[tomtom11]

hello. i have a 335xi and i dont know how to solve this issue. i dont know if this is considered understeer or not. i know understeer would be like going 40mph and going around a sharp bend and the car just goes straight because the tail wont slide out. but what about when your not trying to powerslide or anything and the car just feels like its not very planted around bends on the highway? if i take a slight turn on the parkway the car feels like its wants to go straight instead of turn is that understeer even if i'm not trying to get the back to swing out? i have a staggered setup would this be fixed if i get a square setup? or is this not understeer and instead i should just get like a sway bar and m3 subframe bushings? i already have coilovers so that wouldnt be a solution. thanks guys.

[michaelalex17]

i have the exact same issue in my XI. people say a square setup helps reduce understeer but i dont know if that is only when you are trying to get the rear to slide out. at highway speed i'm obviously not trying to get the rear to swing out but around bends it feels like the car rather go straight. i dont know if a square setup would help that or not.

[tofu-]

front camber makes the biggest difference as well non-staggered tires

[michaelalex17]

Originally Posted by tofu-

front camber makes the biggest difference as well non-staggered tires

when you say as well as do you mean at the same time or going non-staggered helps. when you say camber, can i just make the car set to the most neg camber, i think its around -1. is that enough?

[achien]

use the cheapest solution first to see if it helps:

increase your front tires' pressure.

Originally Posted by tomtom11

hello. i have a 335xi and i dont know how to solve this issue. i dont know if this is considered understeer or not. i know understeer would be like going 40mph and going around a sharp bend and the car just goes straight because the tail wont slide out. but what about when your not trying to powerslide or anything and the car just feels like its not very planted around bends on the highway? if i take a slight turn on the parkway the car feels like its wants to go straight instead of turn is that understeer even if i'm not trying to get the back to swing out? i have a staggered setup would this be fixed if i get a square setup? or is this not understeer and instead i should just get like a sway bar and m3 subframe bushings? i already have coilovers so that wouldnt be a solution. thanks guys.

[michaelalex17]

Originally Posted by achien

use the cheapest solution first to see if it helps:

increase your front tires' pressure.

already did that.

[achien]

you can try softening the springs on the front suspensions, lessen the stiffness of the front sway-bars, or increase the negative cambers on the front tires, but the most effective way (probably the more expensive option) is to increase the width of both front tires or use "softer" front tires than the rear tires.

Originally Posted by michaelalex17

already did that.

[Doyle]

achien: Just stop. You're spreading around alot of wrong information without knowing more.

OP: Oversteer is defined as the car's drive angle being less than the car's steering angle. If you were actually experiencing understeer on the highway, then you REALLY need to slow down. If you are within the speed limits than you are not likely experiencing understeer.

Most likely you are experiencing alot of body roll. As the car turns, and inertia wants the body to continue straight, a loose suspension can be felt as "leaving you behind" after you turn.

Nobody here can give you advice without knowing more about your car. Coilovers, alignment, sway bars, wheel/tire size, tire pressures, etc...

[therealm3]

Originally Posted by Doyle

achien: Just stop. You're spreading around alot of wrong information without knowing more.

OP: Oversteer is defined as the car's drive angle being less than the car's steering angle. If you were actually experiencing understeer on the highway, then you REALLY need to slow down. If you are within the speed limits than you are not likely experiencing understeer.

Most likely you are experiencing alot of body roll. As the car turns, and inertia wants the body to continue straight, a loose suspension can be felt as "leaving you behind" after you turn.

Nobody here can give you advice without knowing more about your car. Coilovers, alignment, sway bars, wheel/tire size, tire pressures, etc...

+1

OP - before spending any more money on parts I would suggest finding your local CCA chapter calendar of events and sign up for the next Car Control Clinic or Street Survival school. Only after learning a bit more about vehicle dynamics and what it is like to actually push your car can you make an informed decision on a true handling upgrade.

[AWD Addict]

Originally Posted by achien

use the cheapest solution first to see if it helps:

increase your front tires' pressure.

That's actually backwards. You'll want to run 4-5lbs more in the rears than the front tires. Even with my staggered setup (265 rears, 235 fronts) this has the car pretty close to neutral. I run 32lbs front, and 36lbs rear.

With a square setup (or at least not dramatically staggered) and moderate tire pressure adjustment, you should be in pretty good shape on the xi.

If you're looking to go even further, the next step is a stiffer rear sway bar. The goal shouldn't be a lot of oversteer any more than you should be seeking a lot of understeer. The goal should be a very neutral, predictable condition when the tires break loose.

