Rev matchers 'probably intend to drive too fast'

[Dr Jekyll]

mybrainhurts said:

Dr Jekyll said:

The letter is referring to Heel and Toe, not rev matching. There is perfectly reasonable argument that in most circumstances the time saving from using heel and toe instead of separation isn't relevant in road driving unless you really are in too much of a hurry.

What a load of tripe.

It's not just about time saving, it's about smooth driving.

No it isn't.

[Johnnytheboy]

Does anyone "intend to drive too fast"?

[martine]

Rick101 said:

Didn't receive that magazine as I didn't bother renewing either Rospa or IAM (national memberships) this year. Total waste of money.

Still confuses me as to why they can't support the clubs that actually do the training and we have to pay them in addition!

Perhaps it's a case of supporting a charity rather than what's in it for you?

The IAM HQ does 'support' local groups but rely on a subscription model for much of their income.

[Pothole]

"opinion column" 'nuff said.

[Rick101]

martine said:

Perhaps it's a case of supporting a charity rather than what's in it for you?

The IAM HQ does 'support' local groups but rely on a subscription model
for much of their income.

What's in it for me is being preached to, whether that be said tripe in magazine or my way is the only way observer.

I love AD, I really do, but these groups can really drain you!

I still contribute to my local groups btw, just don't see any point in paying the national fee too.

[MiggyA]

Dr Jekyll said:

The letter is referring to Heel and Toe, not rev matching.

It seems to me from his comment about 'modern engines, clutches and gearboxes' that he IS conflating heel and toe with rev matching, and seems to imply that we should basically slip the clutch and mash the synchros - anything else would be trying too hard...!

[RobM77]

Rev matching belongs in the same camp as steering smoothly, applying the throttle smoothly, applying the brakes smoothly and choosing the path of least resistance around a corner (provided visibility isn't negatively affected). Why be harder on the car and its grip reserves than is necessary? Anyone who thinks maximising the grip available is a technique reserved for driving near the limits of grip is simply wrong, because it obviously increases your safety, and that's always a good thing. Given limited time to teach someone advanced driving techniques, there are of course more important things to learn, but that doesn't mean that rev matching isn't a good thing.

The other issue is that of mechanical sympathy. Yes, synchromesh gearboxes are designed for mismatched gear speeds, but that doesn't mean it doesn't cause wear. Track rods are designed for dry steering, tyres are designed for mounting kerbs, and oils are designed to lubricate as much as possible during high revs and/or load on a cold engine, but that doesn't mean it's mechanically sympathetic to do any of those things.

Finally, there's psychology. There are plenty of things that make little difference mechanically, but just sound and feel wrong, and I don't think there's any problem with avoiding those things. Cracking knuckles is harmless, but many people don't like doing it. In my opinion, such a person is more likely to possess true mechanical sympathy as well. Hearing the clutch released between mis-matched engine and road wheels is my equivalent of fingernails down a black board or teeth on a fork - it makes me wince.

[waremark]

RobM77 said:

Rev matching belongs in the same camp as steering smoothly, applying the throttle smoothly, applying the brakes smoothly and choosing the path of least resistance around a corner (provided visibility isn't negatively affected). Why be harder on the car and its grip reserves than is necessary? Anyone who thinks maximising the grip available is a technique reserved for driving near the limits of grip is simply wrong, because it obviously increases your safety, and that's always a good thing. Given limited time to teach someone advanced driving techniques, there are of course more important things to learn, but that doesn't mean that rev matching isn't a good thing.

The other issue is that of mechanical sympathy. Yes, synchromesh gearboxes are designed for mismatched gear speeds, but that doesn't mean it doesn't cause wear. Track rods are designed for dry steering, tyres are designed for mounting kerbs, and oils are designed to lubricate as much as possible during high revs and/or load on a cold engine, but that doesn't mean it's mechanically sympathetic to do any of those things.

Finally, there's psychology. There are plenty of things that make little difference mechanically, but just sound and feel wrong, and I don't think there's any problem with avoiding those things. Cracking knuckles is harmless, but many people don't like doing it. In my opinion, such a person is more likely to possess true mechanical sympathy as well. Hearing the clutch released between mis-matched engine and road wheels is my equivalent of fingernails down a black board or teeth on a fork - it makes me wince.

I agree with everything there - but not with a 'need' to heel and toe. I am not clear whether the letter writer intended to write-off rev-matching, or only H & T. I like to use H & T and can argue that it contributes to a smooth flowing drive, but I also find it possible to drive smoothly and with mechanical sympathy without using H & T (and indeed would do so on an Advanced Driving Test). Does anyone use H & T who is not at least to some extent focused on an improvement in progress?

