I need to replace the torsion springs on my overhead shop door and was
i can use springs that are longer and larger in diameter that the current
thinking is a longer bigger spring would have a longer service life than the
ones. Since springology is not my area of expertise i need some opinions
spring experts in the group.
Bear in mind, that the spring rate is proportional to the lenght (double
the length = half as stiff) but the rate increases with the 3rd power of
the diameter (double the diameter = 2*2*2 = 8-fold stiffness).
No you cannot. The springs are quite carefully balanced to the door weight and
height. They get wound up many turns to provide the correct torque, and they
provide a more or less constant torque as the door rises and the spring
unwinds. Even a small change in the spring will mess things up.
When spring preload is critical to 1/4 turn, changing size can result
in unwanted action. The spring may only hold the door after you lift
it or it might just snatch it open the instant you unlatch it.
If your current springs have a short life perhaps they are not sized
--Andy Asberry recommends NewsGuy--
I'm not a "spring expert", but if you can't get the exact spring you
need you have to get as close as you can - if you go only slightly
oversized and approach the torque setting slowly it should be fine. A
radically oversized spring probably will not fit the shaft hardware
If you go way too big on the springs on the 'More Is Better" plan,
the door won't work right. The spring force has to be high enough to
balance with the door fully down, but taper off at the proper rate as
the weight of the door segments gets transferred to the horizontal
track. With the door fully up, the tension needs to be just enough to
hold position, or now your big trouble will be in getting the door
And way oversized springs could be adjusted fine for when the door
is closed, but you'll 'run out of spring' and let the tension cables
go slack and snarl approaching full open - that would be bad.
WARNING! Those springs have some serious tension on them and can
cause Serious Injury or DEATH if you screw up on the tensioning or
tension release procedures. And it's a stupid way to go.
Read the instructions - strike that. Read and FOLLOW the
instructions, and have the proper tools on hand. You need a few
adjustable safety props to support the door and take the torque off
the spring shaft while pulling on the tensioning dog, don't skimp.
And if you invent and build your own tools like the tension-wheel
dogging bar instead of buying them, Make Sure You Make Them Strong
If you have a lot of tension on the tool and the little pin that
engages the dog wheel shears off, at best it's skid-marks time - at
worst it's "Call 911!" time...
Yep, that is exactly how it works. While your door's weight and lift drum
diameter fixes the proper "torque rate" (inch-pounds of torque per turn of
winding), there are an infinite number of springs that will produce a given
torque rate. The garage door industry deliberately chooses very light
springs that have a limited cycle life.
You can calculate torque rates and cycle lifetimes yourself. See the
"dangerous bend" section for formulas at the end of my page:
When I broke one spring and found no ready replacement I drew-up the
springs and had two made by the door service company in my area. It
seems the proper spring will just barely unload when full up which
makes it easy to work with the cables on the drums (as mine is equipped
with). If there was much leftover torque at this point I think I'd
have a problem.
I also found after a short while I had to retorque after the springs
had "worn in" as they had and everything worked out fine. Good luck.
Talk to a *good* garage door supplier, one that does both residential
and commercial. The usual springs are aimed at what folks want to
pay: they're good for a few thousand cycles. Better ones are
available, they just cost more. They can often tell you exactly
what springs to use and how many turns each spring should be torqued
just from the make and model of your door.
Longer-lived springs cost more because they're simply heavier; there's no
"better" or "worse". They're all made from the same A229 alloy oil-
tempered steel wire.
The cycle lifetime is simply a function of the bending stress. A heavier
spring of equal torque rate undergoes less stress during the cycle than a
lighter spring, and thus fatigues less and lives longer.
Think about going back in time. If you have the space, rather than
fiddling with another torsion spring, put in the old-fashioned system of
cables to counterweights (and use the wonderful trick of chain as a
self-adjusting counterweight to compensate as the door is
opened/closed). No springs to break. Once adjusted correctly, so long as
nothing chafes, very little at all that's likely to break or go out of