|
derspi wrote:
> Does it really really matter what you want to call it?
Well usually people want to hear the correct answer when they participate in a forum such as this so I'll have to say, YES. It really DOES matter what I want to call it!!
> The fact of
> the matter is, the car is steering or behaving unexpectedly and this
> can be cause for concern for some people. I don't know the exact,
> precise definition of torque-steer but I do know what tires slipping
> due to poor traction feel (and sometimes, sound) like.
And I'm sure if the rear end let loose when you goosed a Camaro V8 with an open diff, THAT would be torque steer too? I mean, it does cause the car to turn (spin) in one direction or the other depending on which tire has more traction. Much the same as has already been described in your FWD experiences.
> If you can, feel free to enlighten us with a proper definition.
Sure thing. Read below.
> And
> if it is indeed a topic of debate even among journalists and car
> techs then what makes your definition the absolute, correct one?
Probably the fact that Journalists usually don't know their ass from a hole in the ground but that's another story. Most tech will know what it is though.
Well let's see. Torque and steer. Torque that induces unintended steering effects in an otherwise perfectly aligned steering/suspesion setup due to uneven application to the front tires of the vehicle usually induced by asymmetric driveshafts.
Picture two pieces of tubing. They're the same diameter, the same material and the same density. They are however different lengths. Fix them on one end to prevent any rotation of the shaft. Now, on the other end, apply a fixed amount of torque to each of the two shafts. The shorter shaft will resist twisting less than the longer shaft because its length makes it more torsionally rigid. Think about golf clubs. If you made a shaft 44" (standard driver) and put a specific amount of torque on the grip end while securing the head of the club, the grip would rotate a specific amount. Now do the same with a 48" or 52" driver and note that there will be even greater rotation down the length of the shaft because there is a greater length of material of the same density and weight to achieve rotation.
Now think about the powertrain setup on most FWD cars. Because the engine and transmissions are transversely mounted, the flywheel is always closer to one side of the car than the other. The transmission is usually located in between the engine and the firewall. One side of the tranny will house the torque converter which of course connects to the driven/output shaft and the diff. It is because of this asymmetry that manufacturers usually have to utilize one drive shaft that's shorter (usually the driveshaft closest to the torque converter) and one that's considerably longer. Think back to the examply above. The torque end of the shaft is the end connected to the transmission and the fixed end is the tires. The transmission must put torque to the ground in order to get the tires moving. Because is transmits more torque to one side than the other due to the longer shaft ABSORBING more torque than the shorter shafter through torsional rotation/stresses, the shorter end typically spins faster (as it's seeing more torque) causing the car to PULL to that side. THIS IS TORQUE STEER!
When the tires are spinning you can throw torque steer right out the window because you aren't putting any consistent torque into the pavement. Everything in this particular situation depends regaining adhesion. Now should both tires grab at exactly the same time and should the final drive (FWD differential) be transmitting the exact same amount of torque to both shafts at the same time (highly unlikely if the wheels are spinning) and the car STILL pulls consistently to one side, you're also observing torque steer.
The phenomenon is however mostly observed when you romp on it from a standing start or hit the gas causing the transmission to downshift rapidly and impart greater immediate engine torque to the driveline.
Find a really flat, smooth, clean strip of pavement with NO ROAD RUTS/TRAIN TRACKS. Make sure it's plenty wide (empty parking lots are great) and when you're ready put your left foot on the brake, right above the gas and take your hands off the steering wheel. When you pull off the brake pedal romp down on the gas with your right foot. If the car goes straight (assuming you haven't lit up the tires) you have NO TORQUE STEER. If the car pulls to one side or the other then try the whole thing over again to see if it's consistent. If it consistently pulls to one side, you have torque steer. If you're not sure after trying this, find someone with a 1994 or earlier Cavalier Z24 with the 3.1L mill under the hood. You'll DEFINITELY discover torque steer with this POS!!
My GOD. I think I'm approaching epic post length. MUST STOP... must resist urge to continue typing. Must... not... be as nasty to .... Dave in future.... for typing.... long posts. Have a great night everyone. I'm gone.
|
