In a message dated 96-11-04 14:44:35 EST, raven@HALCYON.COM (Mark McCulley)
writes:

<< 
 I'd like to begin a 5-tire rotation on my syncro so that I can get some
 mileage out of my spare. I realize that syncros require identical size tires
 on all four wheels to prevent viscous coupler damage. Is there any risk in
 putting my brand new spare on when the other tires have about 10K miles on
them?
  >>
No problem.  the coupling can take some mismatch.  That is why it is there.  

Dennis