FWD vs RWD basics

[GuvGTI]

May have been shown before not sure if this entirely the right section to be displaying adventurous video clips! But I think tiff needel's a legend.

FWD
http://www.youtube.com/watch?v=jPnGjdZi7bY

RWD
http://www.youtube.com/watch?v=6yS1ViNXg_E


Any more comparisons and techniques to show or discuss on both the different driving styles?

Braking points
cornering
weight balance
etc etc


Thanks

[GravelBen]

Not quite FWD v RWD but having just bought a RWD car (MX5) after 3 4wd Subarus (which I still have one of) I've been learning a key difference between them on the loose stuff - AWD you throw it in sideways under brakes and use the traction to drive out (relatively) straight. RWD it seems you turn it in straighter on the throttle and drive it out sideways. Everything is backwards! (Though not literally unless you get it properly wrong)

[robwales]

Good vids, seeing the Evo and Lister Storm on the tarmac, I searched for their parts.

Lister: http://www.youtube.com/watch?v=vk-p-mi5cHc

But can't find the Evo video though.

[JonRB]

Oh God. Batten down the hatches - I feel another religious war on FWD vs RWD brewing.

[Bob K]

We love Tiff... We love Tiff... Puke!

[GuvGTI]

Bob K said:

We love Tiff... We love Tiff... Puke!

Edited by GuvGTI on Thursday 6th March 23:38

[Range Rover Blue]

But what's the point? it's all a little bit juvenile.

You never see the Stig going that sideways do you?

[Colonial]

It is interesting. I regulary swith between a low powered AWD car (Subaru Legacy 2.2 sedan) and a low powered RWD car (BMW 318is) and a low powered FWD car (Toyota Corolla) for varying roles.

The main car I drive is the BMW. The one I drive the longest distance in is the Corolla. Each requires a different driving approach.

Which do I prefer? Out of these three the BMW by a distant whack, then the Subie and the Toyota way, way, way behind. But then they are different cars I guess.

[Stu R]

Range Rover Blue said:

But what's the point? it's all a little bit juvenile.

You never see the Stig going that sideways do you?

nope, but you regularly see some of Japan's top JGTC drivers going sideways outside of work. Tsuchiya etc have been doing it for many, many years and doing it very well, as have rally drivers and other hooligans, because it's works better than taking a clean line. The reason you don't see it is because it kills tyres. Where that's less of a problem such as in drifting and rallying, you do see it. Lots.

Look on youtube for extracts of the drift bible with Keiichi Tsuchiya. Whilst it's first and foremost purpose is to provide insight into drifting techniques, it also goes a long way towards explaining the various handling traits of the different types of drivetrain and engine positions. It's well worth a look.

Edited by Stu R on Friday 14th March 04:41

[Chris71]

Range Rover Blue said:

But what's the point? it's all a little bit juvenile.

You never see the Stig going that sideways do you?

You could argue that an experienced driver should never need that level of car control on the road and that it wastes time on the track.

The main response is that pratting around like this in controlled conditions could save your life if something unexpected does happen on the road. I don't really feel confident in a car until I have some idea where it's limits are and what happens when you reach them. The second response is that it's just rather good fun - if slightly juvenile.

[RobM77]

Generally speaking, RWD remains more balanced through a corner than FWD. I've raced both (FWD extensively so), and FWD relies on forced weight transfer on the way into a bend to achieve a balance, and therefore maximum grip and the best acceleration afterwards. RWD track technique, conversely, works to achieve a balance at much lower speed on the road. The FWD track technique does not work at low speeds into unsighted bends on public roads, therefore a front drive car is out of balance through most of a bend on the public road, and thus, if you know what you're doing, less safe in the event of an emergency situation where you require lots of grip to take avoiding action. I also find it less satisfying on the road, as I find balance not just safe, but also satisfying.

Do a You Tube search for "wheel drive fifth gear" if you want a demo of the above in how FWD, 4WD and RWD react in an emergency avoidance situation. If, like me, you can't acces You Tube at work, the basic premise is that FWD and 4WD kill the stray penguin, but RWD avoids it.

[m12_nathan]

Stu R said:

Range Rover Blue said:

But what's the point? it's all a little bit juvenile.

You never see the Stig going that sideways do you?

nope, but you regularly see some of Japan's top JGTC drivers going sideways outside of work. Tsuchiya etc have been doing it for many, many years and doing it very well, as have rally drivers and other hooligans, because it's works better than taking a clean line. The reason you don't see it is because it kills tyres. Where that's less of a problem such as in drifting and rallying, you do see it. Lots.

if going sideways is faster than a clean line on a race track surface why do lap times get ruined by a bit of sidewaysness? If the rear wheels are spinning that much they are not providing optimum drive out of the corner.

[RobM77]

m12_nathan said:

Stu R said:

Range Rover Blue said:

But what's the point? it's all a little bit juvenile.

