I need to replace the spare tire in my 1992 944. Part of me wants to buy a full-size rim and tire, which I know will fit in the spare wheel compartment. Another part of me just wants to buy another narrow tire (155/80, 15 inches) and use the old "temporary spare" rim.

Would an ordinary, normal-duty tire mounted on the spare rim allow me to exceed the 50 mph/50 miles limit? In other words, does that limit only arise from the properties of the "temporary spare" tire, and not from the properties of the rim? Or is the spare rim not strong/durable enough to handle full speed use? (I realize that extra driving care would still be required, given the narrow spare's lesser grip.)

I used to run 700-series temporary spare tire rims for winter tires.There is no speed limit, trust me :)

My local tire shop agrees. The 50 mile/50 mile/hour recommendation arises from the temporary spare tire, not the strength of the temporary rim.

Just put decent rubber on the spare rim... and it'll do whatever you need it to do.

As for the original 50/50 limit of the "Special Spare"... I put 300 miles on my old one at 70mph... after I had a blow out at the half way point of a 600 mile trip. Long story, but this is what circumstances dictated at the time.

-Ryan

Tasca Volvo sells a brand new OEM steel rim for 50$ and 10$ shipping. Why mess around? For 60$ to have a full size steel rim sitting in the trunk....just my 2 cents.

Forget brand new- head to the junkyard and fins a nice rim from a volvo of right type (look for an overheated one rather than a smashed one)
Often the tires are in pretty good shape too, and you can get out of there for 15-30 bucks.