supra_natural

What the alignment MFG (Hunter) told my shop about the alignment machines is this:

If its a rolling comp machine... you attach the sensors to the wheels and roll the car on the CURRENT tires... If its a rolling comp you want to have new tires to avoid any kind of "radial" pull issues that might occur. Things like bubbles in the tires will throw off the readings.

If your machine is the type that you lift off the ground, put the sensors on the wheels, then spin the wheels one by one, off the ground... if you have this kind of machine, the tires won't matter like it "could" on a rolling comp.

no matter the machine, or how good you did the alignment. you can still get pulling issues if the tread has a radial pull because of issues like bubbles.

different machines might have different requirements, call your alignment machine rep and ask that person, or put new tires on your vehicle first because that alignment is being done "as is" in that moment.

My shop does about 6 Alignments a day, we have very few come backs for alignment issues. We explain the readings to each customer so they are educated on the numbers and what they mean based on before and after specs on their print out.

slowcivic2k

Read the thread before responding with useless reposted information:

Since the behavior of the tires, new or used, cannot be compensated for on an alignment machine, and the fact that installed alignment equipment aligns to the rim itself, not the tire, means there is no real difference. I'm going to catch flak. Explanation:

The tires should be serviceable during an alignment, meaning they are not overly worn from left to right, that they are the same size, and that they are properly inflated. The vehicle must be evenly loaded as well, and ride height inspected. The alignment machine will take the tires as a constant. Any deviation will be interpreted as a mis-alignment. Example: Try aligning a vehicle with a compact spare tire installed. Since the machine expects a set of matching rims/tires, any alignment angle problem may be construed as a suspension problem to the machine. Most of us though, realize that a compact spare will affect ride height from side to side, and camber, at the least. (It is worth noting to me, that many tire facilities, including Firestone and Tires Plus will check your wheel alignment with a spare tire installed. I've seen it done..... and its great to watch!)

Slight changes in ride height are compensated for in the specifications for any given vehicle's alignment angles. If they weren't your alignment would be very unstable as the tires wear. These small changes in height are not enough to warrant adjustments out of range of factory adjustments. If you change rims and your spring ride height, you are altering a lot of suspension geometry, including bump steer, tie rod angle, scrub radius, and wheel returnability, etc.

In a typical exchange of tires, where the tires are evenly worn, and then replaced with new tires, there will be no noticeable difference in alignment readings, old or new. The only way for that to occur is by technician error (IE loose wheel, wrong tire, poor installation of alignment sensors, etc). Attempting to verify the alignment with a non-serviceable tire will potentially yield errant readings.

I should make an additional note, that new tires may grip the road with the current alignment angles differently, at least until the tire is broken in. The point of aligning a vehicle after a tire change is to help assure the new tires break in properly, and that suspension settling or shifting due to wear and tear is corrected before it has the chance to show up on the new tires.

So, in short, no, it doesn't matter on a stock car, with stock rims and tires, and stock ride height, and a competent alignment technician capable of correctly using the equipment.