[ERVJOHNS]

This is my first post here on E90post. I just picked up a new 335i xdrive with Msport. My first step was to ditch the RFTs and install Michelin Pilot Sport A/S on staggered 18" wheels.

My installer suggested 32psi front and 33psi rear, so I don't know if that is optimum, anybody have any suggestions?

The tires made a huge difference but the car is "floating" and it is driving me nuts.

I have read all of the suspension related threads and I think my options come down to this:

Springs and shocks: Had a good experience with Koni/Eibach on a 2000 Audi A6 that had the same condition, but I don't want to lower the car too much. Bilstein/Eibach also a possibility

Coilovers: Is this overkill? Height adjustability would be nice to control the amount of drop. Any suggestions for the best coilover for the xDrive?

Thanks for any insight you can provide, and please bear with me if this has already been asked and answered.

[MassBimmer]

Def one of the most covered topics..

You can go with H&R Sport Springs on stock shocks/struts (I went this route and am very happy); you could couple the H&R Sport Springs with Bilstein shocks or you could go with H&R or KW V1 / V3 coilovers

There is also the Dinan suspension upgrades (stages 1,2,3) for the 335xi

[pits200]

The Kws have a market for the xi when it comes to coilovers.

Im waiting for the ASTs to come out for the xi. I heard this may be happening around the new year.

Comparing the ASTs to the KWs isn't really a contest in my book.

[fdriller9]

Recommended tire pressures are on your driver's side door jamb.
For my E90 xi it is F:32psi, R:36psi

Springs and shocks will definitely help with the body roll, removing most of the feeling. For a daily driver, I think this will be enough.

One bit of information I have picked up about shocks is that Koni FSDs tend to over/under-react to different driving conditions. I've heard the Koni yellows are much better than the FSDs.

Coilovers are nice for track setups and are usually overkill for the street. However they do have their advantages. You obviously bought an xi so you can drive it in the snow. The reason you get the floaty feeling is because of the higher suspension...there are a number of other things that contribute to it as well.

With coilovers you can lower your car in the spring/summer/fall and raise it for winter without swapping the whole suspension. Obviously you can't do this with a shock/spring setup.

It really boils down to what you intend on using your car for....

[MassBimmer]

^^ None of the Koni's are available for xi's...Bilstein Sports are the only shock/strut available

[Dark_Knight_335]

Swaybars, swaybars... oh, and did I mention swaybars? Most UNDERRATED and most VALUABLE mod. EVER.

[forza1976]

Originally Posted by SDeFranco1

Swaybars, swaybars... oh, and did I mention swaybars? Most UNDERRATED and most VALUABLE mod. EVER.

Maybe only a rear sway upgrade. Too much up front would promote even more understeer. I'd stay away from a front sway upgrade, IMO...

[joed1]

Welcome and congratulations!

[Dark_Knight_335]

Originally Posted by forza1976

Maybe only a rear sway upgrade. Too much up front would promote even more understeer. I'd stay away from a front sway upgrade, IMO...

Shit..really? I ordered both already. Is the front and rear swaybar different structurally? Please let me know

[forza1976]

Originally Posted by SDeFranco1

Shit..really? I ordered both already. Is the front and rear swaybar different structurally? Please let me know

So I'm not suspension expert, just wanted to say that. But the nature of the XI is to understeer due to the higher weight up front and of course the AWD.

Upgrading the sway up front will just increase that a bit due to the stiffer bar and much more planted front. Probably won't be bad, just might enhance the understeer a bit. It's good you got the rear too.

To be honest, I reduced my understeer some extent by going with 245/40 tires all around. I removed the stagger to reduce some rear grip to attempt to reduce the understeer.

Suspension will for sure reduce the OP's body roll but a combination of sways and suspension would likely be a very sweet setup.

Didn't mean to alarm you

[Dark_Knight_335]

Heh, no worries. Just my first time branching out into swaybar territory and didn't know if both swaybars were overkill or advantageous Seemed logical, two axles, two swaybars. But then, with tuning, logic isn't always one's best friend.

[ERVJOHNS]

Thanks for all the good info, I appreciate it!

Sounds like doing the rear sway bar might be the best way to start

[MJR63]

Good news! AST 4100 coilovers are available via custom order through HP Autowerks for xi and x-drive vehicles!

After tons of research I decided to go with the AST 4100's once I found out they were available for xi/x-drive. I have a 2011 BMW 335i x-drive sedan. It is a custom order and takes 4 - 6 weeks but AST is building these by hand. I worked with Harold at HP Autowerks on this order. He is very knowledgeable on BMW suspensions and helped me build a custom setup. Once he gets the custom AST 4100's he is going to match them with custom swift springs. Harold thought I should go with 336lbs springs in the front and 672lbs in the rear. The stock 335 has 145lbs front and 460lbs rear. I could have went with 400lbs in the front and 784lbs in the rear but those are more for the guys who track there car. I just want crisp handling for spirited driving!

