Uneven front tyre wear & steering wobble

Question

I've had my BMW E92 2008 for almost 12 months now, from purchase I've noticed that it likes to chew through the edges of tyres and figured (and was told) that it needed a wheel alignment.

I was unfortunate enough to have hit a roundabout (at about 15mph with the OSF wheel) whilst avoiding an accident with a truck, the result of this was my tracking was totally out and the car wasn't driving straight (steering wheel on the flat would steer the car slightly left).

The repairs were done at the expense of the third party and as part of the repairs I paid for a 4 wheel alignment and fitted new tyres to the front, I spoke with the repair center and they said that the front suspension checked out and all was well. But after 8,000 miles I've noticed that just the front right (OSF) tyre is balding around the edge again, and I'm getting some annoying (maybe unrelated) wobble at 70+ mph.

I've had the car up yesterday on axle stands and had the front tyres off (fitting new rotors and pads) and I've taken a look at the suspension, I cant see anything wrong. There wasn't any give or play on the suspension arms but I've no idea what I'm really looking for. Took the car out after fitting new rotors (the old ones were in a bad state) and it's braking fine but the wobble is still significant and I'm worried that damage has been done to the front suspension or steering. Where is the best place to start looking into this issue? It's due a service and MOT next month so I'm not sure if there going to hit me with a massive bill??

Any help would be appreciated.

UPDATE: Answer to some questions.

• They are low profile 225/40 R18, I do a fair amount of miles 18k per year just on personal to and from work so I should probably be checking the pressures more frequently but I feel I usually keep on top of it (once every 2 weeks)
• I've tried to find my print out of alignment, but I cant find it in with the paperwork I already have. I think I have a copy at the office so I'll check there and update when I can.
• With both of the wheels off, the wear is heaver on the front right tyre (UK right hand drive) than the left but there is definitely wear on both on the outer edge, the inner edge is fine.
• Vibration comes through the wheel, I cant tell if the vibration in the car doesn't feel like it
• It's been wearing tyres un-evenly since I bought the car, the fronts really bald on the edge when I replaced them with about 3.5mm along the other 3/4 breadth of the tyre.
• I do tend to drive the car hard (cant help it, such a nice car to go fast in!)

• Current odometer reading is 91,000 miles had a new wheel bearing on the right side at 78,000 miles

  

Answer 1

Are these low profile tires? if so balding around the inside and outside edges on these can be quite common especially if they are not kept at their max PSI.

The PSI is my first guess. Typically if it's an alignment issue then both front or rear tires will have the same issues. Did the alignment printout show any unusual camber angles? and are both the inside and outside of the tire balding or just one edge?

For the wobbling at 70+ do you feel it through your steering wheel or is it more through the floorboards? How long has it been going on?

which side did you smack the roundabout with left or right? Being in America Out Side Front means Left front tire.

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driving hard will wear out the outer edges of the front tires pretty quick. Depending on how hard you normally take turns 8k out of a tire is potentially completely normal.

Do the treads look jagged? or more of a flat wear as shown in the image below?

The descriptions are not the only causes of these types of wear patterns. you mentioned the edges of the tires are worn is it just the outer edge the inner and the outer or is one noticeably more worn than the other? Also the fact that your right tire is more worn is normal since you will be taking left turns harder than right turns, due to how your roads are laid out, it's opposite if you are on left hand drive roads.

If all your bushings, connections, knuckles, and suspension parts are in good working order and aligned and if you are still rubbing your tires edges you can give yourself a small bit of negative camber, probably 1 degree or so, which will pull the tire tread flat against the ground in a curve giving you a bit more traction while wearing the tread a little bit better.

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Your problem is too much steering mixed with large helpings of go pedal. But if you really really don't want to change then I sugest maxing out the PSI in the tires to keep them as hard as possible and reduce sidewall flex. Rotate all your tires front to rear. Tires with wear on the outside get flipped so the wear is now on the inside.

When you make a gas pedal sandwich with a generous helping of sole and carpet (aka flooring it) around a turn your tires are doing this:

As you can see the tires on the inside of the turn are barely rubbing at all but the tires on the outside are nearly folded over. The higher the PSI the more resistant the sidewalls will be to this.

You can give the car a degree or two of negative camber on the front tires and half a degree of negative camber on the rears. You can see in the image below that there is much less sidewall flex on this Most Always Zipping Dangerously Along (M.A.Z.D.A.) as it takes a right turn.