I've been practicing my double-clutch downshifts recently. My dad raced an MG Midget is SCCA FP when I was growing up and he always double-clutched instead of using just a simple rev-match when braking and downshifting.

However, the general word you read online is that double-clutching is unnecessary on modern transmissions with syncros, but it will save some wear on the syncros. But, so the word goes, the wear that you save is negligible and the syncros will still outlast the life of the car, so just rev-match.

What are everyone's thoughts?

Is the wear you save on the syncros worth double-clutching, or should your just rev-match?

What about the wear on the throw-out bearing? Again, it seems like rev-matching would put slightly more wear on it.

Interested to see other MINI drivers' opinions...

 

I double clutch my down shifts usually, and always when skipping gears.

180k on the original Getrag, and no issues.

Cheers,

Charlie

 

Not hating on the fact that you have gotten 180k out of your transmission but, it is a Getrag the damn things are bullet proof. How many clutches have you had?

 

Double-clutching to protect synchros ... sounds kind of like a bumper guard - protection for something that is supposed to protect.

Bumper guard covers, anyone? :-)

 

Of course the main reason for double-clutching or rev-matching is that awesome smoothness while downshifting. I'm not mainly doing it to protect the syncros.

The question of wear is likely a marginal one on a box like the Getrag, but at least worth discussing...

 

Rev-matching in extreme conditions may be called for but I can't see it's use in daily driving. And I haven't double-clutched since driving my grandpa's 1950 Frazer.

 

I only do it when skipping a gear.

 

Rev match good...saves the syncros...
double clutch, bad...no pluss on a mini tranny...gears are NOT stright cut like on a truck and unlike on a rig/truck, you do not have a front/back rotaing at different speeds....
So single clutch, and revmatch if you are good at it!!

 

I find myself double-clutching just out of habit, I don't it so quickly I don't even think about it. It is however completely unecessary...

I don't even know how that "habit" got started, as I have never really driven vehicles where it was required. I taught myself to do it one day and kept doing it to practice, and its just stuck now

 

Double clutching is also rev matching. But you just aren't using the synchros to get the layshaft up to speed. Its not necessary, but I still do it out of habit sometimes like when skipping gears where I think the synchros would have to work harder than if shifting normally. Normally, I don't double clutch and let the synchros do their thing.

 

Here's a similar thread over on a Honda S2K forum:

http://www.s2ki.com/s2000/topic/9351...cros-wear-out/

 

every downshift is rev matched, downshifting to 1st is double clutched.

 

I was just kidding. I actually don't know much about this stuff from a mechanical standpoint. I do know that double-clutching takes too long for me to use regularly no matter what the benefit.

Speaking of benefits, though - I wonder if any reduction in synchro wear might be offset by increased wear to the clutch pedal?

 

 

Seems like the consensus for everyday driving is...personal preference rules.

For harder track driving, it does seems like regularly double-clutching on downshifts could lengthen the syncros' life significantly. However, if you're not fast enough with it, it will slow you down, so you might still prefer rev-matching.

An interesting post on that S2K forum with a picture of some syncro wear:

Obviously a different box than the Getrag, but the principle still applies.

At the same time, a video of the great Ayrton Senna, using rev-matching, not double-clutching (plus, just amazing driving!):

He was just testing the car, so I don't think he had longevity in mind...

 

Why do you need to double clutch the downshift to 1st? I do it just with rev matching, and I haven't noticed any issues. I do it at around 15-20mph, from 2nd to 1st. So revs are pretty low. The transmission in this car is amazingly smooth.

 

You dont have to but it is smooth because 1st is either double or triple synchroed(dont remember which one). I do it to prolong synchro life.

 

Both techniques will result smooth downshifts - the main difference is double-clutching re-engages the engine to the transmission in neutral when you blip the throttle, so they are spinning at the same speed when you complete the downshift to the lower gear, thus minimizing wear on the syncros.

I can't imagine you're downshifting to 1st often though? 1st is almost always a starting-from-standstill thing for me.

 

Pops & burbles in parking lots. Need 1st

 

This thread exists on almost every standard-shift car's forum. You'll typically get more opinions than you get posters.

There IS, however, one Mini-specific item:

On the R53, there are a few clutch-linkage bushings that are known weak points. When the linkage bushings start to go, the clutch feels like you're pushing a screwdriver through a bucket of rocks with your clutch pedal. Several folks have also had throwout bearing and clutch issues, but there are precious few complaints about synchros going bad.

Given that, on a synchronized transmission like ours, double-clutching trades clutch (mainly clutch linkage and throwout bearing) wear for synchro wear, I'd rather save the clutch/linkage/throwout bearing since the synchros seem relatively pretty tough.

One man's experience, motor on...