Sway Bar Upgrade

[SlickGT1]

Originally Posted by hoaesq

Interesting take . . . thanks for sharing your experince. So my mods for my 05 4.4 will be limited to changing the front OEM struts to the Bilstein HD and loweing with the H&R springs for now. I'll hold off on the sways until I get a feel of the new suspension.

That's a good plan of attack. Get comfortable with the weight of the truck. Notice how it handles. If you think you need sways (you won't) then get them. Don't spend too much on them, because if you see how well you can trow the truck around without them, it will be scary with them.

I also recommend everyone get the rear sway only, for that over-steer effect.

Man, these trucks ride so stiff as is, I just can't imagine making it stiffer.

[PropellerHead]

Originally Posted by SlickGT1

Two reasons why I know sway bars, for street cars, are bullshit.

Wow. I've driven upgraded sways on my 1975 2002 for nearly 20 years. I drive it at the limit on the way to, during and back from Autocrosses. I've had them on my E39 for almost ten years. Adjustable in the rear, even. I even wrote about the differences in settings as I tried each one. It's real and it is up to the driver how he uses them. I drive my supercharged E39 the same way. Full tilt. And of course, on now two X5's for two years. I don't drive it as aggressively as the other two, but it's still closer to the limit than most people will push an X5.

I never once found them to be either dangerous or offset the balance of my cars. In fact, what they do is actually serve to balance the car over the engineered understeer. This is also why they added larger rear tires on most of the sport package cars. Instant under steer. Why do the BMW engineers design for understeer? Because they know people can't drive. They know that when Sally or Sammy gets in the sand as starts to feel the back end swing, they'll always do the wrong thing: lift the throttle.

What happens in a stock BMW is predictable. The rear end stops swinging around and Sally and Sammy feel resolved that their car saved them. In a way, it did.

On the other hand, if you DO know how to drive and you DONT lift when the back end swings around with your new sways, but you do the RIGHT thing: HAMMER the gas and let the throttle take you through the turn with appropriate steering input, you live. In fact, you just had FUN!

Upgraded sways serve to send LESS of the weight of your car from one side to the next. What that does is actually reduce the recoil of the spring- said another way, it adds balance to the possibility you can correct without over correcting and have a whole new problem on your hands- a spin and facing the wrong way.

The ride is more rough. Yes. That's what you pay. What you get in return is a more balanced car that behaves the way that YOU want it to. Not the way some litigation and cost avoiding pencil pushers in Bavaria say that it should.

[hoaesq]

hmm . . . both good points. Lump me in with Sally and Sam. I'm not too concern about ride quality. Any upgrade is going to give the vehicle a firmer ride. If I wanted a "softer" ride, I'd go with the stock sport suspension I have now.

Ultimately, it's a personal decision and somewhat safety issue as well (assuming I drive in snow and sand). My bad boy will only see the street so sways may be the next upgrade but for now I'm going with the firmer strust up front and lower springs and OEM for the rear since I can't seem to find any vendor that carries HD shocks that will work with the rear air suspension.

[JWMich]

Originally Posted by SlickGT1

Do you really think German engineers, the ones who designed your car, the millions invested in RND, don't you think they would have put in bigger bars if they could make the Ultimate driving machine more ultimate?

I'm surprised how much I hear this odd line of thinking around BMW forums - the BMW design gods have wrought the automotive version of the immaculate conception, they are perfect in every way, and you don't need...whatever it is. I just can't get on board, the logic doesn't hold up.

Every vehicle ever made is full of engineering compromises - even the product of German engineers. Nothing on any vehicle ever made is the best it can be. Every element in vehicle design trades off mass appeal against high performance, durability against cost, and a whole bunch more.

[SlickGT1]

Originally Posted by PropellerHead

Wow. I've driven upgraded sways on my 1975 2002 for nearly 20 years. I drive it at the limit on the way to, during and back from Autocrosses. I've had them on my E39 for almost ten years. Adjustable in the rear, even. I even wrote about the differences in settings as I tried each one. It's real and it is up to the driver how he uses them. I drive my supercharged E39 the same way. Full tilt. And of course, on now two X5's for two years. I don't drive it as aggressively as the other two, but it's still closer to the limit than most people will push an X5.

I never once found them to be either dangerous or offset the balance of my cars. In fact, what they do is actually serve to balance the car over the engineered understeer. This is also why they added larger rear tires on most of the sport package cars. Instant under steer. Why do the BMW engineers design for understeer? Because they know people can't drive. They know that when Sally or Sammy gets in the sand as starts to feel the back end swing, they'll always do the wrong thing: lift the throttle.

What happens in a stock BMW is predictable. The rear end stops swinging around and Sally and Sammy feel resolved that their car saved them. In a way, it did.

