I picked up new pedals for my bike to replace one that is making a clunky noise and not spinning freely.

Problem is that the pedal in question is seized. With all my might, I can't get it free.

The other came loose no problem.

Any tricks for loosening a seized pedal?

-Are you turning the correct direction? Non-driveside is righty-loosen.
-Use a better pedal wrench; something with more leverage and better 'bite'.
-Try allen socket and breaker bar on the backside of the spindle.
-Try shooting a little penetrant (like PB Blaster) into the threads from backside.
-Use a heat gun on the crank arm to try and expand it.
-Remove crankarm from bike, clamp in [plastic/protected] vice for even more leverage.

What pedal and what crank?

1. Turn in the proper direction - "the pedal in question" does not tell us which one. If the left one it comes off clockwise (reverse of normal)

2. Use a long pedal wrench or a cheater/extension bar or pipe on a shorter (but strong) wrench. Or just go down to the bike shop and have them remove it.

3. There are additional things one can do (Kroll, heat) but most are not necessary.

if the stuck pedal is not on the drive train (chain) side, it is reverse threads. When you put the new pedals on grease the threads first.

Sometimes its a 2 person job even in the LBS with the right tools.

Transcontinental riders want their bikes shipped home , Stripping it back down is part of the Job.

Pedal removal is Job 1

Wheels on the Ground.. try stepping down on the pedal wrench with your foot

An easy way to remember is that both pedals unscrew by turning over the top to the back.

The 3+ foot long handle of my hydraulic floor jack fits perfectly over my 15mm wrench. Prior to that I had tried penetrating oil, tapping, and heat without success. Once I had enough leverage it was no problem.

Spray penetrating oil on the threads on both sides of the crank, let sit while you get coffee.
Try strapping the opposite crank with a toe strap around the pedal or pedal hole to the chainstay and then putting as much force as you can on the wrench. Add a breaker bar if that doesn't work or try pressing with your foot. (Strapping the opposite pedal to the chainstay was a trick that my LBS used when I had a stuck pedal a few years ago, but they still had to get out the breaker bar and have another person hold the bike down - it was in a stand).

Putting the chain on the biggest chainring will help to reduce damage to yourself if the wrench slips...

I made a video a couple weeks ago with some tips:

Wear gloves. They improve your grip and reduce the risk/concern of knuckle busting.

On the really seized up pedals, I'll use a Park FFS-2 on the crankarm and a 3 ft long iron pipe on the pedal wrench.

I use my 300lb neighbor. Effectively the same as a cheater bar.

my pedals, after being greased and installed and ridden for about six months or a few thousand miles require a hefty amount of force to loosen, both sides. there is often a discernible 'crrrrrr...ack' when they finally give in to the wrench. and i'm of average weight. and i don't overtighten and break out in a sweat like my brother-in-law, when i tighten anything with a wrench either.

Just had this problem on an 80's model Fuji Club. Had to take both crank arms off first. Then, had to disassemble the pedal. Removed pedal platform. Pedal axle stem still attached to the crank arm. Then, I could finally get a big wrench on the axle stem. Laid the crank arm flat on the floor. Took a 14" pipe wrench to the pedal axle. Still had to throw all 205 pounds of my body weight down onto it before the damn things came off. Jeeezzz. That only took about 1-1/2 hours!

The left hand (not chain side) pedal is reverse thread. So it won't unthread while you ride. You may damaged the threads

No more posts like this please. This is just stupid, you haven't provided any useful advice at all. Grease the threads 'to ensure optimal mechanical performance of the new pedals'? Really?

Aren't you curious as to why and how some guy signed up and makes his first post here on a five-year old thread to give a basic lesson with pseudo jargon on threaded fittings?

I mean I understand newbs don't always realize how old the thread is or how active the forum is or what BF posting protocol is... but he must have some purpose. Where do these people come from? Was he Googling to find out for himself and then answered with whatever the previous result told him?

...I am so discouraged by the current evolution of the internet, that I don't even wonder about stuff like this any more.