sovende

If it's as difficult as you are describing, you may have a pedal that has been cross-threaded or has suffered some sort of bi-metallic reaction between the Al crankarm and Fe pedal axle. The former may mean you will need a new crankarm, the latter may or may not require that if the "bond" can be broken AND you're able to chase the threads clean.
Its too bad that the current pedals have only the hex wrench removal option. The amount of force that will be applied with the long lever arms that many are suggesting could easily twist the hex wrench or worse, "round off" the hex opening on the pedal.
Be sure to post on the outcome of your issue. Inquiring minds need to know!

epnnf

Update: Success! Got it off. I put my right foot on the pedal & reached way down w/my right arm for the pipe extension thing I put on the allen hex. It went 'pop' when it broke loose. I thought something broke! Took pedal off, no damage; but the allen hex is showing slight damage. It's probably still usable; not sure. Most previous attempts I used my left arm. I am right handed, and my left arm is a little weak due to unrelated injury. And I had almost given up/resort to taking it to lbs.
Will ride it tmrw.
ty for all support

JanMM

Good job!
Hope your new pedals have wrench flats. I wouldn't buy pedals without them.

cxwrench

Last time that happened to me it was my back that popped! Good work getting it off.

sovende

Glad you were able to get that pedal off without damaging the bike 👍. When installing the new pedals, I recommend thoroughly cleaning the threads on the crank arms and applying a light coating of waterproof grease to the pedal threads. They will be much easier to remove if you need to do so.
I agree with the suggestion to install pedals that have flats for a pedal wrench (usually much thinner than most standard wrenches).
RE: removing pedals, to do so without having to think about the "righty tighty, lefty loosey" or the opposite for "left hand or reverse threading" I use this method. On the side of the pedal to be removed, point the crank arm toward the front wheel and have it parallel to the ground. Place the wrench (either open end or hex key) on the pedal so the wrench is above the crank arm and pointing toward the rear of the bike. Now squeeze the wrench toward the crank arm and the pedal will start to loosen. The "rules" apply to either side of the bike!

Homebrew01

Grease the threads of the new pedals, and just snug them on, no brute force to install.

noglider 

My nmemonic is "the pedal that you put your LEFT foot on is LEFT-threaded."

philbob57

What BF taught me about getting a pedal off without the exactly proper tool was to stand on the wrench. That might be difficult for a hex key.

I live in an apartment, so I don't have room or need for lots of tools. I've got TA cranks and a TA puller, though.

10 Wheels

Put a bag of ice on the area for 20 minutes and it comes off.

crankholio

That's how I remember. And then I remember that bottom bracket cups are opposite of pedal threads.

MAK

I know you got the pedal off but here's a method I use. I use two or three bricks and a towel to prevent damage and position the pedal on them so there's no play at all and use a Lezyne wrench which has great leverage. This would work for an Allen wrench too. Best thing about the Lezyne wrench is that non cyclist friends think it's some sort of a medieval weapon.

LV2TNDM

I would add that in this specific situation, a leverage or "cheater" bar was not the ideal solution. 6mm allen fittings are not really good handling high torque loads often needed to remove pedals.

I think he's lucky he got it off without rounding the allen wrench or pedal, or at least having it slip under the load and then rounding the outer portion of the tool.

I would have rather utilized an impact wrench after ample soaking with penetrating oil. Impact forces are so much better for fittings and tools. If a decent impact wrench hadn't gotten it off, then applying heat to the crank arm would have been another good option.

And someone replied with "apply light grease to the pedal threads" and "not too much torque." I disagree! Apply LOTS of waterproof grease to BOTH pedal threads AND inside of the crank arm. You simply cannot use too much grease. Mix in some anti-seize if you're REALLY worried about stuck pedals. Better yet would be to run pedal taps through those crank arms to ensure the threads were pristine prior to installation of the new pedals.

And don't go light on pedal torque. You life depends on secure pedals. Loose pedals are big problem with bicycle assembly. Agree with the poster who said avoid pedals without flats. Excellent advice. The average person cannot achieve proper torque with a spindly little 6mm allen wrench. Dumb of manufacturers to make pedals with only 6mm allen fittings. The Park PW-4 is THE wrench for pedals. Four different angles so you can ALWAYS find the perfect position for the wrench when applying high force. And yes, ALWAYS push away from bike parts, especially chain rings!!!!