Torque steer

[paul]

ok i know how i hate people reposting old topics but did a search and came up with nothing so im gonna ask ya!



ok on the subject of torque steer.......

for example the new astra VXR (vauxhall) holden for you australians

but anyways , what causes this to happen ? surely if your going on a flat straight road and you put your foot down in a front wheel drive car with a normal front diff that puts down power to both wheels why is it that the one decides to have more power over the other?

i have come to the conclusion that its the different lengths of drive shaft

but not completely sure of the answer

thanks all

[h00t_h00t]

Small differences I think, like the road is just slightly sloped to one side, or one tyre has a little less air in it.

[paul]

what do you mean , this happened to a car that was on a flat road with even surface and the tires were near enough the same pressure , give or take half a psi

[scottie300z]

no lsd? i dont know about that particular car much or at all. But i know that when those idiots w/ automatics try to burn out by using their brakes in their 240sx's they do one wheel burnouts due to the lack of lsd.

[paul]

yes not i was not meaning anything about a lsd , this car does not have one ...

matra help!!!!

[scottie300z]

well my point was, couldnt it lacking a lsd cause one wheel to spin while the other doesnt? That was your question right?

[Matra et Alpine]

You hit it on the head.

Torque "steer" on straigh is down to different length drive shafts.

Even driving on straight the CV joint has a slight angle in the joint to cope with suspension movement. The CV joint on the shorter shaft has more 'bend' and this produces higher fiorces in the joint trying to straighten it.

[spi-ti-tout]

Even driving on straight the CV joint has a slight angle in the joint to cope with suspension movement. The CV joint on the shorter shaft has more 'bend' and this produces higher fiorces in the joint trying to straighten it.

Yeah but aren't the suspensions the same on both sides?
I mean say one is up to - centimeter so doesn't the other one also have to be at the same height so as to create stability?
I understand that suspensions are altered in race cars when kerbs and corners are taken into consideration but on normal cars?

Either I'm not understanding a little or I'm not understanding the whole thing

[KnifeEdge_2K1]

i thought torque steer was cuz of the engine's forces tryin to straiten out the car mid corner, has to deal with the point where the steering axis meets the ground in relation to the center of the contact patch, that being the scrub radius, higher the scrub radius the more the car wants to straiten itself out, kingpin and castor affect this the most i think, camber does a bit because it alters the shape of the contact patch and im pretty sure toe does nothing

[pimento]

Drive shafts is it, it happens going in a straight line too. Things like tyre pressure and wear would make it worse, but the main reason is what Matra said, the unequal drive shafts. Put simply, due to differing losses to various things resisting the power on each side of the diff, different amounts of power get transferred to the road on each side. And once it starts, it's only gonna get worse.

[Matra et Alpine]

Yeah but aren't the suspensions the same on both sides?
I mean say one is up to - centimeter so doesn't the other one also have to be at the same height so as to create stability?
I understand that suspensions are altered in race cars when kerbs and corners are taken into consideration but on normal cars?

Either I'm not understanding a little or I'm not understanding the whole thing

Easiest is if you draw a picture of an offset diff and unequal drive shafts to the wheels. Draw them as if the wheels were at the extreme of suspension travel just to accentuate it. Notice how the drive shaft on one side is at more of an angle than the other.
Voila

The small angles involved ( and the diff loses and tyre radius as pimento says ) don't matter a lot with a car with little power. BUT as you taek everything to the limits it starts to become significant. A 1% loss in a joint is barely noticable with 70hp ( 0.7hp ) but will rip the wheel from your hands with 500hp ( 5 horses !! )

[paul]

sweet cheers all that has been bugging me the last couple of days and i was pretty sure it was the D/S but was not entierly sure why?

thanks for clearign this up , just weird that is has not been brought up before?

[KnifeEdge_2K1]

http://www.sportcompactcarweb.com/ed..._technobabble/

damn it i knew i was right about it !!

[IWantAnAudiRS6]

http://www.sportcompactcarweb.com/ed..._technobabble/

damn it i knew i was right about it !!

As we've come to expect... which is good for those who agree with you, and bad for those who don't

Only happens in FWD, right, because the wheels driving are also the ones being steered, so they can move freely. Cars with less power still torque steer- my friend's brother's (hope that made sense) Mondeo ST24 (Contour SVT to you Yankees) torque-steers.

[Matra et Alpine]

http://www.sportcompactcarweb.com/ed..._technobabble/

damn it i knew i was right about it !!

The question is on the relative quantites all the various methods impart when driving in a stright line.

He also doens't explore the effect of camber.
Performance FWDs will add camber so that the point he calls the "dave" point is closer to where the steering incliniation angle meets the groudn - I don't remember the 'gap' ever having a name so I'm happy to call it the "dave"

IF it was only down to that then the wheel woudlnt' ahve such a STRONG kick. His article is good for explaining cars in corners. But not for explaining the driver experience. He's fixed too many variables IMHO BUT it is contributory and important - and why as I'd said camber gets adjusted and all performance cars will rose joint the front end so they can "tweak" for each track

I can't see the forces lost in the "dave" being sufficient to turn a wheel in a strong drivers hands as the rubber is scrubbing laready and henvce forces are lower.

Also we have the empirical evidenc that if you try it with wheels OFF the ground, the driveshaft torque steer will straighten the wheel.