I need to know the mounting nut size for a rear wheel cylinder on a 1994 Dodge Dakota. I've tried metric and standard wrenches and can't seem to find a size which fits.

 

Must be rounded off if neither a metric or standard will fit. There's really nothing else size wise left.

 

I tend to agree with Jkeaton on this. Another possibility is rust over time has decreased the size of the bolt head. Bottom line is you will have to force it out with something, ie visegrips etc. Worst case, a torch. Or buy a new or used backing plate

 

I don't remember what size it is but I do think that on at least one I had to hammer on a size smaller socket because the bolt was corroded. Find the closest (6 POINT!!!) socket that won't quite fit the bolt and hammer it onto the head. IF you can get it all the way on I'll bet you'll be able to turn it right out.