[NiNeTyOne]

Originally Posted by Julian2485

What's the spring rate for the ers ?

Personally I would up them by 12-15% for a pure street application and have Ben at PSI adjust the dampers to match. When you get a R&T setup form them you get custom valving unless you choose not to (and take an additional discount). If you up the rates, you'll probably want to tweak it.

If I was using it on track I'd up the rates a lot more, but I'd want to consult with Ben @PSI on that after some other tweaks, like further tightening of the subframes w/delrin, beefing up the bar mounts, considering my tire choice/width, etc. It all factors. I'm on 225's for street use and I'd want more rubber on track, maybe 235 or 245.. I'd need to figure out where the weight of the larger wheel/tire hurt braking/acceleration and made any larger a losing proposition given the limited HP.

[Julian2485]

Originally Posted by NiNeTyOne

Personally I would up them by 12-15% for a pure street application and have Ben at PSI adjust the dampers to match. When you get a R&T setup form them you get custom valving unless you choose not to (and take an additional discount). If you up the rates, you'll probably want to tweak it.

If I was using it on track I'd up the rates a lot more, but I'd want to consult with Ben @PSI on that after some other tweaks, like further tightening of the subframes w/delrin, beefing up the bar mounts, considering my tire choice/width, etc. It all factors. I'm on 225's for street use and I'd want more rubber on track, maybe 235 or 245.. I'd need to figure out where the weight of the larger wheel/tire hurt braking/acceleration and made any larger a losing proposition given the limited HP.

I'll contact Ben@psi for more info right now the car handles ok with m3 rsb and rear swaybar and sonic tuning coilovers. Eventually I will get aluminum rsb though and get custom springs for my coilovers. I'll honestly probably go with swift custom springs. Right now i have my front dampers at 22 clicks to stiff and rear 24 clicks to stiff. 24 is the stiffest

[NiNeTyOne]

Originally Posted by Julian2485

I'll contact Ben@psi for more info right now the car handles ok with m3 rsb and rear swaybar and sonic tuning coilovers. Eventually I will get aluminum rsb though and get custom springs for my coilovers. I'll honestly probably go with swift custom springs. Right now i have my front dampers at 22 clicks to stiff and rear 24 clicks to stiff. 24 is the stiffest

My co driver and I were light years apart on preferred damper setups, but we were within a fraction of a sec on lap times. So settings are a personal thing.

How many clicks people have on this or that is so irrelevant it's almost laughable.

When were your dampers last re-valved, what was the temp when you drove what track, where, last? (my ideal high speed rebound settings were 2 clicks different from am to mid-day when the temps rose at Daytona, but I could drive around it within a tenth). My VIR settings bear no resemblance to my Road A settings which are wildly different from my Atlanta setup. Where do you live? What season is it? How good of a driver are you? What are your spring rates? What's your chassis setup? Is it wet or dry? Are the roads shit? Come on..

I've been on Swift, Hyperco and Eibach. I like the Hyperco carbon bellows, but for steel springs, the Eibachs remain my fav. For most drivers the difference will be indistinguishable.

Most any pro driver will tell you their favorite spring is from the manufacturer who pays them sponsorship money. I like the ERS series, but it's mostly because of familiarity across the various rates, and the fact I've never had one fail. Can't say that for H&R.

[NiNeTyOne]

Originally Posted by Julian2485

What's the spring rate for the ers ?

Same, however the springs are different diameter and use a different perch so you can't just swap them out for your OE springs as you can the Pro springs. ERS are flattened at the end of the coil for use with more traditional coilover applications.

Eibach ERS Link

They are available in 50# rate steps. You'd select the rate based on the damper choice and your car. E90, 91, 92 xDrive or RWD would likely all be different as the weight distribution on each car is different.

The rates for the e91 xDrive Sportwagon were what I gave above, but those are rate matched to the FSD and it appears also the Bilstein B8 damper (which is what makes up the B12 kit from what I can see).

If you were running a different shock, say the Ohlins R&T DFV's, then you could probably up the rates by a fair bit due to the increased performance of the damper. I found going to the better Ohlins setup on another car allowed me to up the rate by almost 100# from previous springs (on lesser shocks) without any sacrifice in comfort, and a big step up in handling/response/grip. On the lesser shocks it would have been way over-sprung.

Using the ERS springs on shocks like the FSD and B8 would require custom perches.

[NiNeTyOne]

Originally Posted by Julian2485

What's the spring rate for the ers ?

