Your mother inherits two copies (alleles) of every gene, one from here father, one from her mother. Assuming your maternal grandfather was bald young (mine was), you have a 50% of inheriting this bad gene from your mother. You may also inherit the copy she inherited from her mother, which may be better or worse than the one she inherited from your father. Men have two copies of most genes, except the genes in the sex hormones where the male Y chromosome often does not have a complimentary allele. If baldness factors are on the Y chromosome, then this will be determined by your mother, not your father. However the gene you inherit from her may come from her paternal line or her maternal line, so even if her father is bald you may escape.
I did not, my father started balding in his 40s, but I started balding in my mid 20s, maybe even early 20s, just like my maternal grandfather. I'm certain that I inherited this bad gene from my mother's paternal line.
I'd say if your maternal grandfather is bald you have a high chance of taking after him (up to 50%), depending on if your maternal grandmother has good or bad copies of the same genes.