Defective Schwalbe Marathons?
 

I have tried reseating them a few times each, but the tires wobble side-to-side and up-and-down like this every time. The bead line looks fine every time. I took care not to twist the tubes. Are they defective?

And the wheel is definitely true?

I've never seen that much wobble being caused from just the tire. Try it on a different wheel. I have a GK slick that has a visible wobble, no matter which wheel, but not as drastic as the posted video. Cannot give a definitive from answer from what can be seen on the video.

If the sidewall lines really are equally spaced all the way around on both sides and the rim is running true then that has to be a defective tyre.

Maybe the rim is too narrow. Move the camera around to show the side views.

Are you just jamming air into the tubes or pumping slowly?

With tubes, I find it beneficial to give 2-3 pumps of air and then massage the tire all the way around the rim, helping to set the bead - and then repeating that process until there's too much air in the tubes for the massage to make a difference. Even after that I'll give it a few pumps at a time to let tire find it's happy place.

is the Indicator ridge, just above the beads, showig equally all the way around, and on both sides of the tire?

if so, yep, you have a defective tire.
have you tried soapy water on the beads yet?
is the tube caught under the bead, maybe?
i've seen un-seatable tires before... new Schwalbes typically run tight, IMO
verify that the nipple strip isn't blocking the bead from seating.

how tight did the tire seem when you mounted it?
did you partially inflate the tube before putting it in?

I had exactly this problem with a pair of Schwalbe Marathon tires I bought to replace the Schwalbe Big Apple tires that came with my old Dahon Mariner D8. This was years ago, soon after I started riding and I wasn't confident enough to change the tires myself. I bought them on Amazon (again, before I knew enough not to buy such things there), lugged them down to Roy's Sheepshead Cycle (my LBS), they installed them, and I rode away. I noticed the same wobbling for the front tire. Brought it back, they removed then reinstalled it, with the same issue at which point they determined (and demonstrated to me) the asymmetry in the tire. I contacted Schwalbe and eventually (this was early in the Covid era) they got me a replacement.

If you have done all the checks that others outlined for you, then contact Schwalbe, not sure what effect doing so might have though, but just keep pounding their e-mail system till you get a response...hopefully.

I had a problem with a pair of Hutchinson tires about 8 years ago, the tread came unglued from the carcass, a lot like a recap tire coming apart, both tires did that in less than 250 miles and one month after buying them. I contacted Hutchinson many times, as well as the online bike shop, and neither responded, which fine, that is why I'll never buy any product from them ever again, so they lost a customer, probably not a big deal when they have a million or more customers.

A tire seating tool, such as Park Tool PTS-1, may help. If not a dedicated tool, a wide-jaw wrench may help. I had such situations with some new tire-rim pairs, and being active in seating the tire solved the problem.

Thanks for the comments so far. To answer them:
The wheel is definitely true.
I don't have any other 650b wheel to try them on, and it is on both the front and rear.
The rim is definitely not too narrow, and these tires are actually a little narrower than the stock ones I was replacing. They also wobbled, but not nearly as much.
Definitely pumping slowly with a hand pump. Twice each tire, I let all the air out and massaged them before pumping them back up. No dice.
The indicator is about 1mm from the rim and pretty consistent all the ay around.
I have not tried soapy water. I'll do that next just in case the tube is twisting.
I doubt the tube is caught or it would have popped on me by now with the installing and removing and riding.
The rim strip looks fine and won't move even when I push on it.
The tires were tighter than most tires, but not as tight as the GP5000's I struggled with.
I always inflate the tube partially first, and adjust as necessary to make sure the tube fits inside the tire without twisting or getting pinched.
I haven't tried a seating tool because the indicator line looks good (and because I don't have such a tool). Might be worth a try.

it's sounding more like a bad tire...

does the rim strip extend into the bead seat area at all?
too wide of a strip can cause issues..
the cheapo plastic ones are thinner and slippery...
mark where the worst wobble is, then dismount/re-mount/air up... if the biggest wobble remains in the same area, then i'd definitely say it's the tire, but only after verifying the rim strip is not intruding on the bead seat circumference... the flat area that's alongside the valley, if the rim is that shape...

certain rims are tighter than others, and same goes with tires... put the two together, and the sweat begins to roll...
i've bought a pair of Maxxis about 5 years ago... i finally gave up getting one to seat, and the other was not fun, but FINALLY went on after sitting in the sun on a hot day, at 30 lbs. higher than "max pressure"... i had tried them on several rims at that point, and chose the ones that measured the smallest diameter at the seat.
i used fishing line to measure the rims... and a second set of hands/eyes

i was wondering why "two new Maxxis Knobbies" were so cheap... i found out the hard way.
the seller said he just needed gas money.

ok I'm going to assume the tires are defective. Time to contact the shop or manufacturer.

aside from a tire being defective, I was once reading how "tire wobble" is a thing. I sometimes have that when mounting certain tires & so, I have to massage the tire back & forth on the rim in order for it to run straighter. always been able to sort it out w/o returning a tire

Any tricks to suggest before I make a claim with the company? I tried "pinching" them into the center of the rim and letting them spring back onto the hook after the tube is in, I have tried "pulling" the sections of the tire away from their wobble (like a section too far right gets pulled to the left). I got soapy water on the bead and the tube to let it resist twisting and getting stuck.

I feel like almost every tire has a little "wobble", but this is excessive enough that swear I can feel it while riding. Actually had it on a pair of Goodyears once, and that would make me figure I'm doing something wrong but the replacements they sent me had minimal wobble and rode just fine.

That amount of wobble is quite drastic. Personally, I would stop messing them. If you cause any kind of issue, a claim would likely be denied. Document the issue you have, and what you have done, make the claim soonest.

sounds like you've tried what I would have tried

If you want to try 1 more Hail Mary type of fix, put the tire in a tub of hot water for around 5-10 minutes and quickly mount and inflate while it's still warm. You've got nothing to lose as there is no risk of damaging the tire with this method and negating any warranty replacement.

Have you tried overinflating them? Sometimes that helps just to seat them.

I pumped it up to 5psi over the tire's max on the sidewall, but afraid to go much higher than that.

considering schwalbe tires' tendency to rip sidewalls loose from the bead wires... good plan!
why destroy a good tube trying to seat a bad tire, eh?

The manufacturers test at double the sidewall rating. You won't damage the tire if you only pump it up there momentarily. Seriously, this works very well in many cases. Just watch as you inflate to see if it wants to pop off, and if it does, then stop inflating.

I thought there was risk in damaging the rim if you overinflate? Never had a damaged tire nor rim from the pump, so it's all just what I've heard.

I don't think I would play games with the PSI, if the tire fails then there will be no chance in hell of getting them replaced under warranty.

I guess it pays to know how strong your rim is. I haven't dealt with carbon fiber rims or many other exotic things.