Halachally speaking, do arm-Tefillin straps have to be a specific length?

Question

Strange but simple question.

I own a pair of Tefillin and because of the width of my arms I always struggle to get the final strap wrappings for the arm Tefillin down to my finger knuckles. I can accomplish it but it requires an extremely tight grip and multiple attempts. It makes it hard for me to easily do the mitzvah like other Jews.

Is it legally acceptable to have your strap length increased or is the length a religious standard which no Jew has the liberty of altering?

Are there shops which do this?

Answer 1

There is no universal rule on how long the teffilin straps have to be. The required size is dependent on the one wearing the teffilin. As long as the teffilin are long enough for the wearer, to accomplish what's written below, the teffilin are kosher for him.

Shulchan Arukh, Orach Chayim 27:8

אורך רצועה של יד כדי שתקיף את הזרוע ויקשור ממנה הקשר ותמתח על אצבע אמצעית ויכרוך ממנה על אצבעו שלשה כריכות ויקשור ונוהגים העולם לכרוך על הזרוע ששה או שבעה כריכות: הגה ואין לכרוך הרצועה על התיתורא כדי לחזקה על היד

The length of the strap on the tefillin of the hand [needs to be enough] in order to encircle the arm, and tie a knot from it, and stretch it over the middle finger, and wrap it around his finger three times, and tie it. And the global custom is to wrap it around the arm six or seven times....

There is no problem in buying a longer strap from a trusted sofer or judaica store and asking them to help you replace the old one.

Answer 2

There is no halakha that the arm strap even has to be wound around the arm seven times... just wind it less than 7 times and your problem is roundly dismissed! That it must be seven times is a modern day chumra but people act like Moses gave it.