[rainmakerraw]

waremark said:

I agree with everything there - but not with a 'need' to heel and toe. I am not clear whether the letter writer intended to write-off rev-matching, or only H & T. I like to use H & T and can argue that it contributes to a smooth flowing drive, but I also find it possible to drive smoothly and with mechanical sympathy without using H & T (and indeed would do so on an Advanced Driving Test). Does anyone use H & T who is not at least to some extent focused on an improvement in progress?

That's true, of course. As I said earlier my main issue was his explicit statements that anyone using heel and toe was (1) intending to drive 'too fast' and (2) it was a 'Very Bad Idea' to use one foot for two pedals, as you would certainly end up on your roof in a ditch (because one time a bloke wearing Wellies did so).

[RobM77]

waremark said:

RobM77 said:

Rev matching belongs in the same camp as steering smoothly, applying the throttle smoothly, applying the brakes smoothly and choosing the path of least resistance around a corner (provided visibility isn't negatively affected). Why be harder on the car and its grip reserves than is necessary? Anyone who thinks maximising the grip available is a technique reserved for driving near the limits of grip is simply wrong, because it obviously increases your safety, and that's always a good thing. Given limited time to teach someone advanced driving techniques, there are of course more important things to learn, but that doesn't mean that rev matching isn't a good thing.

The other issue is that of mechanical sympathy. Yes, synchromesh gearboxes are designed for mismatched gear speeds, but that doesn't mean it doesn't cause wear. Track rods are designed for dry steering, tyres are designed for mounting kerbs, and oils are designed to lubricate as much as possible during high revs and/or load on a cold engine, but that doesn't mean it's mechanically sympathetic to do any of those things.

Finally, there's psychology. There are plenty of things that make little difference mechanically, but just sound and feel wrong, and I don't think there's any problem with avoiding those things. Cracking knuckles is harmless, but many people don't like doing it. In my opinion, such a person is more likely to possess true mechanical sympathy as well. Hearing the clutch released between mis-matched engine and road wheels is my equivalent of fingernails down a black board or teeth on a fork - it makes me wince.

I agree with everything there - but not with a 'need' to heel and toe. I am not clear whether the letter writer intended to write-off rev-matching, or only H & T. I like to use H & T and can argue that it contributes to a smooth flowing drive, but I also find it possible to drive smoothly and with mechanical sympathy without using H & T (and indeed would do so on an Advanced Driving Test). Does anyone use H & T who is not at least to some extent focused on an improvement in progress?

Sorry if I misled there - I meant to be quite clear to talk about only re-matching. Most of the time I rev match off the brakes, although I confess this is largely because H&T is quite hard with servo brakes - I otherwise see no issue with BGOL, it's just a rule designed for people who can't H&T in my opinion.

However, heel and toe is useful on occasion, for example when decelerating from speed to take a tight corner or junction, particularly downhill - it allows both a smooth constant deceleration and a consistent show of brake lights to faster cars behind. On steep hills there really is no other way unless you're trying to make your passengers sick and slow up a long way before the turning. I also don't like to turn into corners with the car flat, as it promotes understeer, but I know that's contentious in advanced driving circles The downhill issue is a very real one though.

[DocSteve]

I think he has a point - if you can't H&T well then doing it badly/messing it up on the public road is far more likely to cause an accident than not trying it in the first place. On the other hand, on the race track then not being able to do it, especially in the wet, is more likely to result in an unwanted incident and poorer performance.

All that said, I do think that unless you are driving very slowly then the downhill issue is valid but, again, if you cannot do it then it's not the time to try it out as he is alluding to.

If you can do it well then I don't see the problem - I guess he's simply trying to point out that in most circumstances it's not really a priority for AD on the road and has an unfavourable risk benefit profile for most.

[waremark]

RobM77 said:

However, heel and toe is useful on occasion, for example when decelerating from speed to take a tight corner or junction, particularly downhill - it allows both a smooth constant deceleration and a consistent show of brake lights to faster cars behind. On steep hills there really is no other way unless you're trying to make your passengers sick and slow up a long way before the turning....... The downhill issue is a very real one though.

Well, I too would use H & T for downhill tight bends. However, it is not the only way. You can also achieve a smooth safe mechanically sympathetic result by braking up to the apex, declutching in time to stop the engine labouring, moving the gear lever to the next required gear, but not letting out the clutch until ready to apply acceleration. The classical advanced driving technique would be to accept a gear change without rev matching, probably at low revs, but that goes against the grain.

[RobM77]

As DocSteve says, if you can do it well then it's not a problem. I learnt when I was 17 shortly after I passed my test. That was 22 years ago and I genuinely don't even think about it - it's second nature. In those 22 years of road and track driving I have messed up gearchanges, of course, I even destroyed an engine once, but it's never been due to heel and toe, my errors have always been finding the wrong gear or screwing up my timing.

