Downshifting

[gregdacat]

After reading a blog on another site about downshifting I am a little confused. I fully admit I have never raced nor am a I mechanic, but have driven manual shift vehicles nearly my entire 42 years of driving.

The blogger made the statement, and several other posters agreed, that you should never blip the throttle to rev match when downshifting with the clutch disengaged (pedal to the floor) because it will cause premature wear and damage to the throw out bearing. My question is, "Isn't that exactly what you do when you heel toe?" The left foot pushes the clutch pedal to the floor while the right foot depresses the brake and rolls over to blip the throttle.

So, what it the difference? Why would heel toe not hurt the TOB But downshifting by simply rev matching (in situations where you want to keep the rpms up but are not necessarily braking (up hills, off ramps, turning corners) cause damage?

[san rensho]

They are wrong. In a double clutch heel and toe downshift, which is what I think they are talking about, you put the clutch in, shift to neutral, let the clutch out and with the clutch out, blip the throttle to rev match and then quickly put the clutch back in and downshift.

This is the preferred way to downshift as it puts the least amount of strain on the synchros and leads to maximum gear box life. (Its actually the only way to shift old Alfa Romeos because the synchros come worn from the factory and if you don't double clutch, it will just grind and not go into gear). I suppose with the clutch out there is less wear on the TOB, but I would guess the difference is minimal. What double clutching does is save the gear box, primarily.

On our cars, the synchros are so robust that double clutching is almost overkill, but rev matching definitely helps preserve the gear box and really cuts down on clutch wear.

[flaps10]

I'm just going to leave this here.

https://www.youtube.com/watch?v=FkP5Svl16Qg

[ekam]

Bloggers.

:troll:

[thstone]

Originally Posted by san rensho

They are wrong. In a double clutch heel and toe downshift, which is what I think they are talking about, you put the clutch in, shift to neutral, let the clutch out and with the clutch out, blip the throttle to rev match and then quickly put the clutch back in and downshift.

This is the preferred way to downshift as it puts the least amount of strain on the synchros and leads to maximum gear box life. (Its actually the only way to shift old Alfa Romeos because the synchros come worn from the factory and if you don't double clutch, it will just grind and not go into gear). I suppose with the clutch out there is less wear on the TOB, but I would guess the difference is minimal. What double clutching does is save the gear box, primarily.

On our cars, the synchros are so robust that double clutching is almost overkill, but rev matching definitely helps preserve the gear box and really cuts down on clutch wear.

+1 ^^ What he said. ^^

[j.fro]

Thank you, Flaps10.

[rdass623]

san rancho got that right. alfa gearboxes love to get scratchy quickly if you are not cautious. generally from 1st to 2nd within 20k without double clutching.

[Jim Rockford]

Double clutching is different than heel and toe.
The confusion around all this is rampant.
Here's by far the best video to slowly and articulately explain it all:

http://m.youtube.com/watch?v=X3288FKOe_M

[san rensho]

Originally Posted by Jim Rockford

Double clutching is different than heel and toe.
The confusion around all this is rampant.
Here's by far the best video to slowly and articulately explain it all:

http://m.youtube.com/watch?v=X3288FKOe_M

The difference is really pretty easy. Heel and toe is what you do if you brake while rev matching while downshifting.

[stephen wilson]

I have rev-matched both ways, double-clutching, or with a single clutch movement. I call it a pseudo double-clutch downshift, you just don't let it out in neutral.

It won't matter as far as the throwout bearing, it will be accelerated to the same RPM in either case. It may have more pressure on it while single-clutching, but that's what they're built do do....

[jsceash]

https://www.youtube.com/watch?v=hGYmzFu8sxg
https://www.youtube.com/watch?v=cxlQVegW3UM
https://www.youtube.com/watch?v=qdWSyrqEnE4
https://www.youtube.com/watch?v=Q3hrpkHoyrM

Dozens of these out there to watch notice none of them are hitting the clutch twice on a heel toe or hel side of the foot shift.

