Tires: mixing regular and Extra Load tires, continental tires, rear tires

Question
Hi! I bought a pair o' Continental tires on ebay and noticed, after they were on the car, that they're Extra Load tires (which my car doesn't require).  They felt underinflated at the std. pressure.  Conti's website indicates that XL tires need higher pressures, so I bumped it from 32 to 40 psi.  So two questions: 1. is that too much? 2. the rear tires are still the OE tires at 32 psi; is that OK?  

Answer
Dennis,

There's quite a bit of stuff here:

First - XL tires have the same load carrying vs pressure curve as SL tires, except that the XL's are extended with additional pressure and load carrying capacity.  That means the pressure should have remained the same.

I'm going to bet the real problem is that the SL tires have an OE requirement for handling, where the XL's have more of a ride requirement.

You didn't tell me, but I'll bet the XL's have more tread on them.  If it is a lot - say 3/32nds or more - the better tires ought to go on the rear, so you won't spin out if the vehicle hydroplanes.

And the last bit - the proper pressure for a tire is listed on the vehicle placard, which is usually located on a doorpost or in the glovebox, provided the tire size is the same as listed on the placard.