[Jambo85]

MiggyA said:

It seems to me from his comment about 'modern engines, clutches and gearboxes' that he IS conflating heel and toe with rev matching, and seems to imply that we should basically slip the clutch and mash the synchros - anything else would be trying too hard...!

RobM77 said:

The other issue is that of mechanical sympathy. Yes, synchromesh gearboxes are designed for mismatched gear speeds, but that doesn't mean it doesn't cause wear.

Sorry to be pedantic - but this is PH - as I understand it, to be kind to synchros would require double declutching - is that is what is being discussed here?
Of course rev matching without double declutching is still smoother and mechnically sympathetic to other parts of the system, but synchros are oblivious to it surely?

[RobM77]

Jambo85 said:

MiggyA said:

It seems to me from his comment about 'modern engines, clutches and gearboxes' that he IS conflating heel and toe with rev matching, and seems to imply that we should basically slip the clutch and mash the synchros - anything else would be trying too hard...!

RobM77 said:

The other issue is that of mechanical sympathy. Yes, synchromesh gearboxes are designed for mismatched gear speeds, but that doesn't mean it doesn't cause wear.

Sorry to be pedantic - but this is PH - as I understand it, to be kind to synchros would require double declutching - is that is what is being discussed here?
Of course rev matching without double declutching is still smoother and mechnically sympathetic to other parts of the system, but synchros are oblivious to it surely?

I'm no expert on this by any means, but as far as I know, DDC H&T will spin up the lay shaft and the engine (because you rev match with the engine connected to the gearbox in neutral), whereas SDC H&T just spins up the engine (because the clutch is down during the rev match). With the latter, the synchros will have to match differing gear speeds, yes, but I've always assumed that they have much less inertia to overcome because the engine is at roughly the right speed - they'll be speeding up the layshaft, not the layshaft plus the engine.

[Jambo85]

RobM77 said:

Jambo85 said:

MiggyA said:

It seems to me from his comment about 'modern engines, clutches and gearboxes' that he IS conflating heel and toe with rev matching, and seems to imply that we should basically slip the clutch and mash the synchros - anything else would be trying too hard...!

RobM77 said:

The other issue is that of mechanical sympathy. Yes, synchromesh gearboxes are designed for mismatched gear speeds, but that doesn't mean it doesn't cause wear.

Sorry to be pedantic - but this is PH - as I understand it, to be kind to synchros would require double declutching - is that is what is being discussed here?
Of course rev matching without double declutching is still smoother and mechnically sympathetic to other parts of the system, but synchros are oblivious to it surely?

I'm no expert on this by any means, but as far as I know, DDC H&T will spin up the lay shaft and the engine (because you rev match with the engine connected to the gearbox in neutral), whereas SDC H&T just spins up the engine (because the clutch is down during the rev match). With the latter, the synchros will have to match differing gear speeds, yes, but I've always assumed that they have much less inertia to overcome because the engine is at roughly the right speed - they'll be speeding up the layshaft, not the layshaft plus the engine.

I'm starting to get myself quite confused(!) but for the synchros to 'see' the layshaft plus the engine, that would be changing gear without using the clutch at all? Rev matching essential in that case!

[S. Gonzales Esq.]

You can get a feel for the work the synchros are doing by comparing the effort required to move the gear lever with different techniques.

Get a double declutch right and it's almost like the 'box takes the lever from your hand. The difference between that and simple re-matching can be quite marked, particularly with older, worn or less sophisticated gearboxes.

[paua]

I learned to drive in an Anglia, whilst double de-clutching wasn't "necessary", it certainly made for smoother progress. When I'd been practicing a while, I was able to change up & down without using the left pedal at all.
Now drive air-cooled 6sp single mass flywheel & I still DDC, in combination with HnT, when "necessary". Again - makes for smoother progress.

[mph999]

S. Gonzales Esq. said:

You can get a feel for the work the synchros are doing by comparing the effort required to move the gear lever with different techniques.

Get a double declutch right and it's almost like the 'box takes the lever from your hand. The difference between that and simple re-matching can be quite marked, particularly with older, worn or less sophisticated gearboxes.

Spot on

[mph999]

Jambo85 said:

I'm no expert on this by any means, but as far as I know, DDC H&T will spin up the lay shaft and the engine (because you rev match with the engine connected to the gearbox in neutral), whereas SDC H&T just spins up the engine (because the clutch is down during the rev match). With the latter, the synchros will have to match differing gear speeds, yes, but I've always assumed that they have much less inertia to overcome because the engine is at roughly the right speed - they'll be speeding up the layshaft, not the layshaft plus the engine.

Correct.

Rev matching only simply spins up the engine side of the clutch to match the gearbox side of the clutch. Smooth and eliminates clutch wear on changes.
DDC, spins up the layshaft so that the dog gear that locks the gear onto the shaft, is spinning at the same speed as the gear it's about to mesh with.