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      06-16-2014, 03:20 AM   #1
anom3
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Question regarding rim straighening

So about a week+ ago I had a chance to hit the highway WITHOUT the girlfriend in the car.

I was able to press the car hard, and notice the following:

Once I crossed a rarely-will-i-go-this-fast speed, there was quite a bit of shake to the vehicle in general.

There is 0 shake at normal city speeds, or even very high highway speeds for that matter. I'd rather not say specific numbers, but bare in mind, I'm a very safety orientated person. Lets say this starts happens at about 5500rpm+ @ 6th gear.

I am assuming its probably the rims being a bit bent.

So before I go out and buy new rims, I thought I would give rim straightening a try.

I have a couple of questions, for anyone that knows about this sort of thing:

a) Are "they" able to straighten only very slightly bent rims? Since this pops up during very very high highway speeds, I am assuming the deformation is only very slight.

b) A friend of mine told me there is a chance the rim can break in the process and they will have to weld fix it, basically fucking the whole rim up. How likely is this?

c) A friend of mine also told me that straightening rims is akin to pulling on a beer can tab. Once you do it one time, it softens the rims, raising the chance of deformation "next time" you hit a pothole. True?

Since the rim straightening is quite inexpensive, I thought I would go this route before dumping a shit load of cash on new rims. And besides, I REALLY really like the OEM BMW rims. They suit the car perfectly!

Thanks!
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      06-16-2014, 06:49 AM   #2
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Have the wheels balanced and the bolts tightened to spec. It may just be a wheel out of balance
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      06-16-2014, 07:16 AM   #3
SenorFunkyPants
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As above...its unlikely you have a bent rim but if you do it will show up on the wheel balancing machine - in that case buy a new rim, you won't need a whole set.
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      06-16-2014, 08:00 AM   #4
anom3
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hi petros, may sound like a dump question, but im not quite well versed in this vehicle stuff so...

everywhere online im seeing 88lb / 120nm as the proper torque for the bolts.

does this sound correct for an e92 m3?

just want to make sure i have the proper info before going to get the balance done.

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Originally Posted by Petros View Post
Have the wheels balanced and the bolts tightened to spec. It may just be a wheel out of balance
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      06-16-2014, 10:00 AM   #5
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yes i believe that's correct. i usually just put 90lb ft on my torque wrench. do not overtighten the lug bolts
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      06-16-2014, 11:28 AM   #6
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88 ft-lb is correct, though wheel lugs aren't exactly high-precision torque applications, so you can easily use 90. Hell, a lot of indy shops that use impact wrenches just torque everything to 95 lb-ft or so because that's within reason for basically any car. If that doesn't fix it, it could be a balance issue. I've lost wheel weights at the track before, after which I get some steering wheel vibration even at regular highway speeds. It could also have just been something about the pavement you were on when you did this.

As for your rim straightening questions, I can't answer #2 and #3, but yes it is possible. When I got new front wheel bearings, the shop I used noticed that one of my wheels was very slightly bent, likely due to having dropped that wheel off at the track in an unfortunate spot. The shop basically heated the affected wheel to a rather high temperature to temporarily soften the metal enough to allow it to be reshaped a tiny bit. The result wasn't absolutely perfect, but buying a used wheel probably wouldn't be perfect either, and I wasn't about to spend $850 before tax and shipping to get a new front rim for an issue that doesn't even occur under normal conditions. Even if the rim hadn't been straightened, my issue was probably minor enough that wheel weight adjustments could have cancelled it out anyway.

Which begs the question: Are you seriously contemplating spending that kind of coin to fix a problem that only occurs at speeds you're not even willing to talk about here? Assuming your car is 6MT and you have 19" rims, 6th gear @ 5500 RPM is ~123 MPH, though your speedo will likely be off somewhat at those speeds. Safety-oriented or not, go to the track if you need that kind of outlet. You'll find that a) accelerating hard on the highway is not at all "pressing the car hard", and b) it's a lot more fun to be fast in the corners than floor it down the straights, the latter of which any clown can do. And that doesn't even include the facts that doing those speeds at the track is a lot safer for you and others than doing them on public roads, you don't risk huge fines and/or arrest, and you actually learn what sort of car control is and isn't available at higher speeds. Plus it's just a whole lot more fun than you'll ever be able to have on public roads no matter what you do there.
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      06-16-2014, 12:19 PM   #7
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If you look for a shop that does "Road Force Balancing", you will likely get a better result than you would with old-school spin balancing. I had a slight vibe at 75 mph+ (felt in the steering wheel) when I bought my M3, and the Road Force balancing of the fronts fixed that.
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      06-16-2014, 12:35 PM   #8
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Are your wheels aftermarket or stock? Lots of threads on here about aftermarket wheels causing vibration. Might also check to see if you have/need hubcentric rings if your wheels are aftermarket.
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      06-16-2014, 01:16 PM   #9
anom3
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stock.

Quote:
Originally Posted by whats77inaname View Post
Are your wheels aftermarket or stock? Lots of threads on here about aftermarket wheels causing vibration. Might also check to see if you have/need hubcentric rings if your wheels are aftermarket.
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