Why is it wrong to brake and down-change simultaneously?

Why is it wrong to brake and down-change simultaneously?

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Discussion

DaineseMan

Original Poster:

628 posts

148 months

Sunday 6th October 2013
quotequote all
I know about the saying 'brakes to slow, gears to go' and that, in line with IPSGA, speed and gears are separate stages - but can anyone actually explain to me why it is wrong to brake and down-change simultaneously?

CB2152

1,555 posts

132 months

Sunday 6th October 2013
quotequote all
I don't hold any advanced driving qualification, but I have been told it's so you don't do two things that could potentially make the car unstable at the same time. There are exceptions though, such as turning into a left hand junction going down a hill...

I don't think it's wrong either, might make it less smooth if you don't get the rev match right, but you'd have to be approaching the limit of grip already in order to make it dangerous.

Edited by CB2152 on Sunday 6th October 12:35

MC Bodge

21,552 posts

174 months

Sunday 6th October 2013
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Do a search. It's been argued many, many times. It's a bit like debate between religious believers and atheists/agnostics.

FWIW, it's not wrong. In my opinion.

Done properly, it can help maintain stability, but true believers won't have it.

ch108

1,127 posts

132 months

Sunday 6th October 2013
quotequote all
CB2152 said:
I don't hold any advanced driving qualification, bt I have been told it's so you don't do two things that could potentially make the car unstable at the same time. There are exceptions though, such as turning into a left hand junction going down a hill...
Exactly right. This is what I was taught for my IAM test.

Toltec

7,159 posts

222 months

Sunday 6th October 2013
quotequote all
There is a difference between advanced driving and car control, so for the system used by the iam etc. it is probably due to the emphasis being on the former. This is not a bad thing in a 'walk before you run' sense.

To a biker doing several things at once comes naturally so deliberately not doing the same in a car feels odd.

MC Bodge

21,552 posts

174 months

Sunday 6th October 2013
quotequote all
Toltec said:
To a biker doing several things at once comes naturally so deliberately not doing the same in a car feels odd.
Quite right.

....and the IAM bike course is fairly indifferent to such matters in my experience.

DaineseMan

Original Poster:

628 posts

148 months

Sunday 6th October 2013
quotequote all
MC Bodge said:
Toltec said:
To a biker doing several things at once comes naturally so deliberately not doing the same in a car feels odd.
Quite right.

....and the IAM bike course is fairly indifferent to such matters in my experience.
Interesting point, as I too didn't seem to receive any criticism for overlapping when doing the bike course. But the car course seems to be much more adverse to overlapping between the gear and braking stage.

Nigel Worc's

8,121 posts

187 months

Sunday 6th October 2013
quotequote all
It isn't wrong, it is just a system, it was a useful teaching aid to get new candidates to think about what they're doing and why.

It actually stems from a much earlier period when brakes didn't work on all wheels with the same efficency, so you wouldn't brake in a straight line.

Don't get hung up on it, enjoy the course, then take whatever you've learnt and incorperate into your everyday driving style as you see fit.

DaineseMan

Original Poster:

628 posts

148 months

Sunday 6th October 2013
quotequote all
DaineseMan said:
MC Bodge said:
Toltec said:
To a biker doing several things at once comes naturally so deliberately not doing the same in a car feels odd.
Quite right.

....and the IAM bike course is fairly indifferent to such matters in my experience.
Interesting point, as I too didn't seem to receive any criticism for overlapping when doing the bike course. But the car course seems to be much more adverse to overlapping between the gear and braking stage.
On the bike, I would do 95% of my braking with both brakes, but I would usually be trailing the rear brake at the down-changing stage. Is this contrary to the System?

R0G

4,984 posts

154 months

Sunday 6th October 2013
quotequote all
Its not 'wrong' but the vehicle is more balanced if they are seperated and the driver is then doing one thing at a time and not two so the concentration for each is going to be better

The only time I do both together is below 10 mph when going into first gear in a give way type situation

A bit of practice makes this easy to do

Nigel Worc's

8,121 posts

187 months

Sunday 6th October 2013
quotequote all
It will depend on how much of an anorack your observer is.

I never liked this part of the system, so although I'd use it to demonstrate control and thought over what you're doing, I wouldn't worry much about it.

Bikes are different depending on what braking system they actually have, it isn't so easy to have a "one size fits all" for those.

MC Bodge

21,552 posts

174 months

Sunday 6th October 2013
quotequote all
R0G said:
the vehicle is more balanced if they are seperated
is it, really?

R0G said:
and the driver is then doing one thing at a time and not two so the concentration for each is going to be better
2 separate issues.

R0G said:
The only time I do both together is below 10 mph when going into first gear in a give way type situation
Why not be a bit more freestyle?

