Driver Awareness Course - bizarre advice?

[FiF]

Dr Jekyll said:

ElectricPics said:

Do people really have so much difficulty sticking to speed limits that they need encouragement to start mucking around with gears and settings instead of just concentrating on actual driving? Seems to me to be defeating the object of the exercise.

The car has to be in some gear otherwise it won't move. Trying to select the appropriate gear is hardly 'mucking around'.

Well to be fair to the SAC lecturer that with the 3rd in 30s etc although on the pretext of making it nominally easier to keep to a limit he's actually giving advice to people to make their driving life easier. The real message should be in the context of finding a flexible gear good for both decreases and increases in speed appropriate to their own vehicle, but that's more complicated to get across and easier in the time available to do a paint by numbers version. Witness the "well my vehicle will pull 5th in a 30" type twaddle.

Edited by FiF on Thursday 8th August 07:50

[gdaybruce]

As ever, the answer is 'it depends'. In the Kia Picanto* courtesy car I'm running around in at the moment 4th at 30 is fine. The dashboard indicator urges me to change up to 5th but I prefer to ignore that. In my Boxster, however, 3rd is plenty high enough and it could be 2nd while in my regular daily, a Ford Mondeo 2.0 petrol, I have no idea since it's an auto and does its own thing! (But I suspect it's mostly using 3rd.)

I do recall, however, that when I did my IAM course it was suggested to me that 3rd is generally the most appropriate gear around town, giving flexibility for when a burst of acceleration is required without labouring the engine and indeed, making it less likely that you will inadvertently creep over the limit.

• And by the way, the Kia is proving to be a real fun little car!

[bigdog3]

gdaybruce said:

I do recall, however, that when I did my IAM course it was suggested to me that 3rd is generally the most appropriate gear around town, giving flexibility for when a burst of acceleration is required without labouring the engine and indeed, making it less likely that you will inadvertently creep over the limit.

Why is "a burst of acceleration" required around town? Seems inappropriate in a busy town environment and likely to confuse pedestrians, cyclists and other road users.

[Dr Jekyll]

bigdog3 said:

Why is "a burst of acceleration" required around town? Seems inappropriate in a busy town environment and likely to confuse pedestrians, cyclists and other road users.

Getting back to 30 after clearing a hazard?

[dvenman]

Scrump said:

The community speed watch crew in my village don’t like it when I drive past them at just under 30mph (in a 30mph limit) if I am in 3rd gear in the Porsche. Even though I am under the limit they seem very agitated by the noise and still wave their arms at me.
If I go past in a higher gear they don’t seem as bothered once they see the speed gun reading.

Do it in 2nd, or even 1st - see how much faster they wave their arms then

[FiF]

bigdog3 said:

gdaybruce said:

I do recall, however, that when I did my IAM course it was suggested to me that 3rd is generally the most appropriate gear around town, giving flexibility for when a burst of acceleration is required without labouring the engine and indeed, making it less likely that you will inadvertently creep over the limit.

Why is "a burst of acceleration" required around town? Seems inappropriate in a busy town environment and likely to confuse pedestrians, cyclists and other road users.

In my view the acceleration required is to return to nearer the prevailing limit after slowing down because of a real or potential hazard. It's much easier to do this in a truly flexible gear that is appropriate for both the vehicle and the likely speed range to be covered.

To continue with the 3rd in a 30 example , or 4th or whatever number gear is best for the vehicle and situation, it's far easier to lift off, cover the brake, slow down to around 20 or a bit less say, then when situation allows accelerate back to limit, as opposed to trundling along in 5th, lift off, not much engine braking, touch brakes, engine now unhappy at low revs, must change down, situation past, accelerate and change again. Sorry, labouring the point now, as opposed to labouring the engine.


Sorry Dr Jekyll got there first, and took a shorter route.

[BertBert]

bigdog3 said:

One ABS evaluation test used by manufacturers is split-mu braking. Two wheels on one side of the car run on a low-mu slippery surface whereas the other two wheels run on a high-mu high grip surface.

A manually braked car will lock the low-mu wheels at the effective braking limit. By comparison, the multi-channel ABS car will make use of the extra braking force from the high-mu wheels, hence reducing stopping distance. No amount of driving skill will overcome this fundamental technical advantage.

