the staff of Motorsport Marketing
the staff of Motorsport Marketing Writer
11/20/15 12:33 p.m.


Story by Danny Shields

They were cute, those first Minis that showed up at autocrosses in the ’60s, lifting their inside-rear wheels high as they zipped around corners. People pointed and laughed when the Rabbits took to the track in the ’70s, looking like they could flip over at any moment.

But now, a few decades later, what were once oddities are now the norm. Today, most of the best-selling cars in North America feature front-wheel drive. Still, many drivers have never become comfortable with this “new” breed of car, while others who have joined the front-wheel-drive revolution are looking for ways to get the most out of their machines.

To help those autocrossing front-wheel-drive cars, here are my thoughts on setting up such a car as well as some driving tips that should help maximize performance. You may not agree with all of my views, but at least I hope I can offer you something to think about. I’ll try to minimize the engineering jargon and discuss each topic in simple, car guy terms.

First, we’ll look at acceleration, braking and cornering conditions, and how front-wheel-drive cars are affected differently by weight transfer. Later, we’ll take a look at roll stiffness and shock absorbers, and how these elements can be used to make a car go around corners faster.

Read the rest of the story

GameboyRMH
GameboyRMH MegaDork
11/20/15 1:15 p.m.
At that point [rear wheel lifted], the outside rear tire is carrying 100 percent of the rear weight, and load on the front tires is distributed as evenly as possible, so understeer is minimized. Once that inside-rear wheel is in the air, the rear anti-roll bar has no effect. Like the wheel itself, it could theoretically be unbolted from the car in the middle of the corner.

Huh? The second sentence seemingly conflicts with the first, and with my understanding. When an inside wheel is lifted the sway bar is having as much effect as possible - the spring on the inside wheel, and the unsprung weight of that corner, is free to push down fully on that side of the sway bar, reducing suspension compression on the other side to the greatest extent possible.

Once the inside rear wheel is lifted the sway bar's effect becomes static but maximized - it's fighting suspension compression on the outside as hard as it can. If you could use a Star Trek transporter to make one of the sway bar links disappear at that point, the sway bar's tension would be violently released and the suspension on the outside would suddenly compress further. Making the wheel disappear would also have some effect on the amount of tension in the sway bar, due to the wheel's contribution to unsprung weight.

wbjones
wbjones MegaDork
11/20/15 2:03 p.m.

the only "problem" I have with what he's written is early on when he's discussing which sway bars can be changed … this was obviously written more than 2 yrs ago … that's when the SCCA changed the rules to allow (in Street … formally Stock) changing either bars, front or rear … but only one

otherwise pretty good article

moxnix
moxnix HalfDork
11/20/15 2:16 p.m.

From the Dec. 2004 issue

tacampbell
tacampbell
11/25/15 12:37 p.m.

I was glad to see that the author acknowledged that no matter what suspension mods or driving technique you adapt, accelerating after the apex will always lead to understeer in a FWD vehicle. (See "unwinding" in the Lines section of the text.)

And this is why I just can't get into FWD cars.

I drive for the joy of driving. I don't race. I don't care about shaving .2 seconds off a 3 minute lap time. I drive, every day, because it's fun. And to me, nothing is more enjoyable than pulling hard out of a sweeping curve. You feel the Gs not only pushing you back into your seat, but also against the side bolsters. You press your knee against the door to steady yourself.

And as you accelerate out of the curve, the force gets stronger. You're in control of that force as you push it harder and harder. Everyone talks about the decreasing radius entrance ramp? Yeah - this is what it's all about.

I've tried JCWs and GTIs and other FWD cars with LSDs, but laying in the power while coming out of a curve, no matter how subtly, always results in weight shift to the rear, understeer, and the car drifting over the yellow line instead of holding tight to the shoulder like a RWD car can.

With all the FWD driving approaches in the article you can be in control of how well you slow down. How you carry momentum. How you trail-brake to throw the rear end around. But your influence over the power is minimal - especially through curves where the G forces are the most interesting.

And it's those most interesting G forces that I'm after when I'm looking to have fun.

That's why I just can't get into FWD.

Robbie
Robbie SuperDork
11/25/15 12:45 p.m.

In reply to tacampbell:

Accelerating in a RWD car will shift weight to the rear tires and will cause the front end to 'push' out too.

Wheelspin is another matter, and a RWD may be able to accelerate 'better' (generally more traction before wheelspin), but all cars exhibit the above trait. If you don't believe me, go out to a parking lot, and drive moderately quickly in a moderately tight circle. Now stop moving the steering wheel, and push on the gas. The car will make a bigger circle. Let off the gas, the car will make a smaller circle.

BUT - I love RWD in the snow.

Trackmouse
Trackmouse HalfDork
11/25/15 1:32 p.m.

If anything, driving today in my rwd work van that has studs on the back and no studs in the front has taught me a constantly relearned lesson: under steer sucks.

wbjones
wbjones MegaDork
11/25/15 2:34 p.m.
Robbie wrote: In reply to tacampbell: Accelerating in a RWD car will shift weight to the rear tires and will cause the front end to 'push' out too. Wheelspin is another matter, and a RWD may be able to accelerate 'better' (generally more traction before wheelspin), but all cars exhibit the above trait. If you don't believe me, go out to a parking lot, and drive moderately quickly in a moderately tight circle. Now stop moving the steering wheel, and push on the gas. The car will make a bigger circle. Let off the gas, the car will make a smaller circle. BUT - I love RWD in the snow.

as he (or maybe it's another article I've read recently) pointed out … RWD does the same thing (what Robbie wrote) … or it can result in oversteer when the rear wheels start to spin and the rear then steps out … I've seen many spins due to that exact thing … the FWD's don't usually end up spinning … as the understeer rears it's ugly head, a gentle lift of the the right foot, and the front end finds grip and tucks in … if it's what you're accustomed to, it's just as much fun as a RWD car … plus learning to "drift" a FWD car … I put the quotes there, because all you're really doing is balancing the understeer caused by acceleration, and the oversteer due to the lift off the throttle .. then finding the sweet spot between the 2 … lots of fun

NoBrakesRacing
NoBrakesRacing Reader
11/25/15 5:09 p.m.

balancing the understeer caused by acceleration, and the oversteer due to the lift off the throttle .. then finding the sweet spot between the 2 … lots of fun

I had a first generation lumina that was beautiful at doing that, specially at a bumpy clover leaf on ramp near my college.

