Selecting the correct spiral balance, pivot shoe and stop block

Thanks for posting, Michael. It looks like you have both a Series 900 and Series 600 spiral balance. The color tips you need in each case will probably be Red but it can't hurt to weigh your sash. I also agree that the stop matches our 55-063.

I'm not sure what the pivot shoe might be. I'd like to see a picture of it and I'd also like to know its width and thickness.

Concerning whether to use the Series 900 or Series 600, it's not really a matter of advantage. They're both different balances and are not meant to be interchangeable. That they are interchangeable in your window is curious, but I guess not unheard of. It sounds like the original installers just kind of used whatever they had on hand.

That said, your shoe is over 1/2" thick and I do agree that our 15-015 is the best match. It looks like it'll fit perfectly. The 15-015 is also most commonly paired with the Series 600. The Series 900 is technically compatible, sure, but if I were the installer then I would never pair a balance that skinny with a shoe that thick. There's a good chance your windows were meant to have the Series 600 originally. 

Concerning sash weight, moving up to the Blue probably won't make the windows work better. There's a good chance your windows were hard to open not because of weak springs, but because the balances just lost tension from age and use. One nice thing about spiral balances is that this can sometimes be fixed by charging them with a tool like our 75-006. Giving them two to three turns usually gives them a little life back. Otherwise I think you'll see the same results with a Red tip as you would with Blue.

Sounds good to me! Let me know how it works out, or if you had any questions.