Suspension question

[RKS]

My understanding is that both 4 and 5 BWs come with aggressive camber and toe setting that are optimized for track use at the cost of tire life.
How much "handling" am I missing with a non-track alignment? I may try autocross this Spring but would rather have tires that last more than 12,000 miles.

 

[piranha971]

You will be fine with a street alignment. You "might" be autocrossing for fun, not for prizes. That 0.05 seconds you will be missing is not going to make any difference.

 

[AC2024]

I disagree. I went from the standard street alignment to kind of hybrid street/track alignment (-2 deg front, just adjusted at the knuckle-not strut tower adjustment, -1.75 deg rear, very slight toe in-essentially zero toe with a toe in bias) and noticed a significant difference in turn in even on the street. I did not track the car prior to changing the set up but if its noticeable on street then its likely more so on track. But i guess it depends on your definition of “fine”. The car will work of course with the stock alignment but in my opinion youll be pushing understeer quite a bit.

I am at 10K miles and tire wear looks perfectly fine (9750 miles street 250 miles track)

 

[Roadhawk]

I'm on factory settings and it seems "fine" to me...even today on my Alpine snows... I often drive/corner quite aggressively and the car bites in hard. Even today on my snow tires I had chassis wobble where the tires maintained grip in a very hard fast >90 deg corner. Scarred me a bit....but grip was maintained. I'm no track driver so I don't discount room for improvement and defer to those who know/understand better....but I'm happy with it...

PS - also 10K miles....most (but not all) pretty sedate....tires look good with no noticeable funkiness in wear...

 

[AC2024]

Make no mistake- the first time I ever drove this car on the stock alignment I thought to myself “ this is the best car I’ve ever driven”. It’s actually surprising that turn in, roadholding, and feel can actually be improved!!! YMMV, but i for sure highly recommend it. $200 for an aligment with really no downside (see my comment on 10k miles and still nowhere near worn out)

 

[ngoni]

Make no mistake- the first time I ever drove this car on the stock alignment I thought to myself “ this is the best car I’ve ever driven”. It’s actually surprising that turn in, roadholding, and feel can actually be improved!!! YMMV, but i for sure highly recommend it. $200 for an aligment with really no downside (see my comment on 10k miles and still nowhere near worn out)

Kind sir- could you provide your alignment report/sheet so others might partake in your 'best of both worlds' settings? Thanks in advance.

 

[AC2024]

 

[A Blackwing]

To put simply, i run track alignment year round, huge difference in handling characteristics that is worth the extra tire degradation to me

 

[AC2024]

To put simply, i run track alignment year round, huge difference in handling characteristics that is worth the extra tire degradation to me

Yeah, in retrospect I wish I just went with the track alignment. Next season I’ll likely get it realigned to the full track alignment.

 

[jbawden]

Where the times at? Seems like a lot of feels in this thread and not a lot of lap time data. It’s cool if it feels better, but that doesn’t mean faster times or optimal tire wear are the outcome for 98% street life.

 

[AC2024]

Like I said, I did not have a chance to track the car before I adjusted the alignment so I can’t answer the question about lap times. That said, I don’t really think it’s much of a leap to assume that additional camber will improve lap times, especially considering GM specifies the track alignment with the additional camber. A number I can provide (and did) is that I’ve now have 10,000 miles on the stock tires (>9000 of which post alignment adjustment) and I am still above 50% tire life for sure and see nice even wear which suggests that running additional camber on these cars won’t kill your tires on the street (provided you run light toe I am- which certainly makes the car a bit more darty, but frankly i like it that way and i see it as more of a benefit than determent)

 

[LastGas]

To the original poster's question, the factory street alignment spec is not aggressive. But, these cars sometimes come from the factory with an alignment way out of spec so it may be a good idea to get an alignment. @AC2024 "before" alignment is an example, my car was similar, it came with too much front toe which will make the car not want to turn and hurt tire wear.

