Safe Speed Forums

While doing an advanced driving session I was taught a technique for changing down a gear smoothly when you wanted to keep the same road speed at that instant but have more control over the car. I mentioned this on another forum and they said that what I was doing was worse for the gearbox than just changing down like a normal person ie not bothering to try and minimise the differential in revs between gears and making use of the syncromesh.

The technique was this: for example at 50mph in 5th gear and you want to be in forth you'd depress the clutch, let the revs rise naturally, select 4th and bring up the clutch again. While doing this your foot remains static on the throttle rather than lifting off. The aim is to add the precise revs required to match the change in gear. I was reasonably successful at this and could change up and down fairly seemlessly. I find it quite useful when say coming up behind someone to overtake as it means I keep my speed up and would have the right gear to go past them rather than braking to slow down to get the next gear, then speeding up again to overtake.

Does anyone have views either way on which method is better for a modern (under 20 years old!) gearbox? Forum person mentioned friend taught to do this that snapped a shaft or generally buggered his box quite quickly after having been taught this method. I have always previously braked, selected the right gear and clutch up with a slight feathering of the throttle and possible a bit more clutch slip than I should have to keep it smooth. Just whacking into a new gear and hearing the whirring of the synchro mesh and having the car lurch is not something I would consider!

I would be interested in hearing what others thought, particularly those with a good knowledge and understanding of the stresses and strains on modern gearboxes and how they're designed to be used.

Alas, I DON'T have a good understanding of what goes on inside a gearbox, but, intuitively, I'd have thought that it would make very little difference either way, and what little difference it did make would be better! I have to admit to using the same technique myself on occasions - sometimes by accident as much as anything else, if I'm honest!

I think a lot would depend on how well you managed to match the engine and road speeds. I could believe that done badly, there might be something of a jolt as you let the clutch out - perhaps a bit worse than doing it conventionally with the engine revs dropping off. Did the other poster give any reasons for believeing it was bad?

I would imagine that the smaller the speed differential between the "input" and "output" side of the gearbox, the less "work" the synchros would have to do. In fact, on an old car, I used to sometimes change without declutching at all and when doing this, the technique you describe is pretty much essential. I infer from this, that matching engine speed to road speed must be the "path of least resistance" through the box and therefore, the least wear. Incidentally the car on which I used to do this went to the scrapper with the gearbox working just fine!

I'd be interested to hear any other thoughts on the subject!

Hi
First post by me here.
I know this method as a "sustained rev match" gear change. I don't know what other forum you asked on (consider asking on www.advanced-driving.co.uk), but I think it's one of the smoothest and most mechanically sympathetic ways to change gears, up or down. The only way I've seen smoother is to combine it with double declutching.

Of course when changing up, you don't need to keep as much pressure on the gas, as you want the revs to fall rather than rise.

As long as you rev match reasonably close, don't come off the clutch too quickly or too slowly and allow the syncromesh time to do its work by not moving the selector into the new gear too quickly, it will be a good way to ensure gearbox and clutch longevity.

With the exception of coming off the clutch too slowly or slipping it, gear changes that feel smooth are good mechanically, I think.

Sorry I can't give a more technical explanation than that.

I wonder if they are getting your technique confused with full throttle gear changes?

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Driving fast is for a particular time and place, I can do it I just only do it occasionally because I am a gentleman.
- James May

That is the way I was taught to change gear forty odd years ago, though I would normally manipulate the throttle so the change in revs matches the time taken to move the gear lever. Changing this way puts you in a position to accelerate or slow down using only the throttle.

Engine braking seems to be frowned on these days but back then it was the norm. Brakes were regarded as the least reliable part of the car.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

My first car was a mark 1 escort which used to eat clutch cables every 9 months or so. This led me to getting very good at two things a) changing a clutch cable on the side of the road and b) changing gear without using the clutch. I still do it now and again to keep in practice. Once you master getting the engine revs just right for a down change you can get some really smooth gear changes without the clutch. Changing up is far easier but for down changes it takes a bit of practice. Obviously some gear boxes are "smoother" than others, the mark1 escort gearbox was very good and some toyota ones are too but I have tried it with some cars where the change is a little "notchy".

