Help identifying correct spiral balance

A quick learner from Virginia says:
My single hung vinyl windows have 34" length 3/8" diameter spiral balances. However, they have a black tip, which is not listed as one of the color options for that size of balance (for series 900).

I don't have a convenient way to weigh the window panes. Is it possible for you to estimate the color I need based on the window dimensions?

I have three different window sizes that I need to replace spiral balances on (I've attached an image of one of the windows for reference as well):

42" x 35"
33" x 35"
29" x 35"

One additional question:

I believe that I need a Series 900 Spiral Balance, but I would feel better if someone could take a look at the attached image and let me know if it looks like a Series 900 would connect to my pivot lock shoe (picture attached).

The main thing I'm unsure about is the Series 900 pictures show two sets of metal nubs at the ends of the balance and I can only see one set in my windows (but perhaps the top nubs are resting inside the lock shoe).

Thanks in advance!

User submitted photos of a spiral balance.
Profile picture of Tom
Tom from SWISCO responded:
Thanks for posting. Unfortunately, there is no way for us to determine what your sash weight is based on just the sash dimensions. We will have to know its weight.

I also cannot determine whether or not you have the Series 900 based on this image. They are hard to eyeball when just looking at the spiral. However, if you say the tube is 3/8" in diameter, then I think there's a good chance. I also agree that the second pair of nubs is likely hidden by the pivot shoe.
A quick learner from Virginia says:
Thanks for your quick response, I've taken weight measurements and some better pictures and have some followup questions!

** Followup Question 1 **

I've removed the window and taken what I hope are better pictures of the end of the spiral balance and the pivot shoe.

The diameter of the spiral balance is definitely 3/8". Is this enough information to determine whether I have Series 900 Spiral Balances?

** Followup Question 2 **

Also, I've removed and weighed my three window sizes. They are:

42" x 35" 33.6 lbs
33" x 35" 21.6 lbs
29" x 35" 18.6 lbs

Based on this information, it looks like I could use either Green Tip or White Tip S900 balances for the 18.6 and 21.6 lbs windows and Yellow Tip S900 balances for the 33.6 lbs windows.

Does this look accurate? What would you recommend (particularly where both white and green fall in the weight range)?

** Followup Question 3 **

I'm considering replacing my spiral balances because some of my windows slip down when opened before holding their position. These I might be able to fix by simply adjusting the spiral balance tension.

However, many of them also make snapping / popping noises when moving up and down which sound pretty clearly to be coming from the spiral balance. My assumption is that replacement is my best option in those cases.

** Followup Question 4 **

Finally do you recommend putting any sort of lubricant on the pivot shoe and pivot shoe track to improve ease of window movement? I believe I've read that a silicon-based lubricant works well there.

Thanks again in advance,

User submitted photos of a pivot shoe.
Profile picture of Tom
Tom from SWISCO responded:
I'll answer your questions one at a time: 1) If you have a tilt window and the diameter of the tube is 3/8", then there is a good chance our Series 900 balance will work. However, we can't say anything more by only seeing the tip of the spiral. You will ultimately have to use your best judgement.

2) I'm not sure what tips will work for what as I do not know the length of the three balances. Knowing the sash sizes does not help with this. However, we have a chart under each Series 900 length that shows what kind of weight each tip color can support. Some of them do cross over, but as long as your weight falls within the range of one of the color choices, that color choice should work. Again, you will have to use your best judgement.

3) If your balances are making noise, then it may be time to replace them, yes. It wouldn't be a bad idea to charge them a little first, though, just to make sure.

4) Yes, we recommend silicone spray, as this does not attract any gunk.
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