Inner tube pattern
 

Just replaced an old tube, noticed a strange crossed pattern. I'm sure it's my fault, but I'm still curious how I caused it? The tube is OK otherwise.

https://cimg7.ibsrv.net/gimg/bikefor...a772c34cf.jpeg

Low PSI?

Are those marks on the side of the tube? Tire iron marks? Or is there a similar pattern on the inside of the tire?

One thing I try to do is keep the inner tube untwisted so any damage seen on the tube after being pulled out can be matched with the same spot on both the tire and rim. (And I always mount tire with the label either the valve or the rim weld. I vacillate between the two, Valve is easier and faster but the label gets dirtier from my hands while pumping and the rim weld location has a long history as that is where tubular tire labels are located. Tugs my heart.)

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Yes, the marks are on both the sides of the tube. This pattern goes on both sides all along the tube, not on a specific spot. No marks on the rims or the tire itself.

It’s the threads of the tire casing like those below. It looks like you use talc.
https://cimg9.ibsrv.net/gimg/bikefor...522887bca.jpeg

It also looks like your tire is a 60 thread per inch (TPI) tire. Low thread count tires can be a problem if one of the threads breaks. The messed up portion of the tire above looks like this from the outside.

https://cimg0.ibsrv.net/gimg/bikefor...fa9529a87.jpeg
https://cimg2.ibsrv.net/gimg/bikefor...a71a34d49.jpeg

The tire had a definite snake belly to it.

https://cimg8.ibsrv.net/gimg/bikefor...786d60463.jpeg

Maybe it's when the slightly undersize tube makes contact with the tire when inflating, it "creeps" a bit and leaves "scuff marks"?

That is caused by riding a flat tire.

I don't know if this statement is true or not, but based on Occam's Razor, I like this response.

Don't remember ever riding a flat tire.

​​​​​​I did roll the bike with deflated tires out of my garage this year. Maybe that's it. Strange that this only happened to one tire, the other one didn't have this.

Also thought about it, I sometimes even hear a popping sound when a new tube untwists itself during inflation in the tire. Maybe that's it.

The popping sound is likely the tire seating in the rim. Why would your tube have to untwist? If it is twisted inside the tire, you have installed it incorrectly.

Some tires were/are made by Spanish inquisition to torture those who installs TLRs with normal tubes. Challenge Bianca Pro HTLR is one of these, there is absolutely no easy way to install a non-latex tube without twisting it in a few places. But it's great tire otherwise.

The tube in my photo came off an old Conti Cyclocross tire, I think it was TLR too and I struggled a lot while changing the tubes with it.

Those are just marks from the texture on the inside of the tire from the cords that cyccommute showed you. Next time you have the tire off look on the inside and you'll see the texture that imprinted itself on the tube.

Keep in mind that as you ride the tire squirms around a little and the tube squirms a little inside the tire as well. Over time if the cords are quite proud on the inside they will micro wear a pattern like this into the surface of the tube. It's nothing you did. It's simply the tire's makeup affecting the tube.