Those look like the same forks I've been riding for 2300 miles now, 25 mph over big bumps, etc. I sure did a faceplant when I put a waterbottle in the forks, but that wasn't the forks, it was the bottle mount location on the bikeframe.
There are two kinds of these cheap forks. One kind has an aluminum piece with the steel parts pressed in, as you describe. The other, cheaper one, has all steel, and it's welded. That is what I am using, and I trust it , with 600 watts. Shitty 40 mm travel so it's a dog on dirt trails, but for street bumps it is adequate. I dissected a rusted out one once to see how strong it is at the drops. The answer is plenty strong. The rest of it at the top with the steer tube is all welded so the cheapies are the strongest. I dissected one to be sure the upper and lower fork tubes wouldn't just seperate some day. They wont, without a cutting torch or grinder. There will be an amazing ammount of flex forward and back, especially when braking, that seems to be harmless.
I still don't understand how a moderately expensive fork with an 1 1/8" steel steer tube pressed into an aluminum part is stronger than a 1" steel steer tube pressed into a similar aluminum part. I would accept the argument that both are risky. I still say braking forces are far greater than motor pull. Forces on the dropouts are a different thing alltogether. I like the really cheap ones that are all steel, top to bottom.
On the subject of the dropouts. The squashed tube cheapie forks have exceptionally strong dropouts. I don't have torque arms, and belive I don't need them at 600 watts. The only issue is that a big hub motor will not fit in the space between them. Smaller hubs, such as WE and Chrystalyte 408 can fit, but the forks have to be put in a vise, and squashed some more. There is a how to thread with pics on that. Fitting hubmotors to cheap steel suspension forks, or something like that is the title. I've not touched a golden motor, but I belive there is room for one after some squashing if they are bigger diameter than a WE motor.
One additional thought, Of the cheap stuff on that mongoose bike that is close to identical to mine, Only the front crank and the tires seemed cheap and wore out on my bike. If you do have a choice at the retail store, look for the 48 tooth front sprocket, most will be 44. The 48 tooth allows pedaling at a higher speed, about 25 mph. Everything else seems to be lasting, the rear derailur is fine, brakes are fine, most likely because I tuned the bike before riding very far. From the store, it's likey to be all out of whack. And the tires seem to wear out fast. I have heard of the swingarm wearing out fast, and bottom brackets, but I'm good with 2300 miles on this one. I was figuring on a bike change every 1500 miles or so on such cheap bikes, but so far so good. Once again, here's the pic of mine. For fork closeups, see the hightekbikes.com review in that section of the forum.
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