What to look for when buying a used RE050A?

a6walter1

At the end of last season one of my rear tires got a nasty (non-repairable) puncture. The rest of my tires have at least another season on them, so I want to buy a used RE050A for the rear to run through this season before I buy a set of RE-11's.

I understand that I want to look for the proper size (275/35R/19) but there are other parameters of the tire that I do not know what they are or if they matter. Such as, if the tire has a ZR in the name? From what I read, ZR is the old way of stating that the tire has the highest speed rating, until they split into W and Y. Also, what is the difference between 96Y and 100Y? Furthermore, apparently these tires came in run-flat and non-run-flat versions. I don't think the Z came with RFT tires, but would it matter if the replacement is RFT or not?

Those are just the questions that come to mind, if anyone could shed some light, that would be great!!

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My Journal (2012 PW 7AT)