Sorry by suspension symmetrical I mean that the offsets and contact patch and scrub radius is the same side to side.
On a perfectly level, smooth, straight road with two perfect tyres and equal length drive shafts, you'd not get torque steer regardless of the wheel geometry. But the world isn't perfect, so one slight variation and you get torque steer.
Last edited by TMM; 10-05-11 at 09:30 PM.
mang mang mang
After managing to loose part of my post twice [EDIT] and having someone post in between.
weight distribution will have some influence, as the castor/camber combination means the jacking due to turning creates different loads & moves pressure centres on tyres, if it is all really close they driveshafts/CVs will obviously have more influence. If it is actually at the point of wheel slip/traction loss side to side you obviously then have a significant unbalanced force from the side that is getting drive pulling that wheel/hub forward (assuming non perfect equal torque split from diff as even open centres have internal resistance, & not perfectly straight steering angle & contact patch will have moved relative to wheel centre due to tyre distortion, member flex etc).
As soon as you are not 100% dead straight steering angle the combination of camber, castor, scrub & body roll (or suspension travel over road imperfections moving the wheels to different parts of the suspension stroke & thus changing the geometry & moving pressure centre of tyre on road slightly & moving the steering axis) means you have an unbalanced in the torque acting on the hub on each side of the car. So realistically most will pull both ways depending on the circumstance.
In theory if you have 100% traction both sides, dead flat road, same driveline resistance to each wheel (obviously effected by CV angle, brake drag etc) you will have no torque steer with conventional suspension geometry.
Or if you neutralised the usual suspension parameters (no scrub or mechanical trail) you could have one wheel on ice & one fully gripped up (obviously need an lsd or spool to deliver more torque to the wheel with grip than that created to overcome the inertia of the wheel spinning up with an open diff if you wanted to go anywhere) you would have zero torque steer. Alternative way of looking at the same thing, put enough weight in back corner of car to remove one front wheel & keep it off the deck, spool diff to get drive, normal geometry it would pull hard to the no wheel side, neutralise scrub radius & trail & it wouldn't pull on the steering at all straight or turned.
Conventional strut or double a arm suspension designs that are cheap to make give scrub radius (some is ok, basically contrained by where it is convenient to put rotating joints in) & mechanical trail in combination with castor (very desireable, provides self centering & some weight which allows you to feel how much grip you have as well at the camber change on turning due to castor keeping appropraite tyre contact)
Last edited by Slides; 10-05-11 at 10:26 PM.
to improve torque steer, add more torque
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Urethane control arm/radius rod bushes help this a LOT. All these FWD passenger cars use big, soft rubber bushes.
I changed the lower arm bushes on the TW to urethane and it cured so much shit like torque steer on uneven surfaces, tramlining etc. NVH barely went up at all.
Last edited by Typhoon; 11-05-11 at 11:33 AM.
Life's too short to drive boring cars.