Thanks but I have searched endless sites and videos on this and no one mentions whether the spring actually compresses when tensioned. Before my cables snapped the spring ran almost the full length of the bar but as soon as I release the two screws and begin to tension it pulls to the right side of the door and is quite a distance from where it was.. oh and the link you supplied doesn't work

Shaun
September 2015

Think about it. The spring is to balance the rotating force of the shaft.

Why, oh why doesn't anyone search for themselves? 30 seconds! that's all it took to find a Really Useful Guide.

Scroll down about half way and you will learn how to tension a Henderson spring.

http://www.garagedoor-spares.com/technical-guides/

XX
September 2015