[michaelalex17]

i have a 335xi and wanted to reduce understeer. should i get a front and rear sway bar or just a rear? thanks

[michaelalex17]

anyone?

[Chrisred]

Originally Posted by michaelalex17

i have a 335xi and wanted to reduce understeer. should i get a front and rear sway bar or just a rear? thanks

Start by getting a good set of coils first. Then rear sway with upgraded bushings and if u track car get camber plates.

[michaelalex17]

Originally Posted by Chrisred

Start by getting a good set of coils first. Then rear sway with upgraded bushings and if u track car get camber plates.

i've got that already. i just want to know about upgrading the sway bars

[Chrisred]

Originally Posted by michaelalex17

i've got that already. i just want to know about upgrading the sway bars

Then rear....

[michaelalex17]

someone told me to replace both the front and rears. wouldnt that make my understeer the same as it is now? isnt the point to tighten the back to reduce understeer or am i misunderstanding?

[Doyle]

A sway bar does not equal a sway bar. They all have different rates. You first pick your spring rates, then you "balance" the chassis with the sway bars. You can't know what sway bars will balance the chassis when you don't know the spring rates or the sway bar rates.

Therefore, nobody is able to answer your question as it stands. We need spring rates and bar rates.

[michaelalex17]

Originally Posted by Doyle

A sway bar does not equal a sway bar. They all have different rates. You first pick your spring rates, then you "balance" the chassis with the sway bars. You can't know what sway bars will balance the chassis when you don't know the spring rates or the sway bar rates.

Therefore, nobody is able to answer your question as it stands. We need spring rates and bar rates.

i thought adding an aftermarket sway bar setup ragardless will reduce body roll? i dont understand what my particular rates have to do with anything but as i said before i have no idea about this stuff i have H&R sport springs if that helps with Bilstein sport shocks.

[Doyle]

You asked how to reduce understeer. Understeer =/= body roll. Roll is only a single factor in determining chassis balance. Even then, it is the relative front/rear roll, not overall body roll.

Unfortunately H&R don't advertise their spring rates, so it is a little hard to help you out. I would grab the e90 M3 rear bar and see how that feels.

[Lenaxia]

Originally Posted by michaelalex17

i thought adding an aftermarket sway bar setup ragardless will reduce body roll? i dont understand what my particular rates have to do with anything but as i said before i have no idea about this stuff i have H&R sport springs if that helps with Bilstein sport shocks.

There's a fairly large amount of resources and posts by Doyle and a few others which can be found throughout the XI forums. I learned everything I needed for understanding which sways and shocks I need. Perhaps you should look around a bit.

[michaelalex17]

http://www.e90post.com/forums/showth...light=sway+bar

i found this. as i thought before these people seem to think adding the front sway bar will continue my understeer problem where as the rear will reduce understeer

[4corners]

Originally Posted by michaelalex17

http://www.e90post.com/forums/showth...light=sway+bar

i found this. as i thought before these people seem to think adding the front sway bar will continue my understeer problem where as the rear will reduce understeer

The least expensive effective way to reduce understeer is to add a spacer, 10-15mm, in front. Not the back. Just try it. You'll be surprised.

[pits200]

Originally Posted by 4corners

The least expensive effective way to reduce understeer is to add a spacer, 10-15mm, in front. Not the back. Just try it. You'll be surprised.

This is a good way, but even simpler and the least expensive is to change the psi in the tires.

[michaelalex17]

these are the spacer options on BMS website. 10,12,15,18

i dont know if this helps decide what i should get but heres my rim and tire dimensions.
Tires
Front: 235/35/19
Rear: 265/30/19



Rims
Front: 19x8.5/ET-35
Rear: 19x9.5/ET-33


thank you guys for all your help

[michaelalex17]

the only thing is im concerned about the draw-backs of wheel spacers, such as increased wheel bearing wear.

[eitanshay]

wheel alignments used to work on other cars...

[4corners]

Originally Posted by michaelalex17

the only thing is im concerned about the draw-backs of wheel spacers, such as increased wheel bearing wear.

Nil, rumor, hearsay.

[michaelalex17]

i spoke to Mike at n54tuning and he told me that i should only get a rear sway bar and not a front. i will also look into spacers. can i ask the dealer to put those on when i change back to my summer wheels or is that something that would void warranty if something happens to like my bearings or something? thanks

[michaelalex17]

Alan at **********s told me this:

The of the major function of sway bars is to tune the handling balance of a car. Understeer or oversteer behavior can be tuned out by changing the proportion of the total roll stiffness that comes from the front and rear axles. Increasing the proportion of roll stiffness at the front will increase the proportion of the total load transfer that the front axle reacts and decrease the proportion that the rear axle reacts. In general this will cause the outer front wheel to run at a comparatively higher slip angle, and the outer rear wheel to run at a comparatively lower slip angle, which is an understeer effect. Increasing the proportion of roll stiffness at the rear axle will have the opposite effect and decrease understeer.


you guys were saying u need to know my spring rate etc but doesnt this answer the question without knowing that stuff?

[4corners]

It's my understanding the sway bar is already larger for the XI. Does anyone have the breakdown, 325i, 328i, 328xi, 335i, 335xi, M3?

[michaelalex17]

Originally Posted by 4corners

It's my understanding the sway bar is already larger for the XI. Does anyone have the breakdown, 325i, 328i, 328xi, 335i, 335xi, M3?

your saying the rear sway bar on the 335XI is already bigger than 20mm? i thought it was 13mm

[michaelalex17]

Alan at **********s just found this for me:

335i Rear Sway Bar: D=13MM 33556764425
335xi Rear Sway Bar: D=15MM 33556764427

the m3 one is 20mm. do you think going from 15 to 20 is a big enough difference to do something?