Slipping & Sliding in Snow

[mkhuffman]

@Hammered and @timbop are right about 1PD. It is dangerous in slick conditions, such a as ice and snow. Can you safely drive in those conditions using 1PD? Absolutely. So I agree with @RickMachE that of course the drive mode is less important than the driver, and the driver is always responsible.

Nobody has explained why 1PD is dangerous on slippery roads, so I will try.

I don't know which forum member opened my eyes, but I think it was someone on a Rivian forum. But I used to think 1PD was just like down shifting a ICE vehicle, which works great in the snow. In fact, that is the best way to slow a car in very slippery conditions IMO. But 1PD is not equivalent, even though it may seem it is. I thought it was. It is not.

1PD is designed to stop the car. Downshifting slows an ICE car but will not stop it. 1PD will lock up the wheels, because it is trying to stop the car. Downshifting slows the wheels but keeps them moving. When the wheels have minimal traction, 1PD can lock them up when the driver is not expecting it. All of a sudden the car is sliding and pressing the brakes does nothing because 1PD has already locked the wheels.

If you know this happens, you can keep your foot on the go pedal and avoid locking the wheels. But most people will not be trained to do that. So 1PD is dangerous unless you know what it means. Turning it off is safer for most drivers.

If you have a family member who is going to drive your MME in the snow, and they are not familiar with how 1PD works, turn it off. Or they may end up putting your car in a ditch.

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[Jimrpa]

@Hammered and @timbop are right about 1PD. It is dangerous in slick conditions, such a as ice and snow. Can you safely drive in those conditions using 1PD? Absolutely. So I agree with @RickMachE that of course the drive mode is less important than the driver, and the driver is always responsible.

Nobody has explained why 1PD is dangerous on slippery roads, so I will try.

I don't know which forum member opened my eyes, but I think it was someone on a Rivian forum. But I used to think 1PD was just like down shifting a ICE vehicle, which works great in the snow. In fact, that is the best way to slow a car in very slippery conditions IMO. But 1PD is not equivalent, even though it may seem it is. I thought it was. It is not.

1PD is designed to stop the car. Downshifting slows an ICE car but will not stop it. 1PD will lock up the wheels, because it is trying to stop the car. Downshifting slows the wheels but keeps them moving. When the wheels have minimal traction, 1PD can lock them up when the driver is not expecting it. All of a sudden the car is sliding and pressing the brakes does nothing because 1PD has already locked the wheels.

If you know this happens, you can keep your foot on the go pedal and avoid locking the wheels. But most people will not be trained to do that. So 1PD is dangerous unless you know what it means. Turning it off is safer for most drivers.

If you have a family member who is going to drive your MME in the snow, and they are not familiar with how 1PD works, turn it off. Or they may end up putting your car in a ditch.

Why wouldn’t ABS kick in to prevent wheel lock? And where’s traction control in this instance? It seems like an odd strategy to prioritize battery regen over vehicle control?

 

[Mach-Lee]

When the wheels have minimal traction, 1PD can lock them up when the driver is not expecting it. All of a sudden the car is sliding and pressing the brakes does nothing because 1PD has already locked the wheels.

Wheels do not lock up in 1PD. If wheel lockup is detected, regen is immediately cut and ABS kicks in (friction braking) until wheel slip is no longer detected.

I get ABS with 1PD somewhat often here with the ice and snow. I leave it on unless conditions are really bad. You just learn not to let off the pedal all the way on slippery surfaces.

BTW, the Rivian brakes are different. They don't have blended braking with an electronic booster like we have (1PD doesn't apply hydraulic brakes). So if you use 1PD Rivian can only do anti-lock with the regen which doesn't work as well as traditional hydraulic ABS (it's slower). So it is more likely for an inexperienced Rivian driver to lose control in a high regen mode. Rivian drivers should use snow mode in snow and ice to limit regen.

