tuj

Mazda has on their website a hot-lap at Laguna Seca in the RX-8 with an instructor from the Skip Barber racing school. He drifts nearly every turn, especially 3, 4, and 9. Now granted maybe that was just for a cool video, but if you look at his technique, it certainly looks like the fastest way around (at least in the 8 on street tires).

Certain cars respond differently. I watched a guy at Mid-Ohio in the SCCA club racing championships drift his fox-body every lap, while nearly everyone else took the grip approach, and he was certainly fast in the turns I could see. I read an article by Brian Herta (IRL driver) in R&T where he was testing cars on the track, and he said the only way he could find to get the M3 to go fast was to let it get sideways.

Obviously the show drifts aren't fast, the the so-called dynamic drift is very fast, but also pretty risky. The idea is that your speed in a turn is limited by the amount of grip you can get. But in a drift, you use the momentum of the car to exceed the grip of the tires, and with alot of skill, control the car's trajectory through the turn. By maintaining speed into the turn (in order to break traction), the car carries more speed through the turn, and a good driver will be able to regain traction and accelerate smoothly out of the turn, thereby going faster than the driver who had to brake more on enterance to the turn. Its just like rally expect more subtle since they're on a grippier surface. It won't work in every turn, but in the ones where it can, its usually faster.

Drifts initiated by late braking, shift locks, or the e-brake will never be faster, except for very very tight hairpins where using the e-brake would be.

therm8

Drifting is to auto racing as figure skating is to hockey.

Now rally driving....that's drifting with a purpose.

Mikelikes2drive

seriously drifting is dangerous even if you're on a wet skid pad at a track. safe compared to an empty parking lot and alot safer then on the streets. I have alot of friends who are drift enthusiasts... i am too, i go to all the shows and do it on occassion, but feel guilty everytime cuz i know ppl who have totalled their cars and went to the hospital with only broken limbs thankfully. drifting is fun but not worth the tires if you're not sponsered. ruins shocks and just way too expensive

if drift was faster, you'd see F1 and leman drivers doing it. grip driving is faster.

mike0615

Man, u guys, just use the gutter. :p

Imp

Yeah, already said that.

fizzer

Drifting used to be faster, back when bias-ply tires with mushy sidewalls were used. If you look at old formula 1 footage before aero came into play (pre 1966 or so), almost every turn was taken in a nice little 4 wheel drift... The excerpt below explains the whole thing. I remember a magazine article that talked about drifting vs. racing (C&D or R&T i think). They said that drifting was measureable slower, but only by a couple secs a lap for skilled drifters. I'll try to find the actual source.


When one describes a "drift," we usually associate a car in massive oversteer trying to negotiate corners that have been approached too fast or cars exhibiting too much power for the traction available. Not so long ago, tire technology was based on bias ply tires in race tracks. With these lower grip tires (by today's standards) the race car drivers had to rely on oversteer to change the direction of the car in such way to find the earliest acceleration point of the track. Even open wheeled racers in those days displayed significant oversteer, which is rarely seen these days. With the advent of high grip compounds and radial structure, a higher turn-in response was achieved and the concern for the fastest line became more of a stability issue. The less drift angle, the more stable and therefore more grip as tire's contact patch was maintained even without deformation. In low traction racing such as various rallies on dirt and snow still depends on oversteer to change direction to this day. But enough history...

thats from: http://www.club4ag.com/faq%20and%20t...ft%20style.htm

NAVILESRX8

iTrader: (1)

This forum is awesome.........

XDEEDUBBX

you guys have been watching way too much initial D...

tuj

I think drifting still is faster in several cases. Let's examine. Everyone is probably familiar with the traction circle, which demonstrates that a tire has a finite amout of grip it can give, and that grip can be divided between acceleration, braking, and turning. This gives rise to the classic racing line and style because we want to accelerate, brake, and turn as much as possible when the circuit demands it. Therefore we accelerate as much as possible until the braking point, brake as hard as possible in a straight line, then turn in and try to take the widest possible radius through the corner.

All this is obvious. If we look at the details of the transition between these activities, we see that a good racer is actually tapering off the brakes when he begins to increase the steering angle (trail braking), and is also gradually accelerating as he decreases the steering angle out of the turn. This has the effect of maximizing the usage of the traction circle between components during these transition times. Also, since many turns are not constant radius, you cannot achieve maximum cornering through the entire turn. Instead, there will be some point at which maximum cornering is reached. At all points before or after that period, there is some traction available for braking or acceleration.

So far we have considered the weight of the car on each tire to be static 50/50 F/R, 50/50 L/R. But of course this is not so. We know that friction is caused by the friction coefficients of the two mating surfaces, along with the weight pushing each surface together, in this case, portion of the weight of the car that a particular tire is bearing. More downward force increases friction, but more weight on a given tire also means more inertia acting sideways against the force of friction. If we could get free downward force without increasing weight, we could go faster.. Ah ha! That's what aero is for. But since most of us don't really have effective aero on our cars, especially at the speeds we drive, lets forget that for now.

