Why is wheel alignment needed after control arm replacement?

Multibimmer · 08-19-2015, 08:29 PM

I replaced my 2007 328i's upper control arms (aka throust arms - the more curved of the two control arms) way back in November of 2013, over 15,000 miles ago. I neglected to do a wheel alignment afterwards. I just replaced the lower control arms (the straighter ones), and I've read several places that a wheel alignment is required after a control arm replacement. The tires are wearing perfectly evenly, there's no sign of tramlining, shimmy, vibration, pulling to either side, or any other indication that the alignment is off in any way. So, as it says in my subject line, why would an alignment be needed after a control arm replacement?

In fact, it defies logic. Assuming the car was perfectly aligned when it left the factory, the alignment probably drifts away from spec over time as the suspension components wear, but when major parts like the control arms are replaced, this act should pull the alignment back to factory specs, unless there are significant deviations in the lengths of the factory arms versus their aftermarket counterparts. This would not be true if I had done periodic alignments during the life of the car, which I haven't done.

The other issue is that the only metric that's readily adjustable in these cars is the toe - adjusting camber and caster requires some sort of expensive, special equipment, as I understand it, which of course raises the cost of the alignment. I'm inclined to either do nothing, or just do a simple check/correction of the toe. The tires have maybe 8000-10,000 miles left on them, so maybe I'll do a full alignment when it's time to replace the tires, but I'm not even convicned this makes sense. I'm all for maintaining my car - I've proactively replaced the water pump and thermostat, flushed the power steering fluid a couple of times, drained and refilled the automatic transmission fluid, and the differential fluid, on top of regular oil changes and other critical maintenance. But I also don't want to throw my money away.

So, does anyone have a ture, factual (I'm an engineer, so data speaks loudest and most convincingly to me) explanation (no conjecture, please), or even a sound theory, as to why a wheel alignment should be needed agter replacing the control arms on these cars? Thanks.

feuer · 08-19-2015, 08:38 PM

It is not required but it is recommended. If you car tracks straight and you don't have tire wear just keep driving it and forget about the alignment as that might even make it worse as a lot alignment technicians are incompetent and shop are only looking to make more money.

08-20-2015, 08:43 AM

If you're that handy and an engineer by trade then, at the very least, check the toe yourself. You've trivialized it to a point where this is absolutely something you should be able to do yourself. If it's off: fix it. If not: let it be. It's not rocket surgery.

Post up the results after. You'll more than likely find that you've ended up answering your own question.

simon · 08-20-2015, 09:11 AM

Typically people replace their controls arms with M control arms. The lower control arm is longer and will put your toe out of spec. If you replace with the same arms I don't see why you'd need an alignment.

techwhiz · 08-20-2015, 09:26 AM

Because parts wear and if it has been adjusted as the parts wear it will be out of spec with a new part.

It's cheap. Makes no sense not to get it done.

TheBigYahi · 08-20-2015, 09:45 AM

I think you nailed it on the head. If you've never aligned it as the old parts wore out and are reasonably sure the toe hasn't drifted, new control arms shouldn't require a realignment. In my case, I've been aligned several times over the life of the car due to poor tire wear (especially right rear) so any new components would likely put it out of spec.

Jaronbwall · 08-20-2015, 09:46 AM

Quote:

Originally Posted by simon

Typically people replace their controls arms with M control arms. The lower control arm is longer and will put your toe out of spec. If you replace with the same arms I don't see why you'd need an alignment.

+1 Why wouldn't you get M control arms anyways?...

Multibimmer · 08-20-2015, 05:48 PM

Thanks for the replies. I think the key factor is whether or not the car has been aligned during its life. If not, an alignment shouldn't be necessary after replacing components with stock ones. The fact that my car's tire wear has been so even over the course of nearly 115,000 miles is a pretty strong indicator that these cars's don't need regular alignments, provided the quality of the roads it's been driven on is good. Here in central Texas, potholes aren't a problem, and the roads are very smooth in general, which probably goes a long way toward explaining why my car's alignment seems to have been so stable.

