I understand it's a tendancy for FWD cars like the Mini to oversteer in turns when the throttle is punched, right? I'm tending to notice this now. On my old RWD beemer if I punched it the rear wanted to go away from the turn, but this has to be different physics because the drive wheels were in back. What causes this, and how do you correct for it?

 

As the name implies, it is caused by torque, the force that overcomes esisting motion, or non-motion. Thus, in the case of the MINI, with front wheel drive, it is the force of accelleration, pulling the car to the left. I have found this torque steer to be extremely noticible when accellerating forcefully, even though my LSD should temper it somewhat. Reducing torque, that is, accellerating slowly, compensates for it.

 

I've also noticed that if I deactivate ASC it seems to be a lot better. I think what happens is the spinning wheel gets braked by the computer making a more jerky/torque steer feel. (I have LSD btw)

 

Does ASC involve the brakes? I didn't get DSC, I thought only it used the brakes, not ASC. I do have LSD btw.

 

Torque steer is the car pulling one way or another under hard accelleration. The R56 makes all of its torque starting at 1600 RPM, which exacerbates the issue.

Understeer/oversteer isn't automatic with FWD. It has to do with weight distribution, suspension, and other factors. FWD cars do have to share drive forces and steering forces on the same two tires.

Punching your old RWD in a corner only caused the rear tires to lose their cornering grip, breaking the rear end loose. Making a FWD lose it's grip in a corner won't get you torque steer as much as a good chance to plow straight in the ditch. Why would you be punching the throttle in a corner on any car? It only upsets the suspension. Smooth application of power is the way to go.

 

Oversteer happens when the back wheels lose traction, and the back end starts to swing out (my '66 Mustang liked to do this) Understeer happens when the front wheels lose traction and the car simply won't steer, it just goes in whatever direction it was last pointed. FWD cars tend to understeer, and many car companies, BMW included, tend to build a little understeer into their chassis as it is regarded as safer, though not as much fun.

The new MINI Cooper S seems to understeer and also experiences torque steer under heavy acceleration. Since my car isn't broken in yet, I can't really test to see what can make the handling more balanced. But here are some ideas...

- Get the LSD. I am sure this helps with everything, torque steer, traction in corners, performance in wet and snowy weather as well as dry.
- for really quick take-offs, turn off ASC and DSC. They tend to try and make the car stay as controlled as possible. If you are on the highway at 80+ mph, they are great, but if you are trying to drive like a fool, on purpose, both systems will work hard to thwart you.
- apply power smoothly. I am reasonably sure that mashing on the gas will only cause alot of wheel spin. Fun if you are trying to burn off those crappy tires whilst looking for an excuse to buy new ones, but that's about it.
- Watch your tire pressure. Still trying to figure out what pressures would be best. MINI says 33 all around, but since the car understeers a bit, that doesn't make sense. Probably a little higher in front, maybe 36psi and a little lower in back, maybe 30 - 32?
- Invest in swaybars. Well, at least I am thinking about this. A thicker rear bar will increase oversteer, and/or reduce understeer. Both bars help to keep the car flatter in corners.

Hope this helps!

 

Thanks for those helpful tidbits. BTW my manual says 36psi for the tires.

 

Like others have stated, understeer is when you turn the wheels and don't quite get to where you want to go. You under steered. Oversteer is when you turn More than you want to. You got further in your turn than you want to. Years ago Porsche lost their shirt in a lawsuit because of oversteer. The car overturned and backed into a tree and there was a death. Landmark case(someone can probably correct me on the particulars). Since then, almost all car makers have built understeer into their cars. They seem to think that if it looks to the driver that he'she are going to drive into the tree, he/she will try to slo down. Enough history.....

The very spirited test drive I took in a MCS with LSD would mostly understeer, but would occasionally oversteer. The car requires finesse at 10/10ths. And a firm hand(s) on the wheel. I haven't lived with one yet as I'm a Northwest guy with a long wait from ordering, so my input is only a brief drive. That said, my favorite sandbox is a race track and I spend a lot of time in understeer and oversteer, sometimes in the same corner.

Overall, front wheel drive cars will oversteer much more than understeer.

I'm pretty sure at reasonable speeds, the MCS will be a mildly understeering vehicle with minimal bad habits. The autocrossers hanging around here should have further input.

 

If you drive smoothly, you will experience less torque steer. Just be careful when you accelerate hard.

 

Porsche's are a different car. RWD and rear (or mid) engine. They were famous for "lift throttle oversteer", where if you were in trouble in a turn (rear end coming loose from lack of traction) and took your foot off the gas, the car would go into a spin, unlike a car with the engine in the front where the front weight would just slow the whole car down equally and let it slide laterally to some extent. The Mini is FWD with the weight on the front wheels, opposite from a Porsche. Very different handling characteristics. I'll make sure and appy the gas gently from now on!

 

Really different cars, but I'm geting out of the p car and into the MCS as a daily driver. That said, the MCS is a hoot to drive. FWIW, I can make my porsches under or oversteer easily with the sway bars. Hoping to do the same with the MCS when it gets into my hands.

However, gentle? We're getting MCSs! Fast, agile, go kart handling, good brakes, great mpg......

By the way, really appreciated your int pics as I was able to show the family what a tuscan beige looks like. I'm doing mine with AB/AB

 

Wouldn't torque steer be caused by the torque transfered to the frame of the car via the engine mounts when the engine applies torque to the drive shaft?

With an inline engine, this torque would be inline with the centerline of the car, so I can see this having an impact on steering - loading torque generated forces on one side of the vehicle and unloading the other side. With a transverse engine, the torque is applied crosswise to the car, thereby loading/unloading the front wheels vs the rear wheels. This should not affect steering.

If the torque developed by transverse engine is not evenly distributed to the two drive wheels, then that would impact steering for sure. So is the torque steer felt by MCS owners due to uneven torque distribution by the differential? If true, should this effect have some other name, like uneven torque distribution steer (UTDS)?

Many are reporting a pull to the left on hard acceleration, this should result in oversteer for left accelerating turns and understeer for right accelerating turns. Is this the case?

Would the LSD impact UTDS? I have assumed that the LSD can only do its job when slippage is detected. If hard acceleration does not result in wheel slippage (i.e. a detectable difference in RPM for the two drive shafts), then LSD should not be kicking in. ASC might have an impact depending on what other data the system is measuring, then UTDS steer might be mitigated by a software modification.

As a soon to be owner, I can't yet test this for myself. Am I off base?

 

Wikipedia to the rescue - good description there of torque steer and causes. So, if it pulls to the left, must be better torque delivery to the right side.

 

Here's some useful information relating contact patch, scrub radius, etc to torque steer.

http://www.sportcompactcarweb.com/ed...ble/index.html

http://www.sportcompactcarweb.com/ed...hno/index.html

-JL

 

Got nothing better to do while waiting for my car, so I started to think about this again...

From Wikipedia:

Root causes for Torque Steer are:
Nonsymmetric driveshaft angles, e.g. due to
Nonsymmetric design of the vehicle, e.g. different driveshaft length
Transient movement of the engine
Tolerances in engine mounts
Different driveshaft torques left to right
Suspension geometry tolerances
Unequal traction forces due to road surface (µ-Split) in combination with Kingpin Offset
The open differential cannot fairly distribute torque between the two driveshafts, the power may be transmitted to only one driveshaft


Now the question I have is, some of these can either be designed out of the car (mitigate asymmetric driveshafts by beefing up the longer one) while the others are rooted in the tolerances of the car. If the later, then otherwise identical cars would have differing amounts of torque steer due to differences in their individual tolerances. Does anyone know if this is the case?