What's the worst thing that can happen if I overspec my garage springs?

October 17, 2020 6:22 PM

My garage door extension springs are getting stretched out and janky, so I want to replace them. Problem is, they are supposed to have a color coded mark on the ends but it looks like it wore all away, so I have no idea which weight rating to use. I read that 140 lb is pretty typical, but that's just a guess based on internet searches. If my door is much lighter, am I doing any harm by over speccing the springs? Thanks!
posted by gzimmer to Home & Garden (7 answers total)

Best answer: The spring counterbalances the weight of the door, so what you need to do is weigh the door. Literally.

If you use the wrong weight, the door will be hard to open or close, and if it’s enough wrong it will want to want to open or close all on its own. Too big is no better than too little; if you over counterbalance the door, the spring will overbalance gravity and pull the door open.
posted by doomsey at 7:21 PM on October 17, 2020 [4 favorites]

I just had a spring break but was fortunate to have the label on an adjacent one. In my Googling I see my P728C p/n is also a description: 28" Plug-End Spring (.177" #7 Wire). The "C" suffix is for a clip that I already have. So if you have some good measuring sticks you can make a fair guess by inspecting the ones you have (cross your fingers it is not a Low Force version)

As a sanity check I just measured mine:
- The painted wire measures Ø.192" using a caliper... the link has a smarter method.
- The length of the unstretched coils is 28" + one turn.
- Bonus: the Outside Diameter of the coil is 1.27"

btw, the label in the spring I installed yesterday is now just hanging on by a corner.
posted by tinker at 7:51 PM on October 17, 2020

Call an overhead door company and ask. Tell them what size your door is and material, they should be able to recommend the right spring.
posted by disconnect at 9:58 PM on October 17, 2020 [5 favorites]

Measure the spring. Total coil length, wire diameter, coil diameter.

Honestly? If you're asking this question, maybe call in a professional. I'm a total DIYer, but garage door springs can kill you.
posted by notsnot at 5:54 AM on October 18, 2020 [28 favorites]

I agree with notsnot; I am a big DIYer, but unwinding and winding a garage door spring is a job that I will happily pay a pro to do. That's one job that I will absolutely nope right out of.
posted by xedrik at 7:29 AM on October 18, 2020 [2 favorites]

Big DIYer here as well but like electrical stuff, but there are a lot of unknown parameters around spring size and tension - getting it wrong could kill somebody down the road. I would say though, to be aware that garage door service companies can be pretty scammy (at least those around me in Toronto). If you need new rollers, decline.
posted by bonobothegreat at 8:17 AM on October 18, 2020

Response by poster: Thanks for your advice. I found this youtube video to be the most informative
posted by gzimmer at 2:56 PM on October 21, 2020