Based on my experience running a CT4 with the full track alignment (popped the pins and have the full 2.5 degrees of camber) at track days and on street, I think GM (no surprise) got it right with the street vs. track spec. The street-spec is the way to go unless you are doing multiple track days a year. The track spec has significant tramlining (big difference from street spec) and is a bit less stable (small difference). It will also give you worse straight-line traction due to the camber on the rear tires. So, if you don't track the car the track spec will be all pain and no gain. If you are driving 8/10ths+ on the track, then the track-spec is important. The added camber means more grip and tire life on track (not on the street) and the minimal toe means a little better turn-in. And you can leave it on year-round, it's not like it makes the car undriveable or have massive tire wear, but it is somewhat worse.

If you want something a little more dialed-in with minimal negatives, maybe help on that occasional autocross, I'd suggest running the street alignment camber spec but with the toe set to the track specs. You'd have a little bit better turn-in and minimal downside. But that's deep into car-nerd land and you're certainly be fine doing 100% what GM recommends.

 

[A Blackwing]

I only tracked it with the track spec alignment.

On the street the track spec for me feels like it has much sharper turn in and reduces the slight understeer it had before the alignment.

 

[Mike Martz]

I tracked my car with both stock alignment and track alignment at two different tracks. I use the Cosworth Pi Toolbox to analyze laps and found while I was generating slightly more G-forces in the corners, the lap times were not significantly different (less than 2%).

Different tires respond differently to camber and the guys who run TT events on 200 TW tires will recommend different tires depending upon how much camber you can dial-in. I haven't enough experience with the stock tires and a heavy car to be an expert but I don't believe the Michelin PS4's that come on our cars are terrible camber sensitive.

But again, it you are running competition events on 200 TW or full race tires; all that goes out the window.

I also agree with other posts that the track alignment doesn't seem to impact tire wear very much and I ran it all the past summer and will probably do the same next year.

Bottom line is that you will be fine running the car in stock alignment and while it is nice to have the option for a track alignment and might "feel" better, I am not sure it impacts lap times much. Go out and have fun first and then decide how serious you want to get.

 

[AC2024]

I see the points in the previous couple posts. I cant find much to argue with-except one point.

The BW (ESPECIALLY the 4 BW) is literally all about feel. If you want a faster lap time, an M3 will get you there. What draws folks (including me) to the BW and away from BMW is the driving experience; the feel!

So, I agree that my feel-o-meter for turn in and cornering performance is far from scientific. However, i will stand by that it does feel better, livlier, confidence inspiring, more neutral vs the slight understeer bias at the limit. These things make the driving experience far more enjoyable to me regardless of lap time.

Although now i am very curious and want to turn laps in both specs to find out the quantitative impact

 

[Z51L9889]

These are all good comments. What alignment settings you choose ultimately comes down to how and where (street/track) you drive. The comment made above about wide variation in the factory alignment is spot on. Regardless of how you drive, it is a good idea to at least get the alignment checked after you have 4-5000 miles on the car, and have it adjusted if necessary. In my experience (35+ years as a suspension engineer for GM and others, plus dozens of track days and several hundred autocross runs), it takes at least a few thousand miles for all the suspension components and mounts to "wear-in" before the alignment settings stabilize. It varies based on the vehicle configuration and other factors, but it is not unusual for noticeable changes in alignment to occur from new. Also, please note that incorrect toe settings are more likely to cause rapid/uneven tire wear than camber (up to a point). You can get away with running high negative camber settings in many cases *if* you set a slight amount of toe-in (like 0.1-0.2 degrees total) both front and rear with the cross toe as close to zero as you can get it. However, large amounts of negative camber (like the factory track settings) will make the tire wear situation much more sensitive to how you drive the car. If most of your use is street driving, and particularly large amounts of highway driving, you will definitely see increased wear rates on the inner edges

I currently have 6500 miles on my car on the factory alignment. The tire wear is even so far, but I am planning on an alignment this spring before I do my first track days in the car. I will probably aim for camber settings of -2 degrees max front, and -1.5ish degrees rear with slight toe-in all around.

Hope this info is useful.