I'm sorry, that doesn't make any sense. A non-abs braking system can and will make use of the brake force on the high-mu side, just the the low-mu wheels will be locked.

With ABS it will kick in to stop the low-mu wheels locking. That might marginally increase the brake force on the low-mu side. So I don't understand the nuance regarding split-mu and braking distances other than ABS stopping better than if the wheels were just locked.
Bert

[bigdog3]

Dr Jekyll said:

bigdog3 said:

Why is "a burst of acceleration" required around town? Seems inappropriate in a busy town environment and likely to confuse pedestrians, cyclists and other road users.

Getting back to 30 after clearing a hazard?

Court_S said:

Regarding the 30 in 3rd, my cars have always been happy in 4th for that speed.

Precisely Why drive in 3rd at 30mph increasing fuel consumption, emissions (especially CO2) and noise pollution when your car will happily pull 4th gear? When a hazard is encountered just slow down and change down - that's what's the gear lever is for. If you can't cope with this simple technique, buy an automatic or battery electric car

Smooth regular progress without sudden changes of speed would seem most sensible in town

[InitialDave]

BertBert said:

I'm sorry, that doesn't make any sense. A non-abs braking system can and will make use of the brake force on the high-mu side, just the the low-mu wheels will be locked.

With ABS it will kick in to stop the low-mu wheels locking. That might marginally increase the brake force on the low-mu side. So I don't understand the nuance regarding split-mu and braking distances other than ABS stopping better than if the wheels were just locked.
Bert

The ABS equipped car doesn't pull to the high grip side.

[bigdog3]

BertBert said:

bigdog3 said:

One ABS evaluation test used by manufacturers is split-mu braking. Two wheels on one side of the car run on a low-mu slippery surface whereas the other two wheels run on a high-mu high grip surface.

A manually braked car will lock the low-mu wheels at the effective braking limit. By comparison, the multi-channel ABS car will make use of the extra braking force from the high-mu wheels, hence reducing stopping distance. No amount of driving skill will overcome this fundamental technical advantage.

I'm sorry, that doesn't make any sense. A non-abs braking system can and will make use of the brake force on the high-mu side, just the the low-mu wheels will be locked.

With ABS it will kick in to stop the low-mu wheels locking. That might marginally increase the brake force on the low-mu side. So I don't understand the nuance regarding split-mu and braking distances other than ABS stopping better than if the wheels were just locked.
Bert

Yes a manual braking system can increase braking force on the high-mu surface even when low-mu wheels are locked. But I used the word "effective" for a reason.

A locked tyre will not generate lateral force. So the car will struggle to negotiate road cambers and even gentle turns but will understeer or spin readily. Good drivers will reduce pedal effort when experiencing wheel lock rather than lose control of the vehicle. Racing drivers certainly do.

[bigdog3]

InitialDave said:

The ABS equipped car doesn't pull to the high grip side.

Although direction of "pull" depends on whether scrub-radius is positive or negative.

[InitialDave]

bigdog3 said:

Although direction of "pull" depends on whether scrub-radius is positive or negative.

True, I think most cars are positive/outboard scrub.

I think Porsche 924s are negative/inboard scrub, right?

[bigdog3]

InitialDave said:

True, I think most cars are positive/outboard scrub.

I think Porsche 924s are negative/inboard scrub, right?

Negative scrub-radius became popular with introduction of Front Wheel Drive to improve stability. So most modern cars have negative scrub.

I believe negative scrub has been adopted on some Rear Wheel Drive cars as well. Not sure how Porsche engineered their 924...

[InitialDave]

OK, interesting, I can see the logic to it being beneficial with FWD, yes.

[BertBert]

bigdog3 said:

Yes a manual braking system can increase braking force on the high-mu surface even when low-mu wheels are locked. But I used the word "effective" for a reason.

A locked tyre will not generate lateral force. So the car will struggle to negotiate road cambers and even gentle turns but will understeer or spin readily. Good drivers will reduce pedal effort when experiencing wheel lock rather than lose control of the vehicle. Racing drivers certainly do.

So it's less to do with reduced braking distances per se, but increases in control by not having locked wheels.

[BertBert]

Whoa, we are now back in SP&L. Need to make comments about the legality of ABS and locked wheels rather than their effectiveness now

I'm sure locking wheels is a/ illegal and b/ invalidates your insurance.

