Heel and Toe etc etc
Discussion
Hi,
have read a number of posts about heel and toe and not over lapping brakes and gears etc. A thought occurs, how does this advice change to reflect modern cars?
I run an m5 which blips the throttle on the gear change, doesnt have a clutch so I can change gear without my hands leaving the steering wheel using the paddles and then it changes gear much much faster than I could manually.
The software the car runs stops the rear wheels locking up under engine breaking etc
So, is the IAM/Rospa upto date with modern car gizmos or is the advice still the same?
S
have read a number of posts about heel and toe and not over lapping brakes and gears etc. A thought occurs, how does this advice change to reflect modern cars?
I run an m5 which blips the throttle on the gear change, doesnt have a clutch so I can change gear without my hands leaving the steering wheel using the paddles and then it changes gear much much faster than I could manually.
The software the car runs stops the rear wheels locking up under engine breaking etc
So, is the IAM/Rospa upto date with modern car gizmos or is the advice still the same?
S
The Sytem advice - namely brake followed by gear changing - stands.
http://www.ridedrive.co.uk/tipoffs19.htm
gives explanation.
The DSG system has definately raised the bar as far as paddle shift boxes are concerned. Personaly I don't like them and I would always spec an H gate on any road car I owned. Some more rudimentary Paddle shift systems still require a driver input rev match / H&T to work properly, but as the manufacturers raise their games the dumbing down continues.
1950trevorP said:
The Sytem advice - namely brake followed by gear changing - stands.
http://www.ridedrive.co.uk/tipoffs19.htm
gives explanation.
That's Julian Smith's opinion. There is nothing official about it (much of the article is excellent, I am only challenging the small section on alternative transmissions).http://www.ridedrive.co.uk/tipoffs19.htm
gives explanation.
IAM advice has always been to fully understand the transmission of your car and use its features appropriately. In automatics with smooth sequential changes it can be advantageous to overlap braking and gearchanging, as suggested by the OP. This can well apply in the M5. In my DCT M3, if I need multiple downchanges for a hazard, I generally make the earlier changes under braking, leaving the last change to be made as I reapply the gas. My criteria are: downchanges should be smooth and should not destabilise the car, appropriate gear should be engaged before applying significant gas.
The bit I would dispute is this: "Which component parts, out of the following that are fitted to your car, are the cheapest to replace, brake pads or clutches and gearboxes? Let’s wear the brakes out first shall we?"
Deceleration using engine braking does not cause excessive clutch and transmission wear. Clutch wear occurs when you slip it - starting off or low-speed manouevring. The wear caused by a rev-matched gearchange is negligible. And the load on the transmission is far less than the load of more than mild acceleration since combustion pressure will always be a lot more than compression pressure. Deceleration using engine braking does save on maintenance, and the "economic" argument for avoiding it is not valid.
Deceleration using engine braking does not cause excessive clutch and transmission wear. Clutch wear occurs when you slip it - starting off or low-speed manouevring. The wear caused by a rev-matched gearchange is negligible. And the load on the transmission is far less than the load of more than mild acceleration since combustion pressure will always be a lot more than compression pressure. Deceleration using engine braking does save on maintenance, and the "economic" argument for avoiding it is not valid.
Pigeon said:
The bit I would dispute is this: "Which component parts, out of the following that are fitted to your car, are the cheapest to replace, brake pads or clutches and gearboxes? Let’s wear the brakes out first shall we?"
Deceleration using engine braking does not cause excessive clutch and transmission wear. Clutch wear occurs when you slip it - starting off or low-speed manouevring. The wear caused by a rev-matched gearchange is negligible. And the load on the transmission is far less than the load of more than mild acceleration since combustion pressure will always be a lot more than compression pressure. Deceleration using engine braking does save on maintenance, and the "economic" argument for avoiding it is not valid.
Deceleration using engine braking does not cause excessive clutch and transmission wear. Clutch wear occurs when you slip it - starting off or low-speed manouevring. The wear caused by a rev-matched gearchange is negligible. And the load on the transmission is far less than the load of more than mild acceleration since combustion pressure will always be a lot more than compression pressure. Deceleration using engine braking does save on maintenance, and the "economic" argument for avoiding it is not valid.
The only part I would question relates to the main sources of clutch wear. Starting from rest (especially on a steep hill) is likely to produce the most rapid wear, but low speed manoevering need not produce much wear if done using low engine speeds. I find this can be done at idling speed unless there is a significant gradient involved.
Best wishes all,
Dave.
I always tell my pupils to use just a touch of gas in low-speed manouvering, but to be honest most modern cars can do it at idling speed. I agree that if you match the revs perfectly when downshifting, clutch wear is negligible. Excessive revs accompanied by excessive clutch slip when pulling away from rest is the best way to wear a clutch out quickly in my opinion (I always cringe when they do that).
Evangelion said:
I always tell my pupils to use just a touch of gas in low-speed manouvering, but to be honest most modern cars can do it at idling speed. I agree that if you match the revs perfectly when downshifting, clutch wear is negligible. Excessive revs accompanied by excessive clutch slip when pulling away from rest is the best way to wear a clutch out quickly in my opinion (I always cringe when they do that).
I feel your pain. Some people display a serious lack of mechanical sympathy.Best wishes all,
Dave.
I think it depends entirely on your views on what's best when driving, and on that there will always be debate.
