LeftieBiker
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Re: Steering get heavy with high torque when cornering

Fri Jan 27, 2017 10:02 pm

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.


This just isn't true. Cars get snowed into parking spaces all the time, or stop on snow-covered ice, only to fail to move again, all without leaving the street. And let's not assume that I'm talking about me driving one old Volvo. I mean several different models, shapes and weights of older Volvos, RWD American cars like Mavericks, Valiants, Concords, etc. I've also driven FWD cars like the 323/Tracer hatchback, Honda Civics, 90s Camry, Gen III Prius, etc. So while my experience is largely pre traction control*, it isn't small. I think that Vitaminj's experience is mostly with RWD cars that are designed for traction and handling, not everyday mass market cars. Most FWD cars, BTW, will recover from an understeer-slide better if light to moderate power is applied, and most RWD cars won't fishtail if you back off the throttle.


* The Gen III Prius would be better off with no traction control. It paralyzes the car on ice, and turning it off is amazingly difficult.
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VitaminJ
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Re: Steering get heavy with high torque when cornering

Sat Jan 28, 2017 10:30 am

LeftieBiker wrote: This just isn't true. Cars get snowed into parking spaces all the time, or stop on snow-covered ice, only to fail to move again, all without leaving the street.

"and if there is then drive wheels won't matter"

And let's not assume that I'm talking about me driving one old Volvo. I mean several different models, shapes and weights of older Volvos, RWD American cars like Mavericks, Valiants, Concords, etc. I've also driven FWD cars like the 323/Tracer hatchback, Honda Civics, 90s Camry, Gen III Prius, etc. So while my experience is largely pre traction control*, it isn't small. I think that Vitaminj's experience is mostly with RWD cars that are designed for traction and handling, not everyday mass market cars. Most FWD cars, BTW, will recover from an understeer-slide better if light to moderate power is applied, and most RWD cars won't fishtail if you back off the throttle.


* The Gen III Prius would be better off with no traction control. It paralyzes the car on ice, and turning it off is amazingly difficult.


"Vitaminj's experience is mostly with RWD cars that are designed for traction and handling"

Yes, RWD is more conducive to traction and handling, my entire point. If you are building a car about traction and handling, you start with RWD. If you are building a car on a budget, you use FWD. If you are building a car to go in snow you use AWD.

Regarding FWD cars recovering from understeer with throttle, that's another myth. That myth is also applied to AWD configurations. If you are understeering it's because of loss of traction on the front tires while turning. Just as ABS is used to allow drivers to steer while panic-braking while not sliding straight forward; using throttle while steering will cause your car to drive straight forward. I mean it's purely physics, why is putting more torque through a tire that's slipping going to make it slip less? I am a driving instructor so I teach people how to drive on race tracks and icy lakes, FYI.

Cars with more rear weight bias will be more prone to oversteer when lifting off the throttle.
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LeftieBiker
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Re: Steering get heavy with high torque when cornering

Sat Jan 28, 2017 2:40 pm

"and if there is then drive wheels won't matter"


A FWD stuck on a patch of ice is much more likely to be able to drive off it than a RWD car, especially one with no added weight.

"Vitaminj's experience is mostly with RWD cars that are designed for traction and handling"

Yes, RWD is more conducive to traction and handling, my entire point. If you are building a car about traction and handling, you start with RWD. If you are building a car on a budget, you use FWD. If you are building a car to go in snow you use AWD.


You aren't reading the sentence as I intended. I mean that the specific RWD cars you drive were designed for better than usual traction and handling. Traction and handling are not default design advantages of RWD.

Regarding FWD cars recovering from understeer with throttle, that's another myth. That myth is also applied to AWD configurations. If you are understeering it's because of loss of traction on the front tires while turning. Just as ABS is used to allow drivers to steer while panic-braking while not sliding straight forward; using throttle while steering will cause your car to drive straight forward. I mean it's purely physics, why is putting more torque through a tire that's slipping going to make it slip less? I am a driving instructor so I teach people how to drive on race tracks and icy lakes, FYI.


I'm sure the technique doesn't apply on frozen lakes, but it definitely isn't a myth. When a FWD car tries to go straight in a turn, it's usually because of marginal traction, not zero traction. Adding some throttle causes a little wheelspin in the driving wheels; because they do still have traction they pull a little harder, and the car turns. Try this for yourself on an actual snowy road sometime, if you don't believe me.* That technique has gotten me out of trouble many times. If I want to drive on a frozen lake, though, I'll look you up first. ;-)

* EDIT: it's possible that traction control prevents this trick from working when it's on. If you want to test it, turn off the traction control.
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The most offensive, tasteless phrase in use here is "Pulled the trigger." I no longer respond to posts that use it.

arnis
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Re: Steering get heavy with high torque when cornering

Sat Jan 28, 2017 5:03 pm

These are old rules of auto-mobility, like:
FWD cars are easier to get moving if stuck;
FWD is budget, RWD is more expensive;
FWD acts better on slippery curve.

First was true when there was a heavy engine in the front.
EV's don't have anything heavy, except battery.
weight distribution is always near 50:50, no difference if stuck in something.

Second is true if you need the transfer power from front to rear.
Electric vehicles have motors where they need to be

Due to 50:50 distribution RWD is as good as FWD, or even better if accelerating.
FWD can pull you out a little bit more, true.

iMiEV is RWD. Nothing fancy there.



On an incline RWD EV is much better than FWD EV. Rear wheels have more weight on them.
RWD design is more reliable.
RWD has better tire load distribution. This also results in more even wear.
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