MC Bodge

21,552 posts

174 months

Sunday 6th October 2013
quotequote all
Nigel Worc's said:
It will depend on how much of an anorack your observer is.
in my experience, the ROSPA examiner was a fundamentalist. Anything other was a "race track technique".

p1esk

4,914 posts

195 months

Sunday 6th October 2013
quotequote all
DaineseMan said:
I know about the saying 'brakes to slow, gears to go' and that, in line with IPSGA, speed and gears are separate stages - but can anyone actually explain to me why it is wrong to brake and down-change simultaneously?
Well I certainly can't, because I don't think it is wrong, so long as you make appropriate changes to your speed, and have a suitable gear engaged.

Best wishes all,
Dave.

R0G

4,984 posts

154 months

Sunday 6th October 2013
quotequote all
When braking the vehicle is 'nose heavy' so releasing the brake makes the vehicle balanced - I think that is a physics fact

p1esk

4,914 posts

195 months

Sunday 6th October 2013
quotequote all
R0G said:
When braking the vehicle is 'nose heavy' so releasing the brake makes the vehicle balanced - I think that is a physics fact
That may be so, but surely it isn't simply a matter of a vehicle being balanced or unbalanced. There are degrees of balance, or the lack thereof.

So long as we avoid having the vehicle unbalanced to such an extent that it is becoming unstable, I don't see that much harm is being done. As I see it, we need a sufficiently good state of balance that we have decent stability which gives us the ability to perform sudden manoeuvres when needed to respond to emergency situations. Apart from that, I don't think it matters that much.

In any case, when we talk of balance, do we mean having approximately equal weight on all four wheels? I hope not, because many cars never have that, even when stationary on level ground.

Mandat

3,881 posts

237 months

Sunday 6th October 2013
quotequote all
p1esk said:
R0G said:
When braking the vehicle is 'nose heavy' so releasing the brake makes the vehicle balanced - I think that is a physics fact
That may be so, but surely it isn't simply a matter of a vehicle being balanced or unbalanced. There are degrees of balance, or the lack thereof.

So long as we avoid having the vehicle unbalanced to such an extent that it is becoming unstable, I don't see that much harm is being done. As I see it, we need a sufficiently good state of balance that we have decent stability which gives us the ability to perform sudden manoeuvres when needed to respond to emergency situations. Apart from that, I don't think it matters that much.

In any case, when we talk of balance, do we mean having approximately equal weight on all four wheels? I hope not, because many cars never have that, even when stationary on level ground.
In terms of balance, it means that the nett forces acting on the car at that point in time are zero. (i.e. the car is either at rest or travelling at a constant velocity)


p1esk

4,914 posts

195 months

Sunday 6th October 2013
quotequote all
Mandat said:
p1esk said:
R0G said:
When braking the vehicle is 'nose heavy' so releasing the brake makes the vehicle balanced - I think that is a physics fact
That may be so, but surely it isn't simply a matter of a vehicle being balanced or unbalanced. There are degrees of balance, or the lack thereof.

So long as we avoid having the vehicle unbalanced to such an extent that it is becoming unstable, I don't see that much harm is being done. As I see it, we need a sufficiently good state of balance that we have decent stability which gives us the ability to perform sudden manoeuvres when needed to respond to emergency situations. Apart from that, I don't think it matters that much.

In any case, when we talk of balance, do we mean having approximately equal weight on all four wheels? I hope not, because many cars never have that, even when stationary on level ground.
In terms of balance, it means that the nett forces acting on the car at that point in time are zero. (i.e. the car is either at rest or travelling at a constant velocity)
In that case it seems inevitable that we'll have some degree of imbalance whenever we negotiate a curve. I have to admit I'm getting confused (but not worried) by this. After 56 years of driving I'm fairly happy about what feels right and safe, and what doesn't. cool

...and I do like your 'nett' rather than 'net', though I suspect you're in a tiny minority by spelling it that way.
Are you a bit aged, like me? laugh

davepoth

29,395 posts

198 months

Sunday 6th October 2013
quotequote all
R0G said:
When braking the vehicle is 'nose heavy' so releasing the brake makes the vehicle balanced - I think that is a physics fact
No, you have that the wrong.

The car is in balance when the centre of gravity of the car stays in the same place. Travelling around a constant radius curve, braking at a constant rate, or accelerating at a constant rate (not going to happen) will all put the car in balance, exactly the same as travelling along a straight road at a constant speed.

Making an abrupt change to a control will take everything out of balance. The CofG will shift, and as the suspension and tyres adjust to that, everything squirms around a bit, which shifts the centre of gravity a bit too. That's what we try and avoid.

boxedin

1,351 posts

125 months

Sunday 6th October 2013
quotequote all
dunno, as a biker, its perfectly normal.

As driver, works fine whilst going downhill on twisty parts of the Route Napoleon, even more so on the N102.