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Discussion Starter · #1 · (Edited)
Alright, recently I've been talking about wheels for the XI and that's been answered quite well.

So now my next question is how do I get this 325xi to handle really well for autocross without breaking the bank, It's supercharged and a few other goodies, so horsepower isn't much of a problem.

As the car sits now, it is lowered because of FK coil overs, and has adjustable rear camber arms.

I know these cars under steer a lot, and I hate under steer especially on a higher horsepower heavy weight that already enters the corner slow. It doesn't allow for any early corner rotation of the rear to pivot around a cone to power out. Also it means that in the event of under steer, you're entire run is ruined because you probably plowed some cones over or went way beyond the corner.

What alignment specs do these car like, what other mods go a long way in terms of turning?

I'd love for other people who have experience in autocross to comment on what they think would make the car, although any suggestions are greatly appreciated.

Thankyou!
 

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I have -1.6* camber all around, a hair toe out up front and a hair toe in on rear. Front tires usually get about 2-3psi more than the rears for optimum contact patch (this will vary depending on your setup, just chalk your tires and go from there). Front Konis are firmed up a lot, rear Rob43 shocks are about half firm. H&R rear sway on middle holes. I run this setup all the time for both DD and autox, works pretty well. I'm only on Eibach springs which do allow a noticeable amount of body roll but handling was sacrificed for comfort.
 

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I don't know if you've bought or mounted any new wheels yet, but if you haven't do you possibly own a set of staggered wheels ?


Rob43
 

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Discussion Starter · #4 ·
I don't know if you've bought or mounted any new wheels yet, but if you haven't do you possibly own a set of staggered wheels ?


Rob43
I can buy a local set of 17x8 and 17x9. I read your post about putting the wider tire upfront and that was actually my original idea to have the wider track upfront. Although I didn't want to tire size difference and ultimately ruin the awd.
 

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I can buy a local set of 17x8 and 17x9. I read your post about putting the wider tire upfront and that was actually my original idea to have the wider track upfront. Although I didn't want to tire size difference and ultimately ruin the awd.
That's good, I'm glad you found that.

Your Xi drivetrain will handle up to ~3% of an overall front to rear outside tire diameter difference. So this should Not be an issue.

Example:

225/45-17 front = 25"

245/40-17 rear = 24.7"

This equals roughly 1% of a difference.


Rob43
 

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Discussion Starter · #6 ·
Would you suggest that doing that then with the different tire sizes?

Also what else do you suggest for suspension tuning?
 

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Would you suggest that doing that then with the different tire sizes?

Also what else do you suggest for suspension tuning?

Tires: Yes, But.....

The B. RE71R is an expensive tire that wears quickly, so as much as I'd like to tell you to buy a staggered set of them & mount them to corresponding staggered wheels, this would be a very expensive purchase "IF" you didn't get the outcome you desired.

If there was any way that you could borrow a set of style 68 wheels & tires from a buddies 330Ci & run the 245/40's up front and the 225/45's in the rear as a 20 minute test to see if you like it, that would be best. Then you'd really know if you should move forward with this Idea.

Suspension: You could follow Matts plan, he has things dialed in pretty good. If you went that direction, maybe consider a firmer set of springs.



Rob43
 

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Discussion Starter · #8 ·
Tires: Yes, But.....

The B. RE71R is an expensive tire that wears quickly, so as much as I'd like to tell you to buy a staggered set of them & mount them to corresponding staggered wheels, this would be a very expensive purchase "IF" you didn't get the outcome you desired.

If there was any way that you could borrow a set of style 68 wheels & tires from a buddies 330Ci & run the 245/40's up front and the 225/45's in the rear as a 20 minute test to see if you like it, that would be best. Then you'd really know if you should move forward with this Idea.

Suspension: You could follow Matts plan, he has things dialed in pretty good. If you went that direction, maybe consider a firmer set of springs.