Personally (and these are entirely my own views so please don't flame me for it), I've always believed that it's best to sequentially change down for corners and hazards. This gives the following advantages:
a) You're always in the right gear for the speed you're doing, so if emergency action is required the car has the revs necessary to make it easier to control. This especially applies in a front drive car, where a lot of power can be required to correct oversteer.
b) The blips required to change gear are performed from a more responsive rev zone and are smaller. Typically you'll be blipping from 2k or 3k to 2.5k to 3.5k. If you block change at the end of the braking zone, you'll be waking the engine and its ancillaries up from near idle, which not only takes longer, but isn't that great for the engine either. Accuracy with a large blip is also tricky.
c) If you wish to balance the car into a corner by blending braking into steering, sequential changes allow you to make one application of brakes and perform this, which is much slicker than braking, off the brakes to an interim speed (and high revs!) and back on again. This is hottly debated on here though.
d) If you are approaching a hazard which might require you to proceed or stop at any time, you can proceed swiftly and when the time is right without changing gear first. Examples of such hazards are parked cars and roundabouts.
e) it pushes back the attention grabbing gear change to the safe zone prior to the hazard, rather than loading it up near to the hazard. Bear in mind that the IAM method described above won't just involve any ordinary gearchange (see b above). Obviously one could avoid BGOL and this issue by just braking earlier though (but I'd argue that approach is not making good progress...).
As for disadvantages:
a) It's been unscientifically proven on track that many drivers find threshold braking easier if they block change at the end of a braking zone, but I'm not sure that applies on the road really. I'm also not sure I agree with this for track use (due to accuracy of blip issues), although that's out of scope for this discussion.
b) Some driver's seem to find heel and toe difficult, and some cars don't allow it.
c) Sequential shifting uses engine braking more, which exacerbates engine wear.
The new gizmos that blip for you remove b, and I think a is a marginal disadvantage, so I would say it simply revolves around (c) and whether you're comfortable with that or not.
Personally (and these are entirely my own views so please don't flame me for it), I've always believed that it's best to sequentially change down for corners and hazards. This gives the following advantages:
a) You're always in the right gear for the speed you're doing, so if emergency action is required the car has the revs necessary to make it easier to control. This especially applies in a front drive car, where a lot of power can be required to correct oversteer.
b) The blips required to change gear are performed from a more responsive rev zone and are smaller. Typically you'll be blipping from 2k or 3k to 2.5k to 3.5k. If you block change at the end of the braking zone, you'll be waking the engine and its ancillaries up from near idle, which not only takes longer, but isn't that great for the engine either. Accuracy with a large blip is also tricky.
c) If you wish to balance the car into a corner by blending braking into steering, sequential changes allow you to make one application of brakes and perform this, which is much slicker than braking, off the brakes to an interim speed (and high revs!) and back on again. This is hottly debated on here though.
d) If you are approaching a hazard which might require you to proceed or stop at any time, you can proceed swiftly and when the time is right without changing gear first. Examples of such hazards are parked cars and roundabouts.
e) it pushes back the attention grabbing gear change to the safe zone prior to the hazard, rather than loading it up near to the hazard. Bear in mind that the IAM method described above won't just involve any ordinary gearchange (see b above). Obviously one could avoid BGOL and this issue by just braking earlier though (but I'd argue that approach is not making good progress...).
As for disadvantages:
a) It's been unscientifically proven on track that many drivers find threshold braking easier if they block change at the end of a braking zone, but I'm not sure that applies on the road really. I'm also not sure I agree with this for track use (due to accuracy of blip issues), although that's out of scope for this discussion.
b) Some driver's seem to find heel and toe difficult, and some cars don't allow it.
c) Sequential shifting uses engine braking more, which exacerbates engine wear.
The new gizmos that blip for you remove b, and I think a is a marginal disadvantage, so I would say it simply revolves around (c) and whether you're comfortable with that or not.
Edited by RobM77 on Monday 10th August 09:46
I think the Ridedrive advice on non-manual gearboxes looks a little blinkered to me by the way of trying to shoe-horn something in to the System.
Having been driving a 91 porky 4 speed tip for a few months now, I can attest that trying to get it to do what you want (hold the gear and pseudo-block-change) in the approach to a hazard is nigh on impossible and not worth the effort. You have to work to get the best out of the gbox features. So hazard approach letting the box decide the change points is absolutely fine.
Also drove a 7 spd merc auto before that and had similar problems (but with more messages "gearchange denied").
[pointless and pathetic rant]
As an aside, did I mention how much I hate the wretched pseudo-rationale that goes alongside generally good stuff written about driving? All that twaddle about clutch, gears and brakes and sequential changing. Oh yes I might have mentioned it along with my hatred of mantras, brakes are for slowing, gears are for going. Is that conclusion subject to rigorous peer review? Oh no, doesn't need to be because it rhymes!!!
[/moan, moan, moan]
Bert
Having been driving a 91 porky 4 speed tip for a few months now, I can attest that trying to get it to do what you want (hold the gear and pseudo-block-change) in the approach to a hazard is nigh on impossible and not worth the effort. You have to work to get the best out of the gbox features. So hazard approach letting the box decide the change points is absolutely fine.
Also drove a 7 spd merc auto before that and had similar problems (but with more messages "gearchange denied").
[pointless and pathetic rant]
As an aside, did I mention how much I hate the wretched pseudo-rationale that goes alongside generally good stuff written about driving? All that twaddle about clutch, gears and brakes and sequential changing. Oh yes I might have mentioned it along with my hatred of mantras, brakes are for slowing, gears are for going. Is that conclusion subject to rigorous peer review? Oh no, doesn't need to be because it rhymes!!!
[/moan, moan, moan]
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