Bert

[RSTurboPaul]

FiF said:

bigdog3 said:

gdaybruce said:

I do recall, however, that when I did my IAM course it was suggested to me that 3rd is generally the most appropriate gear around town, giving flexibility for when a burst of acceleration is required without labouring the engine and indeed, making it less likely that you will inadvertently creep over the limit.

Why is "a burst of acceleration" required around town? Seems inappropriate in a busy town environment and likely to confuse pedestrians, cyclists and other road users.

In my view the acceleration required is to return to nearer the prevailing limit after slowing down because of a real or potential hazard. It's much easier to do this in a truly flexible gear that is appropriate for both the vehicle and the likely speed range to be covered.

To continue with the 3rd in a 30 example , or 4th or whatever number gear is best for the vehicle and situation, it's far easier to lift off, cover the brake, slow down to around 20 or a bit less say, then when situation allows accelerate back to limit, as opposed to trundling along in 5th, lift off, not much engine braking, touch brakes, engine now unhappy at low revs, must change down, situation past, accelerate and change again. Sorry, labouring the point now, as opposed to labouring the engine.


Sorry Dr Jekyll got there first, and took a shorter route.

I have heard of real life examples where being in a gear that allows 'maximum control and reserve' (as I heard at an HPC day) means being able to 'squirt' out of the way of someone failing to stop at a junction or RAB as you pass it / go across it, meaning they don't wipe your rear quarter out.

[FiF]

BertBert said:

bigdog3 said:

Yes a manual braking system can increase braking force on the high-mu surface even when low-mu wheels are locked. But I used the word "effective" for a reason.

A locked tyre will not generate lateral force. So the car will struggle to negotiate road cambers and even gentle turns but will understeer or spin readily. Good drivers will reduce pedal effort when experiencing wheel lock rather than lose control of the vehicle. Racing drivers certainly do.

So it's less to do with reduced braking distances per se, but increases in control by not having locked wheels.

That's the point I was trying to make about vehicle squirming about with varying and changing friction surfaces, the overall result of the vehicle recognising the situation, maximising retardation on each wheel individually, yet where that would destabilise the vehicle and give other problems, then manage the situation to keep control as best possible and return to maximum braking effort asap. Can't do that as effectively by simple manual control.

[MB140]

gazza285 said:

Just smile sweetly and keep your mouth shut. Your opinion is neither wanted nor welcome.

Not had to do one myself (weren’t available when I last got points).

My friend and his wife both did the same one at the same time. My wife and I were meeting them in the pub after. My mate was ripping at the amount of bks and condescending talk down to you tone the tt had used. Hell he had a 30 minute rant just to get his pent up anger out at the crap. Said if there’s a next time he is taking the points because it took every ounce of restraint not to go and batter the life out the little .

[FiF]

RSTurboPaul said:

FiF said:

bigdog3 said:

gdaybruce said:

I do recall, however, that when I did my IAM course it was suggested to me that 3rd is generally the most appropriate gear around town, giving flexibility for when a burst of acceleration is required without labouring the engine and indeed, making it less likely that you will inadvertently creep over the limit.

Why is "a burst of acceleration" required around town? Seems inappropriate in a busy town environment and likely to confuse pedestrians, cyclists and other road users.

In my view the acceleration required is to return to nearer the prevailing limit after slowing down because of a real or potential hazard. It's much easier to do this in a truly flexible gear that is appropriate for both the vehicle and the likely speed range to be covered.

To continue with the 3rd in a 30 example , or 4th or whatever number gear is best for the vehicle and situation, it's far easier to lift off, cover the brake, slow down to around 20 or a bit less say, then when situation allows accelerate back to limit, as opposed to trundling along in 5th, lift off, not much engine braking, touch brakes, engine now unhappy at low revs, must change down, situation past, accelerate and change again. Sorry, labouring the point now, as opposed to labouring the engine.


Sorry Dr Jekyll got there first, and took a shorter route.

I have heard of real life examples where being in a gear that allows 'maximum control and reserve' (as I heard at an HPC day) means being able to 'squirt' out of the way of someone failing to stop at a junction or RAB as you pass it / go across it, meaning they don't wipe your rear quarter out.

Well yes, but I deliberately avoided that side of things to avoid upsetting Brake members, after all every time you exceed by 1mph a fluffy cat dies or something.