You never see the Stig going that sideways do you?

nope, but you regularly see some of Japan's top JGTC drivers going sideways outside of work. Tsuchiya etc have been doing it for many, many years and doing it very well, as have rally drivers and other hooligans, because it's works better than taking a clean line. The reason you don't see it is because it kills tyres. Where that's less of a problem such as in drifting and rallying, you do see it. Lots.

if going sideways is faster than a clean line on a race track surface why do lap times get ruined by a bit of sidewaysness? If the rear wheels are spinning that much they are not providing optimum drive out of the corner.

Max grip is usually achieved in a slight drift. A typical modern tyre on dry tarmac will see that at around 4%-10% slip, depending on the tyres being used. This is why cars accelerate faster without TC turned on, and ABS needs to allow a bit of slip to stop a car optimally.

Some slower corners will result in a sideways style being beneficial, not to grip, but to the line and positioning of the car; so you trade one off for the other. Generally speaking though, the fastest laps are within this small slip window.

[Dr Jekyll]

Colonial said:

It is interesting. I regulary swith between a low powered AWD car (Subaru Legacy 2.2 sedan) and a low powered RWD car (BMW 318is) and a low powered FWD car (Toyota Corolla) for varying roles.

The main car I drive is the BMW. The one I drive the longest distance in is the Corolla. Each requires a different driving approach.

Which do I prefer? Out of these three the BMW by a distant whack, then the Subie and the Toyota way, way, way behind. But then they are different cars I guess.

So out of interest, what are the differences and are they related to which end is driven as opposed to other differences between the cars?

And why is FWD regarded as anathema by true petrol heads, but 4WD as a good thing?

[RobM77]

Dr Jekyll said:

And why is FWD regarded as anathema by true petrol heads, but 4WD as a good thing?

Front wheel drive is commonly disliked by petrolheads because most petrolheads like balance and they like to interact with a car in a corner. The nose led stance of a front drive car doesn't allow this interaction and interest, because fundamentally front drive cars are out of balance steady state in a bend. The only way round this problem is to go barelling into bends full whack like you would on a race track, which is of course not practical on the public road. I admit, a lot of dislike of front drive is probably lack of understanding of how to drive properly, but for the most part front drive isn't terribly satisfying or interesting.

Also, accelerating from a standing start is a joke in a front drive car, because you create a situation where the rear wheels get more grip and the fronts get less. To have the front wheels being driven in such a situation is, to put it bluntly, crackers. Oh, and then you've got torque steer.

Personally, I find front drive ok on a race track, and it's nice if you want to drive sideways a lot, because oversteer is easier to control in a front drive car. Other than that, give me rear drive anyway.

As for four wheel drive, I find this dull as well. Maybe it's an image thing from rallying coupled with the extra traction off the line.

For the record, I've owned FWD, RWD and 4WD cars, and raced FWD and RWD.

[m12_nathan]

RobM77 said:

m12_nathan said:

Stu R said:

Range Rover Blue said:

But what's the point? it's all a little bit juvenile.

You never see the Stig going that sideways do you?

nope, but you regularly see some of Japan's top JGTC drivers going sideways outside of work. Tsuchiya etc have been doing it for many, many years and doing it very well, as have rally drivers and other hooligans, because it's works better than taking a clean line. The reason you don't see it is because it kills tyres. Where that's less of a problem such as in drifting and rallying, you do see it. Lots.

if going sideways is faster than a clean line on a race track surface why do lap times get ruined by a bit of sidewaysness? If the rear wheels are spinning that much they are not providing optimum drive out of the corner.

Max grip is usually achieved in a slight drift. A typical modern tyre on dry tarmac will see that at around 4%-10% slip, depending on the tyres being used. This is why cars accelerate faster without TC turned on, and ABS needs to allow a bit of slip to stop a car optimally.

Some slower corners will result in a sideways style being beneficial, not to grip, but to the line and positioning of the car; so you trade one off for the other. Generally speaking though, the fastest laps are within this small slip window.

As I said - 'spinning that much' - highly unlikely that the drift guys are within the optimal level of slip

[RobM77]

m12_nathan said:

RobM77 said:

m12_nathan said:

Stu R said:

Range Rover Blue said:

But what's the point? it's all a little bit juvenile.

You never see the Stig going that sideways do you?

nope, but you regularly see some of Japan's top JGTC drivers going sideways outside of work. Tsuchiya etc have been doing it for many, many years and doing it very well, as have rally drivers and other hooligans, because it's works better than taking a clean line. The reason you don't see it is because it kills tyres. Where that's less of a problem such as in drifting and rallying, you do see it. Lots.

if going sideways is faster than a clean line on a race track surface why do lap times get ruined by a bit of sidewaysness? If the rear wheels are spinning that much they are not providing optimum drive out of the corner.

Max grip is usually achieved in a slight drift. A typical modern tyre on dry tarmac will see that at around 4%-10% slip, depending on the tyres being used. This is why cars accelerate faster without TC turned on, and ABS needs to allow a bit of slip to stop a car optimally.

