Is it normal for a garage door to feel this heavy when opening it manually?

A properly balanced 16-foot garage door should never feel that heavy. Even a heavy insulated steel double door should only feel like lifting 10 to 15 pounds once the springs are doing thier job, and you should easily be able to stop it at waist height without it crashing back down or rocketing upward. If you had to throw your entire back into it, your **torsion springs** are significantly under-tensioned or just completly fatigued from years of daily cycles.

What ussually happens is that the opener motor has been masking the problem for years. Modern openers have plenty of horsepower to brute-force a 200-pound deadweight door off the concrete, wich quietly chews up the internal nylon gears without giving you any obvious warning. The springs can look completely intact with no visible breaks, but steel loses elasticity over time and stops doing the heavy lifting.

As for the clunking sound, that is typically just the spring-loaded latch on the trolley snapping hard back into the carrier on the belt or chain. If the door was sitting slightly misaligned when the motor kicked on, it hits with a loud metallic whack when it grabs the carriage. Take a quick look up at the drums in the top corners just in case. If the lift cables are still wrapped cleanly inside their grooves without slack, fraying, or tangling, you didn't mess up the cable tension.

Have a local door tech come out to balance the door and re-tension the springs. Torsion assemblies store a terrifying amount of energy, and winding them without the right bars and technique isn't worth the ER visit. Once the balance is dialed in, you'll be able to lift that 16-footer with one hand. And if outages are common where you live, looking into an opener with a built-in battery backup will save you the headache next time.

While you wait on a tech for the springs, pull the cover off your opener and take a look inside. I went thru this exact same thing two years ago, and my motor housing was filled with white plastic shavings. The nylon drive gear was half ground down from hauling that dead weight for years. Grabbed a $15 gear kit online and swapped it out in an hour before it completly stripped out on me.

Also check if your rollers are actualy spinning. Two of mine were completely seized and just dragging metal-on-metal in the track, wich made manual lifting ten times worse.

Beyond the counterbalance assembly itself, you really should inspect the condition of your rollers while the door is disengaged, becasue worn-out or completely seized steel rollers lacking proper radial ball bearings will slide rather than rotate, creating absurd friction against the vertical and transitional track radius. If any of those stems are binding in the hinges or the bearings are packed with petrified grease, you are essentially dragging static steel wedges up a stamped track, which artificially inflates the perceived heft of the door panel even before accounting for whatever spring fatigue you have going on.

If you never want to yank that red emergency cord in the dark again, grab a Chamberlain B970. It has an integrated battery backup that effortlessly runs the opener for dozens of cycles when the grid dies, plus the belt drive is dead quiet.

I swapped my old unit out for that exact Chamberlain after an ice storm trapped my car a few winters ago, and it completley eliminated the outage panic. definately get a tech to balance the door first, but adding an opener with dedicated battery power makes power cuts a non-issue.