I found this post else where on google, hope it helps
Greeting! I've was changing brakes on vtz T25(same tractor as belarus 250).It's 95% chance that You don't have to change them You just have to adjust.Brakes are in rear differential housing and if You want to change them You have to take entire housing apart from gearbox.It is a whole day job per brake if You doing it for first time.These belt brakes dont brake as well as drum or disc brakes but they do their job.To adjust unscrew 4 screws on top cover(5*15cm) on each side differential housing.In there there are two nuts,unscrew them.Under them is one biger for adjusting,tight it.There are also 3 setscrews outside housing for adjusting when brake is not hit.screw them to the end and than unscrew them for 2 turns.That should be it!
I also just found this too,
The tractor has internal band brakes,to adjust them there is a little half moon cover on each side of the rear housing that you access from the back of the tractor.There are 4 bolts you remove and take thes covers off.You will then see the band with 2 nuts on it ,one is the locking nut.Loosen the first not and tighten the inner nut until your adjustment comes up to where you have an inch or two of play in your pedals.Tigthen your locknut back up and reinstall the covers.
Don't know which you have but if you look at your repair manual and this maybe something will seem the same.
Good luck . . .John