Rob43

I mean I've already gone through a couple sets of Direzza ZIIs so I understand cost and wear rate. I'll see what works out in my favor in the next week or so I guess.
 

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Tire size should be 245/40/17 all around. Max front camber (no less than -3.5) with slight toe out. Run the rears with a degree less camber than front and zero toe to start. Get the biggest rear bar you can and start it full stiff. In the rain, back off the rear bar a notch and front camber a degree. 7k rpm redline is helpful.
 

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Discussion Starter · #10 ·
Tire size should be 245/40/17 all around. Max front camber (no less than -3.5) with slight toe out. Run the rears with a degree less camber than front and zero toe to start. Get the biggest rear bar you can and start it full stiff. In the rain, back off the rear bar a notch and front camber a degree. 7k rpm redline is helpful.
The car has an active autowerke supercharger kit and modified Dinan Ecu, Dinan cat back and headers, I'm imagining that it has a 7k redline, Ill have to see when I get it running soon.

How hard is it to get the -3.5 degrees of camber in these cars?

What rear bar would you suggest?
 

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To get anything more than -1.7* of camber you're going to need camber plates up front and camber arms around back. I have the factory alignment pins knocked out which gives another .1-.2* of adjustment. If you go lower than the Eibachs you will get some more camber (probably close to 2*?). Just be mindful of what you really want. Does the car see snow or gravel? How often do you drive it? Seriously take everything you can into consideration. On my setup I am currently 5th out of 60 or so people in my local overall autocross standings. A great car makes a decent driver good, but a good driver makes a decent car great. Since you already have the coilovers and camber arms I would start with spending a weekend to really dial in your setup AFTER you get a solid alignment. Figure out what pressures your tires are happy at, what the dampening/rebound should be set at, etc.
 

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OP, for a good handling upgrade, you may want to consider poly front control arm bushings. The stock units are oil filled and get sloppy quickly on the XI. I may even know someone who can get you these pre-pressed.:hi:


.
 

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Which sway bar fit XI model ? the same as non-xi ?

You can Only upgrade the rear sway bar from a RWD E46 chassis. Good choices would be: 1) Hotchkis 25mm rear bar 2) UUC 23.8 rear bar 3) Any brand 21mm with two mounting holes.

The only thing you can do to the front sway bar is upgrade the bushings to 90 or 95 Sh A to help make it firmer.



Rob43
 

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The one thing about the Hotchkis bar is that NOBODY has them in stock...... I went H&R but probably should have gone UUC. The UUC bars are on sale now for an AMAZING price too, probably going to snag one.
 

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The car has an active autowerke supercharger kit and modified Dinan Ecu, Dinan cat back and headers, I'm imagining that it has a 7k redline, Ill have to see when I get it running soon.

How hard is it to get the -3.5 degrees of camber in these cars?

What rear bar would you suggest?
Oh- I got you confused with the guy in the other thread that just installed camber plates. I run Ground control front camber plates and hotchkis rear bar. Those two items along with tire pressure adjustments let you drastically change the handling of the car.

Call hotchkis directly and ask if they have any in stock.
 

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The one thing about the Hotchkis bar is that NOBODY has them in stock...... I went H&R but probably should have gone UUC. The UUC bars are on sale now for an AMAZING price too, probably going to snag one.
I wish I had both to swap in and out to see which performs better. My instinct is that a thicker bar would help the handling more hence the hotchkis.

Note: The XI and RWD handle differently due to weight and being AWD. So its somehwhat comparing apples to oranges.
 

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I wish I had both to swap in and out to see which performs better. My instinct is that a thicker bar would help the handling more hence the hotchkis.

Note: The XI and RWD handle differently due to weight and being AWD. So its somehwhat comparing apples to oranges.
If I do snag the UUC bar I would be willing to let my H&R bar (or UUC depending on which I like better) go for cheap. It has less than 4k miles on it right now.
 
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