12 replies to this topic

[Ross Stonefeld]

Here in the states we've been getting a lot more WRC coverage during the off season as they try to find something to fill the off season. The amount of slip angle they use confound me. In my experiences just whipping down the road to get some milk when its snowy, it seems the fastest way to drive is like a regular racing car. Very smooth, not lots of opposite lock power sliding. All those rally games seem to give the same result (yeah, its only a game but still). Especially the tarmac rallies. When they induce a total opposite lock turn in for a tarmac hairpin, it just seems too much. They're obviously right otherwise they wouldnt be doing it, but why the high slip angles? The Junior Formulae cars use some hard compounds and even some grooved tires, and they're slip angles arent that high. Is it something to do with the AWD of rallying or the fact that they are seeing the corners for the first time and just give a lot of entry speed and slow it down before they go off the road?

[Wolf]

Ross, I think they know the bends by heart rather than see them for the first time.;) I always thought that fastest way through a bend is drift for high speed corners and a oversteer with opposite lock through a hairpins & such. And I think they do it because with oversteer and opposite lock they throw the car in the corner at higher speed since they loose it faster that way... OK, one can get things wrong more easy that way, but with their car-control it looks nothing but a little twitch or going half a dozen inches off-line... Even Moss, in his 'Design & Behaviour...' wrothe how many drivers used slides (usualy artificial understeer to slow the cars down, if they had braked too late)- and I think that's what they are doing nowdays, only that it's intentional (and using oversteer, since we're talking about hairpins here). That's my 2c woth, at least.

[mat1]

I think they do it
1. because they don't know the bends that good
2. (more important) because they don't know the conditions of the road exactly.

The "ideal line" of course is fastest, but if you take that line 100%, you assume you know the bend and the conditions exactly. If you get is wrong (the bend is somewhat more slippery than expected, or something), you end up in the scenery. Driving the way they do it gives more room for correction.

Does this make sense?

mat1

[AndreasNystrom]

yes, they use slides when they arent so sure about the corner.
That was in the magazine motorsport anyway, and today the notes used are much better, and therefor they dont need to use powerslides as much.

[AS110]

A rear wheel drive car on gravel gets the rear end out in a big full opposite lock powerslide.This feels natural,and is very easy to do.
A 4WD does it a lot different.You don't get the rear out as far,and have to keep turning IN to the turn.Look at the rally cars,they only get on opposite lock for corrections,and sometimes the front wheels are just pointing sraight ahead.This feels very strange to me,you need so much more speed coming into the corner,the corner speed needs to be higher,and you need to use the throttle harder.This is comparativly speaking of course,it's just harder to get loose with 4WD.

[Yelnats]

Having driven my very curvey road in both snow, ice, gravel and tarmac configurations for the last thirty years I have some ideas on this topic that I'd like to throw out for discussion.

At speed on loose gravel I found high slip angles to be essential to cut through the loose marbles to the firmer surface below. If you try to drive conventional slip angles on loose surfaces you end up riding on the top of the poorer traction materials and slideing of the road or having to travel at reduced speeds. Even the tarmack on my road is contaminated with dirt and sand on most corners and slides must be used to sweep the materials away. Loose Snow has a similar effect and demands slides.

But bare ice and tarmack are different kettles of fish and slides are wasteful or in the case of ice, deadly unless you have carbide studs! Of couse I know this road very well and you will note that the Scandanavian drivers are in a similar situation at home which explains there success in these ralleys where they continue to use high angle slides. So familiarity hase nothing to do with the style of driving, indeed my experiance is that the more familiar the driver is with a road, the wilder the slide.

[AS110]

Yes,I agree on cutting through the gravel.I used to like running skinny crossply tyres,the stiff sidewalls would sweep the gravel away,getting down to the hard pack below.On thick gravel a berm would build up on the outside of the tyre,also helping.
Radials are too soft on the sidewalls,and the stones work underneath the tyre,lifting it up on top of the loose stuff.Wide radials are unconrolable.Rally tyres must of been developed to solve this problem,as they sure don't seem to have any trouble.But they do use narrower tyres for loose gravel.
The only way to cope with gravel(on 2,3 or 4 wheels)is balls out aggression,anything less and you are in trouble,safer to just drive like an old man.I have to go a long way to find snow,so my experiance of snow driving is limited,but finding ice in a corner on a motorcycle is interesting!

[mikko4500]

Originally posted by Ross Stonefeld
Here in the states we've been getting a lot more WRC coverage during the off season as they try to find something to fill the off season. The amount of slip angle they use confound me. In my experiences just whipping down the road to get some milk when its snowy, it seems the fastest way to drive is like a regular racing car. Very smooth, not lots of opposite lock power sliding. All those rally games seem to give the same result (yeah, its only a game but still). Especially the tarmac rallies. When they induce a total opposite lock turn in for a tarmac hairpin, it just seems too much. They're obviously right otherwise they wouldnt be doing it, but why the high slip angles? The Junior Formulae cars use some hard compounds and even some grooved tires, and they're slip angles arent that high. Is it something to do with the AWD of rallying or the fact that they are seeing the corners for the first time and just give a lot of entry speed and slow it down before they go off the road?

