Question Of Understeer.

[leftone]

Ive noticed that my 04 325i has some pretty substantial understeer in certain situationions which leads me to question the whol 50/50 weight balance thing. If the wieght was 50 50 at stand sitll that means in motion that it would be off by lets say 46 54 meaning when heading into a turn the that front end is lighter, and heavier if braking into the turn. Just curious if preloading the wieght to counter the effects of shifting would help in understeer? any thoughts?

[Gulelin]

BMW builds understeer into the suspension setup, because it's safer for the average person. You can probably get throttle induced oversteer if you really want to with a RWD set-up, which is why they set it up that way.

[leftone]

understeer is more dangerous i would think? turning the wheel when trying to avoid something but the car still going straight..... am i right?

[Trigati]

Originally posted by leftone@Oct 6 2004, 11:47 AM
understeer is more dangerous i would think? turning the wheel when trying to avoid something but the car still going straight..... am i right?

[snapback]206036[/snapback]

To be honest I believe Oversteer is more dangerous to the average driver. This uses the premis that the 'average' driver will usually brake as a first reaction to anything.

When understeering a modern car (ABS, even brake load), a stab on the brakes not only brushes off a bit of the excess speed but also help shifts weight forward, increasing front end grip. These immediatly reduce the understeer and help you to turn and miss that 'something'.

When oversteering a dab at the brakes causes the oversteer to increase (if the car oversteers only fractionally this doesn't happen, the brakes scrub speed enough for the rear end to regain traction - we are talking Real Oversteer here). Over steer can often be described as the rear trying to overtake the front, and decelerating the front even more....
So to correct oversteer you should turn into the direction of the skid (usually the opposite way to the turn than caused the departure from normal driving).



The reason this is less safe for the average driver (above the fact most drivers brake first, think later) is that the right amount of steering is essential. Not enough and the oversteer will continue until it reaches the point of no return, and you're going backwards. Too much and you'll over correct and end up oversteering the other way. If you really get this wrong you'll swing back and forth, travelling in a wavy line straight, until you hit 'something', spin or scrub all your speed off.

Another point with oversteer, which is far more grey and open to opinion, is how much throttle to apply. In a front wheel drive, floor it. With a real wheel drive it is far harder to judge. You need enough to keep the car stable, but not so much that the oversteer effect continues.

Anyway....I'll leave it here with the following disclaimer..."This is just how I understand it, I may be wrong and welcome any correction. Most importanly don't try this based on my advice, please don't try to prove this, I would hate it not to work!!!"

Mine's a Guiness...

[leftone]

thanks for the info, it just a little frustrating when im taking a turn at higher than normal speeds and the car doesnt want to go with me in the direction i have the front wheels pointed. but thanx for the info very informative