You should, of course, not be breaking loose your tires on public roads.

[jcarv20s]

"That's actually backwards. You'll want to run 4-5lbs more in the rears than the front tires. Even with my staggered setup (265 rears, 235 fronts) this has the car pretty close to neutral. I run 32lbs front, and 36lbs rear.

With a square setup (or at least not dramatically staggered) and moderate tire pressure adjustment, you should be in pretty good shape on the xi.

If you're looking to go even further, the next step is a stiffer rear sway bar. The goal shouldn't be a lot of oversteer any more than you should be seeking a lot of understeer. The goal should be a very neutral, predictable condition when the tires break loose.

You should, of course, not be breaking loose your tires on public roads."

AWD Addict,

I just purchased nearly the same vechile as you options, year and everything (minus exterior color). Are you running the 235/265 setup on your 189's or are you running that on your 19's? I wanted to get rid of the RFT's and was wondering if I could run that size on the 189's (mostly concerned with rubbing). I'm using stock suspension and probably will be for a while until I decide on some coilovers but won't be slamming the car since CT roads blow.

[achien]

"Understeer, a problem that mainly affects front-wheel drive cars, occurs when the driver turns the wheel but the car keeps going straight or does not turn as expected. This is usually caused by the driver trying to take the corner too fast, but there are ways of correcting it by simply adjusting the tire pressure."

Read more: How to Reduce Understeer | eHow.com http://www.ehow.com/how_7890016_redu...#ixzz1tAU0lhm3

http://www.ehow.com/how_7890016_redu...-pressure.html

http://homepage.ntlworld.com/terry.c.../handling.html

Originally Posted by Doyle

achien: Just stop. You're spreading around alot of wrong information without knowing more.

OP: Oversteer is defined as the car's drive angle being less than the car's steering angle. If you were actually experiencing understeer on the highway, then you REALLY need to slow down. If you are within the speed limits than you are not likely experiencing understeer.

Most likely you are experiencing alot of body roll. As the car turns, and inertia wants the body to continue straight, a loose suspension can be felt as "leaving you behind" after you turn.

Nobody here can give you advice without knowing more about your car. Coilovers, alignment, sway bars, wheel/tire size, tire pressures, etc...

Originally Posted by AWD Addict

That's actually backwards. You'll want to run 4-5lbs more in the rears than the front tires. Even with my staggered setup (265 rears, 235 fronts) this has the car pretty close to neutral. I run 32lbs front, and 36lbs rear.

With a square setup (or at least not dramatically staggered) and moderate tire pressure adjustment, you should be in pretty good shape on the xi.

If you're looking to go even further, the next step is a stiffer rear sway bar. The goal shouldn't be a lot of oversteer any more than you should be seeking a lot of understeer. The goal should be a very neutral, predictable condition when the tires break loose.

You should, of course, not be breaking loose your tires on public roads.

[Doyle]

Originally Posted by achien

"Understeer, a problem that mainly affects front-wheel drive cars, occurs when the driver turns the wheel but the car keeps going straight or does not turn as expected. This is usually caused by the driver trying to take the corner too fast, but there are ways of correcting it by simply adjusting the tire pressure."

Read more: How to Reduce Understeer | eHow.com http://www.ehow.com/how_7890016_redu...#ixzz1tAU0lhm3

http://www.ehow.com/how_7890016_redu...-pressure.html

http://homepage.ntlworld.com/terry.c.../handling.html

Your definition of understeer is correct.

Tire pressure: The "ehow" contributor is dead wrong. Under/oversteer is all about the relationship between the car's weight transfer and how that effects grip front v. rear. Grip is determined by the tire's contact patch. Increasing PSI reduces contact patch. Think about the concept of "pounds per square inch". The idea is to maximize tread use accross the tire by adjusting tire pressure. If the OP is running 40psi hot, then increasing the tire pressure makes the situation worse. I have a thread here about optimal tire pressures.

Suspension set-up: Making the assumption (dangerous) that the OP has coilovers that run a soft rate, why would you want to add body roll and thus exaggerate the weight transfer? The last thing a MacStrut front suspension needs is additional roll and weight transfer in the front. Adding negative camber is correct.

Tires: Mixing tires is a direction that someone who can't identify understeer does not want to go. Squaring the tires corrects understeer for only one portion of a corner. Do you know what portion of the corner the OP experiences understeer?

However, first and foremost the OP needs to learn to identify what understeer is, how/why/where it occurs, and how to correct the driver's inputs in order to correct it.

