Serpentine belt tension with hot engine

[Greenjeep1]

I have noticed that the serpentine belt on my 98 XJ is a lot tighter at normal engine running temperature, than with a cold engine. Has anyone else noticed this? Should the belt tension be correct with a hot or cold engine? I am using a Gates belt, is the brand of belt important?

 

[langer1]

If you can tell a differance between hot and cold then your belts loose.