Can some one explain why front wheel drive cars get torque steer? I know it when I feel it, but what it the mechanical explaination?

 

I would think it has to do with the differential not allowing the wheels to spin freely as they would want to in a turn. When you make a turn, each wheel moves at differing speeds.

 

Most front wheel drive cars only put power to one wheel. Some have limited slip( of a sort) but usually one wheel gets more power than the other.

So when you put a lot of power to the driven wheel you get torque steer.

My old 89 SHO had terrible problems with that. I could barely get out of a driveway turning into traffic if there was any water on the road.

That's why I like RWD American cars. That's also why you don't see any FWD top fuel dragsters or F1 or Indy cars.

Just my opinion.

Jim Henderson

 

im pretty sure its a combination of those 2, but what i understand it to be is when u jump on the gas in a front wheel drive car, the car pulls to the left or right a little bit

 

Torque steer most noticeably occurs when a FWD vehicle pulls to one side while being driven straight and under heavy acceleration. It is typically due to the front axles being of different lengths and, given the geometry of the tire positions and the "pumpkin", there will be more pull (force, not torque) on one side of the car. This can be visualized by imagining that you were looking down on the top of the car and noting the position of the pumpkin relative to the tire positions and the center of gravity of the car. Now look at, and think about the two front axles of different length (as levers); with more/less equal torque applies to each tire there are equal forces between the tire and road, yet the longer axle will result in a greater pulling force on one corner of the vehicle body when viewed/visualized as just mentioned.

One way the problem has been solved (reduced anyway) is to replace the one piece long axle with a two piece member. It consists of a section of straight shaft and the remaining section of axle is the same length as the short axle on the other side of the car. The center section of the two piece assembly is secured to the transaxle or whatever via a support bearing. Now there are two axles of equal length.

BTW, torque steer is not caused by axle windup; any axle windup will be so insignificant that it will not be noticed by the driver.

 

Great explanation…….your hired

 

For what?

The "explainer of things related to drivetrain forces" here at FTE?

 

Really, it's just applying basic physics to a "real world" situation. I regret that it could not be explained with less words; oh well.

 

Its also somewhat eliminated in the high performance full time four wheel drives like audi, porche, mercedes, VWs and a few others. I finally got to see one of those VW W8 engines,but I'm still not sure about them.
you really get to experience torque steer on ice, then its exagerated to a very noticable degree, its kinda like the car suddenly developes a bad understeer.

 

Torque steer also applies to airplanes, helicopters and boats. A boat with a clockwise rotating prop will tend to drift off to the right and never really go in a straigt line by itself for long. Air planes with more than one prop have counterrotating props to keep its nose pointed straight ahead. And we all know what happens to a helicopter when it loses its tailrotor, it will spin violently in the direction the main rotor is spinning.

 

Borderman, most multi prop aircraft do not have counter turning props. they almost all turn the same way. and they use rudder/elevator and aileron trim settings to offset these problems.

for ex C-130 4 props. turbo props at that. it just uses trim settings to keep the plane straight and level, and no not computer operated trim settings. your aircraft have 6 trim tabs. one on each wing, each horizontal stab, and two on the rudder. the trim tabes on hte right wing and right horz stab are permanently set, there are adjustments, but in flight they cannot be adjusted, along with I believe the top tab on the rudder. these also get adjusted to compensate for balanceproblems caused by cargo.

the 3 otehr tabs are controlable from inside the flight deck, for either minor in flight adjustments or if the perma set tabs are not exactly correct. they are also used by autopilot for minor adjustments instead of controlling the whole rudder.

A trim tabs size is maybe 1% the size of the actual control surface. so the aileron trim tab on a 130 is roughly 2-3 square feet in surface area on the top side, same for the bottom. whereas the aileron is approx 500 sq feet surface area.


If you wish to know the principle about how they work, let me know :P this is also part of my job knowing how they work.

sorry to go off-topic...

 

The torque steer effect in front wheel drives vehicles isn't the same thing as it is with props, both air and water. the counterrotating props are almost exclusively used in high performance twins. Four or more engine prop aircraft don't have the proplem and can use the same rotation on all engines. with high performance twins the tips of the props are literally pushing up on the air on one side and down on the other, so planes like the P 38 used counter rotating props to cancel the effect. Boats do almost the same thing with high performance twin props, the more trim you use to cancel the effect the more drag you have and the less efficient the craft is. With single prop craft its pure torque, the harder you push the prop one way the harder the craft tries to spin in the opposite direction. BMW motor cycles do the same thing, when you get on the throttle the bike has a slight tendency to lean away from the drive shaft rotation, the bike is trying to spin in the opposite direction of the drive shaft.
I kinda miss my old audi. it was fun in packed snow and ice if you cranked the wheel all the way to the stop and put it in reverse it would spin hard in circles, just don't do it with drunks in the back seat.

 

Actually the C130 has a set amount of offset built into the vertical stab to offset the forces caused by the 4 props.
Just my $.o2