Understanding Weight Transfer

[boxsey]

I would like to start by saying how interesting and informative this forum is. I have already spent many hours reading the different threads, taking in the advice and having a few chuckles along the way. Now onto my question.

Is it possible to 'manage' the weight transfer of a car or can you only react to it? I'm interested in both front and rear engined cars but mostly mid-engined cars with RWD (i.e. my own car).

My guess is that some management of the weight transfer is possible. My reason for thinking this is that on an S bend (left then right) after steering through the left bend, I momentarily turn the wheel to the straight ahead position before turning into the right section of the bend. By doing this I feel that I am bringing the weight of the car back to the middle before steering in the opposite direction i.e. trying to avoid throwing the weight from one side to the other too quickly.

I look forward to hearing your thoughts and descriptions of what is actually going on with the weight of the car whilst driving.

Edited by boxsey on Wednesday 29th November 16:51

[GreenV8S]

See my comment on Tuesday 14th November on this thread about turning in smooth and early. Yes it is possible, it's important if you want to make smooth and comfortable progress and vital when you are driving near the limit of grip.

[Big Fat F'er]

boxsey said:

My guess is that some management of the weight transfer is possible.

Boxsey - it definitely is, as well described by Green (and others) in the thread shown (and others if you can be bothered searching).

You probably do some of it without thinking, including setting it up for normal cornering, s-bends, acceleration/decelaration on the straight. Thats on the road with everyday driving. If you're on the track or rallying you will defnitely be managing it if you want to stay on.

The more you know it's there, the more you'll feel it in the seat of your pants.

BFF

[boxsey]

Cheers guys. I haven't read the thread above yet, it was already on my list but I got too engrossed in a number of others especially the 'Headlight flash' one. I did a search on both 'weight' and 'transfer' during the last year but nothing came up. Hence starting a topic.

[gridgway]

I dropped my 16yr old son off on saturday for a day with Pentti Airikkala at his rally school. I could only listen to the intro and come back at the end, but Pentti was talking about the effects of weight transfer and the use of left foot braking in rallying esp in fwd cars. Very interesting stuff.

I got a demo drive by the master when I went back to pick up my son - fantastic esp the scandinavian flick! Not really advanced driving on the road though!!

Graham

[mph999]

For normal road driving - I'm sure I'll get shot down for this (gulp) ...

To manage weight transfer just drive smoothly ...

(ok, I'll explain)

1. Changing up, let the speed, just for a moment, stay static just before you change up - result weight moves forward so when you remove the gas it doesn't go forward in one go.
2. Slowing down, use brakes, 3 stage, 1. Gently on 2. Firm braking to get speed off, 3. Gently off.
3. Cornering, turn wheel "gently" and smoothly. Read road, get speed correct BEFORE bend, then just before you start to turn back on the gas to maintain speed, as bend opens up apply gentle but progressive acceleration, if safe.
4. Throttle, gently on, gently off.
5. Changing down, match revs or doube-de-clutch

Job done

ps. "Fast" left-rights are a bit tricky to balance though ... practice

Edited by mph999 on Wednesday 29th November 22:02

[TripleS]

mph999 said:

For normal road driving - I'm sure I'll get shot down for this (gulp) ...

To manage weight transfer just drive smoothly ...

(ok, I'll explain)

1. Changing up, let the speed, just for a moment, stay static just before you change up - result weight moves forward so when you remove the gas it doesn't go forward in one go.
2. Slowing down, use brakes, 3 stage, 1. Gently on 2. Firm braking to get speed off, 3. Gently off.
3. Cornering, turn wheel "gently" and smoothly. Read road, get speed correct BEFORE bend, then just before you start to turn back on the gas to maintain speed, as bend opens up apply gentle but progressive acceleration, if safe.
4. Throttle, gently on, gently off.
5. Changing down, match revs or double-de-clutch.

Job done

ps. "Fast" left-rights are a bit tricky to balance though ... practice

Edited by mph999 on Wednesday 29th November 22:02

That doesn't deserve to get shot down at all.

Item 5 though - it's not a matter of matching revs or double de-clutching. Double de-clutching is also about matching revs.

Best wishes all,
Dave.

[mph999]

TripleS said:

mph999 said:

For normal road driving - I'm sure I'll get shot down for this (gulp) ...

To manage weight transfer just drive smoothly ...

