Who knows what it is?

Yep - Was taught it when I did my HGV.

Yep - use it on every downshift. Probably no need for it on majority of cars but does help to smooth out gear changes and is a good skill to have...

Chris

It's a good skill to have with gearboxes that need it. For those that don't, it just wears out your synchros by making them engage twice with each gearchange.

Yes but what is it? And why would you do it in a modern car ?

It's a way of matching the speeds of the various shafts in the gearbox so that the gears engage smoothly. In a modern car with a gearbox in good condition, the synchromesh does this for you.

You change down (usually not necessary changing up), in two stages. Disengage the higher gear, leaving the gear lever in neutral, and maintaining a slight pressure on the throttle. Bring up the clutch briefly to re-engage the input shaft. Now dip the clutch again and engage the lower gear.

If your gearbox has worn synchros, you will notice some grinding on changing down quickly. This technique will smooth that out for you.

Edit: and now I've spoilt the poll. Col if you want to delete this post feel free.

I do it (but I'm young :P)

Dad taught me, and I practice, and got it sorted. Use it all the time now

never got taught it when learned to drive, did on the lorries by a mechanic when i brokedown and needed to limp home, but rarely use it.

I blip on a downchange (when driving a manual - not in the Roadie) but don't typically engage the clutch whilst doing it.

Isn't that what syncromesh is for?

I blip on a downchange (when driving a manual - not in the Roadie) but don't typically engage the clutch whilst doing it.

Blipping, or sustaining the revs, is probably the best thing to do with a modern car.

Yep - use it on every downshift. Probably no need for it on majority of cars but does help to smooth out gear changes and is a good skill to have...

Chris

And here we most certainly do disagree. All DDC does with a synchro box is wear the clutch quicker, and slow down your gear changes.

I blip a bit, but don't really double declutch. I do know what it is though.

And here we most certainly do disagree. All DDC does with a synchro box is wear the clutch quicker, and slow down your gear changes.

Which bit are you disagreeing with?!

Chris

Which bit are you disagreeing with?!

Chris

Using DDC with a synchro box. It's completely unnecessary, and, as I said, just causes wear and slows your gearchanging.

Using DDC with a synchro box. It's completely unnecessary, and, as I said, just causes wear and slows your gearchanging.

Probably no need for it on majority of cars but does help to smooth out gear changes and is a good skill to have...

It also depends which cars you drive regularly. Some of the higher powered performance cars seem to respond better to DDC..... As for wear, I've never replaced a clutch or any syncros in any car I've owned and my gear change is hardly any slower than without DDC - all comes down to how quickly you can match revs. Unless of course you cheat and clutch drag your gearchanges which also causes wear!

Chris

Chris, let's remember that I don't do track driving (not even track days). I therefore tend to change down for 3 main reasons:-

1) To select a lower gear for a tight corner, which I need to brake for. In this case I'll not even start changing until I'll get more or less the right revs for turn in and apex speed in the new gear with a single block change.

2) To obtain extra power for an overtake, or to help set the car for a high G corner. In this event I'm not braking, and can rev match without doubling the clutch.

3) To obtain extra engine braking down a hill. In this case I'll try to sort out the gear before I hit the steep bit, and the argument in (2) applies.

If I have to brake to deal with slowing traffic in front of me, or a speed limit, I'll brake first, and change gear later (well if necessary; the TDi110 can hold 30 in top on a flat road).

Oh... and for anyone who still doesnt know what DDC is... i reccomend you watch Bullitt

Nick, the way you said that, makes it sound like Heel & Toe. I presume they're similiar?

I know what it is as I can remember my dad talking about it and my brother using the technique on his first fiesta. Never had to use it mind, but a do occasionally blip the throttle a little on downshift. Agree with Ken though.

A handy link to "The chase" out of Bullitt can be found here -

YouTube - Bullitt (the chase)

The chase starts at about 2 minutes 50 secs in.

by 3:47 you should here Steve McQueen DDC'ing (that extra blip of throttle during gear changes) and again by 7:10.

Strangely the bad guys don't DDC at all.

Once did it by accident in my first car (Volvo 340) on the motorway.

I was trapped in the middle lane by trucks and faster cars doing about 90mph (or it seemed so at the time) past us so at a suitable gap went for 4th gear but missed - leaving it in neutral, as my foot hit the accelerator to the floor, I'd already realized what had happened so off the power, the clutch went in again and onto 4th gear to try again.

Made the perfect DDC power down-change noise - mightily impressing my mates who were in the car.

They all thought I'd done it on purpose to keep the revs higher - I never let on I'd just missed the gear.

Sold both my old Land Rovers last year - 1964 and 1967 Series IIa SWB models, both with no synchro as standard on first or second. I am old enough to know how to do it but if any of my mates drove them the noise was painfull!

As with everything Land Rover, speed was not the thing, you needed mechanical appreciation, patience and a steady hand to drive one of those smoothly.

The last car I did this with was an allergy (or was that allegro), but this was some time ago.

When I sold it on I found the replacement car, an escort, didn't really need it.

It's "outwith my control" now (with the DSG).

Nick, the way you said that, makes it sound like Heel & Toe. I presume they're similiar?

Heel'n'toe is the next technique in the list. Get Andy Walsh's video if you want to see a man with 3 feet in action! :P

Heel'n'toe - when braking hard, and needing to blip the throttle, or sustain revs for a downchange, keep most of the right foot on the brake pedal, but use the right edge of the sole to manipulate the throttle pedal. If you choose to double-declutch at the same time, good for you!

H'n'T only really works under heavy braking. Under anything less, the right edge of the foot tends to over pump the throttle and you get lots of roaring noise, and not very good down changes.

I can demo H'n'T, and DDC separately, but not together. If you watch Andy Walsh's video, he will show you how to combine H'n'T with left foot braking ... your mind will boggle ...

Yep use it most of time on downshift and when driving LGV's