Tire change (and Thanks for help on Sears Battery)

[Minven Wang <mwang@stern.nyu.edu>]

Last week I went to Sears and get the International Series battery (CCA 
650) for $70.  I've called around and all others have is a Delco battery 
(CCP450), so I decided on Sears.  So far so good.  Thanks to all who helped!

Now the new question (misfortune always come in pairs):  My right front 
tyre hitted a screw maybe yesterday and was flat 
this morning.  So I got the tyre replaced.  I asked whether I 
should replace both front tyres together.  The guy at the shop looked at my 
tyre and said it looks OK and no need to replace both.  But the Audi 
owner's manual says replace at least both tyres in the same axial together.
So what's the net wisdom on this?

The new tyre I got is Firestone 185/70R14 tRIUMPH 2000 w/s. ($45)
The old one is Perrilli P300 same size.  Both tyres are radial but the 
tread pattern is a little different.  I've put a nickel in the treads of the 
old and the new tyre.  The difference of the tyre wear is about 2 mm.  

I hesitated to replace both tyre, due to the consideration that in NYC, 
there are all kinds of stuff on the road.  Sooner or later the other tyre 
will go.  Also put on two new tyres may attract unwanted attention from the 
local thugs.  But I'd like to know what's the potential hazard for 
uneven tyres.  What if I put a little more air in the old tyre so to 
balance out?

Thanks!

Minven