(ok, I'll explain)

1. Changing up, let the speed, just for a moment, stay static just before you change up - result weight moves forward so when you remove the gas it doesn't go forward in one go.
2. Slowing down, use brakes, 3 stage, 1. Gently on 2. Firm braking to get speed off, 3. Gently off.
3. Cornering, turn wheel "gently" and smoothly. Read road, get speed correct BEFORE bend, then just before you start to turn back on the gas to maintain speed, as bend opens up apply gentle but progressive acceleration, if safe.
4. Throttle, gently on, gently off.
5. Changing down, match revs or double-de-clutch.

Job done

ps. "Fast" left-rights are a bit tricky to balance though ... practice

Edited by mph999 on Wednesday 29th November 22:02

That doesn't deserve to get shot down at all.

Item 5 though - it's not a matter of matching revs or double de-clutching. Double de-clutching is also about matching revs.

Best wishes all,
Dave.

thanks mate ... fair point about 5, I just meant to offer a couple of alternatives as x2 de-clutching is harder ...

Martin

[GreenV8S]

TripleS said:

That doesn't deserve to get shot down at all.

Item 5 though - it's not a matter of matching revs or double de-clutching. Double de-clutching is also about matching revs.

Best wishes all,
Dave.

I agree it's good, but I would say (5) would be better just to say match revs (avoid sudden torque transient), double declutching isn't really relevent to smoothness / weight transfer.

[willibetz]

I particularly like your use of the word "manage", Boxsey.

The weight transfer is an inevitable consequence of the forces acting on the car.

As a driver, awareness of this phenonenum is prerequisite to "managing" the rate at which weight transfers to provide better grip. It's particularly important in cars which pitch, lean or have an odd weight distribution. Your Boxster is taut and has wonderful weight distribution, so if you want to experiment try to get an old 911 as a loan car when your Boxster is next serviced!

[Big Fat F'er]

mph999 said:

For normal road driving....To manage weight transfer.... just drive smoothly ...

Well said that man.

[boxsey]

willibetz said:

I particularly like your use of the word "manage", Boxsey.

The weight transfer is an inevitable consequence of the forces acting on the car.

As a driver, awareness of this phenonenum is prerequisite to "managing" the rate at which weight transfers to provide better grip. It's particularly important in cars which pitch, lean or have an odd weight distribution. Your Boxster is taut and has wonderful weight distribution, so if you want to experiment try to get an old 911 as a loan car when your Boxster is next serviced!

Indeed, I am very lucky because of the superb handling that the boxster provides the driver with. Getting the boxster has brought the joy of driving to me and the desire to get better at it rather than just using a car to commute like I guess 95% of drivers do. I've already experienced it on a track and loved it. I guess that's when I first really appreciated the weight of the car shifting around and prompted me to think that I would be able to drive the car better if I understood what was going on with the weight shifts.

My particular model, although an auto that I drive mostly in manual mode, has no other driver aids and is the first RWD car I've had since a MKII Escort Mexico when I was a youth. Therefore, although the boxster handling is very neutral and flatters the driver, I know it has the potential to bite me if I abuse it.

Already, I've committed the above 5 points to memory and put them into practice on my commute to work this morning. For example, by using smooth and progressive steering inputs (as per point 3) at a roundabout, I felt a sensation of grip and control that was very, very satifying. Totally different to the feeling that I normally have which is one of tensing up in preparation for the back end to break away and having to correct it.

I like the advice about the 911 and would be interested to hear more about how to manage that heavy back end swinging around as an old one (993 or 964) is on my future shopping list!

[willibetz]

Older 911's pitch quite dramatically. So, for example, it's important to load the front end before braking heavily. They will slow very quickly if driven in this way, but lock a wheel even more quickly if you panic and just hit the middle pedal.

As for the rear end, the traction of 911's is almost without parallel. They're simply sensational. Again, you need to consider how weight distribution is affected by moving from brake to throttle or vice-versa. As Jackie Stewart is keen on saying (in an accent that my keyboard won't mimic!) "don't open the throttle until you know you can keep it open".

My experience of the models that you mention is that their handling is influenced by wheelbase. The 996 is much easier on the limit than the 993, in large part because there's a little more room between the front and rear wheels. A 964 on the limit is a sight to behold, but pretty rare unless you count Rohrl or Manthey amongst your friends...

