I’m curious how important it is to rev match on a downshift with a manual transmission? I’ve driven manual cars for many years and have never done this. I recently read that doing it is a good idea because it reduces clutch wear. Does it really make that big of a difference in the life of the clutch?
I’m not talking about some extreme downshift from 5th to 2nd at 60mph. I’m talking about a typical downshift that would raise the revs ~500-1000 RPM, like going from 4th to 3rd at 40 mph.
I tried practicing it a bit today but I found it pretty awkward, and certainly not fun. It required a bit of concentration/time to get the revs to the right number prior to reengaging the clutch (not to mention having to take my eyes off the road).
I don’t think it will save ANY wear and tear on your clutch. It might save some wear and tear on your transmission’s synchronizers if it is done correctly. It’s called double clutching (or more technically double de-clutching on downshifts). Say you’re shifting from fourth to third gear. The technique requires stepping on the clutch and putting the transmission in neutral, releasing the clutch while you’re in neutral, blipping the to match the RPM you will be at in the lower gear, stepping on the clutch again, and downshifting. With practice, you will be able to make it sound like you’re driving an automatic.
DO NOT yield to the temptation to shift without using your clutch. Your car was not made for that.
Minimizing clutch slippage will minimize clutch wear, whether upshifting or downshifting. It’s just that simple.
MG McAnick is going one step further and suggesting double-clutching, which will minimize wear to the transmission as well.
That procedure is as follows:
disengage clutch
put transmission in neutral
release clutch
blip throttle to match engine revs to where they’ll be once the clutch is released in the lower gear, or possibly a little higher
disengage clutch again
put the transmission in the next lower gear
release the clutch.
Note that all clutch releases are very quick, absolutely no slipping is used. This procedure will match the speeds of all transmission parts as they’re engaged as well as matching clutch to engine speeds, so there’s very little wear to anything. The downside is it uses fuel. Also, once mastered, it’s done so fast that it takes no longer than a normal upshift.
Why is there any need for chronically forcing downshifts? Try filling a Dixie cup to within 1/4 inch of the top and sitting it on the dash, and driving without splashing out of the cup.
+1
That’s how I learned to drive stick as well, Rod.
With my 52 truck, I used to have to double clutch because the synchros were bad. First gear is a granny gear, second is about right for cornering but third will stall you out or chatter if you’re trying to do anything but ‘whip’ around a corner - and whipping around a corner with an old truck like this is a really a contradiction in terms as that’s near impossible. You have to downshift from third.
If you don’t adjust the speed downshifting, it wouldn’t mesh and it would really drive like an old truck, crunching gears and stuff. On the upside, people do move out of your way with all that violence happening.
After a while, I got so used to it where I wouldn’t even need to use the clutch by ‘floating’ the gears in and out. If you develop a feel for it, you can just slip into a gear without trouble.
I wouldn’t suggest learning that on a new car because your gearbox will take a beating in the process, though. I’ve since replace the transmission.
They say double clutching saves the synchros which makes sense but it isn’t an easy skill to learn. There’s a Steve McQueen video out there that shows that skill off really well. He shifts so quick, it looks like he’s just running through the gears but he’s doing a lot of fancy footwork.
. disengage clutch
2. put transmission in neutral
3. release clutch
4. blip throttle to match engine revs to where they’ll be once the clutch is released in the lower gear, or possibly a little higher
5. disengage clutch again
6. put the transmission in the next lower gear
7. release the clutch.
This will do NOTHING to extend clutch life. In the days before synchronized transmissions, this procedure was used to prevent gear-grinding. Most of the wear on your clutch occurs when you are starting off from a dead stop. What you are doing will accelerate the wear on a critical clutch component, the throw-out bearing…
Rev matching is something professional truck drivers do because their transmissions don’t have synchronizers and must be synced manually. In a car or light truck, your manual transmission synchronizes the gears before they mesh, so taking the extra step of revving the engine before you downshift will mostly waste gas in an average car.
Synchros match the speeds of the gears internal to the tranny, but they don;t match the speeds of the tranny input shaft & clutchplate with speed of the flywheel and pressure plate. Yes, “rev matching” will save clutch wear. But you need not get fancy. I’ve alway just blipped the gas when downshifting. And the only clutch I’ve ever worn out in 45+ years of driving was my pickup, and that one lasted 295,000 miles even with having taught two kids to drive on it.