Talking to the Ohlins engineer in Sweden today it became clear that the numbers that Eibach is quoting for the Pro rate on the front is just wrong, and is likely in the high 300's. We're gunna talk to the Eibach guys in Germany to get some straight info on the front rates.

I'll get the ERS rates tomorrow, that's easy to get. Nice thing about those springs is they come in 50# steps. My guess is high 300's up front and high 400's rear. Will let you know what they say.

[TEC]

Has anyone tried double adjustable Koni yellows on the xdrives? This use to be the go to shock for daily/autocross/track setups.

[NiNeTyOne]

343 Front 400 Rear on the Ohlins road and track

[Taskmaster]

Originally Posted by TEC

Has anyone tried double adjustable Koni yellows on the xdrives? This use to be the go to shock for daily/autocross/track setups.

Ask ajsalida

[NiNeTyOne]

Originally Posted by E30_335i

I don't track a Xi, but the chassis is not that different than mine. Save the money on coilovers, they do no good on track. Heavy sway bars ruin the handling too. A bigger front bar, Bilstein B6 shocks, and the M3 control arm upgrade and you will be good to go. Braking is always a problem till you move to a big brake system. The OEM calipers just can't take the heat.

A bigger front bar, because surely, these cars don't understeer enough as it is.

#facepalm

[boro92]

+1 no bigger front bar needed.
Maybe on E30s, E36s this was relevant.
With E90, because the lower knuckle has 2 ball joints, it means the actual pivot point of the knuckle is out in space (read - lower pivot point is farther away), yielding a more desirable camber curve - despite the thing being a strut car.


I detail out what the car needs in a blog post. I too have spent considerable time on setup (less on parts - but more on setup!) to make the xdrive work. Apart from coding the thing so that the awd system does not get in your way (read: bmw built in so much safety crap into xdrive, brakes and rear ediff that even with full traction off, the computer is doing things to intervene - this applies to rwd cars as well). The biggest thing is loosening up the car. From factory, it's setup to be very safe--at the great expense of having a car that you can work with (read: manipulate as a driver).

You can't over lower the car - even beyond 1 inch. The rear toe is not as adjustable as desired and as a result, dropping the car (even on eibach prokits) will yield rear toe-in at levels that really lock the rear axle down. Great for street, great for confidence but not great if you're trying to set the car up to freely rotate based on driver inputs.

So depending on ride height, you will need to get rear toe-links to keep that in check. Front camber plates - ideally one that is not bushing based. There's too much deflection in the front rubber shock mounts that even if you remove the alignment pins and get some camber, the front end washes out very early no matter what you do. Take that deflection out, and you will have a car with much higher grip limits on the front axle.

From an alignment perspective, that's going to boil down to how you want the car to drive...but the big things on xdrive are - keeping alignment in check, removing front end deflection and playing with rear roll stiffness.

Regarding swaybars, NinetyOne has it down 100% right. Actually, even on *stock* xdrive swaybars, I am lifting up the inside rear tire on every corner at a local circuit - this is with trail braking of course. Putting a rear bar is just going to make this happen sooner (read: rotation can begin earlier)....so consider that as well - and if that fits your driving style. Detailed musings on the topic here: http://dreamingin302ci.blogspot.ca/2...ve-handle.html

[NiNeTyOne]

Originally Posted by boro92

+1 no bigger front bar needed.
Maybe on E30s, E36s this was relevant.
With E90, because the lower knuckle has 2 ball joints, it means the actual pivot point of the knuckle is out in space (read - lower pivot point is farther away), yielding a more desirable camber curve - despite the thing being a strut car.


I detail out what the car needs in a blog post. I too have spent considerable time on setup (less on parts - but more on setup!) to make the xdrive work. Apart from coding the thing so that the awd system does not get in your way (read: bmw built in so much safety crap into xdrive, brakes and rear ediff that even with full traction off, the computer is doing things to intervene - this applies to rwd cars as well). The biggest thing is loosening up the car. From factory, it's setup to be very safe--at the great expense of having a car that you can work with (read: manipulate as a driver).

You can't over lower the car - even beyond 1 inch. The rear toe is not as adjustable as desired and as a result, dropping the car (even on eibach prokits) will yield rear toe-in at levels that really lock the rear axle down. Great for street, great for confidence but not great if you're trying to set the car up to freely rotate based on driver inputs.

So depending on ride height, you will need to get rear toe-links to keep that in check. Front camber plates - ideally one that is not bushing based. There's too much deflection in the front rubber shock mounts that even if you remove the alignment pins and get some camber, the front end washes out very early no matter what you do. Take that deflection out, and you will have a car with much higher grip limits on the front axle.

