to get the best acceleration out of the corner.

The reason racers heel/toe is to keep the chassis from getting upset when the drive wheels and engine are reconnected when the clutch is let out.

The heel/toe's goal is raise the revs of the engine to match what the revs will be in the lower gear at the car's speed when the clutch is let out. If the revs are not matched, the rear tires will need to speed up the engine and that causes extra load on the tires and transmission. If braking in a straight line, the car can wag its tail and even cause a spin. If trailbraking, a spin is much more likely.

Heel/toe does nothing for synchro life. Double clutching (sometimes called Double declutching) on downshifts is the way to increase synchro life.

2nd to 4th downshifts, done properly, are not any harder on a transmission than going through the gears in order.

[gliding_serpent]

Originally Posted by winders

2nd to 4th downshifts, done properly, are not any harder on a transmission than going through the gears in order.

Yup. The trick is just matching the rpms correctly

Mind you, my Tii just did not like 4th to 2nd, but it was probably driver error. Hitting 3rd probably made me time things better and not rush.

[tirwin]

I have a friend that went to the Porsche Driving Experience at Barber Motorsports. He ended up with none other than Hurley Haywood as his instructor. He was early in his Porsche ownership and Hurley was telling him he HAD to learn to heel-toe. So Hurley demonstrated and my buddy was making valiant efforts to do it right but was not getting the hang of it. His lack of ability started to be a sort of running gag until the lightbulb finally came on for him.

I try to practice at every opportunity. It is like the heavens parted when you finally get it. My brake pedal still seems higher than it should be when fully depressed. I used the Rennline accelerator pedal that raises and extends the side of the pedal and it helps. I keep tinkering with the setup. Still not right to me. It seems like what is comfortable is a little different for everybody though.

I still re-read Vic Elford's Porsche High-Performance Driving Handbook from time to time. I think his explanation is the first time I really got the concept.

[Charles Freeborn]

Originally Posted by winders

Wow. So much misinformation here.

Racers heel/toe when they need to be in a lower gear after braking for a corner to get the best acceleration out of the corner.

The reason racers heel/toe is to keep the chassis from getting upset when the drive wheels and engine are reconnected when the clutch is let out.

The heel/toe's goal is raise the revs of the engine to match what the revs will be in the lower gear at the car's speed when the clutch is let out. If the revs are not matched, the rear tires will need to speed up the engine and that causes extra load on the tires and transmission. If braking in a straight line, the car can wag its tail and even cause a spin. If trailbraking, a spin is much more likely.

Heel/toe does nothing for synchro life. Double clutching (sometimes called Double declutching) on downshifts is the way to increase synchro life.

2nd to 4th downshifts, done properly, are not any harder on a transmission than going through the gears in order.

This ☝︎.

[Coastr]

Originally Posted by McLovin

Heel and toe is super easy to learn, *if* the pedals are set up properly for it.

I have an old BMW that has the gas and brake pedals in perfect position for heel and toe. In that car, I heel and toe every downshift. I do it automatically now, without thinking about it.

It's fun when you hit it just right and have a super smooth corner entry downshift. Technically, it's a little easier on the drivetrain, I suppose, too.

Air cooled 911s, I think, have some pedal adjustability, but I don't think there's enough to get it really perfectly "right." The gas pedal is usually way too low. At least in my car it is.

I've seen lots of aftermarket gas pedals available, with adjustability. Those seem designed mostly to make heel and toe easier.

Once you learn it, you can do it in any car, even with poorly set up pedals. But it's not as fun or easy.

What year is your 911? I have read that the pedal position for us models changed when the 55mph speed limit was brought in. The idea was that the foot felt right when at the speed limit. I understand the correct position of a 911 pedal is more upright, which felt bad at 55mph cruise.

[gliding_serpent]

I learned how to heel toe watching a video hurley haywood had on youtube with an automotive joirnalist in a 997 gt3. Practiced in my computer sim rig (with clutch and 6 speed) and then the real thing was quite easy.

[KaiB]

Just for grins. Not that Scott knows anything about going fast, but his post above is absolutely correct and elegant in its simplicity. (You may thank me later Winders...).

Many people complain about the difficulty of the h/t blip. I simply will maintain that if one cares at all about driving that one should ABSOLUTELY learn to do it, and do it well.

