rdg@hpfcla.UUCP (rdg) (05/29/85)
Subject: How to *really* handle a front wheel drive car
No question about it: I love my Saab, but it has one small problem. The
wrong set of wheels are driven! Well, perhaps "wrong" isn't the right
word - maybe "front" is better. The fact is, I find it relatively easy
to handle a rear-wheel drive car. With proper use of the brakes and
throttle, you can make it do whatever you want - drift, slide, etc.
How do you perform comparable tasks with an understeering, front-wheel
drive car, such as the Saab? What's the best technique for taking the
car around various types of turns?
I'd appreciate any words of wisdom on this problem, as well as driving
tips in general.
Rob Gardner {ihnp4,hplabs,hpbbn}!hpfcla!rdg
Hewlett Packard or hpfcla!rdg@hplabs
Fort Collins, Co. 80525kanner@tymix.UUCP (Herb Kanner) (06/01/85)
In article <13200026@hpfcla.UUCP> rdg@hpfcla.UUCP (rdg) writes: > >Subject: How to *really* handle a front wheel drive car > >No question about it: I love my Saab, but it has one small problem. The >wrong set of wheels are driven! Well, perhaps "wrong" isn't the right >word - maybe "front" is better. The fact is, I find it relatively easy >to handle a rear-wheel drive car. With proper use of the brakes and >throttle, you can make it do whatever you want - drift, slide, etc. >How do you perform comparable tasks with an understeering, front-wheel >drive car, such as the Saab? What's the best technique for taking the >car around various types of turns? During a 7-year stay in England, I owned nothing but FWD cars. The first snowy day was a shock to me, my previous cars in the U.S. having been VW beetles and an old Porsche, both oversteering cars in which, when you got in trouble, responded favorably to acceleration. Well, when I felt a bit of slide rounding a curve, my reflex action was to give it a bit of gas. Surprise, surprise--I went off the curve on its tangent! I found many books in the British libraries on high-level rally driving, with tips on FWD. I remember two of them and will pass them on; I have used them both. The first has to do with going over hump-back bridges, which are common in England. They are so humped that at 50 or 60 mph you will literally leave the ground for a moment like a ski jumper. The trick with the FWD car is to tromp on the gas at the crest of the bridge. The acceleration loads the front end, holding you on the ground. The second is the "hand-brake" turn for very sharp cornering. Start the turn, press the clutch, and jab sharply with the hand brake, which momentarily locks the rear wheels. The car starts to slide around. When you are aimed in the direction you wish to go, release the clutch and accelerate. I tried it at a safe speed on snow, and it really works. Professional rally drivers do it at high speed on dirt roads. As a general rule, with the caveat that all rules have exceptions, with a FWD car letting up a bit on the gas when you are in trouble will get you out of trouble. I guess that is why beginning drivers find them user-friendly. -- Herb Kanner Tymnet, Inc. ...!hplabs!oliveb!tymix!kanner
pauldan@hou2e.UUCP (P.SAUNDERS) (06/04/85)
>>How do you perform comparable tasks with an understeering, front-wheel >>drive car, such as the Saab? What's the best technique for taking the >>car around various types of turns? > >As a general rule, with the caveat that all rules have exceptions, with a >FWD car letting up a bit on the gas when you are in trouble will get you >out of trouble. I guess that is why beginning drivers find them >user-friendly. Hmmm. I'm not sure about *your* fwd car, but with mine, the general rule is to accelerate your way out of trouble. There have been many times when I've used full right foot to pull my way through a turn. FWD cars are especially fun in the rain (or snow?); when going around a curve, if you start to slide, hit the gas and steer into the curve. A problem with this: once you begin to slide and decide to accelerate through the curve to stop the slide, you are committed to accelerating through the curve. You are using the engine's power to hold your car in it's line, and if it's a long curve, you can run out of power or reach the "point of no return" (the speed at which if you go any faster, the car will break loose from the curve; but you *must* accelerate to stay in the curve; so no matter what, you crash and get hurt). However, on normal public roads, it's pretty difficult to approach these limits. On a race track it's easy to, and this is a major reason why there are no fwd race cars even though they are theoretically faster through a turn. Dan Masi
doncr@hammer.UUCP (Don Craig) (06/06/85)
Re: How to turn a Saab (170 lines) I rallied for a number of years at the Canadian National level, both as co-driver and driver, and owned a Mini Cooper S (fwd!!) which I drove 'spiritedly' in Montreal winters. I have been hauled out of ditches twice in the same afternoon during a blizzard in the Eastern Townships of Quebec, and have rolled three times while rallying. Be warned. Practice the following in an EMPTY parking lot with a wet, snowy, or icy surface. Professional rally drivers reach their peak twenty years after they start competitive driving (if they make it). Handbrake turns were much favoured by rally drivers in the fifties and sixties, when speeds were lower. They are used today only in emergencies, because they are difficult to accurately control, and tie up a hand better used to shift gears. They will give more oversteer (i.e., a tendancy to spin) than almost anything else you can do while driving. Used in the street, where speeds are much lower (even for Roger Ramjet) than in competition, they are good