FW: varchar vs char - update statement

[Julien Chavanton]

I have a database with several tables that can have up to 100 000 rows
there is ~100 updates every seconds and ~100 select query on the same
table using locks.

The update is always on the same field a varchar(15), I believe it will
be recommended to change it to char(15) to improve performance of the
update since the required space is not reserved with a varchar(15) type.

Is this assumption right?