On the other hand, if you DO know how to drive and you DONT lift when the back end swings around with your new sways, but you do the RIGHT thing: HAMMER the gas and let the throttle take you through the turn with appropriate steering input, you live. In fact, you just had FUN!

Upgraded sways serve to send LESS of the weight of your car from one side to the next. What that does is actually reduce the recoil of the spring- said another way, it adds balance to the possibility you can correct without over correcting and have a whole new problem on your hands- a spin and facing the wrong way.

The ride is more rough. Yes. That's what you pay. What you get in return is a more balanced car that behaves the way that YOU want it to. Not the way some litigation and cost avoiding pencil pushers in Bavaria say that it should.

You are correct, but only because you know how to drive. At least that's what I am assuming because you too autocross and road race. Same here. But for the average X5 owner, this is not the case. I have seen some severe loss of control when "upgrading the sways".

Either way, if you think a 5k lbs truck can be the next lapping machine, go for it, just those that aren't experienced in loosing control, should take it easy in foul weather.

[SlickGT1]

Originally Posted by JWMich

I'm surprised how much I hear this odd line of thinking around BMW forums - the BMW design gods have wrought the automotive version of the immaculate conception, they are perfect in every way, and you don't need...whatever it is. I just can't get on board, the logic doesn't hold up.

Every vehicle ever made is a full of engineering compromises - even the product of German engineers. Nothing on any vehicle ever made is the best it can be. Every element in vehicle design trades off mass appeal against high performance, durability against cost, and a whole bunch more.

Yes compromises that balance the car for the average driver. Can the more advanced driver overcome those compromises before upgrading the sways? Yes you can, I for one know that I will never enlarge the sways on this car. There is too much negative, especially for me in NYC.

Once you upgrade the sways, I hope you also upgrade the tires. There is a reason track cars still stick to the road, with sways so thick and solid that you can't get any body roll.

[JWMich]

Originally Posted by SlickGT1

Yes compromises that balance the car for the average driver. Can the more advanced driver overcome those compromises before upgrading the sways? Yes you can, I for one know that I will never enlarge the sways on this car. There is too much negative, especially for me in NYC.

Once you upgrade the sways, I hope you also upgrade the tires. There is a reason track cars still stick to the road, with sways so thick and solid that you can't get any body roll.

Seems to me, then, that your last two posts contradict your original position - you're acknowledging that the engineers who designed my X5, with their millions in R&D, don't try to make their design decisions so the "ultimate driving machine" becomes more ultimate. Instead, they "balance" the car for the average driver and deliberately design in understeer, for example, to accommodate people who can't drive.

I think the actual info value in this thread is probably the idea to give thicker rears a try first and see whether that feels better than the designed-in understeer. Thanks for that. And FWIW, yeah, I've been around long enough to know better tires should come first - that OE design compromise sucked, too.

[Icer006]

Originally Posted by Turbo_Bimmer

Why do people change front and rear sway bars?
I mean, the X5 understeers, so installing a stiffer rear bar would help by inducing a bit of oversteer.
Going with 2 bigger bars would make the X stiffer, but the understeer would still be present.

I don't think you'd want to oversteer the X5 with such a high center of mass.

I agree with Slick, adding sway bars for a street car is useless.

[SlickGT1]

Originally Posted by JWMich

Seems to me, then, that your last two posts contradict your original position - you're acknowledging that the engineers who designed my X5, with their millions in R&D, don't try to make their design decisions so the "ultimate driving machine" becomes more ultimate. Instead, they "balance" the car for the average driver and deliberately design in understeer, for example, to accommodate people who can't drive.

I think the actual info value in this thread is probably the idea to give thicker rears a try first and see whether that feels better than the designed-in understeer. Thanks for that. And FWIW, yeah, I've been around long enough to know better tires should come first - that OE design compromise sucked, too.

Not sure how I'm contradicting. I still stand by the fact that a 5k lbs SAV, or most other street / family / daily driven cars, do not need a sway bar upgrade. Maybe if you are ballsy enough, roads around you are in excellent condition, and you know what you need to do when the rear end tries to overtake the front end, then give it a shot. Maybe it's what you want out of your sav.

My 06 4.8is, is more than capable around turns with the stock sways. I am actually staying away from putting on sticky summer tires due to the fear of me flipping the truck.

Maybe the logic in your guys cars is different from the 4.8is. Maybe that's why it handles bad, or seems to be bad.

[Bulk]

Great Post Slick and I totally agree about the sway bars but I also acknowledge that when the BMW engineers were designing the E53 they had the technology from 1997-1998 and when they do a facelift that's all it is, the guts of the X5 weren't changed until 2007. Technology is advancing daily, different compounds, alloys and engineering advances will always make an after market part better than it's older counterpart just because it's more modern, so I don't think you can write off an after market part just because the original engineers didn't do it.

My 5c