Alignment and tires sequence?
 

The answer seems obvious to me, but I had a conversation with a mechanic a couple of years ago at a local pub who advised getting alignment done before getting new tires (on a car that showed uneven wear on the fronts and was pulling left). I thought it made more sense to put the new tires on and then do alignment, as the suspension geometry would reflect the correct contact points on the road. If you tried to align with badly worn tires, wouldn't you then be aligning to how those tires contact the ground and throw off the geometry for when the new tires are installed? He was insistent, I disagreed, and we went back to our pints and continued with other car talk subjects. FWIW, I think he was a few pints ahead of me! 🍻

Fast forward to the present: my son's elderly 525i needs new front tires due to an obvious alignment issue. I'm inclined to get the tires first, then schedule an alignment ASAP. What say ye? Thanks!

first get new tires, then do the alignment.

Guys at alignment shops may look at a new set of tires and say "these look great, no alignment problems here" and maybe not do a thorough check. If they see worn tires from an obvious alignment problem, they may take a much closer look.

New tires then align. A decent alignment shop knows the sequence and knows you want to preserve the new tires! At least you didn't buy used tires. They're a bit on the hook if the new tires start to go bad immediately or the alignment feels incorrect.

Ya, thanks. You all are confirming my thoughts on how to proceed. I'm baffled by that mechanic's view and was wondering if there was any possibility that I was missing something. Maybe he was speaking from the experience of seeing people get new tires, failing to follow through with alignment and chewing up a set of new tires, but he didn't say that. And even so, if the alignment is set for bad tires, it will be off when the new tires are put on, and they won't wear properly, and the car probably won't drive quite right. Jeez, neeess to say, he ain't my mechanic!

It would be nice for the tech to look at the old tires to diagnose the alignment problems, but it's better to align on new tires. Pretty easy solution these days, just take pictures of the old tires with your phone (be sure to document the location) and show them to the alignment shop.

New tires AND alignment at the same ship. That way they can see how the old tires wore.

To me a set of old worn tires are of no use to anyone. He has to set the alignment to a factory spec. or specific use such as performance driving use and the tires aren't in the equation really. He's setting the alignment to the wheel, not tire anyway.
This of course discounting a bent frame or other terrible unknown problem thats rare.
Unless you're paying a premium, you're getting a factory align number at most.