Some slower corners will result in a sideways style being beneficial, not to grip, but to the line and positioning of the car; so you trade one off for the other. Generally speaking though, the fastest laps are within this small slip window.

As I said - 'spinning that much' - highly unlikely that the drift guys are within the optimal level of slip

Ah, that isn't fast, no.

[Alpinestars]

RobM77 said:

Do a You Tube search for "wheel drive fifth gear" if you want a demo of the above in how FWD, 4WD and RWD react in an emergency avoidance situation. If, like me, you can't acces You Tube at work, the basic premise is that FWD and 4WD kill the stray penguin, but RWD avoids it.

I don't think this was a particularly good test. Faced with the same hazard, most drivers would come off the throttle or stamp on the brakes, and then it does not matter whether you have FWD, RWD or 4WD. As for the BMW having DSC, FWD cars also come with DSC/ESP so the roundabout test was also a bit pointless.

I understand your point that on a FWD car the front tyres are being asked to both power the car and to steer it so the threshold at which they lose grip (and hence understeer) is generally lower. However, around a bend the worst thing that can happen under power is that you understeer, when this happens most people back off which should counteract the understeer. With a RWD car under power, there is a chance of oversteering, and backing off would make it a lot worse.

Surely left foot braking is the answer on a FWD car?

[RobM77]

Alpinestars said:

RobM77 said:

Do a You Tube search for "wheel drive fifth gear" if you want a demo of the above in how FWD, 4WD and RWD react in an emergency avoidance situation. If, like me, you can't acces You Tube at work, the basic premise is that FWD and 4WD kill the stray penguin, but RWD avoids it.

I don't think this was a particularly good test. Faced with the same hazard, most drivers would come off the throttle or stamp on the brakes, and then it does not matter whether you have FWD, RWD or 4WD. As for the BMW having DSC, FWD cars also come with DSC/ESP so the roundabout test was also a bit pointless.

I understand your point that on a FWD car the front tyres are being asked to both power the car and to steer it so the threshold at which they lose grip (and hence understeer) is generally lower. However, around a bend the worst thing that can happen under power is that you understeer, when this happens most people back off which should counteract the understeer. With a RWD car under power, there is a chance of oversteering, and backing off would make it a lot worse.

Surely left foot braking is the answer on a FWD car?

The key point though is balance. In a given corner in a front drive car, the front is closer to the limit than the front; let's say 50% front 20% rear. This is both under power for obvious reasons but also due to the balance of weight in the car (oily bits all up front; it's made like that cause it's cheaper). When you come across a diesel spill or need to make sudden corrective action, you're therefore more likely to breach the limit because the front's closer to it. So add 55% to both those figures I mentioned and you get a car that's 5% understeering (possibly into oncoming traffic) and still got 15% grip left at the back. If, instead of being 50%:30%, a car is balanced at 40%:40% (same cornering speed though - 40+40 or 80% of the limit), adding 55% makes no difference - still within 5% of the limit from and rear. The only way of achieving this balance in a front drive car is to enter the bend really fast, which isn't practical or safe on the road. In a rear drive car, at normal road speeds, the forces are naturally balanced out by virtue of the drive/steering split and the weight distribution, and therefore the vehicle is more balanced. This is also why a smooth and balanced racing technique is safer than the clunky IAM technique at low speed on the road, but that's a matter for discussion another time maybe!

Regarding understeer and oversteer, understeer loses steering control and oversteer retains it. I know what I'd rather have! When was the last time you saw a motorbike or mountain bike rider hold an understeer slide in a bend? An oversteer balance is deliberate in the two wheeled world because it retains control.

That lengthy description above is basically summed up by what happens in that video. The extra grip is needed, and it's only the BMW that retains grip and control out of the three cars. As it happens, the limit is breached in all the cars (less so in the BMW because it starts out more balanced), but because it's oversteer, the BMW uses less of the road to gather things up because Vicky still has control over the car. If there had been a car coming the other way you can see why this is an important point!

Ergo I'll drive FWD, 4WD and RWD on the road, but I feel safest in rear drive. I also feel safer with a responsive balanced setup, rather than an understeerey one, and I also feel safer using the techniques I've learnt in racing to balance the car than with what I've been taught in advanced road driving technique (RoSPA and IAM).

I'm afraid I can't comment on left foot braking. I never found it necessary when racing front drive, and haven't thought it safe to experiment on the road. I also haven't owned a front drive road car since I was 22!

Edited by RobM77 on Wednesday 19th March 15:06

[GravelBen]

No doubt plenty of companies that make AWD cars will show you demonstrations of how they react better to those situations than 2wd cars

To be honest for safety, control and point-to-point pace on slippery, loose or inconsistent surfaces RWD just can't really compete with AWD. And FWD is somewhere back in the distance still trying to get traction off the line.

Edited by GravelBen on Wednesday 19th March 20:23