garehaan

Wow, makes me jaleous. Can't wait to get mine on the track.
You did a good job there, good feeling for the perfect line.
Post some pics of your tires please, can imagine what they look like

CRRobert

I will try to get a picture up later. I can tell you that I think there is positive camber in the front, and that this led to the outside edge of the tire, past the tread towards the sidewall, getting worn. Posted question about this in the main forum.

The tires have been through two track events, and have held up pretty good, except for what I noted above.


FYI, on my trip to and from Las Vegas, averaged about 23 mpg, but on the track, 12 mpg.

Rudy

I didn't see the question on the main forum but I think that the front tires don't have positive camber. What I think you're seeing is the outside edge wearing due to the hard cornering that you put the tires through. When you corner at a high speed, the tire flexes and will tend to "roll" toward the outside edge. This will cause the outsides to wear.

If you were driving straight ahead and the outsides were wearing, I'd say you have positive camber but that's not the case here. As a matter of fact, that's why the rears have negative camber -- when you corner hard, the tires flex to the outside which, when combined with the negative camber, actually causes the tire to make solid contact instead of only the outside edge. In other words, if you go straight on a negative camber tire, you'll wear the inside first. If you corner heavily on a negative camber tire, you'll wear them evenly...

CRRobert

Rudy,

I will try to get some pictures up later, but I still think that the fronts need to go more toward the negative camber. Just in normal spirited driving, it seems to go too far, and then on the track day, it went almost onto the sidewall. The insides are still barely untouched.

CRRobert

Here is a picture of the outside. The red arrow is where the spirited driving in the mountains pushes it out too, and the white arrow is where it went out to on the track.



Here is the inside, and you can see that the white arrow shows the limit of the wear not even close to the outside, and this was from the track day.

Rudy

Thanks for the pics. Every time I've tracked a street car (mostly BMW and M- this type of wear is commonplace. I understand what you're saying -- add some negative camber and you will solve this problem.

I suspect it's not that easy -- doing this will most likely create new problems. I'm thinking strait line stability would suffer greatly as well as a whole host of other problems. I'm not an expert at race car setup but I'd love to hear what others with more experience think...

CRRobert

I just want to know what the range BMW call is in spec, so I could have them keep it in spec when I take it in for an alignment, but on the negative camber side of the spec if that makes sense.

Probably won't be able to get rid of it all, but think that it may help.

Rudy

CR, last year I spent two days thrashing AMG cars on parts of the F1 course at Indy. As you know from these types of events, you spend time driving the cars and you spend time watching other participants and instructors drive the cars.

One thing I remember seeing was the way that the outside front wheel looked when a car was being pushed hard. The tire flexed (rolled) so much that it looked as if the rim was going to touch the pavement at any time! We did a figure-eight exercise in one of the parking lots and I was able to stand there and watch the Michelins (one of the event's sponsors) scream. After the event, the tires looked much like the the tires in the pictures you posted.

I looked in TIS for alignment information and found a bunch of details on how to do the alignment, etc. There is also some specs but it's kind of difficult to figure out. The following documents are a sample of some of the things that I found. (Once you see them, you'll know why the alignments on our cars shouldn't be done by anyone except a BMW dealer with the proper equipment -- especially if you have active steering!)

General information and definitions:
RA__General_information_and_definitions.pdf
Alignment specifications:
TD_Wheel_alignment_E60___E61_Series.pdf
Normal position & Inspection conditions:
TD_Wheel_alignment___Normal_Position___Inspection_Conditions.pdf
Kinematic Diagnosis System (KDS) and environment:
SBT_Kinematic_Diagnosis_System_and_environment_BMW_KDS.pdf
Adjusting front axle with KDS:
RA_Adjusting_front_axle__with_KDS_toe_and_camber_.pdf
Adjusting rear axle with KDS:
RA__Adjusting_rear_axle__with_KDS_.pdf
Enjoy!

CRRobert

Thanks Rudy,

As I read it, the front wheels are -12' plus or minus 20'

and the rears are -2d plus or minus 20' right? I did not specifically see the fronts versus rear labeled.

this definately explains some of the difference. The rears on my tires did not roll over as much as the front.

When I get back to Denver and have it aligned, I can give a indication of what I would like done. I will try to update this thread to what my current settings are.

hopefully that helps, or I will need track tires so I don't where out my nice PS2's on the track in a couple of sessions.

Thanks for the vid link also.

Rudy

The document that shows the specs certainly is confusing.

I think you're right that the fronts are -12' ?20' and the rears are -2? ?20' but all I can say is make sure a BMW dealer does the alignment and concurs with what you're thinking. If it were my car, I wouldn't feel comfortable telling the tech what to set things to with my limited understanding of all these measurements, etc.

What did you think of the video? Did you see how it looked almost like the rims were ready to make contact with the asphalt?