for abrupt 90 degree and 180 degree turns of the car body. They do NOT alter the original vector of the car when properly applied. That happens after the car body has turned and the tires have a new slip angle (the difference between the direction in which the tire is pointed and which the road is moving). If the road is dry asphalt, handbrake turns are also noisy. Handbrake turns require that the handbrake operate on the rear wheels of the car. This unfortunately excludes the Saab, whose handbrake operates on the front wheels. If the car is rear handbrake, front wheel drive, handbrake turns are fairly easy. Start the car into the turn so that the suspension compresses on the outside. You should be understeering at this point (it doesn't look like you'll make it). Pull on the handbrake (with the release depressed!) the right amount (:-) (relatively violently) and the car will suddenly(ish - depending on its polar moment (tendancy to resist doing this)) oversteer/ start to spin. Start to steer into the potential spin immediately. Also release the handbrake at the right time (:-) (relatively soon). The length of time the handbrake is applied and the promptness with which the driver turns into the potential spin control the amount of turning the car body actually does. The extra trick (which requires some practice) for rear wheel drive cars is to dip (depress) the clutch for exactly the duration that the handbrake is applied. I last saw handbrake turns used as a regular high speed technique at the World Rally Championship level by the great British driver Roger Clark when he visited Canada in 1977 with the Ford of England team. The rear brake discs had twin sets of calipers, one set operated by the footbrake, and one set operated by the hydraulic handbrake. And at every service stop (every 1 - 3 hours of competitive driving), his mechanics would change the handbrake pads. I believe his Ford Escort (the old European kind) finished third overall. And now the Saab. A very interesting but somewhat eccentric car capable of high performance indeed. Handbrake turns are not available because the handbrake works on the front, but other things can be done. The world expert in Saab driving is the Swede Stig Blomqvist, who won the world rally championship in 1984 (although that was in the somewhat similarly handling (can understeer like a pig) Audi Quattro). Stig rallied a Saab in Canada in the summer of 1978, and was the first man to win a Canadian National Rally in a production class car (only safety modifications allowed from stock). (The American John Buffum (Vermonter actually) is the only other man to have done this, he did it in a Volkswagen GTI.) I did one not very successful rally as co-driver (tells the dummy behind the wheel what to do) for the Canadian Saab factory team. Blomqvist's style in car handling makes sure he NEVER gets caught out by understeer. He does this by entering the tighter corners in an attitude of gross oversteer (near the limit of the steering gear to turn into a potential spin). As the corner progresses he unwinds the steering wheel until the front wheels are more or less lined up with the direction the car is pointing. If the corner tightens up, he doesn't unwind the wheel. To achieve the oversteering entry attitude several things can be done. On any front wheel drive car, lifting your foot from the throttle will provoke oversteer. If you do this violently, you will get a lot of oversteer, especially if the suspension is already compressed on one side of the car from having started a turn. Turning into the potential spin immediately controls how much turning you get. The other technique that oversteers a front wheel drive car is 'left foot braking'. Most low performance street machinery has what is known as a front brake bias. Usually about 60% of the braking force of the footbrake is applied at the front wheels and the remaining 40% is applied at the rear. This promotes understeer under braking, so that Aunt Millie in a panic skid will not spin, but will tend to go in a straight line towards her impending doom. More sophisticated drivers want to be able to turn sharply while braking hard, and are prepared to turn into a potential spin to retain control. This requires at least a neutral brake bias (50 - 50) and preferably a rear brake bias (say 40% front, 60% rear). A fully prepared rally car has brake bias adjustable from a lever beside the handbrake, so the driver can vary the amount of rear brake bias (never saw anyone set it for front brake bias), depending on the road tightness and surface condition. I would guess my RX-7 SE has about 55% rear bias and 45% front. My Mini Cooper was permanently set up with 70% rear and 30% front (ho ho ho). Brake bias can be adjusted by replacing or modifying (or removing in the case of the Mini) a device that sits somewhere in the hydraulics and is known as a 'proportioning valve'. Do not see your dealer for this modification, unless he is very understanding. For cars that cannot be modified due to various rules (competition, insurance, safety), a similar effect can be achieved by putting a softer brake lining on the rear shoes or pads, and by putting a harder (so-called competition) brake lining on the front pads. Stig Blomqvist's production cars always had the hardest possible linings on the front, the softest possible on the rear. (His full blown cars usually had the proportioning valve hard over for rear bias.) With brake bias to the rear, a driver can set his car up in an oversteering attitude by depressing the foot brake once the suspension on the outside of the turn is compressed. If he depresses the brake with his left foot, his right foot is