So can weight transfer actually help us? Sure, provided that the extra force against the tire sideways (or forward or backwards) is less than that of the extra friction provided by the extra force downwards. In some cases this can be extreme. Take sport bikes under braking. The most effective braking in terms of straight line stopping eventually transfers 100% of the weight to the front tire, and the rear wheel lifts clear of the ground. So trail braking, besides maximizing our usage of the traction circle, can also increase grip where we need it, in this case the front wheels during turn in.

So far we have considered cases that utilize the traction circle. But what happens when we exceed it? Most tires will slip to some extent; others will loose nearly all of their traction. This is a component of the tire design and chemical composition. For most of us, on street tires or even r-compound tires, when the tire exceeds its potential grip, the loss in grip is not dramatic. Our cars slide, but not so much that we instantly crash into a wall like those IRL dudes. But it should be obvious that any time a car is sliding in any direction, it has exceeded the limits of traction of its tires in some direction.

However, when a tire exceeds the limits of traction in one direction, that does not necessarily mean that we cannot utilize the tire's traction in another direction. For example, if you were to put a car on ice and give it a hefty shove straight sideways, the car would slide to the side, but you could still accelerate and move the car forward while it was sliding. You could probably not accelerate as much as if the car was not sliding sideways, but you would still have some grip to push the car forward.

Now we must confront some unknowns. There is some curve to which the traction of a tire drops off corresponding to how much you have exceeded its traction limit. If you only exceed this limit by a small amount, the drop in traction is small. The result is that your car slides a small amount. But, given the right tire, its reasonable to assume that when we slide sideways very slightly due to cornering forces exceeding the traction limit, we still have a significant amount of traction left for forwards/backwards force. Therefore we can still brake or accelerate effectively, although I do not think we can accelerate or brake as strongly as a tire that is cornering at its maximum, but has not exceeded the traction limit.

We said before that ideally we want to accelerate as much as possible in a straight line. Therefore we should try to take the widest possible line through a corner to maximize the speed we can carry through the corner. Basically the bigger the radius, the less severe the angle change is on the tires. If the angle change is very severe, then we will have to slow down to avoid overloading the tires. Here, the sideways force is resisting the inertia of the car to change the car's direction. The bigger the magnitude of direction change, and the faster we enter the turn (carrying more inertia) the more the tires have to work. Ideally we enter at a speed that is perfectly matched to the direction change angle, which is as wide of a radius as possible without running off the circuit.

Actually that's not quite true. We actually want the quickest path through the corner, so we want to balance the shortest physical distance and maximum speed at which we can travel through the corner (maintaining grip) to maximize the shortest time. Basically the fastest line is not usually the shortest physical path, nor the widest radius path, but some balance of the two.

This balance is unique to each vehicle, which is to say there is a unique line that maximizes a vehicles attributes to get through the corner quickest. On a sport bike, this may be a line that is 'squared off' which is to say a line that has a smaller radius, and therefore slower cornering speeds, but results in being able to brake deeper into the corner and begin accelerating more quickly. In a Miata, it may be just the opposite, a line that emphasizes a wide radius to carry speed through the corner and make up for the lack of power on acceleration.

So when do we get to the freakin' drifting? Well lets imagine a drifter entering our turn. He enters with the same speed as a grip driver, but then uses some combination of inputs to change the angle of the car in the turn. This may be braking combined with steering, excessive torque to the back wheels, or a more moderate weight shift/steering input combination. In any case, the car turns some, then the rear exceeds the sideways grip maximum. Since the front still has grip (or more grip than the rear, if both ends have exceeded the grip), the rear begins to slide toward the outside of the turn faster than the front, changing the car's angle. Since we are moving the two ends of the car at different rates, we are changing the angle of the car faster than would be possible if we had not exceeded grip.

We are trading the distance the rear slides for rotation of the car. At some point, the rear's traction equals that of the front's, although lets assume that both front and rear are still over the grip potential of the tires for the sideways angle we are now at. The car will now slide evenly towards the outside of the turn. However, we are not inputting any more sidesways forces into the tires, aside from the inertia we are already carrying, so as they slide sideways, the tires are using their friction to slow the car's sideways movement.

We can now begin to gradually use the tires to accelerate, even though the sideways forces of the tire are over the grip limit. We are willing to trade the distance the car is sliding for the ability to travel that distance outwards at a speed higher than what would normally be possible. We are also getting to direct acceleration forwards. Eventually the tires will slow the sideways progress of the car to the point where the car's sideway's inertia is no longer in excess of the tire's grip.

So was the drift any faster? Well, it will only be faster if all of the following are true:
-the tires still have some significant grip sideways after their traction limit sideways is exceeded sideways. We need this to slow the car's outwards travel to keep from flying off the circuit.

-the tires still have significant fowards grip after their traction limit sideways has been exceeded. We need this to get a benefit from getting the car pointed out of the turn earlier.

-and the combined benefit of entering and traveling through part of the turn (sideways) at higher than normal (grip) speeds, along with the earlier acceleration results in a faster traversal of the corner, which it almost certainly will, provided that the above two points hold for the situation. This assumes that traction will return to the tire at nearly the same threshold as which it was exceeded, and that we don't have any other forces, like areo, that will be affected by an early angle change.

