Loose and Vague Steering

[mimarcos]

First thing someone is likely to say is "search it" so I thought I should say that I already did put a little effort into finding an answer. And I kind of did, in this post: http://www.zpost.com/forums/showthre...loose+steering. However, I'd like a little input on this issue, I think my circumstances are a little different.

I have an '06 Z4MR, with about 8500 miles on the clock. Lately, actually for a while, I've felt like the car has had very loose steering. On straight lines, I'm tramlining all over, driving like a moron that can't keep his car in a straight line. The issue is present predominantly in straights, but it also is ever so slightly present in turns. Barely noticeable while turning, though.

The steering wheel also feels like it has too much play in it, definitely in straight lines, but also noticeable when I go over bumps. The wheel used to snap when going over imperfections, now it just... wobbles? That's not the right word, but it's not as crisp in its feedback.

A lot of this seemed to start right after my first HPDE event last year. I'm trying to make sure I'm not just romanticizing how the car "used to drive" in my mind, but there is definitely something different than the day I took it home, and the 6 months of summer that year.

All signs seem to point to FCABs - except for the 8k miles bit.

First thing I did was change the tires. They were the OE tires. They were a little dry rotted, so I figured maybe the sidewall wasn't great. I switched to Bridgestone Potenza S-04 Pole Positions. Not much changed.

Next up, I had an alignment done. Try as I might right now, I can't find the paper I was given showing me the exact figures. Long and short, most numbers were off by just a bit, except for the front left toe - it was actually out. The tech brought the numbers back to BMW recommended, despite me asking for a little more toe-in in the front. I actually think this made things a little worse.

So, does anyone have any suggestions for why I might be experiencing this vague and loose steering? Anything would help tremendously.

Thanks!

[The HACK]

It is not unusual to have the rubber FCABs to deteriorate over time causing them to weaken and crack under duress. Given the fact that this car is an '06 with 8k miles, that's 1,000 miles per year, and based on your description, it is entirely plausible to suspect the FCAB is damaged.

[mimarcos]

Originally Posted by The HACK

It is not unusual to have the rubber FCABs to deteriorate over time causing them to weaken and crack under duress. Given the fact that this car is an '06 with 8k miles, that's 1,000 miles per year, and based on your description, it is entirely plausible to suspect the FCAB is damaged.

Thank you very much for the response. I was thinking that aging could have contributed, but it seemed like I was coming across a lot of stuff suggesting it was mileage related.

Any thoughts on front toe-in?

[The HACK]

No thoughts on front toe. It's all personal preference. I ran my car for over 6 years with a moderate toe-out of 1/16". It ate up the inside of my front tire like no one's business. But I didn't care, the car responded so well on the track and I was okay with the jittery front end on freeways. Now that I'm running 275mm front tires with 3.5 degrees of negative camber, running any significant toe-out would eat through the R-comps faster than I can flip them, so I dialed in about 1/16" total toe-in.

Toe-in affects steering response at the expense of tire wear. Where as camber affects steering response and mid corner grip, also at the expense of tire wear. So all things considered, I would maximize available camber, then dial back a little bit of toe-in if you want to conserve your tires, or if you use your tires on the street as well. Otherwise, go with max camber and a little bit of toe-out for best performance if you only use the tires at track (or get them for free).

[mimarcos]

Originally Posted by The HACK

No thoughts on front toe. It's all personal preference. I ran my car for over 6 years with a moderate toe-out of 1/16". It ate up the inside of my front tire like no one's business. But I didn't care, the car responded so well on the track and I was okay with the jittery front end on freeways. Now that I'm running 275mm front tires with 3.5 degrees of negative camber, running any significant toe-out would eat through the R-comps faster than I can flip them, so I dialed in about 1/16" total toe-in.

Toe-in affects steering response at the expense of tire wear. Where as camber affects steering response and mid corner grip, also at the expense of tire wear. So all things considered, I would maximize available camber, then dial back a little bit of toe-in if you want to conserve your tires, or if you use your tires on the street as well. Otherwise, go with max camber and a little bit of toe-out for best performance if you only use the tires at track (or get them for free).

Thanks, again. I will wind up using my tires on track/street. This year and last, I've done one HPDE per year, but I'd like to up that to 2. I also wish I could get tires for free but I'd settle on one pair per year if it came to it. I also drive around 4k miles per year, so I think 1 set of tires per year would be easily doable.

I think I have to do a little more research on toe-in. I thought toe-in would make street and track driving a little less loose, at the expense of harder steering and increased tire wear.

[The HACK]

Toe-in WILL make steering less "loose" feeling, as in it doesn't wander around basically following every nook and cranny and change in "crown" of the road. But if your steering is "loose" on a smooth track surface, it indicates other problems than what's related to toe IMO.

Basically, toe-in front will give you high speed stability, while toe-out front will give you lightning quick response to your steering input, but as your speed increases it will also have a tendency to tramline more. It's a give and take. Toe-in will wear the outside of your tires more, toe-out will wear the inside of your tires. So for me, with a 3.5º negative camber, with any amount of toe-out it will accelerate the inside tire wear. While before, at 2.5º negative camber, I was willing to live with a little bit of toe-out since the car is used on track so much (leading to a more "even" tire wear).

[RedDotRacer]

I recently aligned to -2.25 camber up front with 3/16 toe in for mainly a street car at a very reputable alignment shop. Car seems to handle ok. What sort of wear should I expect here? Should I neutralize the toe to 1/16 in instead? Don't mean to threadjack. It's a helpful discussion.