Steering get heavy with high torque when cornering

[like2bike]

I noticed this issue occasionally for years and it doesn't seem to be getting better or worse. The steering get heavy when applying high traction motor torque when cornering. It's a little dangerous but always recovers when the torque is lessened. Has anyone else noticed this? Anyone have an explanation for it?

[VitaminJ]

It's called Torque Steer. It is the torque of the motor running through the driveline and into the tires affecting the steering angle and feel. It's just the physics of front-wheel drive cars. Very pronounced on the Leaf as it has 187ft-lbs of torque and a normal FWD car like a Honda has about 100 ft-lbs.

https://en.wikipedia.org/wiki/Torque_steering

[GetOffYourGas]

The current Leafs make 187 ft-lbs. The older ones, like mine, produce 207 ft-lbs. That's by far the most of any FWD car I've ever owned.

I, for one, am hoping that EVs will bring a renaissance of RWD cars. EVs can have a lot of (battery) weight over the rear wheels. The motor is small enough to place in the rear too. So traction shouldn't be a concern. And when it is, the instant response of an electric motor makes for much better traction control.

[VitaminJ]

Heck yes RWD for all! Really FWD just came about as a way to easily package the engine and transmission and create a larger interior volume in a smaller car, increase efficiency, and reduce weight. Myths about FWD being better in the snow and the like came from marketing people. There is much less reason for FWD with electric, and the only reason the Leaf and others are FWD is because they are based on gasoline cars.

[LeftieBiker]

How old are you, vitaminj? I grew up with RWD, especially Volvos, and while I liked driving them they weren't great in snow without good snow tires. Weight in the trunk also helped, which I understand a BEV might not need. It isn't a myth though that, for the same set of tires and roads, most FWD cars will handle better in winter conditions than most RWD cars. Tesla, for example, offers several RWD models, and they don't do especially well in snow -just adequately.

[VitaminJ]

How old are you, vitaminj? I grew up with RWD, especially Volvos, and while I liked driving them they weren't great in snow without good snow tires. Weight in the trunk also helped, which I understand a BEV might not need. It isn't a myth though that, for the same set if tires and roads, most FWD cars will handle better in winter conditions than most RWD cars. Tesla, for example, offers several RWD models, and they don't do especially well in snow -just adequately.

I am old enough to have owned 10 cars in my life. RWD, FWD, and AWD with turbo, V8, and slow engines. I used to daily drive a Miata year-round in Colorado and even took it snowboarding a few times. I never got stuck when driving my Miata. FWD is "safer" for new drivers and inexperienced drivers because it will understeer instead of oversteer, and the natural reaction when sliding is to panic and take your foot off the gas. In FWD you take the foot off the gas, front end settles down, weight transfers forward and you can steer again. RWD when you take the foot off the gas, weight comes forward, rear end gets loose, and that scares inexperienced drivers.

The fact of the matter is, when you point the nose uphill your weight shifts to the rear tires. My Miata will climb hills my Honda never could, same weight, same tires. RWD also usually means 50/50 weight distribution which means better traction when turning and when going downhill you have better rear wheel braking so you're not counting on only 2 tires like a nose-heavy FWD.

[GetOffYourGas]

An anecdote - a friend of mine had a RWD BMW 328i. With traction control and snow tires, that thing was really hard to make slip in the snow. Would it have been better with FWD? Maybe. But it was better than my older Honda Civic (FWD) beater with snow tires but no traction control.

Yes, that's one data point. But it's probably more recent than your old Volvo. And that's my point. Newer technology solves the old RWD in the snow problem.

My understanding has always been that it was about weight. In an ICE, the majority of the weight is up front, over the front axle. Therefore, a FWD car would have more traction than an equivalent RWD car. With an EV, that doesn't have to be the case. I've talked to RWD Tesla owners at NDEW events, and they seem pleased with their cars' performance.

I think Tesla got it right. Start with a RWD car. If that's not good enough for you, go straight to AWD. Skip right over FWD completely.

[VitaminJ]

My understanding has always been that it was about weight. In an ICE, the majority of the weight is up front, over the front axle. Therefore, a FWD car would have more traction than an equivalent RWD car.

When static, maybe. People think that "engine front engine heavy front engine heavy tires make good grip!" but in reality a BMW will have the same weight on the front axle as on the rear axle.

Now we're driving down the road, the situation has changed to a dynamic one. We need rear tire grip when we accelerate because we are RWD, good because accelerating transfers weight to the rear. Ok now we're braking we need all 4 tires to grip, good we have 50/50 weight distribution so even with weight shifting forward, there is still 40% on the rear tires to help stop.

Now we're driving a Leaf. We want to accelerate, we press the gas, the weight shifts to the rear tires and now the front tires have less grip than when it was just parked there! Ok time to brake, weight comes forward, 60-70% is over the front tires and the rear tires are hanging out in the breeze not doing anything.

[GetOffYourGas]

The Leaf is pretty well balanced for weight as well. Largely due to the heavy battery placed in the middle of the car.

Maybe I'm mistaken, but your examples all seem to assume traction. What happens when you lose traction while in motion?

Also, there are a lot of people who believe (rightly or wrongly) that RWD will get them stuck. That implies a static scenario, in which case the weight on the drive wheels absolutely matters.

[VitaminJ]

Yes the Leaf is still 56/44, better than most FWD but still nose heavy. There is always some level of traction unless the tire is in the air. Driving on snow/ice is a low traction scenario, so each tire is constantly changing the amount of traction or slip it has. It's the relationship between where the drive wheels are, where the weight is, and how the driver transfers the weight that makes a difference.

People believe what they believe rightly or wrongly. There is no scenario where a car just becomes stuck in place, and if there is then drive wheels won't matter. Cars get stuck by being driven into banks, into ditches, off the road, over curbs, up a hill, or other places they shouldn't be. Having drive wheels that receive increased traction on acceleration, and a more balanced chassis, are the keys to staying out of those places.