I was considering going with KW V1's or V3's but hear they squeak and have other problems. I was also considering the H&R coilovers but hear they have rusting problems.

Here is a great review of the AST's on a non x-drive 335i:

http://www.e90post.com/forums/showth...light=AST+4100

Link to AST Site:
http://www.ast-usa.com/ast_testing_facilities.php

Link to HP Autowerks:
http://www.hpashop.com/main.sc;jsess...D.qscstrfrnt05

Thanks!

Mark

[Professor///M]

Originally Posted by ERVJOHNS

My installer suggested 32psi front and 33psi rear, so I don't know if that is optimum, anybody have any suggestions?

Check out the manual, it has different specs for each tire for the weight of your vehicle & size of the rim.


My summers are 36/41, my winters are 33/41.

I'd double check those numbers, sounds low. I haven't seen much under 34 in our cars

[ajsalida]

Originally Posted by MJR63

Good news! AST 4100 coilovers are available via custom order through HP Autowerks for xi and x-drive vehicles!

After tons of research I decided to go with the AST 4100's once I found out they were available for xi/x-drive. I have a 2011 BMW 335i x-drive sedan. It is a custom order and takes 4 - 6 weeks but AST is building these by hand. I worked with Harold at HP Autowerks on this order. He is very knowledgeable on BMW suspensions and helped me build a custom setup. Once he gets the custom AST 4100's he is going to match them with custom swift springs. Harold thought I should go with 336lbs springs in the front and 672lbs in the rear. The stock 335 has 145lbs front and 460lbs rear. I could have went with 400lbs in the front and 784lbs in the rear but those are more for the guys who track there car. I just want crisp handling for spirited driving!

I was considering going with KW V1's or V3's but hear they squeak and have other problems. I was also considering the H&R coilovers but hear they have rusting problems.

Here is a great review of the AST's on a non x-drive 335i:

http://www.e90post.com/forums/showth...light=AST+4100

Link to AST Site:
http://www.ast-usa.com/ast_testing_facilities.php

Link to HP Autowerks:
http://www.hpashop.com/main.sc;jsess...D.qscstrfrnt05

Thanks!

Mark

Good to know. I was lusting over AST 4100/4200 kits the other day and dismayed no XI versions. Some good pics here:

4100

http://www.elephantmotorsports.com/b...kit-p-576.html

4200

http://www.elephantmotorsports.com/b...kit-p-577.html

[ERVJOHNS]

Does pressure vary for RFT vs non RFT or would it be the same?

Also, what is the best rear sway bar to go with? I don't track the car, just want a less body roll, as I said in my original post. Also good to know about the AST solution.

Thanks

[MeeTsenPu]

Originally Posted by PAMidge

Check out the manual, it has different specs for each tire for the weight of your vehicle & size of the rim.


My summers are 36/41, my winters are 33/41.

I'd double check those numbers, sounds low. I haven't seen much under 34 in our cars

36/41 is what I run on my summers which are Non-RFT. Cant go by the door jam since the sidewalls aren't as stiff as the RFT. My winter tires are the stock all season RFT and I use whatever is on the door jam.

BTW I have Eibach springs and Bilstein sport shocks, great combination!

[IN54NITY]

Originally Posted by MJR63

Good news! AST 4100 coilovers are available via custom order through HP Autowerks for xi and x-drive vehicles!

....

http://www.e90post.com/forums/showth...light=AST+4100

Link to AST Site:
http://www.ast-usa.com/ast_testing_facilities.php

Link to HP Autowerks:

http://www.hpashop.com/main.sc;jsess...D.qscstrfrnt05

Thanks, and well done. Hopefully someday this ~doesn't~ have to be a custom order. We all expect a review Mark.

>I'd stay away from a front sway upgrade, IMO...

+1, but I guess you can always try it.

On a side note, I know a local buddy SCCA racer who consistently got ~slower~ lap times when he added a stiffer rear sway to his RWD car. He just wasn't getting the same grip. He took them off, and his lap times dropped again to his norm. My point is they aren't necessarily a good thing for your style of driving and/or car.

[ajsalida]

Also the XI rear bar is already much larger than the RWD-only version if I am not mistaken. And don't you have to drop the rear subframe to swap bars anyway?

[Doyle]

Originally Posted by SDeFranco1

Can anyone confirm this? Should I just not put the effin swaybars on at all?

Damn shit's gettin complicated

It depends on the suspension set up you are running.

It seems the advice that makes the most sense to me is adding the M3 sway bushings to the front bar and then adding the M3 rear bar.

But this only works if the spring rates, alignment, and wheel choice support this.

[Dark_Knight_335]

Thanks man. There are always some great level headed minds in this forum to bring the rest of us to our senses

[MJR63]

I actually had the UUC front and rear sway bars on order but after speaking with Harold at HP Autowerks I canceled the order. With the AST 4100 coilovers he said almost all the body roll will be eliminated. He said sometimes he actually has to remove after market sway bars to get to car to handle correctly.