Hello!
>About the PPM-1: I don't understand Cyrillic alphabet that much so I could recognize that. Thanks for that<
You are welcome, dear SuperTank17!
>About BMP-1SM: Since it's Czech variant than shouldn't it be called BVP-1SM? And are you sure it's a Czech variant and not a Czechoslovak variant?<
I will check this tonight using additional sources. And inform you, of course. The problem is that book by Malyshev has the chapter Czechoslovakia / Czechia / Slovakia and it is not very easy to answer on your question exactly because of this. I thought it was Czech variant.

>I also would like to know what do you mean by "driving wheels" since you already told me that they aren't roadwheels. Than what are they? Return rollers?<
If I remember correct - there are four main types of wheels of AFVs: roadwheels, return rollers, idler wheels and driving wheels (drive sprockets). I mean driving wheels (the most forward wheels of BMP-1, one on each side, gear wheels). Perhaps, drive sprockets are more common name for them.

Regards, Vladimir