Where to find a fixed bracket for a 4x4 steel basketball post?

Finding a retail bracket specifically for a 4-inch square post is a nightmare beacuse most consumer hoops either use a 3.5-inch round pole or jump straight to a 5-inch or 6-inch square for pro-style systems. Since your post is alredy 10.5 feet tall, you are actualy in a great spot because you do not need an offset bracket that adds height. You just need something to bridge the gap between the post face and the backboard mounting points. If you aren't handy with a welder, look into square U-bolts designed for 4-inch trailer frames or heavy fencing. You can buy two or three sets of these and use them to strap a pair of heavy-duty steel channels or even two pieces of 2x2 angle iron vertically to the post. Once those vertical rails are bolted tight, you can drill holes in them to match whatever backboard you end up buying. It is a lot more secure than the generic universal brackets that usally just use thin carriage bolts. Another option is to check out companies that sell wall mount basketball kits. Often, the frame that holds the backboard to the wall is flat on the back. You can take that flat frame and bolt it directly through your 4x4 post. Since it is 7-gauge steel, you will need a high-quality cobalt drill bit and some cutting oil to get through it, but Grade 8 bolts will hold up to your boys hanging on the rim much better than any adjustable piston ever would.

If the old arms are still there but just the piston is dead, you might also consider just pinning the arms in place. If you can manhandle the hoop to exactly 10 feet, just drill straight through the adjustment arms and the main post, then slide a heavy steel bolt through. It effectively turns the whole thing into a fixed-height unit without having to buy a single new bracket. Just make sure you use a large enough diameter bolt so it does not shear when they start dunking.

I was acutally wondering about the height. If the post is 10.5 feet tall, won't the backboard sit way too high if it's bolted directly to the face? I'm a total newbie with metalwork, so I'm curious if there's a way to drop the rim height to exactly 10 feet without it being a huge project. Also, do you think I'd need a special extension arm? I'd be worried about people running into the post if the backboard is flush against it. Is it hard to drill thru 7-gauge steel with just a regular hand drill, or do I need some heavy-duty shop tools for that?

You definitely need some overhang if the boys are hanging on the rim. Bolting a backboard flat to that post is asking for a collision. Most heavy-duty extension arms provide 2 to 4 feet of offset, which is the safety sweet spot. Since your post is 10.5 feet, a fixed-arm kit that clamps on is your best bet. These arms usually have a slight drop in the design, which shoud naturally bring the rim down to exactly 10 feet. If you find a bracket meant for 4-inch round poles, just swap the rounded U-bolts for square ones from a tractor supply store. It’ll be way beefier than the original setup.