My pedal wrench fits a bit loosely?
So I was working on getting the pedals off a bike and I noticed that my 15mm pedal wrench fits just a little bit loosely on the wrench flats. It's a department store bike, but it does have a 3-piece crank.
My question is, is there any chance the pedal flats on this bike are actually 9/16"? I read that 9/16" flats are usually associated with pedals on one-piece crank bikes. But 15mm comes out to 0.59", and 9/16" is 0.56". So if this bike does use the 9/16" for some reason, that would seem to fit an explanation of why my wrench seems to have a little bit of play in it...
And yes, I'm aware of the reverse thread on the left pedal, so it's not something as simple as that.
Sorry for the really basic question, but I couldn't seem to find the answer for sure. The reason I ask is because the right pedal is REALLY stuck tight, and I don't want to ruin my wrench by pulling with gorilla force when it doesn't fit right.
(P.S. - any tips on loosening up that right pedal would be helpful. This bike has been through a couple rough winters and may have some significant rust/corrosion going on. I'm guessing the threads were never lubricated during installation either. I was thinking of blasting it with a WD40 spraydown to try to break up anything that's making it seize up - I don't care if it attacks the pedal grease, since I was getting ready to clean out and repack the pedal bearings anyway.)