[semclane]

To set the stage, I am autorossing a 2015 M235i equipped with the M-Performance LSD and running 245/40-17 Dunlop Direzza II Star Specs on17x8 Kosei K4R wheels on all four corners. Not too long ago I took it to a local independent BMW shop for a mid cycle oil service and a couple of other trivial things. While I was there I had them do an "Autocross" alignment.

Since then I have had a problem keeping the rear under control in sharp turns. Drifting may be fun, but its not the fastest way around a corner. The alignment has 0.22 degrees of tow-out in the rear.

In a previous life, rear toe-out was a good thing in my low powered Miata, but i'm questioning its application with the HP/Torque of the M235i and the limited space for wider tires (especially as I want to keep the square set up).

Any experience out there re: zero rear toe vs toe-out on our cars?

[i8ur911]

Not to sure what the dealer, assuming it was done at a dealer, would do for an "autocross" alignment.

Remember that there is no adjustable camber in the front. Also, the factory rear camber setting is around -1.2*, I believe......which is VERY little. Toe out is definitely going to loosen up the rear a touch, but shouldn't turn it into a "drift" car.....especially with a LSD.

I'd recommend adding some F8x LCA's up front, or camber plates, and dialing in more negative in the rear.

I currently run -1.7* in the front and -2.3* in the rear. The car feels pretty neutral, but could use more front camber (-2.5*).

You can also lower your rear toe psi to help fix your issue.

Hope this helps.

[semclane]

Thanks for the input. First off it was not a dealer alignment - it was an independent shop that specializes in BMWs.

I do have the LCAs up front. Camber is -1.7 in front and -1.4 in the rear. I may have had the pressures too high. This week I was running 37 front and 35 rear. I'll try lowering the rears at the next event.

I'm going to try to get into another local independent BMW shop that is a bit more performance oriented for another alignment before the next event.

[Liquidpaper]

I've been playing with my alignment since I got my car and got some camber plates put in. After a lot of trial and error, I settled on F -2.25, R -2.0; 0 toe front, and 3/32 in on the rear.

I do track days (rather than autocross), so I think you would need a looser back end for autocross. I had an older alignment that was supremely toss-able, but very, very hard to keep control of under high-speed (80mph +) cornering. I think it was -2.25, -1.75, and the same toe as above.

Since you only have LCAs (and not full camber plates), I would suggest putting some bite into the rear (maybe put the same camber on all four corners) and see if the rear is a little more planted.

[i8ur911]

I would try messing with tire pressures first....that's easy to play with. I've run anything from 30psi cold front and rear to as much as 35psi cold front and rear. I'm using PSS's.

If you still can't get a good "feel", then I'd dial in some more negative camber in the rear.

Let us know how you make out either way.

[Pparana]

Originally Posted by semclane

To set the stage, I am autorossing a 2015 M235i equipped with the M-Performance LSD and running 245/40-17 Dunlop Direzza II Star Specs on17x8 Kosei K4R wheels on all four corners. Not too long ago I took it to a local independent BMW shop for a mid cycle oil service and a couple of other trivial things. While I was there I had them do an "Autocross" alignment.

Since then I have had a problem keeping the rear under control in sharp turns. Drifting may be fun, but its not the fastest way around a corner. The alignment has 0.22 degrees of tow-out in the rear.

In a previous life, rear toe-out was a good thing in my low powered Miata, but i'm questioning its application with the HP/Torque of the M235i and the limited space for wider tires (especially as I want to keep the square set up).

Any experience out there re: zero rear toe vs toe-out on our cars?

Autocross is pretty much all mid and low speed, set toe out totals +.3 +.5 front, toe in total - .3 rear. Camber max front ,rear .5 or .7 less than front.

You do not want toe out in rear, suspension has a lot of bump steer in rear (toes out on own). You will end up with snap oversteer in aggressive turns.

More rear camber than front will cause the car to understeer or push. Toe out in front will allow you to turn in quicker.

This allingment will be busy on the road, requiring lots of correction, but would be the best for autocross

Would it be a good track allingment, no.

[Pparana]

Originally Posted by Liquidpaper

I've been playing with my alignment since I got my car and got some camber plates put in. After a lot of trial and error, I settled on F -2.25, R -2.0; 0 toe front, and 3/32 in on the rear.

I do track days (rather than autocross), so I think you would need a looser back end for autocross. I had an older alignment that was supremely toss-able, but very, very hard to keep control of under high-speed (80mph +) cornering. I think it was -2.25, -1.75, and the same toe as above.

Since you only have LCAs (and not full camber plates), I would suggest putting some bite into the rear (maybe put the same camber on all four corners) and see if the rear is a little more planted.

Double your toe in on rear, and that would solve the issue for high speed. You have too much rear camber for only running 2.25 in front. Your correcting the bump steer with camber, correct it with more rear tow and you will have a more balanced car at all speeds.

[StealYourFace]

Originally Posted by Pparana

Autocross is pretty much all mid and low speed, set toe out totals +.3 +.5 front, toe in total - .3 rear. Camber max front ,rear .5 or .7 less than front.

You do not want toe out in rear, suspension has a lot of bump steer in rear (toes out on own). You will end up with snap oversteer in aggressive turns.

More rear camber than front will cause the car to understeer or push. Toe out in front will allow you to turn in quicker.

This allingment will be busy on the road, requiring lots of correction, but would be the best for autocross

Would it be a good track allingment, no.

This-

Use chalk on the sidewall to see if the tire is rolling over to adjust your pressures.