Coming in hard into the curve, let it do a touch of understeer, release some throttle on the bumpy part and let the rear end swing around, back on the throttle to stop the rotation and continue with the dance for the 270 degrees of the turn under the bridge.

Gravity, skinny, cheap tires and light weight back of car all came together nicely. Being young and foolish helped. Good times...

Bobzilla
Bobzilla UltimaDork
11/25/15 5:55 p.m.

Yes, a properly setup FWD will drift, and is a crap ton of fun to drive. Is it C6Z fun? No... but there's no good way to put down 500whp to the front wheels of ANYTHING and make it turn as well.

But I digress. I've hadthe understeery pigs. Hated the feeling. Now I"ve got the tail happy not-quite-a-pig that actually does what you tell it to. Love it. Since I'm not buying a C6Z anytime soon, I'll just have to be happy with what I have.

tacampbell
tacampbell New Reader
11/25/15 8:00 p.m.

Robbie's right - applying power in any car will transfer weight off the front tires and can cause a bit of push. But my point is that since the front wheels are not simultaneously applying power in a RWD car, there is not the double-whammy of also breaking traction just because of the torque on the tires that a FWD car would be applying. Those little contact patches up front have a hard time both laying down power and applying steering force simultaneously, regardless of any weight transfer issues.

I can see the beauty in the finesse that wbjones and NoBrakesRacing describe, it just doesn't give me the same kind of thrill.

I know most of it is because I grew up on RWD cars. Big V8s, driving on unpaved roads in rural Minnesota where the joy of hugging the inside edge of the ditch with your front wheel as you use the throttle to control your way around a dusty corner going far faster than your mom would approve of (no track day can EVER compare...)

But, being an over 50 dinosaur, I believe I'm part of a dying breed.

Knurled
Knurled MegaDork
11/25/15 8:04 p.m.
GameboyRMH wrote:
At that point [rear wheel lifted], the outside rear tire is carrying 100 percent of the rear weight, and load on the front tires is distributed as evenly as possible, so understeer is minimized. Once that inside-rear wheel is in the air, the rear anti-roll bar has no effect. Like the wheel itself, it could theoretically be unbolted from the car in the middle of the corner.
Huh? The second sentence seemingly conflicts with the first, and with my understanding. When an inside wheel is lifted the sway bar is having as much effect as possible - the spring on the inside wheel, and the unsprung weight of that corner, is free to push down fully on that side of the sway bar, reducing suspension compression on the other side to the greatest extent possible.

There's no conflict. Once you lift a wheel, changing roll stiffness on that end doesn't affect handling, just how far off the ground the lifted tire is.

The other end "changes signs" with respect to roll stiffness's effect as well. On an A2-chassis Golf, which can corner on three wheels in the McDonald's drive-thru, you DECREASE understeeer by increasing front roll stiffness.

Once you are driving a three wheeled vehicle, all that matters is keeping the contact patches relatively flat, and making the non-lifting end stiffer gives it more traction, not less, and changing roll stiffness at the lifting end has no effect on handling.

Knurled
Knurled MegaDork
11/25/15 8:10 p.m.
Robbie wrote: In reply to tacampbell: Accelerating in a RWD car will shift weight to the rear tires and will cause the front end to 'push' out too.

Ayup. Anybody who thinks RWD means acceleration removes understeer is being ham-fisted with the throttle.

That is one of the things I adore about my RX-7... throw it into a corner all crossed up, add throttle and the car straightens out. Any time you can get out of trouble by going faster as opposed to lifting is pretty sweet in my book. So I keep adding more and more power to the car

NoBrakesRacing
NoBrakesRacing Reader
11/25/15 8:24 p.m.
tacampbell wrote: I can see the beauty in the finesse that wbjones and NoBrakesRacing describe, it just doesn't give me the same kind of thrill. I know most of it is because I grew up on RWD cars. Big V8s, driving on unpaved roads in rural Minnesota where the joy of hugging the inside edge of the ditch with your front wheel as you use the throttle to control your way around a dusty corner going far faster than your mom would approve of (no track day can EVER compare...) But, being an over 50 dinosaur, I believe I'm part of a dying breed.

RWD has my heart but have had good fun with FWD. First car was an 82 Malibu, followed by two g-bodies, learned to drive in the dirt roads around farms outside of Miami. Then a couple b-bodies interspersed with k-5 blazers and a lot of mud. G-forces make me smile but the teenager inside of me loves dirt being kicked by the rear tires and looking forward through the drivers window. I'm only in my forties however.

lateapexer
lateapexer New Reader
11/26/15 6:10 a.m.

Autocrossed Mini's in the late sixties and early seventies. It was not uncommon to back off the rear drum adjusters so that the brake bias was almost entirely on the front. Not sure how effective it actually was, but oversteer was provoked. We used to do it in drag racing and eliminate the rear drums from the equation. Probably was as effective as a louder exhaust.

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