one cheap mofo and his garage door

Alright this isn't about me, although I am also a cheap mofo. The cheapie in question is my friend. The door is around 8'x7' and the springs are extension type.
I replaced one broken spring (I wanted to buy 2 but you can guess what happened) The old spring didn't have any color code, but the length and width were the same as the new 150# spring. I also replaced the carriage of the old genie screw 1/2 hp, because it's teeth were stripped. Also, I remounted the door end of the opener's track as it wasn't centered over the midpoint of the door.
After trying the opener a few times, I noticed the door wasn't sitting equally left/right in the opening which seems to cause some stuttering as the door closed. Also, one of the fixed pulleys is out of alignment by 10 degrees or so, presumably this happened when the opposite side's spring broke and the bad pulley's side took the entire weight of the door.
My questions:
-Does the 150# spring mean that the set is for a door that weighs 300#?
-If I replace the other spring with 150# (and replace/realign the pulley), would the springs be TOO STRONG for this door?
-If the springs are reasonably close in their capacity, can appropriate adjustments be made to 'equalize' them?
I just found this n.g., it looks cool. Thanks for any assistance!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
whence wrote:

The springs are marked and sold according to weight when used in pairs. Two springs marked 150 lbs are used on a 150lb door.

Get a bathroom scale and place it under the door with no springs attached. Then you'll know what the correct springs should be. You may still need to go one higher or lower, but this is where to start.

Only if they are the correct weight springs for the door to begin with. And then in the doors I have experience with, the settings on both sides were the same. I'd first make sure everything is right with the door to begin with. If the pulley is out of alignment, fix it. If the door is going up/down uneven for some reason, that may be why the spring broke.
Also make sure you install the safety cables that come with new springs.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The info trader4 gave you is good.
The BORG (Home Depot) where I am (Portland, Or.) has a good, free handout, in the same area where they stock the garage door extension springs, about how to weigh the door.
I'd never replace just one sping of a pair. Thats an invitation to problems of just the type you are describing. In addition, replacing only one guarantees that you'll be doing the job again in a year when the other one breaks.
I understand that your frugal friend didn't want to buy the second spring. He's awfully free with your donated time, labor and expertise. Me, I'd have simply told him that if he didn't buy two and replace both he was on his own. YMMV.
As to identifying the weight capacity of the old spring, there is usually a painted area on the very end of the spring, on the loop where it hooks onto the fixed post at the inside most point of the garage door frame, and on the end of the loop where it hooks into the traveling pulley. Frequently worn and faded, but still "seeable".
An alternative is to literally count the coils in the spring. Get some little 'dots' made from a peel and stick mailing label. Count every ten or twenty coils and mark with a 'dot'. When you get to the end of the spring, count the 'dots' and multiply by whatever number ou have in each segment, giving the total number of coils. Measure the diameter of the coils and go get a "X" diameter coil by "Y" coils spring.
Of course you could always take the unbroken one of the old spring pair with you to the vendor and get a replacement pair matched by diameter and length.
As to your 3 questions:
1. In an extension spring system, a pair of 150 # springs lift a 150 pound door. To lift a 300# door in an extension spring system, you need a pair of 300# springs.
2. If its a 150# door, two 150# springs are what you need. Two 150 # springs will not be too strong. But you need to weigh that door or definitively identify the capacity of the old springs.
3. No, you can't "adjust" two unequal capacity springs. And you can't "adjust" one brand new and one old spring of the same theoretical capacity. The old sringis worn and suffering metal fatgue, even though it has not yet broken. It doesnt have the same elasticity as a new spring of the same nominal capacity. They won't work well together.
--
Jim McLaughlin

Reply address is deliberately munged.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.