From an alignment perspective, that's going to boil down to how you want the car to drive...but the big things on xdrive are - keeping alignment in check, removing front end deflection and playing with rear roll stiffness.

Regarding swaybars, NinetyOne has it down 100% right. Actually, even on *stock* xdrive swaybars, I am lifting up the inside rear tire on every corner at a local circuit - this is with trail braking of course. Putting a rear bar is just going to make this happen sooner (read: rotation can begin earlier)....so consider that as well - and if that fits your driving style. Detailed musings on the topic here: http://dreamingin302ci.blogspot.ca/2...ve-handle.html

FINALLY someone else speaking sensibly!

[TEC]

Well I'm going to kindly disagree.
I will say I havent had a chance yet to put my car on the track yet as winter still persists. Maybe I will change my mind after, but right now...
I put UUC front and rear sways on my car and in conjunction with the sealed monoball front arms the car now sticks, turns and feels the way I wish it had from the factory. Its a night and day difference.

[Julian2485]

My car was night and day once I installed m3 subframe bushings and m3 rear swaybar

[Jeff@TopGearSolutions]

My personal experience:

The addition of the Front Sway Bar upgrade from UUC was night and day. It not only reduced understeer but kept camber from going positive in the corners. This increased the contact patch in the corners, resulting in more grip.

On stock sway bars the car would understeer and push through the turns -tires would be squealing like pigs. Not only that but the car by no accident had less roll in the front, increasing confidence in the vehicle.

Again, my personal experience.

I know there are a lot of theories in this thread and some have some merit in other platforms and suspension geometry, however, On the E9X X drive chassis it begs for the FSB Upgrade.

If you haven't done it, try it before knocking it. It is the single best modifications I've done to this vehicle.

I understand the theory of larger/thicker FSB add "understeer" this is a very very broad remark that doesn't transfer over to every chassis.

[NiNeTyOne]

Originally Posted by Jeff@TopGearSolutions

My personal experience:

The addition of the Front Sway Bar upgrade from UUC was night and day. It not only reduced understeer but kept camber from going positive in the corners. This increased the contact patch in the corners, resulting in more grip.

On stock sway bars the car would understeer and push through the turns -tires would be squealing like pigs. Not only that but the car by no accident had less roll in the front, increasing confidence in the vehicle.

Again, my personal experience.

My personal experience turns 1:54's on the Daytona Road Course in a pre 991 Cup car. The idea that a front bar will loosen a cars handling is just pure nonsense.

I've been setting up racecars and cars for the track for nearly 25 years now.

You need to go buy the book "The Art & Science of Racecar Development & Tuning" by Carroll Smith and read it cover to cover a couple times, paying close attention to Chapter 6.

While you may think you feel something, your butt does not get to re-write the laws of physics. Front bars with higher rates add understeer, full stop.

[jwebb335xi]

Originally Posted by Julian2485

My car was night and day once I installed m3 subframe bushings and m3 rear swaybar

How long does it take to do the RSBs??

[B@man335]

Originally Posted by Jeff@TopGearSolutions

My personal experience:

The addition of the Front Sway Bar upgrade from UUC was night and day. It not only reduced understeer but kept camber from going positive in the corners. This increased the contact patch in the corners, resulting in more grip.

On stock sway bars the car would understeer and push through the turns -tires would be squealing like pigs. Not only that but the car by no accident had less roll in the front, increasing confidence in the vehicle.

Again, my personal experience.

I know there are a lot of theories in this thread and some have some merit in other platforms and suspension geometry, however, On the E9X X drive chassis it begs for the FSB Upgrade.

If you haven't done it, try it before knocking it. It is the single best modifications I've done to this vehicle.

I understand the theory of larger/thicker FSB add "understeer" this is a very very broad remark that doesn't transfer over to every chassis.

Jeff,
Did you also do RSB on the XI?

[miker2013]

Originally Posted by Julian2485

My car was night and day once I installed m3 subframe bushings and m3 rear swaybar

can you elaborate on effect of the bushings and rsb on your ride? do u have stock suspension on your xdrive?

[Julian2485]

Originally Posted by miker2013

can you elaborate on effect of the bushings and rsb on your ride? do u have stock suspension on your xdrive?

It helped stiffen the suspension. Then rear was no longer squirmy and helped the car stay flat on the road

[Julian2485]

Originally Posted by jwebb335xi

How long does it take to do the RSBs??

I had a shop do it

[B@man335]

Originally Posted by Julian2485

I had a shop do it

How much did that run you?

[Julian2485]

Originally Posted by B@man335

How much did that run you?

Around 400