[achien]

Try reducing your front tire pressure down to 20 lbs and see how loud it screams when you corner (and how much under-steer you will have).

A large contact patch will do nothing for you if your tire pressure doesn't hold up. if you need a large contact patch, use wider front tires instead, not decrease the tire pressure on the front tires.

There is nothing we can do about the weight transfer of the vehicle (other than removing non-essential items like seats, carpets, radio, or air-conditioner) because the chassis is designed this way.

OP is asking for opinions on the forum because he doesn't want to spend thousands of dollars asking for advice from a local tuning shop. If we just tell him to go to a local tuning shop for advice, he could have skipped this forum and save himself time.

Originally Posted by Doyle

Your definition of understeer is correct.

Tire pressure: The "ehow" contributor is dead wrong. Under/oversteer is all about the relationship between the car's weight transfer and how that effects grip front v. rear. Grip is determined by the tire's contact patch. Increasing PSI reduces contact patch. Think about the concept of "pounds per square inch". The idea is to maximize tread use accross the tire by adjusting tire pressure. If the OP is running 40psi hot, then increasing the tire pressure makes the situation worse. I have a thread here about optimal tire pressures.

Suspension set-up: Making the assumption (dangerous) that the OP has coilovers that run a soft rate, why would you want to add body roll and thus exaggerate the weight transfer? The last thing a MacStrut front suspension needs is additional roll and weight transfer in the front. Adding negative camber is correct.

Tires: Mixing tires is a direction that someone who can't identify understeer does not want to go. Squaring the tires corrects understeer for only one portion of a corner. Do you know what portion of the corner the OP experiences understeer?

However, first and foremost the OP needs to learn to identify what understeer is, how/why/where it occurs, and how to correct the driver's inputs in order to correct it.

[Doyle]

Originally Posted by achien

Try reducing your front tire pressure down to 20 lbs and see how loud it screams when you corner (and how much under-steer you will have).

A large contact patch will do nothing for you if your tire pressure doesn't hold up. if you need a large contact patch, use wider front tires instead, not decrease the tire pressure on the front tires.

There is nothing we can do about the weight transfer of the vehicle (other than removing non-essential items like seats, carpets, radio, or air-conditioner) because the chassis is designed this way.

OP is asking for opinions on the forum because he doesn't want to spend thousands of dollars asking for advice from a local tuning shop. If we just tell him to go to a local tuning shop for advice, he could have skipped this forum and save himself time.

Did you read my thread on optimal tire pressures? Show me where I told the OP to drop his front tire pressure. I essentially said "it depends". I didn't provide specific advise because I don't know more info. OP may be running 20psi or he may be running 40psi. My point was that blindly giving generalized answers is wrong.

There is absolutely something we can do about weight transfer: we can slow/shorten it or decrease it. Slow it through increased spring rates and sway bar rates. You can decrease it by widening track, or decreasing the lever between the roll center and center of gravity. Or, the OP can learn that slow in fast out is the best way around a turn and decrease the weight transfer that way. Also, increasing the amount of roll up front, increases the distance that the weight is transfered. This is multiplied by the lever arm between the CoG and roll center, and then dramatically deteriorates the front suspension geometery. This increases understeer with MacStrut front suspensions.

I didn't send him to a tuning shop. I advised him to go learn how to control his car. BMWCCA, SCCA, street survival, local tracks, etc. My last track day cost $180. That will do more good than either asking random people that have never seen/driven his car what to do.

I also just realized that this thread is like a primer on logical fallacies: red herring, false authority, non-sequitor, straw man, hasty generalization, affirming the consequent, etc... Take note, this is not how you should establish an argument!

[monkey_wrench]

Take some performance driving courses. It will teach you how to drive and take turns properly.
After that's said and done, and you still have an understeer problem, I'd look into the car.

[AWD Addict]

Originally Posted by jcarv20s

AWD Addict,

I just purchased nearly the same vechile as you options, year and everything (minus exterior color). Are you running the 235/265 setup on your 189's or are you running that on your 19's? I wanted to get rid of the RFT's and was wondering if I could run that size on the 189's (mostly concerned with rubbing). I'm using stock suspension and probably will be for a while until I decide on some coilovers but won't be slamming the car since CT roads blow.

That's my summer tire setup (19"). I'm running a 225 width setup front and rear with my winters for better snow performance. Those won't work on your 18" winters.

[AWD Addict]

achien, no offense, but I think you should stop advising people on this matter.