[CoBeerToad]

Clutches are for sissies. Just rev it slightly to pop it out of gear, then rev it a bit more and slide the shifter down a gear.



P.S. Does anybody know of a place where I can buy new synchros?

[JayG]

:

Originally Posted by CoBeerToad

Clutches are for sissies. Just rev it slightly to pop it out of gear, then rev it a bit more and slide the shifter down a gear.



P.S. Does anybody know of a place where I can buy new synchros?

We don't need no stinkin clutch!

[san rensho]

Originally Posted by jsceash

https://www.youtube.com/watch?v=hGYmzFu8sxg
https://www.youtube.com/watch?v=cxlQVegW3UM
https://www.youtube.com/watch?v=qdWSyrqEnE4
https://www.youtube.com/watch?v=Q3hrpkHoyrM

Dozens of these out there to watch notice none of them are hitting the clutch twice on a heel toe or hel side of the foot shift.

Because they are not double clutching since the gear boxes have synchros, just like our cars. You don't have to double clutch, its just the technique for downshifting that puts the least wear on the synchros and gear box.

Heres a" from the testicles point of view" video of double clutching alternating between just a straight double downshift to a heal and toe double clutch.

https://www.youtube.com/watch?v=Vw-MewZRsAM

[coreseller]

Originally Posted by flaps10

I'm just going to leave this here.

https://www.youtube.com/watch?v=FkP5Svl16Qg

I'll bet I've watched that video 100 times, 23 seconds is pure sex. He's a bit heavy on the throttle for rev matching but it honestly MADE the video lol.

Greg, regarding your driving, your method is exactly how I've been driving for 35 years. I use to do the double clutching thing occasionally to amuse myself, too much work. Besides, our method is the lazy way to impress the uninitiated.........

[thstone]

Originally Posted by jsceash

https://www.youtube.com/watch?v=Q3hrpkHoyrM

This makes me really want a sequential gearbox!

[jaykay]

Originally Posted by thstone

+1 ^^ What he said. ^^

Do any double de-clutch down shift on the track to save wear? Never did this on track myself but do do it in my Jeep all the time

How about double clutching on up shifts for second to third....which can really notchy when things get hot?

[PaulE]

Transmission internals are beyond my full comprehension, but if you don't double clutch, will the throttle blip spin the gears to make the rev match as you downshift? In other words, does blipping the throttle with the clutch pedal to the floor make any of the transmission gears spin? It seems to me that anything going on in the transmission in this instance is coming from the differential and driveshaft in a non-transaxle car.

[lmnsblu355]

Originally Posted by PaulE

Transmission internals are beyond my full comprehension, but if you don't double clutch, will the throttle blip spin the gears to make the rev match as you downshift? In other words, does blipping the throttle with the clutch pedal to the floor make any of the transmission gears spin? It seems to me that anything going on in the transmission in this instance is coming from the differential and driveshaft in a non-transaxle car.

When down shifting, the engine RPM is actually slower than it will be when you engage the lower gear. The blip will speed up the engine before the clutch engages so the car doesn't abruptly slow as the clutch is let out. Smoothes out the downshift and doesn't upset the balance of the car.

[PaulE]

Originally Posted by lmnsblu355

When down shifting, the engine RPM is actually slower than it will be when you engage the lower gear. The blip will speed up the engine before the clutch engages so the car doesn't abruptly slow as the clutch is let out. Smoothes out the downshift and doesn't upset the balance of the car.

Ok thanks. So if we don’t double clutch we’re just getting the engine speed up to smooth the downshift, not getting the lower gear spinning faster to match the engine speed, we’re letting the synchros do that work. I learned to drive a manual in a 1960 Austin Healey Sprite with questionable synchros on second through fourth and an unsynchronized first gear, so I still double clutch when down shifting.