There should be no excuse (unless the driver has an ortho problem) for not expending the effort to figure out which position on the pedals works. Some actually heel/toe, others toe/heel, and some roll the slightly angled foot...most do a combination. WHATEVER IT TAKES, DO IT.

I tell my students that the roll of the foot can be practiced at all times in all vehicles. It must be automatic and conditioned and as much of a habit as flushing the toilet. Barefoot, in sandals, workboots covered with mud, it can and must be practiced in all vehicles. If your daily driver has an automatic tranny, then the move can be practiced (i.e. rotation of the foot) without actually blipping the throttle. Sitting at a stop in neutral it can be practiced and sitting in the garage muttering "zoomoom" it can be practiced. Flexibility can be improved beneath the dining room table.

NO DRIVER can call himself one unless his H/T is perfect, secondary in nature and automatic in all conditions in virtually all vehicles.

[wayner]

I also point to Winder's post. Great explanation.


...and, for those who missed Hurley's demonstration on the last page of this thread, here it is again.

Originally Posted by wayner

Watch Hurley explain it at 12:00 in to this video

[Driven97]

The '09+ Nissan 370z (w/ sport package) has a defeatable automatic rev match feature. There's sensors in the shifter (or trans, who knows) that knows what gear you've picked, and the ECU will trigger the electronic throttle to open to the exact rpm needed for that gear.

Seemed like a super gimmicky thing when I first read about it, but dang, talk about a cheat code, it works perfectly in practice.

I know for sure the C7 Corvette 7-speed manual does it now, and I think maybe BMW/Mini do it too. Not sure if anyone else picked it up, but all manual cars should do it these days.

[Bill Verburg]

Originally Posted by winders

...

Heel/toe does nothing for synchro life. Double clutching (sometimes called Double declutching) on downshifts is the way to increase synchro life.

2nd to 4th downshifts, done properly, are not any harder on a transmission than going through the gears in order.

That is correct, except I don't believe that double clutching has any effect on syncro life. Double clutch is a way to shift a transmission that lacks syncros, it is a way to manually speed up or slow down shaft speeds via the clutch. In a constant mesh fully syncro trans the syncros always have to initiate the synchronization process first via friction on the cones on both faces then by mechanical engagement of the syncro teeth.

Porsche air cooled trans from 901 thru 911, 915, g50 all consist of 2 shafts, one is locked to the engine via the clutch the other is locked to the rear drive wheels at all times. W/ constant mesh gears, all gear sets(drive/driven) always mesh w/ their mates on the other shaft.

the upper shaft is the input shaft the lower is the output shaft


Only one gear set at a time is locked to the input and output shaft. The sliders slide on a hub which is always fixed to it's respective shaft, both the gear and the syncro have similarly shaped synchronizing teeth, the slider has a female cone and female teeth that match a male cone and male teeth on one side of the syncro, the syncro also has a female cone and tooth set on the other side and the gear has a male cone and tooth set that matches this. The syncro has a small amount of play until compressed between the gear and slider by the slider motion, friction is generated by the male/female cone arrangement on the syncro and gear respectively. This friction initiates the syncronization process which is completed when the syncro teeth can engage the slider completely this allows the slider to complete it's engagement.



Ignoring 5,6 and R here is the heart of the transmission

This is a g50, the others are similar, the trans is in neutral w/ no gear set locked to the shafts


To select 1st gear the 1-2 slider is moved by the selector fork to the left, it slides on a hub which is locked to the shaft engaging the syncro cone/tooth mechanism, friction between the cone and slider synchronizes the speed of the shaft and gear, once the speeds are synchronized the teeth can be fully engaged

To shift up to 2nd
the shift rod moves the 1-2 slider to the right, again the syncro cones contact the mating cone surface on the gear speeding it up via friction so that the syncro teeth can engage and complete the speeding up process, one this is done the slider completes the move fully engaging the 2nd gear



a downshift from 4 to 3 is initiated by the shift rod moving the 3-4 shift sleeve on the input shaft to the left, the cone engages the slider via friction speeding the input shaft up to match the speed of the wheel driven output shaft, once they are close to the same speed the syncro teeth can engage completing the synchronization and allowing the slider to fully engage the 3rd gear teeth on the input shaft. An engine blip causes the newly speeded up input shaft speed to match the resulting engine speed w/o undo shock from excessive rotating part acceleration.