available to depress the throttle, and he can balance the angle of the car's body by playing his right foot against his left. This works because applying throttle while braking significantly reduces the effect of the front brakes, provoking even more rear brake bias. It even worked on my father's fwd Pontiac, which has about 70% FRONT brake bias, but it gets the front brakes and engine very hot, and the car handled so badly I was probably wasting my time. To get a feel for this in an EMPTY parking lot with a slippery surface: Approach the turn at a reasonably rapid pace. Start to turn in for the corner, compressing the suspension on the outside of car. With power in but good, sharply rap the brake pedal with your left foot. When the car starts to oversteer (if you did it right) be very ready to turn into the direction of the potential spin. And practice practice practice if you intend to try it anywhere else. The sooner you get hard pads on the front, and soft shoes/pads on the rear, the easier you will be on your drive train. To sum up, lifting your right foot will always give you oversteer on a front wheel drive car. If you do this violently, you will get a lot of oversteer, which you can then balance and control. If you want to oversteer while braking, either adjust your brake bias to the rear, or apply power and brakes at the same time which achieves the same effect. Stig Blomqvist uses all of these tricks and then some. In competition, front wheel drive cars are typically faster in the tight and twisty sections than rear wheel drive cars, but somewhat slower in the fast corners. This is because a front wheel drive car can only get oversteer while slowing down, but a rear wheel drive car can get oversteer while speeding up as well. This is if ALL other things are equal, which they never are. Driver ability counts for a lot. (Last year's production class world rally champion was driving a Golf GTI, fwd.) Fast driving of four wheel drive cars (Quattros, Peugot 205's, Lancia Delta's, funny RX-7's) is another subject.
geoff@denelvx.UUCP (Geoff Baum) (06/06/85)
Having owned two Saab 96s, one Saab 99, and two Honda Civics I would like to pass on the following comments about one subscriber's suggestions for "How to turn a Saab?". My comments are based on 12 years experience driving the above mentioned front-wheel drive cars, combined with lots of playing with them in all weather conditions, especially on snow and ice. >Hmmm. I'm not sure about *your* fwd car, but with mine, the general rule >is to accelerate your way out of trouble. I used to beleive this and applied the rule religiously. It definitely DOES work under certain conditions, when the car is NOT being pushed to its limits. This technique will pull the front back toward the inside of a turn if you are correcting for the car's inherent understeer. If the car is really skidding, don't try accelerating. The front wheels will loose traction once they start to spin, and you will be in a complete side slip. >if you start to slide, hit the gas and steer into the curve. A problem with >this: ... you can run out of power or reach the "point of >no return" (the speed at which if you go any faster, the car will break loose >from the curve; but you *must* accelerate to stay in the curve; so no matter >what, you crash and get hurt). As stated before, if you are correcting for understeer, accelerating into the curve MAY help. As this subscriber correctly pointed out, however, if you put the car into a real skid, it will go off the edge. The correct way to induce oversteer in a front wheel drive car (or to get it headed back around the turn when it is sliding to the outside) is to increase the traction on the front wheels while decreasing the traction on the rear wheels. This can be done in several ways, most of which have been mentioned. The most subtle method is to take your foot OFF the gas. This causes the car to pitch forward slighty and increases traction on the front wheels which then take you through the turn. The second method is to TAP the brakes (lightly); this has the same effect only more so. The third method is to lift off the gas AND hit the brakes. The brakes have to be modulated carefully here. The rear wheels may lock a bit and start to skid to the OUTSIDE of the curve, which is just what you want in order to get headed in the right direction. The last and most drastic method is to lock the hand brake; this affects only the rear wheels and can spin you around faster than you can think. Probably the easiest way to see how this all works is to go to an empty parking lot and try the following: Turn the steering wheel to its lock and accelerate until the car starts to slide (or until you can't stand it any more), then quickly lift your foot off the gas (don't depress the clutch). You should notice the car nose into the center of the circle. Applying the brakes when you lift of the gas will accentuate this effect. Try it, you'll like it! The best way to learn all of these techniques is at very low speed (5 mph) on a slippery surface (snow or sand is best). Once you are comfortable at that speed, try them at higher speeds on dryer surfaces. As for how to induce oversteer, try shifting into a lower gear and accelerating; the front wheels should spin, and off you go (figuratively, of course). >this is a major reason why there are no fwd race cars even though they are >theoretically faster through a turn. There are MANY front wheel drive race cars, and have been for YEARS! They have been cleaning up road rallys for a long time and are only now being challenged by four wheel drive cars. What about the Miller race cars that were unbeaten (at Indy?) for years.
