Randy Pobst: Front-wheel-drive understeers? Think again. | Articles

Front-wheel drive understeers, right? Everybody knows that. Don’t you? 

But wait, did you ever drive a 1988 CRX? Ever see PD Cunningham in one of his RealTime Racing Acura Integra Rs? I sure did, in the windshield and the mirrors of my Tri-Point Engineering Mazda6 back in the good ol’ days of World Challenge Touring Car competition. No push.

[Restoring one of the most iconic Acura Integra Type Rs]

Fact is, they don’t have to. Why would they? Standard answer is all that weight on the front, right? 

Well, just hang on a minute. Isn’t that weight why they’re good in the snow or rain? Why wouldn’t that work in the dry, too? And Randy, aren’t you always preaching about weight management? How does transferring weight and load to one end of the car or the other make it stick better, not worse?

Have I got you thinking? Any driving instructor worth their sunburn will advise you not to lift suddenly in a corner ’cause it throws weight forward and makes the rear light. If weight improves grip in front when you lift in a corner, why would it hurt grip in the front of a car, especially a FWD?

Well, I’ll tell ya one of the main reasons: because almost all front-wheel-drive cars have the same size tires all around. Yep, think about that. What are the tires sizes on powerful rear-drive cars, especially mid- or, God forbid, rear-engine cars? The same? Hay-yull no. Some examples: 2024 Porsche 911 GT3 has 255/19 fronts, 315/20s rears; Ferrari SF90 gets 255/20 fronts, 315/20 rears. Now let’s come down to earth: Mustang GT Performance Package has 255/19 fronts and 275/19 rears. 

Toyota GR86? 215s all ’round. Yeah, it’s balanced. FWD is not.

It makes sense to size the tire to the load, and that’s where the front-drives get in trouble. These are all street cars, so where does most of the load go when you add people and luggage? Yep, on the rear. So for safe, full-load handling, a FWD needs enough rear rubber to handle it. Safety ruins the fun–again.

[Wheel width: Is wider always better?]

And what about the CRX and race cars I mentioned? These cars were required to run the same size on all four corners, so they all used the trick of rear steer. In 1988, Honda introduced an utterly amazing suspension designed to minimize the understeer typically found in FWD–and in their low-priced daily driver Civics. Man, I loved them for that. It went away a couple generations later–just too expensive. But wow, in ’88 we got an incredible rear trailing arm that carefully steered the rears out. 

On our Mazda6 race cars, we could move rear mounting points to create the same effect. With the rear steer, we could soften the rear springs a lot. Getting on the gas would then transfer weight back, squat the suspension, and use the designed-in bumpsteer to toe out a little and drive off the corner with minimal understeer. Magic! Thanks, Craig Nagler and Tri-Point.

Because a front-wheel drive delivers the power to the front tires only, to be balanced on throttle, it has to be a little tail-happy off throttle. But this is perfect for aiming at the apex on the way into the corner. Get it right, and it’s very fast and even fun to watch. (Again, watch those old RealTime Acuras.)

But these tricks are really just steering around the real issue: The front tires should be bigger than the rears on FWD. Just like a Porsche but backward. Size the tire to the load. Logical. 

Just be aware that if you throw wider fronts on there, your car will probably oversteer a lot because you’ve been running stiff springs and bars and other tricks for those not-ideal same-size tires.

More and more, I have seen this setup in the modern world. And if you cannot change wheel or tire size? Pump up the rear pressures to deliberately reduce grip and force the car to be more balanced. Free and effective.

So remember, front-drives definitely do not have to understeer.

Comments

I’m going to use this column to shamelessly share old World Challenge videos I found on YouTube:

 

Tom1200

PowerDork


9/11/24 11:29 a.m.

All I will say is watch Minis ruuning at  Goodwood

In reply to Tom1200 :

Mini guys would put casters in place of the rear wheels if the rules allowed it.

As noted, the Mini’s are a great example of this.  I once asked a guy about his mini, and how you keep it from constantly understeering.  He said: “I can make it oversteer as much as I want if I set it up right”

Having done some sim racing with racing Mini’s, those things are looser than…. 

Blair’s philosophy on FWD car set-up…

“The front third of the car is what matters, the 2nd is where you sit, the third is a trailer the rules unfortunately require you to tow around the course” 

“The rules force you to have 4 tires, use all of them” 

 

The world is going away from 1000lb rear springs and urinating dog corner entry poses but still see too many cars being fought around autox courses set up that way. 

My neon that was set up for rallycross is a wonderful driving car on the dirt it oversteers just enough to be really nice. By far the best front wheel drive car that I have ever driven I’m very fortunate to have been able to experience it 

In reply to Colin Wood :

God I miss Speedvision…  

 

Perhaps I do need to give FWD a chance. I just havent driven one with sporting pretense much.  

1. 1991 Pontiac Grand Am (clapped out TURD)
2. 2003 Chevy Malibu (low mileage example, decent power, but meh)
3. 2006 Mazda5 (cant say I chuck that around much)

and one autocross run in celica that had won Solo Nationals…  but it was a small lot and the car was on snow tires…  Yes, Yes I could make it oversteer. Or Understeer…  Or full sideways all wheel drift…

I first noticed FWD (as others have said above) in an old Mini that a cousin vintage raced at Blackhawk Farms and Road America.  So thanks for introducing a dose of reality.  Or is confirmation bias “the droid I seek”?

YouTuber and (former?) racer Brian Makse often concludes his videos with “and remember, cars don’t understeer by themselves.”

In reply to pilotbraden :

I recall talking to guys who raced in a neon spec series when the cars were new and I asked “what are you doing to get that oversteer out there?”

One guy simply said “we’re all running about 60psi on the rear tires.”

I thought “welp, that’ll do it.” 

Notice that the rear steer used to reduce understeer provides toe OUT. More evidence that your trackside guide is wrong. 

CR Hammond

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