[miker2013]

i had some work done on my vehicle and had an alignment done, i have staggered 18" m sport wheels on my xdrive with bs reo50 rft tires... i asked the tech if there was a way to tighten the front end steering up a bit and he said he could

i got a printout of how they aligned it but i lost the page but i am sure both front wheels numbers were shown in red meaning they weren't to the normal spec... i do remember that the top of the alignment specs said 18" in wheels, isn't there a specific alignment spec for the 18" staggered?

anyway, i love the way the car drives and it is a little crisper on front end but i am getting a back and forth pulsing in the wheel on a lot of different road surfaces, not all road surfaces but a lot... comes and goes, is not related to speed as it can happen at lower speeds too

i know the rft tires are rough but i have had them before and never had anything like this... car tracks straight as an arrow and there is no noticeable difference in this vibration/pulsing at higher speeds... tires are new

so i guess my question is, what alignment settings can tighten up front end steering? could they cause some of the issues i am having or is it related to something else?

[Shrike360]

I believe if you increase caster (which will be limited on a stock vehicle), it will increase steering effort. That may be what you want, but you really need camber/caster plates to control it.

If you want better front end feel, also take a look at the bushings discussed in this thread: http://www.e90post.com/forums/showthread.php?t=1108425

[AtlasM]

The xi has a slow steering gear ratio, something like 18:1 vs. 14:1 on the rwd car. Kinda the worst thing about the xi, really. You can do a little bit with alignment and bushings but neither of them will change the steering gear.

More positive caster will give you a bit more turn-in response. The more positive caster, the more negative camber your tire gains when you turn the steering wheel, which gives more grip and turn-in response. It also will make your steering effort higher. But you need camber/caster plates as caster is not factory adjustable.

I have the Ground Control xi camber plates which have a minimal caster adjustment. My alignment guy was able to adjust the car from +6 to +9 degrees caster but with my bigger wheels & tires, the +9 was rubbing too much on the oil cooler grille in the front of the passenger side fender well. I'm back at +6 now. I'm running -2.25 degrees camber so that already helps the steering and the extra caster wasn't too much of a difference.

I also have the Strongflex red front tension strut bushings. These are the softer of the two options from Strongflex.

Overall, the steering gear is slow, but with my upgraded tires, shocks, springs, bushings & alignment it handles nicely and feels great. Just have to turn the wheel more than I'd like.

[Shrike360]

Originally Posted by AtlasM

The xi has a slow steering gear ratio, something like 18:1 vs. 14:1 on the rwd car. Kinda the worst thing about the xi, really. You can do a little bit with alignment and bushings but neither of them will change the steering gear.

More positive caster will give you a bit more turn-in response. The more positive caster, the more negative camber your tire gains when you turn the steering wheel, which gives more grip and turn-in response. It also will make your steering effort higher. But you need camber/caster plates as caster is not factory adjustable.

I have the Ground Control xi camber plates which have a minimal caster adjustment. My alignment guy was able to adjust the car from +6 to +9 degrees caster but with my bigger wheels & tires, the +9 was rubbing too much on the oil cooler grille in the front of the passenger side fender well. I'm back at +6 now. I'm running -2.25 degrees camber so that already helps the steering and the extra caster wasn't too much of a difference.

I also have the Strongflex red front tension strut bushings. These are the softer of the two options from Strongflex.

Overall, the steering gear is slow, but with my upgraded tires, shocks, springs, bushings & alignment it handles nicely and feels great. Just have to turn the wheel more than I'd like.

Seriously, wish we had options for a quicker rack on the xi. Driving a 31 year old saab while my car is in the body shop for the week, and the steering is sooo much quicker. Screwed up parking on my first attempt because of that.

[tetsuo111]

Originally Posted by Shrike360

Seriously, wish we had options for a quicker rack on the xi. Driving a 31 year old saab while my car is in the body shop for the week, and the steering is sooo much quicker. Screwed up parking on my first attempt because of that.

http://www.e90post.com/forums/showthread.php?t=1262407

I looked in to retrofitting a quicker ratio steering rack from the M3. The challenge is the front subframe. xDrive is a reversed, mirror image of the RWD subframe. Where the standard RWD steering racks are attached to the aft subframe member, the xDrive racks attach to the forward subframe member. I believe but can't confirm that the different rack attachment locations may also require a longer steering column.

