I've been told that "cupping" is behind the rotational noise that I hear driving down the road. I've also been told that struts may be the cause of this. Would I be better off going to the dealer or a private mechanic? Any insight would be great...thanks
The dealer might have some insight, but if they say you need 4 new tires right off the bat, I'd think you'd want to have a good explanation as to why. Otherwise, find a good indy shop (if it's BMW-only, all the better), see what they have to say, and see if they have a referral to a good indy alignment shop. I'd think you'd likely be able to look at the tires and see evidence of the cupping. http://www.partsamerica.com/Maintenance/MaintenanceTireProblem.aspx
How many miles are on the car, what tires are on there now, are they the original tires, do you drive mostly on interstates or mostly on local roads? In my experience, cupping of tires is usually the result of alignment problems.
it has about 45k miles...off the top of my head the tires are continentals. As far as I know the tires are the originals....the car only had 17k miles when I bought it. During my commute I'm on an interstate for about 15 minutes. The surface streets I'm on are pretty nice but the interstate is like grand canyon.
At about 45k miles it might be nearing time for new tires. I've had several different brands of tires get noisy as they approached the end of their lives. How close to the wear bars are you? If the tires do not look excessively cupped but are just about worn out and the car is not handling oddly, I don't think you have any alignment issues. Just worn out tires. Although I it doesn't sound like your struts are causing problems, keep in mind that stock BMW dampers are pretty much toast not long past 50k miles. They lose their ability to damp out bumps and will reduce stability over bumpy curves.
Tire wear, cupping, strange noises In my experience with my 2000 E46, cupping in inevitable considering the negative camber alignment that is partly responsible for the excellent handling of a BMW. With almost 2 degrees of negative camber, the inside of the tire effectively runs at a smaller radius than the outside. As the tire rolls the inside of the time rolls ahead of the outside until it 'snaps' back. This action causes an oscillation in the tread resulting in adverse wear spaced around the wheel. If this effect happens to occur at a spacing that is regular and repeating, then areas of the time will be subject to adverse movement and wear. The first tires I put on my car lasted 45,000 miles and became horribly noisy from about 10,000 onward. The dealer yelled at me for getting that much mileage. "You don't drive hard enough...." Obviously, if I drove harder than I would wear them out before they became noisy, or, at least, that would seem to be his theory. HOWEVER, when I switched from Michelin Sport AW tires (the above noisy tires) to some Bridgestone top-of-the-line AW tires, the cupping phenomenon did not occur. Ultimately, they started becoming noisy at the end of their life, but no cupping and associated loud growl. So what does this mean? The sidewall flex and stiffness of the radial belt combine to create a dynamic system with its own inherent resonance points. Some tires have very flexible sidewalls. Some tires have layered belts with noise dampening compounds that allow inter-layer belt movement in an attempt to tune out resonance. The combination of belt properties and sidewall flex will determine an overall longitudinal flex frequency that defines the squirm between the different outside and inside rolling radii of a negatively cambered wheel. The higher the sum frequency, the quicker the tire will 'snap' back to compensate for differential rolling distances. The Michelin apparently rolls far enough between 'snaps' to space wear zones far enough around its circumference to create a low frequency annoying howl as the cups are formed. Driving with them I was always accompanies by a grumpf-grumpf-grumpf buzzing from the front end as the tires went in and out of sync (slight difference in tread oscillation due to negative camber). The Bridgestone probably 'snapped back' much quicker or its belt was flexible enough to effectively keep the rolling distance differential in check, thus preventing the cupping phenomenon. HOWEVER (2), I am not getting as much wear out of the Bridgestones as with the Michelins. Maybe I'm taking the dealer's advice and driving harder in a desperate attempt to stave off cupping by wearing out my tires as fast as possible..... The cupping problem will always be with us. Negative camber alignment is the culprit. The wider the tire, the greater the problem as the rolling differential between outside and inside increases with width. Keeping the suspension tight is important to minimize wheel movement that would accompany any tire oscillations, especially insuring that the front suspension bushing and ball joints are not compromised. Proper rotation helps, but, ultimately, the laws of physics will win. Consider it a cost of BMW membership.
Say that again! I do believe that's the most original written sound approximation we have on the forums thus far and check it out - 324453 & lcjhnsn have join dates of 1970! Gosh, those must have been the early days of the internet & forums, eh?