For a road car, there's little to beat a 3.2 Carrera for involvement (in my unbiased opinion, natch).

WilliBetz

[GreenV8S]

There's another side to the issue of driving smoothly. There are times when it is better *not* to drive smoothly. If you do everything smoothly then as you approach the limit of grip nothing happens, nothing happens, nothing happens, ..., and then the car starts to slide and you have to respond. If you don't know exactly where the limit is, then it is hard to anticipate and you end up driving purely reactively. This means the breakaway can be quite dangerous when it happens if you aren't expecting it.

I haven't seen this technique taught anywhere, but when I'm trying to drive as past as possible in uncertain conditions (or even just trying to drive safely in really treacherous conditions) I go out of my way to find where the limit of grip is. I do this by deliberately provoking small slides by stabbing the throttle or twitching the steering. Since the input is short, I remove the source of the slide as soon as it starts without having to react to it so it never developes into a big slide. By noting how much provocation it took to initiate the slide I can judge how much grip there was available. If I'm trying to reach the limit then I'll push harder to use more of the available grip and then provoke it again to see how mre is left. The amount of provocation gets smaller and smaller and eventually they sort of join up and I end up just hovering either side of the limit of grip trying to avoid the slide.

The end result is the same as driving smoothly and gradually pushing harder and harder then collecting each slide as it starts, but you get there a lot quicker. That's important if you only have one lap to set a time, or want to know before you reach the first snow-covered junction how much distance you're going to need to stop.

[boxsey]

willibetz said:

Older 911's pitch quite dramatically. So, for example, it's important to load the front end before braking heavily. They will slow very quickly if driven in this way, but lock a wheel even more quickly if you panic and just hit the middle pedal.

WilliBetz

Ahhh. The mist has suddenly cleared! I was wondering what was actually meant by 'loading up'. From what you say above, you load up the front of the car by progressive braking and once the weight has moved forward, brake harder to set your road speed for the bend. So again, smoothly on and off the brakes is a key to managing the 'front to back' movemnent of the weight.

Right, I'm off to do some more testing.

[trackdemon]

GreenV8S said:

There's another side to the issue of driving smoothly. There are times when it is better *not* to drive smoothly. If you do everything smoothly then as you approach the limit of grip nothing happens, nothing happens, nothing happens, ..., and then the car starts to slide and you have to respond. If you don't know exactly where the limit is, then it is hard to anticipate and you end up driving purely reactively. This means the breakaway can be quite dangerous when it happens if you aren't expecting it.

I haven't seen this technique taught anywhere, but when I'm trying to drive as past as possible in uncertain conditions (or even just trying to drive safely in really treacherous conditions) I go out of my way to find where the limit of grip is. I do this by deliberately provoking small slides by stabbing the throttle or twitching the steering. Since the input is short, I remove the source of the slide as soon as it starts without having to react to it so it never developes into a big slide. By noting how much provocation it took to initiate the slide I can judge how much grip there was available. If I'm trying to reach the limit then I'll push harder to use more of the available grip and then provoke it again to see how mre is left. The amount of provocation gets smaller and smaller and eventually they sort of join up and I end up just hovering either side of the limit of grip trying to avoid the slide.

The end result is the same as driving smoothly and gradually pushing harder and harder then collecting each slide as it starts, but you get there a lot quicker. That's important if you only have one lap to set a time, or want to know before you reach the first snow-covered junction how much distance you're going to need to stop.

This is a great point, and one worth a thread of its own. With the uncertain grip levels prevalent at this time of year, this is something I practice even on roads I know well and whilst it goes against the grain for orthodox performance driving and maximizing available grip it gives an invalueable gauge of the amount of grip available underfoot(tyre).

[combover]

GreenV8S said:

There's another side to the issue of driving smoothly. There are times when it is better *not* to drive smoothly. If you do everything smoothly then as you approach the limit of grip nothing happens, nothing happens, nothing happens, ..., and then the car starts to slide and you have to respond. If you don't know exactly where the limit is, then it is hard to anticipate and you end up driving purely reactively. This means the breakaway can be quite dangerous when it happens if you aren't expecting it.