Here are some syncros and a broken 3rd gear, the gear broke from shock loading


here a shift fork and a steel syncro(upper) and brass syncro lower, the male half of the brass syncro cone, where the initial synchronization friction is generated, is towards the viewer

[Bill Verburg]

Originally Posted by Driven97

The '09+ Nissan 370z (w/ sport package) has a defeatable automatic rev match feature. There's sensors in the shifter (or trans, who knows) that knows what gear you've picked, and the ECU will trigger the electronic throttle to open to the exact rpm needed for that gear.

Seemed like a super gimmicky thing when I first read about it, but dang, talk about a cheat code, it works perfectly in practice.

I know for sure the C7 Corvette 7-speed manual does it now, and I think maybe BMW/Mini do it too. Not sure if anyone else picked it up, but all manual cars should do it these days.

Late Cayman, Boxster, 911 have this auto blip feature too.

[Quicksilver]

Originally Posted by Bill Verburg

That is correct, except I don't believe that double clutching has any effect on syncro life. Double clutch is a way to shift a transmission that lacks syncros, it is a way to manually speed up or slow down shaft speeds via the clutch. In a constant mesh fully syncro trans the syncros always have to initiate the synchronization process first via friction on the cones on both faces then by mechanical engagement of the syncro teeth.
. . .[/img]

Double clutching definitely has an effect on syncro life and you have kind of explained it in the last line above.

If you don't double clutch the syncros have to absorb the energy of any mismatch in gear speed to ensure engagement. The process of absorbing that energy is friction wear. When you double clutch correctly there is no speed mismatch so there is no energy to absorb hence no frictional wear.
To put it another way: Is there any syncro wear when you shift a transmission when the car isn't running? No because the relative speed between the engagement slider and the gear being selected is zero.

------------
Also a clarification on your second sentence:
Double clutching is a way to shift a manual transmission and it is also required to shift a transmission that lacks syncros, ...
Double clutching can be done on most any manual transmission and if you feel the engagement through the shifter it makes it go into gear noticeably smoother and with less force.
(Hell, on my truck I double clutch on the up shifts too. A light weight flywheel and doing it for years makes it effortless.)

[bpu699]

Interesting thread... Trying to practice double clucthing while tracking the 930...

It is HARD. Usually the double clutching is needed when you are going into a slow corner, and want to somehow use 1st gear to exit... Getting into 1st gear while driving at speed almost always seems to grind otherwise...

But it seems risky...

You are flying into a corner, trying to double clutch AND blip the throttle, usually, you are mid turn too... If you screw up the braking, the laws of physics and the immovable object theory will tap dance all over your head...

The gears on a 930 are soooo far apart...

[KaiB]

Originally Posted by bpu699

Interesting thread... Trying to practice double clucthing while tracking the 930...

It is HARD. Usually the double clutching is needed when you are going into a slow corner, and want to somehow use 1st gear to exit... Getting into 1st gear while driving at speed almost always seems to grind otherwise...

But it seems risky...Are you SURE you need 1st? (I don't disagree that some cars want to be double clutched to get there at times, merely asking)

You are flying into a corner, trying to double clutch AND blip the throttle (double clutching usually requires TWO blips. If you're flying into the corner, you shouldn't be TRYING to double clutch - given your terms), usually, you are mid turn too...(If you're FLYING into the corner and find that your shifting occurs mid-turn, you're going too quickly for your skills) If you screw up the braking, the laws of physics and the immovable object theory will tap dance all over your head...

The gears on a 930 are soooo far apart...

Just sayin'...

[bpu699]

Originally Posted by KaiB

Just sayin'...

I am an amatuer...

If you are going into a hairpin turn, you generally have to get down to about 30mph in that turn... or less...

If I stay in second, and I apply the throttle at the apex, I have lost all momentum... Car is at 3000rpm, maybe...

I thought exiting in 1st (good to 50mph or so?) would be quicker...

Maybe the key is applying throttle WAAAY earlier, and calculating when boost will kick in... Though that doesnt sound like the best idea (I know the pro's do this)... Would rather be applying throttle when the car is already in a straight line...

Open to all idea's...