08-19-2015, 08:29 PM	#1
Multibimmer New Member 4 Rep 17 Posts Drives: 2007 328i Join Date: Aug 2010 Location: Austin, TX iTrader: (0)	Why is wheel alignment needed after control arm replacement? I replaced my 2007 328i's upper control arms (aka throust arms - the more curved of the two control arms) way back in November of 2013, over 15,000 miles ago. I neglected to do a wheel alignment afterwards. I just replaced the lower control arms (the straighter ones), and I've read several places that a wheel alignment is required after a control arm replacement. The tires are wearing perfectly evenly, there's no sign of tramlining, shimmy, vibration, pulling to either side, or any other indication that the alignment is off in any way. So, as it says in my subject line, why would an alignment be needed after a control arm replacement? In fact, it defies logic. Assuming the car was perfectly aligned when it left the factory, the alignment probably drifts away from spec over time as the suspension components wear, but when major parts like the control arms are replaced, this act should pull the alignment back to factory specs, unless there are significant deviations in the lengths of the factory arms versus their aftermarket counterparts. This would not be true if I had done periodic alignments during the life of the car, which I haven't done. The other issue is that the only metric that's readily adjustable in these cars is the toe - adjusting camber and caster requires some sort of expensive, special equipment, as I understand it, which of course raises the cost of the alignment. I'm inclined to either do nothing, or just do a simple check/correction of the toe. The tires have maybe 8000-10,000 miles left on them, so maybe I'll do a full alignment when it's time to replace the tires, but I'm not even convicned this makes sense. I'm all for maintaining my car - I've proactively replaced the water pump and thermostat, flushed the power steering fluid a couple of times, drained and refilled the automatic transmission fluid, and the differential fluid, on top of regular oil changes and other critical maintenance. But I also don't want to throw my money away. So, does anyone have a ture, factual (I'm an engineer, so data speaks loudest and most convincingly to me) explanation (no conjecture, please), or even a sound theory, as to why a wheel alignment should be needed agter replacing the control arms on these cars? Thanks.
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08-19-2015, 08:38 PM	#2
feuer Major General 4276 Rep 9,206 Posts Drives: wife crazy! Join Date: Apr 2015 Location: Chicago, IL iTrader: (5)	It is not required but it is recommended. If you car tracks straight and you don't have tire wear just keep driving it and forget about the alignment as that might even make it worse as a lot alignment technicians are incompetent and shop are only looking to make more money.
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08-20-2015, 08:43 AM	#3
FCobra94 Guest 0 Rep n/a Posts Drives:	If you're that handy and an engineer by trade then, at the very least, check the toe yourself. You've trivialized it to a point where this is absolutely something you should be able to do yourself. If it's off: fix it. If not: let it be. It's not rocket surgery. Post up the results after. You'll more than likely find that you've ended up answering your own question.
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08-20-2015, 09:11 AM	#4
simon Second Lieutenant 65 Rep 222 Posts Drives: E92 Montego Blue 328i Join Date: Mar 2005 Location: Atlanta, GA iTrader: (1)	Typically people replace their controls arms with M control arms. The lower control arm is longer and will put your toe out of spec. If you replace with the same arms I don't see why you'd need an alignment.
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08-20-2015, 09:26 AM	#5
techwhiz Colonel 453 Rep 2,973 Posts Drives: e90 335i Sedan - Arctic Join Date: Feb 2012 Location: Bay Area, Ca iTrader: (4)	Because parts wear and if it has been adjusted as the parts wear it will be out of spec with a new part. It's cheap. Makes no sense not to get it done. __________________ Arctic Metallic\CF Splitters, Spoiler, Mirror Covers\LED Tails\LSD\Tinted\Coded\Apex Square SM10-19"\LED Angel Eyes\Gloss Black Grill\Integrated V1 & Galaxy Tab\M-Performance Brakes\Cobb Tuned\xHP Flash\Resonator Removed and -> is your friend.
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08-20-2015, 09:45 AM	#6
TheBigYahi Private First Class 40 Rep 164 Posts Drives: 2006 330xi 6MT Join Date: Jun 2014 Location: Syracuse, NY iTrader: (0)	I think you nailed it on the head. If you've never aligned it as the old parts wore out and are reasonably sure the toe hasn't drifted, new control arms shouldn't require a realignment. In my case, I've been aligned several times over the life of the car due to poor tire wear (especially right rear) so any new components would likely put it out of spec.
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08-20-2015, 05:48 PM	#8
Multibimmer New Member 4 Rep 17 Posts Drives: 2007 328i Join Date: Aug 2010 Location: Austin, TX iTrader: (0)	Thanks for the replies. I think the key factor is whether or not the car has been aligned during its life. If not, an alignment shouldn't be necessary after replacing components with stock ones. The fact that my car's tire wear has been so even over the course of nearly 115,000 miles is a pretty strong indicator that these cars's don't need regular alignments, provided the quality of the roads it's been driven on is good. Here in central Texas, potholes aren't a problem, and the roads are very smooth in general, which probably goes a long way toward explaining why my car's alignment seems to have been so stable.
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