I haven't seen this technique taught anywhere, but when I'm trying to drive as past as possible in uncertain conditions (or even just trying to drive safely in really treacherous conditions) I go out of my way to find where the limit of grip is. I do this by deliberately provoking small slides by stabbing the throttle or twitching the steering. Since the input is short, I remove the source of the slide as soon as it starts without having to react to it so it never developes into a big slide. By noting how much provocation it took to initiate the slide I can judge how much grip there was available. If I'm trying to reach the limit then I'll push harder to use more of the available grip and then provoke it again to see how mre is left. The amount of provocation gets smaller and smaller and eventually they sort of join up and I end up just hovering either side of the limit of grip trying to avoid the slide.

How often do you do this on the average drive? I wouldn't have thaught this a particularly good method, as road surfaces and available grip change all the time. You would need to do it quite often for the theory to really work in practice.

[GreenV8S]

combover said:

How often do you do this on the average drive? I wouldn't have thaught this a particularly good method, as road surfaces and available grip change all the time. You would need to do it quite often for the theory to really work in practice.

Whenever I'm planning to do something that may take me near the limit of grip and I'm not sure where that limit is. If it's snowing for example and I'm in the tiv, it'll be at the start of virtually every slowing down manoeuver and periodically during every descent, because it's so easy for the level of grip to go from 'little' to 'none'. If I'm sprinting and I am not familiar with the track, or don't know what surface conditions are like, or suspect they may have changed since the last run, or may vary between different parts of the track, I'll play with it as necessary to find out what the level of grip is and try to work up to the limit as soon as possible. By the same token, when I'm sprinting in rainy conditions I'll spend a great deal of time sliding a small amount. It's when the car isn't sliding that I'm concerned and feel threatened.

If I'm driving on the road I'm obviously nothing like as agressive in terms of the amount of grip I use. I'll have a rough idea how much grip there is from the steering weight, but I still want to know reasaonably accurately because it's so easy to cross that line. The more exuberant I'm planning to be the more attention I'll pay to knowing the grip level available. One advantage of the tiv is that there is so much power on tap and such positive steering response that I can do this more or less on demand, it only takes a momentary bite on the throttle or brakes, or a slightly more positive than normal turn in, and I can feel the car start to move and feel how it responded to the provocation. This isn't something I'd plan to do when there's anyone around me, but it's not something that I would expect to upset people around me if they did see it. It's just me giving the impression of being an even worse driver than normal.

If I'm driving in the slow car in normal conditions this is irrelevent because I don't plan to be anywhere near the limit of grip, I will know very roughly how much grip there is from the look of the road and I don't need to know more accurately than that because I know I'm not going to be anywhere near the limit.

[willibetz]

I've seen some names use this technique when adapting to a new car or conditions on track, but never seen any driver that I rate use it routinely on road.

The distinction, I'd hazard, is environmental...

On track you want to exploit available grip from the moment you start to brake to the exit of the corner that you braked for (it's said that a good track driver finds the limit and "walks a tight rope", but a great driver can jump on to it). Changes in grip over time are typically gradual, or indicated by way of flags.

On the road, grip is changing all the time and sometimes dramatically within the course of a single bend. Skilled drivers that I've been fortunate enough to sit with use observation to predict the available grip and then manage the car without troubling those limits (acknowledging that the available grip may disappear suddenly).

I don't doubt that you have the pedigree, skill and judgment to use the technique that you describe in any environment, but that good judgment might extend to not advocating it to others.

For mere mortals, the presumption that ice and snow afford little grip is probably safer.

WilliBetz

[GreenV8S]

willibetz said:

On the road, grip is changing all the time and sometimes dramatically within the course of a single bend. Skilled drivers that I've been fortunate enough to sit with use observation to predict the available grip and then manage the car without troubling those limits (acknowledging that the available grip may disappear suddenly).

I don't doubt that you have the pedigree, skill and judgment to use the technique that you describe in any environment, but that good judgment might extend to not advocating it to others.

I agree; this is how I put it:

GreenV8S said:

If I'm driving in the slow car in normal conditions this is irrelevent because I don't plan to be anywhere near the limit of grip, I will know very roughly how much grip there is from the look of the road and I don't need to know more accurately than that because I know I'm not going to be anywhere near the limit.

I haven't advocated this as something that all drivers should do in normal driving, I've presented it as a curiosity which contradicts the accepted wisdom that smoothness is always good.

Edited by GreenV8S on Friday 1st December 11:26