Ahh, another topic to make a Finnish guy happy.;) First of all, they don't see the corners for the first time, there's a practice period for every rally where the drivers and co-drivers drive through the stages and write notes for themselves.

About tarmac hairpins, the common technique is to use a lot of entry speed and then use the handbrake (which applies to the rear wheels, naturally enough) to swing the tail around and that again requires a lot of opposite lock but in the end it's the fastest way for negotiating the corner. Just as a sidenote, I like doing that myself here in the winter, especially when I need to turn the car around in a rather tight space. It's so much simpler than going through any backing up-turning-around excersizes...



Mikko

[Ross Stonefeld]

Im still not convinced though. If the fastes way through a tarmac hairpin is full opposite lock, how come they dont do it in regular circuit racing? Slip angles seem to be double the max of what yu'd see in circuit racing (just using tarmac rallies as an example)

[Bex37]

Originally posted by Ross Stonefeld
Im still not convinced though. If the fastes way through a tarmac hairpin is full opposite lock, how come they dont do it in regular circuit racing? Slip angles seem to be double the max of what yu'd see in circuit racing (just using tarmac rallies as an example)

I would guess it is because:
- the drivers are so used to this style of driving
- the cars are set up for this style of driving
- you can only slide a car in massive oversteer on tarmac when you are not at the absolute limit of cornering speed (or you will end up in the scenery). The fact that rally drivers do not do 50 laps of the same circuit would have to make them be a little conservative on mid-corner speed. You know yourself that driving on the absolute limit of mid-corner speed provides the occasional mistake even when you HAVE driven through the same corner 50 times. You are definitely not going to drive at this same limit when you only get a few chances at the corner at best (and each time the road surface is different). So it is natural to oversteer out of the corner in such circumstances as you are able to put heaps more power down (as compared to cornering at maximum corner speed where a small powerslide would put you into the fence).

Anyway, thats my opinion.

[mikko4500]

Originally posted by Ross Stonefeld
Im still not convinced though. If the fastes way through a tarmac hairpin is full opposite lock, how come they dont do it in regular circuit racing? Slip angles seem to be double the max of what yu'd see in circuit racing (just using tarmac rallies as an example)

The opposite lock is achieved by using the handbrake, which makes it different from any other powerslide/opposite lock method. It doesn't kill the speed much, it just breaks the tail loose. In essence you could call it an artificial 180 degree spin. The AWD of WRC cars plays a role here as well, it compensates for the higher slip angle.

As an example of that, a few years ago Citroen built an FWD car for the rally of Corsica and other tarmac rallies, and with drivers who knew the local roads well and kept their driving really clean with no slides at all, they were bothering the big WRC teams. In dry weather, that was. Whenever it rained, the AWD cars just ran away from them because they could use the high slip angles on the slippery surface with relatively less loss in time than keeping the driving style clean would've caused.

It's also about what Bex37 said. Race track drivers need to memorize track and remember where they have to brake and if the conditions change, they can pretty much figure out the necessary changes in a few laps. Rallies are driven on normal public (or private) roads where each corner is different, the conditions change often and there are just so many variables involved that trying to using absolutely optimal braking and entering speeds and so forth is impossible.


Mikko

[François]

I think you forgot to talk about one very important thing:
As you say, rally drivers can not reach the highest mid-speed corner, so they need to put the power through the tires and the road as early as possible for the next straight line.
The best way to put full throttle before the end of the corner with a good control is to put the car in line with the following straight line as soon as possible by using oversteering and controling it by using oposite lock.
That is my point of view for the loose surface: using sliding is the best way to keep the throttle fully open from the mid corner and then if you are too slow, you reducing the slide, if you're too fast, you make the car slide more to waste energy and hence speed.
Sliding is the best compromise Speed / Margin of Safety.

[mikko4500]

Originally posted by François
I think you forgot to talk about one very important thing:
As you say, rally drivers can not reach the highest mid-speed corner, so they need to put the power through the tires and the road as early as possible for the next straight line.
The best way to put full throttle before the end of the corner with a good control is to put the car in line with the following straight line as soon as possible by using oversteering and controling it by using oposite lock.
That is my point of view for the loose surface: using sliding is the best way to keep the throttle fully open from the mid corner and then if you are too slow, you reducing the slide, if you're too fast, you make the car slide more to waste energy and hence speed.
Sliding is the best compromise Speed / Margin of Safety.

Yes, that's true, the essence of driving fast on gravel and snow.

I didn't think about how I was expressing what I meant too well, the whole AWD/FWD thing was about applying that oversteering and opposite lock issue. Driving a FWD makes that virtually impossible on tarmac (on more slippery surfaces, with certain setups lifting the throttle while turning might cause a tendency to oversteer so much that you need to apply opposite lock, but this isn't often desirable), while an AWD has the traction advantage in this respect, as it delivers power via all wheels.

In essence, a typical AWD rally car is driven through corners in slightly oversteering four-wheel drift, where the loss of traction at the front is not caused by high speed (as in the old wingless Formula One cars) but by the engine power. Driving a FWD car in the same way would just result in a massive understeer, and a RWD car would tend to oversteer a lot, so you couldn't apply as much power. The AWD combines the best of those worlds and therefore it's a winning combination in rally driving.

I hope all that makes sense.;)



Mikko