Mach-E can use regen or hydraulic ABS (or both) whenever it wants regardless of where your foot is. It really doesn't matter whether you are braking with 1PD or the brake pedal because the Mach-E will handle it the same way. Just two different ways to input a braking request but the computer decides the output (brake by wire).

 

[Jwolf91]

First, winter with the MachE for me and I have noticed whisper mode is the best for snow/ice covered roads. First AWD vehicle for me and as long as I keep the acceleration under control runs great!

 

[mkhuffman]

Wheels do not lock up in 1PD. If wheel lockup is detected, regen is immediately cut and ABS kicks in (friction braking) until wheel slip is no longer detected.

I get ABS with 1PD somewhat often here with the ice and snow. I leave it on unless conditions are really bad. You just learn not to let off the pedal all the way on slippery surfaces.

BTW, the Rivian brakes are different. They don't have blended braking with an electronic booster like we have (it doesn't apply hydraulic brakes). So if you use 1PD it can only do anti-lock with the regen which doesn't work as well as traditional hydraulic ABS (it's slower). So it is more likely for an inexperienced Rivian driver to lose control in a high regen mode. Rivian drivers should use snow mode in snow and ice to limit regen.

Mach-E can use regen or hydraulic ABS (or both) whenever it wants regardless of where your foot is. It really doesn't matter whether you are braking with 1PD or the brake pedal because the Mach-E will handle it the same way. Just two different ways to input a braking request but the computer decides the output.

Wow. That's awesome. Ford has done some great work on our cars for sure.

I should not have assumed the MME had the same issue as Rivian owners were reporting. Also, I read about the issue prior to snow mode getting sent out via OTA. Definitely snow mode is the way to go in a R1.

 

[dtbaker61]

@Hammered and @timbop are right about 1PD. It is dangerous in slick conditions, such a as ice and snow. Can you safely drive in those conditions using 1PD? Absolutely. So I agree with @RickMachE that of course the drive mode is less important than the driver, and the driver is always responsible.

Nobody has explained why 1PD is dangerous on slippery roads, so I will try.

1PD is only 'dangerous' if your lift your foot too fast and create too much regen for traction available. Full regen is pretty much the same as 1/2 throttle....

My MME (Select AWD) has max output around 200 kW, and max regen around -100kW. In unbridled, if you lift your foot suddenly, that amount of regen is similar to a pretty solid stab on mechanical brakes.

In very slippery conditions I like to plug in the ODB2-CarScanner display on my phone, and watch my output/regen power out of the corner of my eye. This gives me pretty good feedback on how much power/regen I can apply before breaking loose.

It takes a lot of practice to overcome old habits... lifting your foot 'off the gas completely' to roll over ice spots is the wrong thing to do. With practice, I find 1PD far better than 2pd because you dont lose time moving your foot from one pedal to the other, and if you keep an eye on power, you can be VERY delicate with both acceleration and braking.

 

[Lalji]

Been driving around on ice for three days in Portland. Whisper, 1PD, Michelin ICE X tires. Zero issues up or down steep hills. It runs like a dream.

Same, the tires are the most important aspect in a situation like this.

I have the Michelin X-Ice SUV Snow and I haven't had a single issue in about 6 inches of snow here in Canada.

 

[Lalji]

Do you have dedicated winter tires on your vehicle? Allot of folks place allot of emphasis on 4 wheel drive or all wheel drive, thinking it's a replacement for dedicated winter tires, but unfortunately that's not the case, particularly when coming to a stop. Don't forget the MME is a heavy girl, with a curb weight that is essentially the same as a gas F-150 truck. That's allot of momentum riding on only 225mm of rubber. If your riding the original all seasons, she doesn't stand much of a chance.

That said, I am riding on a set of 4 235/55/19 Michelin X-Ice SNOW SUV Winter Tires, and my Mach-e feels very confident and stable in the snow and ice, as long as you are driving according to conditions.

Agreed!!! 4x4 is NOT a replacement for winter tires. I have the same ones, they are amazing.

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