[Biturbos4] Rear caliper pistons on B5

[Jonathan Conta]

Apologies ahead of time if this has been covered - I'm new to the list.
 
I spent a day this past week swapping out my stock pads (2000 S4 otherwise currently unmodified - yet....) for some Mintex "red box" pads, both front and rear.
When changing the rear pads I was able to get the stock pads out without a problem, but when I went to compress the caliper pistons to fit the new ones in, I had a hell of a time getting them to retract back into the caliper.  I bought one of those pad compressor tools at Pep Boys and nearly ruined the thing putting so much torque on it pushing the pistons back in.
 
Has anyone else run into this?  Or am I staring some sticky/about-to-freeze caliper pistons in the face?  I did eventually get them back in and the new pads on, and I must say my initial experiences with the Mintex pads have been outstanding - much more even braking, less "grabby" than the stock pads, and significantly less brake dust.
 
Thanks much,
 
Jon