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

http://www.singster.co.uk/mascot%20mar-apr%202003%20(4).html

My 'bike box

And things haven't changed much over the years.

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The world runs on oil, period. No other substance can compete when it comes to energy density, flexibility, ease of handling, ease of transportation. If oil didn’t exist we would have to invent it.”

56 years after it was decided it was needed, the Bedford Bypass is nearing completion. The last single carriageway length of it.We have the most photogenic mayor though, always being photographed doing nothing

It is a good technique in that its less strain on the engine for the revs to drop down (for the engine to spin down) when re-engaging the clutch and gears as opposed to them having to rise (spinning the engine up), theirs also a similar technique used in motor-racing "heel and toe" where the driver uses his left foot for the clutch, yet brakes (with toe)and blips the throttle (with heel) at once with his right foot to increase the revs whilst downshifting, to minimise engine strain, and also particularly in rear-wheel drive cars, to reduce destabilising the rear end of the car under braking.

Was just about to make the point that LD-01 has touched upon. Even with every electronic stability aid on the market, one sure fire way to get the back to step out wildly in a RWD car is a clumsy downchange under heavy braking, without making any effort to match the engine revs. Done violently enough on the entry to the corner it can be a close simulation of a handbrake turn, and every bit as dramatic!

I learned to drive on ancient tractors with crash boxes, and to this date I instinctively match engine revs on both up and down changes. In any gearbox this can only reduce wear, and the idea that this could ever cause damage to the box is pretty much diametrically opposite to any engineering principle I can think of!

Unfortunately it seems this is a dying art. So much so that it seems car makers are making it ever harder to even accomplish. If you try and "heel and toe" in many VAG cars they chop the throttle automatically, in the misplaced belief that pressing both pedals at once must be a mistake. Paradoxically, many modern cars run throttle mappings that prevent the throttle being snapped shut quickly (apparently to reduce emissions), which means that if you want to match the engine revs on an up change you have to wait an age for the engine managemnet to allow the throttle to decay.

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Ticketo ergo sum : I scam therefore I am!

Haven't mastered heel and toe, mainly as I haven't tried it! Tend to either brake and change down when engine speed is right or change down and match revs then alter road speed with throttle position if it is just a slight adjustment. Nearest I get to sophisticated is the odd bout of left foot braking but that has been mainly to scrub off the crud on the brakes if the car has been standing around a bit too long.

It is possible to do the rev match badly and it does feel worse than just a straight downshift so I think it is something that needs to be mastered properly.

I used to double-declutch and heel-and-toe years ago but modern gearboxes are so good that these techniques are not really necessary now.

Both my cars now have sequential/auto boxes and are just great for persons of middle age.

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Malcolm W.
The views expressed in this post are personal opinions and do not represent the views of Safespeed.

The New Nissan 370Z, in regards to its new SynchroRev Match feature
I don't work for Nissan, but this is one of those 'the car can do it better in a pinch, so let it' features that's simply a great idea, like ABS.

If the feature performs the task better than a properly trained human being in what a human being would reasonably consider 'a stressful situation', it's a good and worthwhile feature.

Rev-matching on downshifts is both safer and mechanically gentler; that's why it should be done whenever reasonably possible.

I suspect that this feature should become standard in all 'standard-shifting cars' in about ten years, and I applaud every rev-matched downshift, regardless of whether done by Car, or Driver.

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The Rules for ALL ROAD USERS:
1) No one gets hurt
2) Nothing gets hit, except to protect others; see Rule#1
3) The Laws of Physics are invincible and immutable - so-called 'laws' of men are not
4) You are always immediately and ultimately responsible for your safety first, then proximately responsible for everyone's
Do not let other road users' mistakes become yours, nor yours become others
5) The rest, including laws of the land, is thoughtful observation, prescience, etiquette, decorum, and cooperation

So in response to the OP, we all seem to agree that matching engine speed to gear speed can only be a good thing and should in no way put extra strain on the gear box (just the opposite in fact).

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

But if, like me, you have a lovely old pre-cat V6 with a nice light flywheel, the revs will rise and fall pretty much as fast as your foot does!

...now where's that "feeling smug" smiley???!


Seriously, it's one of the biggest contributors to the width of my grin every time I get in the "old shed", hard to say why, I just love it!