It may be possible to fabricate a work-around, but the required effort borderlines on heroic. I think that a RWD rack could be modified by welding attachment bosses to the rack, to align with the xDrive subframe.

Another option is installing a "steering quickener". This is a gear set that goes in between the steering wheel and steering rack. The gears are toothed to alter the ratio. The downside is that even the steering quickener needs to be welded to the steering column, although there are some products that claim bolt-on installation. I also chose not to go this route because I wanted to avoid introducing compliance in the column.

I agree with Atlas, a quicker ratio rack would be a very welcome option for drivers who are passionate about handling.

[miker2013]

so basically my first post in this thread was to ask, what alignment settings (camber, caster, toe in or toe out) could be tweaked to tighten the slower steering response on the xdrive.... i had my dealer adjust my alignment (not sure what they did) and i have noticed the steering to be a little more direct, they said i will go thru tires a little quicker but i don't care... i should have asked which setting they changed but regardless it did make a difference

[ucdbiendog]

Originally Posted by tetsuo111

http://www.e90post.com/forums/showthread.php?t=1262407

It may be possible to fabricate a work-around, but the required effort borderlines on heroic. I think that a RWD rack could be modified by welding attachment bosses to the rack, to align with the xDrive subframe.

To that end, would you need to code the DSC module? Reducing the gearing would require fewer steering wheel turns for a given response by the vehicle, so i would think it would drive DSC nuts without doing anything

[matteblue3er]

What is your idea of "tighten?"

The only thing the tech can do is toe the front wheel out on a stock suspension. Toeing the front wheels out will increase turn in response. The car will react more quickly to steering inputs but it will also tend to tramline much easier, as you have experienced. Toe out will also increase inner tire wear.

Personally I have toe set to zero in the front on my xi. Remember on an AWD car, the front wheels naturally toe in under load due to being driven. RWD front wheels do the opposite and toe out under load.

[miker2013]

Originally Posted by matteblue3er

What is your idea of "tighten?"

The only thing the tech can do is toe the front wheel out on a stock suspension. Toeing the front wheels out will increase turn in response. The car will react more quickly to steering inputs but it will also tend to tramline much easier, as you have experienced. Toe out will also increase inner tire wear.

Personally I have toe set to zero in the front on my xi. Remember on an AWD car, the front wheels naturally toe in under load due to being driven. RWD front wheels do the opposite and toe out under load.

thanks for the post

i should have asked what they did but i believe it was to adjust the toe out as u mentioned... i don't mind the tramlining to be honest, i have run flats so i am already used to it

by "tighten" i did mean just to quicken the turn in response

i just recently had my winter winter tires and wheels (17" hakka) put on and am also liking the adjusted settings on those wheels, i don't mind a little extra tire wear

[3002 tii]

Originally Posted by AtlasM

The xi has a slow steering gear ratio, something like 18:1 vs. 14:1 on the rwd car. Kinda the worst thing about the xi, really. You can do a little bit with alignment and bushings but neither of them will change the steering gear.

More positive caster will give you a bit more turn-in response. The more positive caster, the more negative camber your tire gains when you turn the steering wheel, which gives more grip and turn-in response. It also will make your steering effort higher. But you need camber/caster plates as caster is not factory adjustable.

I have the Ground Control xi camber plates which have a minimal caster adjustment. My alignment guy was able to adjust the car from +6 to +9 degrees caster but with my bigger wheels & tires, the +9 was rubbing too much on the oil cooler grille in the front of the passenger side fender well. I'm back at +6 now. I'm running -2.25 degrees camber so that already helps the steering and the extra caster wasn't too much of a difference.

I also have the Strongflex red front tension strut bushings. These are the softer of the two options from Strongflex.

Overall, the steering gear is slow, but with my upgraded tires, shocks, springs, bushings & alignment it handles nicely and feels great. Just have to turn the wheel more than I'd like.

How's the NVH with the GC Xi plates?

[tetsuo111]

Originally Posted by ucdbiendog

To that end, would you need to code the DSC module? Reducing the gearing would require fewer steering wheel turns for a given response by the vehicle, so i would think it would drive DSC nuts without doing anything

Yes, I agree DSC / DXC would need to be accounted for with the change in steering ratio.