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When a vehicle's alignment is off, people say the car "pulls" to one side or the other. However, if you've never gotten to feel a bunch of cars in varying states of alignment, it's hard to tell whether there's too much pull. How much pull is acceptable before the damage you are doing to the tires warrants going to get your alignment adjusted?

  • If I try to let the car go where it wants to go, the result is quite varied. Presumably this is related to the state of the car when I let go. When trying to gauge alignment, is it best to use my best case, worst case, or average case behavior?
  • How straight is "good enough? For perspective, my best case scenario let me drive about a quarter mile while letting the car do what it wants before I got close enough to leaving my lane that I chose to intervene. My worst cases started to leave the lane in the range of 5-10 seconds.
  • I definitely notice a preference for the car leaving the lane to the left. Should I assume that is my car's alignment, or is that something which could simply be a side effect of how I, as a person, choose to center the vehicle in the lane before testing?

A related question: Wheel Alignment: Just how bad is bad? (but in their case they are taking measurements off of the car directly. I'm looking more for heuristics).

  • Drift or pull cannot be used reliably to judge wheel alignment. 90% of the pull cases we test are traced to defective tires. Vehicles with significantly improper toe angle settings can track straight. – Fred Wilson Nov 2 '16 at 6:37
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No amount of pull is acceptable. In order to gauge the alignment properly:

  1. drive on a flat road (most roads are inclined to that rainwater runs off, usually the center of the road is a lot flatter)
  2. drive straight
  3. let go of the steering wheel

The car needs to go perfectly straight. If it doesn't, your alignment is off and you will start shredding your tires. If it's off by a little bit, you will shred your tires slowly. If it's off by a lot...

  • I think shredding is too strong of a word, if it is slight it won't be that critical – method Nov 2 '16 at 5:04
  • @method Probably too strong a word, yes, but it is what is happening to the tires, be it gently. – tlhIngan Nov 2 '16 at 5:28
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Its actually rather rare for a vehicle to travel straight without drifting a little bit. I call it drifting as this gives a lesser impression of a fault rather than the word 'pull'. If a vehicle actually 'pulls' to one side its probably set up inaccurately. Once setup properly though, even the weight of a light passenger etc can assist in giving a vehicle different steering characteristics with regard to drifting across a lane slightly.

Normally if tracking etc is set up properly a vehicle will still drift a small amount to the left due to the camber of the roads surface which is designed to allow water run off it. If this crown & camber in a roads surface wasn't present many roads would have far more standing water around when it was wet, so they are built with a camber.

As an ex technician ('ex' due to injury) I would always set my own cars up as best I could, THEN.. if I noticed slightly excessive tyre wear one way or another I would tweak my track rods very slightly through the year to get the best tyre longevity possible, yes this may have effected grip levels very slightly from manufacturers settings, but I definitely got my money's worth from tyres that in the end would wear almost perfectly evenly.

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