Thursday, November 26, 2009

E46 BMW 3 Series alignment, done the right way

Every time you go to a shop to mount your tires, the installer will most likely try to sell you an alignment. They're in business to make money, and always seem love to take advantage of your ignorance. For the most part, you never need it. Yes, you read right: I said never.

(climbing atop my soap box)
As most well informed people know, and any honest mechanic would tell you - a car only really goes out of alignment if it has been hit, or if there as been some unusual wear and tear put on the suspension. Unusual? Think hitting curb or diving into a pot hole at a relatively high speed. Other than that, if your tire wear is normal - don't waste your money on getting an alignment. What's normal tire wear you ask? It's not necessarily what you think. Your tires don't necessarily have to wear right down the center, or evenly for that matter. For example, E46 BMW's (and most other BMW models for that matter), tend to wear the front tires on the outside more, and the rear tires right down the middle. This, is considered normal. BMW introduces some negative camber in their suspension to allow for improved cornering. Don't let a tire shop tell you otherwise. Also, BMW recommends, against conventional wisdom, to never rotate your tires; but I'll leave that discussion for another post.
(ok, now that that's over)

My car had a nagging bump-steer problem. This is characterized by your steering wanting to pull right or left when you hit a bump on the road, especially under moderate to hard braking. It's actually pretty annoying, especially driving on city streets laden with undulating surfaces.

After installing a Myle suspension kit which a new set of lighter lower control arms and associated bushings and linkages, my steering got somewhat better, but wasn't totally cured.

After doing some research I found out the correct procedure for aligning BMW's is by using weights. These are bags that are placed inside the car so simulate a load. Only then, does the trained technician (often only found at BMW stealerships) will begin to take measurements with his Hunter DSP600 alignment machine. In the front, BMW's have adjustments for CASTER and TOE only (see actual printout below). For the rear wheels, you can only modify the CAMBER and TOE.

If you call an independent BMW shop, and they don't use weights in the alignment procedure, or claim they're not needed, I would suggest you hang up. If you're going to get any sort of calibration done, you don't want "good enough". You want it to be within the manufacturer's specifications under the right conditions. Always ask for a before and after printout. My alignment ended up costing me $179.00+tax from the dealer. You'll typically only pay for 1 hour labor. If you ask for a discount, these days, even most dealers will try to accommodate you. It never hurts to ask.

I almost never go to the BMW dealer, or send anyone else there for anything other than warranty issues. This would be one of my very few exceptions.