I got to thinking about my "double clutch" comment in the "how many 6sp" thread...

What is the purpose of double?

After thinking about it, I tried it a different way, and didn't have any different result.

Here's the scenario...

When driving on a straight, you may want to downshift to pass without hitting the brake, (ala heel-toe)

Why do we double clutch, or push the clutch to disengage, shift to neutral, release the clutch and blip throttle, then engage clutch to go into lower gear?

I've tried just clutch to disengage, while in neutral, blip the throttle, (as your foot is not on the brake), and in the same motion shift into the lower gear and disengage. No difference.

What am I missing?

 

Double clutching isn't necessary on syncronized gearboxes. By blipping the throttle while in neutral (clutch engaged), you can bring the set of gears you're downshifting to up to speed before engaging them. If anything, it prevents some wear and tear on the synchronizers during hard downshifts, but it really isn't necessary unless you're driving a big rig with an unsynchronized gearbox. Blipping the throttle while the clutch is disengaged, whether in neutral or not, doesn't do anything.

E

 

It minimizes wear and tear on the syncros. when you rev in N with the clutch disengaged it will match the speed of the syncros also...

The best non technical way to explain it is think about when you're slowing down in Neutral to a stop sign and you're getting ready to put the car in first as you slow there's a certain speed, about 7-10 mph where the shifter just slips into 1st without any pressure anything higher say 20 mph you'll have to JAM the damn thing into first... If you double clutch it'll be easier to get into 1st...

But having said all that syncros have advanced so much theres really no need to double clutch but its still fun and its an art.

Oh... trucks... 18 wheelers need to double clutch... I dont think they have syncros...

 

EBMCS03 must have been reading my mind

E

 

As pointed out, it is an art -- maybe fun, but my view is that most drivers do not master it and will in fact cause more harm than good to syncro's and the drive train in general.

Cal