We are also assuming that we are driving a car with perfect handling, ie a car that easily utilize the full corning potential of each of its tires and exhibits neutral handling. For a car that cannot fully utilize one end, ie a FF car with lots of understeer, the drift is also effective because it can rotate the car quicker, and make utilization of the rear tires by getting them into the turn with higher than normal inertia.

So its easy to see why rally drivers drift. They give up grip intentionally to change the angle of the car, then they use the traction that remains while sliding to slow and stop the travel of the car toward the outside of the turn, while also using forward acceleration to push the car out of the turn. You may say this only works on dirt, but its my believe that for some car/tire/corner combinations this is the fastest way through the turn. Its likely that where you don't see drifting, like F1, the cars' light weight, low cg, excellent suspension, aero, and supremely stickly tires cause one or more of the above 3 points to fail to hold. Aero is a big one, since changing the angle of the car early while its still going sideways greatly decreases the amount of air over the wings. This is one reason why the rally guys use so many verticle slats in their wings; it catches the air when the car is sliding sideways to slow its sideways movement, and direct the over the horizontal portion of the wing in a perpendicular manner. In F1, its also likely that the tires are not condusive to gripping after their limits have been exceeded, or that this behavior causes excessive wear.

So there's my take. Sorry for being so lengthly, but I'm convinced that drifting, done right (not the showy drifts, but subtle, low-angle drifts) is the fastest way in some car/corner/tire combinations, and I think the physics bear it out.

fizzer

Your analysis is pretty sound, except for some pretty big assumptions. The first is this line:
Remember the friction circle? Its a circle, not a square, for a reason

Also, your assuming that the friction avaiable does not drop off dramatically as the slip angle increases. This IS NOT TRUE for modern radial performance tires (like the ones that came on our 8s). However this IS TRUE in loose surface racing, as mentioned previously, and for older and skinnier bias-ply style tires. Bias-plys had a much more shallow dropoff in thier slip angle vs friction curve, so 4 wheel drifts, done correctly, were the fastest way around a lot of corners. Also, the compounds tended to be harder so they didn't build up heat as quickly.

Check out this article for a more scientific explanation than I care to write
http://www.insideracingtechnology.com/tirebkexerpt2.htm

Here's an excerpt about what I'm talking about:
'After the peak of the curve, lateral force can fall off 30% within a few degrees of extra slip angle. At these high slip angles most of the contact patch is sliding, producing a lot of heat and wear.'

Most importantly is the heat and wear. I'll agree that the situation you defined could hold true, but for one corner only... after that the tire heat is past optimal and a more conservative path through the next corner is needed to try to bring down the temps. (More than one lap could be necessary to get the temps back down after even one 'drift' at full pace). However, this is why you will see race drivers occasionally use a whole lot more slip angle than normal in a corner. (depending on the types of cars/tires in the race) . You'll often see this more often at the end of a race, when the drivers can tell how much tire they have left and know they can spend some tread life in exchange for a chance at an overtake.

TrackAddict

Here is a tidbit I picked up from an experienced racer and driving instructor last weekend doing a HPDE. Older bias tires had a maximum slip angle of 12-15% meaning when you cornered at their limits you were turned in 12-15% more than the trajectory of the car. Thats why you see older race cars going sideways though most corners. It gave them better exit speed. Today's tires have a 4-6% slip angle meaning it is normal while cornering at the limit to be drifting (slightly). This was evidenced at the track last weekend where most of the street cars driving close to the limit would have a slight drift through the turns especially ones you carried some speed through. Slower turns caused a bit of understeer (in line with the slip angle mentioned above). The instructor went on to say that F-1 cars use tires designed to have less than a 1% slip angle. They do not drift at all and that is fastest for them. I am no drifting expert nor an experienced racer but every road racer I have listened to has stated that the wild drifts you see are the slow way around the track. Even on Fifth Gear when Tiff compares 2 or more cars, when he does a fast lap, he drives grip. When he is just having fun or showing off, he drifts. So, unless you are a F-1 driver, a mild drift through a corner (even Nascar does it) is normal. But, it isn't a tire roasting, smokey, sideways slide to get the lowest lap time.

NAVILESRX8

iTrader: (1)

......drifting is fun...plain and simple... 5 pages of scientific evidence is not needed to convince people to like it. If someone doesn't like it or doesn't "believe" drifting is a sport, who gives a f**k.

Dark8

I don't think the debate is about whether drifting is fun or not. It is fun. The debate is about whether drifting around corners is or isn't faster than conventional road course driving techniques.

mrtux

i was thinking about getting into the drift scene. i was planning on taking a course out on the track down in southern california over the summer.

i was wondering for those of you experienced ones out there... if the mazdaspeed springs/shocks will work fine and suitable for drifting? or should i invest more into coilovers like the tein flex? i understand coilovers give more adjustability in height and stiffness and was curious how those also played into drifting? im asking this because i have the ms springs/shocks now and was curious if they were good enough to handle and suitable to work with drifting or should i try trading them and go for coilovers.

thx

BigOLundh

iTrader: (1)

if it works in initial d, than it has to work for me

Imp

I read it on the internet, it's got to be true. :D