I remember my first drive in a British Sports car quite well. I was five or six years old and the car was an MGA with three large holes in the floor. Being British, the gentleman driving it explained to me that the revving of the engine was partly in aid of “declutching”. Given the state of the floor it made sense to me that we were about to lose the clutch too-being totally ‘de-clutched’!
Recalling this to a friend he found it terribly amusing and explained that in Canada, it was simply known as double declutching and again knowing a bit about British cars, I thought it only wise to have a double clutch – I knew aircraft had twin brake systems, so why not two clutches?
Well time marches on, and I find there ate still people who arc rather confused about these terms, but are not about to risk their status in the inner circle by admitting it! So here it is, read this in the privacy of your own home and get even more confused.
First of all let’s deal with the “double declutching” issue. This is really only the British term for ‘double clutching’ and makes reference in some way, I suppose, to the fact that it is usually a downshifting maneuver in disengaging the clutch. The first stage in a full ‘heel and toe’ gear change is the simple use of double clutching. On its own this is a fairly simple little dance of the toes and it goes like this:
1.You are driving along in your TR/MG or whatever in third gear for example, approaching a corner and preparing to shift to second. You brake with the left edge of the ball of your right foot as usual.
2.Depressing the clutch with your left foot the shift lever passes through neutral – as this happens you release the clutch pedal out again half way, thus setting the mechanics of the clutch Assembly in motion again.
3.Then fully depress the clutch to complete your shift into second.
That my friends is a double declutching. It might sound odd in print but is quite simple in action. Practice it in the driveway, with the engine off so you don’t hit anything. The aim is to keep the engine and the clutch plates turning at the same speed for the moment when they engage themselves. Your car will thank you especially if you have an older vehicle that lacks effective synchromesh.
Heel and Toe
The next step is a true “Heel and Toe”. Naturally it goes without saying that this does not really involve your heel and toe! The name is just to make it harder to understand! (Actually it stems from a rather odd set up in the old Ferraris where the clutch and the brake pedals were switched – but that’s another matter.) The technique involves combining the double clutch method with a second technique that keeps the engine RPM at a level to match the next gear to be engaged.
Everyone has had the experience of changing down into a lower gear and having the engine forced into screaming high revolutions. The other thing that happens is that the weight of the car suddenly shifts forward due to the ‘engine braking effect’. If you happen to be going into a corner this can be enough to lighten the rear end and send the tail out on a visit to the front end! Here’s where the heel and toe technique comes in. Unless you have a third leg you have to brake and ‘blip’ the gas with your right foot. The tricky part is timing it all right and keeping the brake pressure steady while you do the ‘blipping’.
A note of warning here. If you practice this in your driveway as I suggested for double clutching, some of the newer cars will flood as a result of the gas pedal movement (yes! even without the engine running) So if this happens just go off and have a cup of tea and let things settle for a while before heading off to try it in motion. Here we go:
1. Begin the downshift as before, using the left edge of the right foot to brake. Depress the clutch and shift into neutral.
2. Now, as you’re half releasing the clutch, swing (or rock) the right edge and heel of your brake foot over onto the gas pedal and squeeze it gently to bring up the engine RPM. With experience you’ll get to know how much is enough.
3.Then depress the clutch and complete the shift into second. The plates should have been spinning from your double clutching and the engine RPM, which dropped while you were shifting, was brought back up to the level needed by the next gear ratio. Everything just slipped together without a murmur, and there was no forward weight shift or unwanted acceleration of the car. Swing your right foot fully on to the gas, and you’re off down the straight.
Confused? I was too, and I “sort of know” how to do it. Actually the brain is not capable of doing this at all – the method has to leave the area of your brain and become a fluid physical skill. You drive along and your hands and feet do it all, without you really being aware of it; it’s a great technique to master!
By Chris Ball, Technical Editor, Toronto Triumph Club