I would not use it because you'd have to buy an extra to replace it everytime. An exception would be if you were alright with an old used tire as the spare. That is ok with me, with the exception of the CR-V, the exposed tire situation is a little different. We don't use the spare cover on it because it's somewhat old, plus we have alloys, so the bare rim actually looks better anyway...and you need a new tire to get away with it exposed and still look tidy.
Extending lifetime of any given set of tires has limited benefit too. Obviously, the cost for aquisition of 5 vs 4 negates any benefit of extended lifespan for the set. Another reason, for me, is I like to buy newer models of tires, and buying 4 is more often that I can select a old prefered model or new one that looks interesting.
One good use for the new spare tire from the factory, is used as part of a set or as a pair with another matching one. Generally, I think of tires in pairs or sets of four. Buying 2 new ones seems so natural, mostly all of my logical rotation plans and schemes for winters etc, would be blown by incorporating five. The brainiac/simpleton answer to this question might be that 4 is divisible by 2 and 5 is not. Two axles, two tires...get it?
![[Duh!]](/forums/graemlins/pat.gif)
Finally, the spectre of 5 "dog" tires verses getting stuck with only 4 that you don't like is not as bad. My AWD Audi manual not only indicates a 4 tire rotation, but keeping them on the same side. This makes sense w/directionals. Afaik, cross-rotation is only for when you have a wear problem like cupping.
I run 4 different mounted sets (all fours + doughnut) on the Audi and the used 1998 CR-V got an extra set of (4) rims/tires from a 2005, the same day we bought the vehicle.
One more thing, directional tires??? Even as a spare, you only have a 50%/50% chance, 5-tire rotation would be completely messed-up. If you get a new directional tire as #5, buy a match and use it as a pair.
[ January 20, 2006, 09:13 PM: Message edited by: Audi Junkie ]