Did you appreciate the “heal and toe” work of the driver in “Double Clutch Downshifts”? On an early corner he downshifts three ratios while braking hard (listen to the tire noise) and then comes out the of corner hard on the throttle. What a ride.
When heel-and-toeing, I just use one side of my foot on the gas and the other side on the brake.
Getting to the topic, I don’t know how essential matching revs on a downshift regarding clutch wear, but it is certainly proper technique when driving, and it is smoother. I think a lot of downshifting is unnecessary. I don’t downshift through every gear to slow down. Cars have brakes these days that are more than adequate. I’ll often just downshift one gear before braking to a stop (like 6th to 5th or 5th to 4th), but matching revs is not a big deal, as my foot is still on or near the gas at that point. When downshifting for more power or to keep the RPM from dropping too low, same thing.
I wouldn’t downshift to slow down. The brakes are much cheaper parts that do the job just as well and more easily. I only downshift for more torque, such as to climb a hill, or to accelerate from a lower speed after slowing down. In either case I’ll be on the accelerator anyway, so revving the engine appropriately while letting out the clutch pedal just makes sense for smoother and quicker clutch engagement. I never apply accelerating force until the clutch is fully engaged (pedal up) except when starting from a stop. This prevents much more wear than rev matching.
I do sometimes double clutch, because the transmission in my old car sometimes fights me when I downshift to third gear. If you don’t have any trouble downshifting, I wouldn’t do it. All shifts, up and down, should be on the easy side. I have friends who enjoy throwing the shift lever all around as quick as they can move it. When upshifting, you can feel when it puts up the least resistance, and finding the shift rate with the least resistance is the best way to do it. When downshifting there will usually be resistance, so you want to ease it into gear.
One bit of racing footage that I still remember ten years later was Dale Earnhardt Sr. in the corvette at the Daytona 24hrs the month before he was killed. They had a camera pointing at his feet, and did a whole lap watching him steer, brake, clutch, and accelerate around the road course. Magic. I don’t remember if he had to double clutch though. The entire heel-and-toe was very calm and smooth, remarkable when braking from 200 mph into the chicane.
Gee I have another alternative, skip the downshifting put in neutral and use the brakes, Course I had to complain when the rear brakes went out at 98 k, cant brakes even make it to 100k, but never a new clutch!
I learned to double clutch when I drove a truck as a teenager, where if you didn’t double clutch you couldn’t down shift at all in some of the gears. So it’s inbred now with me. I would have a hard time not double clutching. About all I can say is that I’ve double-clutched my early 90’s Toyota Corolla (manual xmssion) since it was new, and put 200K miles without any clutch problems to date.
I think about all one can say is it doesn’t hurt, and might help reduce clutch and xmission wear.
But I doubt the reduced wear is very important in modern cars with synchro transmissions and modern clutches.
Interesting how many people are still talking about downshifting causes clutch wear in a rev matching thread.
To the op, you really shouldn’t look stare at the tach when rev matching. You should ease on the loud pedal until the engine sounds right for the combination of your target gear and road speed. As mountain bike said, you don’t need to be spot on unless you’re a truck driver. With practice, the engine sound should get you close enough.
"This will do NOTHING to extend clutch life. In the days before synchronized transmissions, this procedure was used to prevent gear-grinding. Most of the wear on your clutch occurs when you are starting off from a dead stop. What you are doing will accelerate the wear on a critical clutch component, the throw-out bearing… "
Sorry C-man, but I didn’t say it would extend clutch life, I said it would minimize transmission wear. It will do just that, since it effectively minimizes the job the synchronizer blocking rings need to do. It was, as you say, done to drive transmissions that weren’t synchronized at all.
As for prematurely wearing out the throwout bearing, well, done correctly double-clutching spends very little time with the bearing loaded. I could make an argument that the rev-matching eliminates enough clutch slippage that the heat NOT generated more than makes up for any mechanical wear on the bearing. But I guess it’s a bit of a trade-off, a little more bearing wear or a little more transmission wear. Six of one / half a dozen of the other.