Well that is not good news.

I was hoping to go up to at least a 30T just to make sure I had extra low for climbing, but having to replace a RD to get there is more trouble and expense than I'm willing to incur.

Thanks for the input though. Better to know this before buying parts I can't use.

Again, no experience with SRAM. However, Shimano RD specifications are conservative enough such that they can usually handle 2T more than the rated largest cog.

If you know the model and year of your bike, you should be able to look up what specific RD you have and from there the max cog and wrap specifications.
You can exceed the wrap safely if you size the chain for the big-big combo, you just won't be able to use the small ring with some of the smaller cogs.
Exceed the max cog at your own peril, unless you get one of the hanger extenders (I have no experience with these)

I just got the Ultegra 12-30 from Jensen, it is a pretty good deal.

Good luck!

Thanks for the photos. That appears to be the older RD, from 2008-2012 or so.

You may need to start a new thread on here to get better / more people to respond, hopefully with more experience with SRAM Red of that era. The title on this thread asks about hub/cassette so different topic

A pic in the big chainring & biggest cog could be included so they can see what your current chain looks like with the lower (tension) pulley in the forward position.

OP: FWIW, my experience using SRAM chains on a Shimano drivetrain has been that they work flawlessly with Shimano ders/chainrings/cassettes and are reasonably long-wearing. Plus, some of them can be found at good prices. That's particularly true of their 6/7/8 speed "830" chain.

I've also had good experiences with KMC and Shimano chains as well.

But as noted above, pretty much any major-brand 10-speed chain should work for your newest bike.

Edited to add: whichever way you go, I'd strongly recommend installing it with a quick link. It's much easier to remove a chain for cleaning and/or maintenance if a quick link is present.

If you end up using a chain without one (until recently many Shimano chains used special "snap off" pins for final connection after sizing, and many still might use them), KMC and SRAM make and sell quick-connect links. I'm a fan of KMC's variety, as they can be found in both single-use and reusable variants with not too much difference in price, for all speeds up to at least 11-speed (haven't had a need to investigate 12- or 13-speed quick links).

Wipperman also makes chains and quick links; they're pricey but reputedly of great quality. Their quick links ("Connex") are of a different design that apparently doesn't require any tools for removal. Some people who've used them swear by them. I've never used them, so I can't comment on their merits.

Thanks for the info, guys. I suppose if I just happen to stumble on a great deal for either a SRAM or Shimano 10 speed RD, I might revisit the project. But the idea of replacing the RD to make this work is prohibitive to me considering I have regular road bikes that already have the gearing I want.

You currently have a SRAM rear derailleur, which means a SRAM shifter. A Shimano rear derailleur will not work on your bike

your image shows a SHORT CAGE der.... it won't work well with more than a 28 tooth Cassette... a mid cage will handle up to 32, depending on the front gearing...

how often are you pushing the 53 front and oh, say.. the 14-16 range in the rear? not often?

ever shift to the 11 in the rear when in the 53 front?
only on long downhills, and then not at a high cadence?
Get a COMPACT 50-34 crankset instead of all this swapping and worrying... and then get the 11-28 cassette on your present wheel.

the closer to physical limits you get, the more finicky the drivetrain will be.... and the chain can remain the same with the 50-34, 11-28 combo.... with maybe a couple links shorter... The other swapping, etc. option will require a longer chain to go with the longer der. cage and larger cassette...

https://www.sram.com/en/sram/models/rd-red-b1