Wow! And I thought there as nothing left to invent after they'd mastered ignition systems that sorted out their own advance and retard!

Seriously though, despite being something of a luddite when it comes to all these smart-arsed driver aids, I have to grudgingly admit that I'm simply not the sort of calibre of driver that can better many (if any!) of them! I'd certainly like to try such a system.

I don't have a problem with technology, per se, but a 'technology' that can be easily outperformed by an average driver isn't worth the parts cost.

To give a very brief example ...
Based on the fact that, originally, ABS worked by unlocking locked brakes ten times per second, if an ABS system needs more than 115% of the ideal 'threshold of, but not quite locked' stopping distance to stop that vehicle, its calibration is insufficient, thus thumbs down.

Of course, ideally, it would be impossible to lock the brakes. Put another way, it would constantly keep each wheel right at the threshold of lockup - something a prefessional driver might be able to do with ideal conditions in an ideal car. (I believe that version of ABS is still a way's off.)

If the guys at Car & Driver say the system does what it's supposed to do 100% of the time, regardless of the difficulty level of the rev-match, how much better could it possibly perform? Thumbs up!

On the other hand, I regularly steal parking spaces from people who think that their Lexus LS460 should parallel park their car for them, not just for kicks, but because that's my way of saying that Lexus hasn't fully developed this technology.

_________________
The Rules for ALL ROAD USERS:
1) No one gets hurt
2) Nothing gets hit, except to protect others; see Rule#1
3) The Laws of Physics are invincible and immutable - so-called 'laws' of men are not
4) You are always immediately and ultimately responsible for your safety first, then proximately responsible for everyone's
Do not let other road users' mistakes become yours, nor yours become others
5) The rest, including laws of the land, is thoughtful observation, prescience, etiquette, decorum, and cooperation

Welcome Custom24

Ah Paul did this when we were chatting about downshift techniques and clutches followed by long chats about corners and so on.
He too had totally mastered the skill of matching the perfect revs to gear, going up or down, and so showing the lack of the need for the clutch.

I worry about damage to the clutch or drive mechanicisms if I get it wrong. I tend to always use heel and toe finding it rapid and smooth. Paul showed me when I had only had my first car back in '85, and I quickly mastered it (in principal), it is totally automatic now.

I cannot say how it may work with new modern clutches, but I would assume done wrong it may cause much damage. I am a firm believer in skill and control by the driver and if you want aids then they are rapidly getting better, and drivers are welcome to them, but for me I want total control, and as little electronics (that can break down), as I can get away with.

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.

Nissan will only match revs for you if you
a) purchase the feature
b) leave it on
c) use the clutch

_________________
The Rules for ALL ROAD USERS:
1) No one gets hurt
2) Nothing gets hit, except to protect others; see Rule#1
3) The Laws of Physics are invincible and immutable - so-called 'laws' of men are not
4) You are always immediately and ultimately responsible for your safety first, then proximately responsible for everyone's
Do not let other road users' mistakes become yours, nor yours become others
5) The rest, including laws of the land, is thoughtful observation, prescience, etiquette, decorum, and cooperation

I had a thought on this the other day ... I know that Paul mentioned something like - when the gear selected does not match the engine speed (esp relates to when the engine has to match the wheels), that is when the drive shaft is at the most stress and hence why they can break.
It is the forced 'raised' speed that is the problem. When going up the gears it is less of an issue but getting it right every time is the aim (obviously) and when it goes wrong is the problem.
I am sure I can show you how to heel and toe, as that stops any worry of too low revs. Higher revs is the 'safer' option but match is the ideal. In essence you just have to learn (manuals are helpful) what gear what revs graphs and lots of practice to get it just right.

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.

Although in fairness, driveshafts don't break THAT often! I think if there is a detrimental effect at all it would just be on the life of the synchromesh - and even then, not much. I guess it's muchmore important for passenger comfort and, perhaps, tyre adhesion in low grip conditions. I used to have a mate with an old rear wheel drive Transit whose "party piece" would be to use the gearbox for "handbrake turns" by finding a good wet, greasy bend, and going from (say) 4th to 2nd at 50 and banging the clutch out! It used to work remarkably well too - but he did eventually break a half shaft!