Coil balance weight issue

A quick learner from united states says:
Here is a photo of my original coil.

So, my 1st window' coil balances broke, and since the original parts says 10, I bought from you S140-10L and S140-10R, installed, and when open and close the window, I really need to push and pull, with a LOT of force. I asked the question back then, I was advised to weigh the window panel, so I did, and roughly it is 17.2 pounds. So I was told to buy 2 S140-9L and S140-9R, but since I have other windows I can use, I didn't do anything further.

Then my 2nd window coil balance broke, with what I know, I weighed the window panel, same 17.2 pound, so I placed order for 9 pounder. Side note, I got a 4 pounder from you also.

So I installed the 9R on my 2nd window, also tight, not as bad as my 1st window, but definitely tighter than my other original windows. Then since I am in self quarantine and have plenty of time, I took out 10R and installed 4R on my 1st window, tightness is better, but still a lot tighter than my original window. Then I took out 4R, and only have 10L to support the panel, the tightness is almost the same as my original window. Here is my question, my window is 17.2pound, seems like 10L alone is good enough to support, is your 10Lin metric system, maybe 10 kilogram? Will your coil balance lose some strength over time, maybe 2 years from now it won't be as tight? If not, what do you think is the best way for me to reduce all the tightness in my 2 windows now?

This is a long email like I said I am social distancing and not going anywhere. :)

Hope u have an answer for me.
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Casey from SWISCO responded:


When customers come to us with problems using the S140 coil balances, many times it's due to the fact that this system is not an exact replacement for what they originally had. Many customers opt for the S140 because it comes preassembled but if it's not what you originally had, it's not going to work properly. Could you send us a photo of one of your original coil systems removed from the window? That might give us a better idea of what the problem could be. Thank you!

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