bhs@siemens.UUCP (06/07/85)
Rob: There seem to be at least two accepted ways of turning a Saab. The easier one of the two, which both work at a point close to the performance limit, which is what you are worrying about, is to snap your foot of the throttle suddenly. This will typically cause your car to suddenly switch from understeer to oversteer in such a way that the car can actually hang it's tail out, at which point you step on it again. The second way is in fact a tricky variation on the first. What you have to learn is to accelerate and brake at the same time. In order to understand this one, which is favored by rally drivers, you must look at the force vectors on your tires in this maneuver. Your tire can handle a lateral acceleration of only a certain amount. This lateral acceleration can be either centrifugal force from cornering (centripetal force for the purists ), acceleration, or braking, or any combination of the above. Thus, if you imagine yourself whaling around a turn, all four wheels will be subjected to a certain amount of cornering force. If you now accelerate, your front wheels will, in addition, be subject to a second force caused by the torque of the wheels. Your rear wheels will not have this vector of force applied to them. If you now step on your brakes, all four wheels will suddenly have this retarding force applied to them. However, remember that your front wheels have the other accelerative force on them too- a force going the other way. The trick is to apply gas and brakes in such a way that the two forces counteract and cancel each other- leaving a greater net force on the rear wheels, which will break out sooner than the front wheels. This technique suddenly exposes the importance of front- rear wheel braking power balance, which is why pro racers will try to have a variable regulating valve for the brake system. Tricky? Another application of this theory will explain why rear wheel drive cars are easier tturned by stepping on the throttle- the torque on the rear wheels will break off the adhesion. BTW: I believe that Saab parking brakes work on the FRONT wheels, not the rear wheels as in most cars. The gas and brake method is now quite accepted, however it is a new method. It is believed that as late as 1967 only 7 people in the world knew how to do it. Bernard H. Schwab Siemens RTL, Princeton, NJ
mhg@wjh12.UUCP (Goldstein) (06/12/85)
> >>How do you perform comparable tasks with an understeering, front-wheel > >>drive car, such as the Saab? What's the best technique for taking the > >>car around various types of turns? > > > >As a general rule, with the caveat that all rules have exceptions, with a > >FWD car letting up a bit on the gas when you are in trouble will get you > >out of trouble. I guess that is why beginning drivers find them > >user-friendly. > > Hmmm. I'm not sure about *your* fwd car, but with mine, the general rule > is to accelerate your way out of trouble. There have been many times when > I've used full right foot to pull my way through a turn. FWD cars are > especially fun in the rain (or snow?); when going around a curve, if you > start to slide, hit the gas and steer into the curve. A problem with > this: once you begin to slide and decide to accelerate through the curve > to stop the slide, you are committed to accelerating through the curve. > You are using the engine's power to hold your car in it's line, and if > it's a long curve, you can run out of power or reach the "point of > no return" (the speed at which if you go any faster, the car will break loose > from the curve; but you *must* accelerate to stay in the curve; so no matter > what, you crash and get hurt). However, on normal public roads, it's pretty > difficult to approach these limits. On a race track it's easy to, and this > is a major reason why there are no fwd race cars even though they are > theoretically faster through a turn. > > Dan Masi I'm glad I don't drive near any of you: first: Saab hand brakes operate on the FRONT wheels. An attempt to use the handbrake method will get you in BIG trouble, especially if you manage to lock the wheels. If your in a turn and its slippery, goodbye. Second: accelarating is definately the WRONG thing to do if your sliding wide in a turn - you have lost traction up front. accelerating will make the tires totally loose their grip and you will continue to slide in your current direction (probaly off the road). GET OFF the gas and let the tires regain traction. - I should know - I've spun a few saabs in the snow!