I actually don't know what pattern it is! Good question, I'll check tomorrow.
Somewhere there's a micro-analysis of trailers from back when I was shopping for one. I'd realized that every time I borrowed a trailer I had to fix it before either using it or returning it:
The trailer I borrowed to bring Brownie home threw tread on two of the four tires, but waited until I got back to my driveway to do it. So I replaced the two tires. And it didn't have a spare.
I learned from that and swore I'd never take a trailer out again w/o a spare, so when I borrowed my neighbor's trailer I added a spare.
Then I got the invitation to come get Big Blue, and Brandon said he had the right trailer for it, but it "needed a little wiring". Turns out it had been in a grass fire and it didn't have any wiring - to the lights nor to the brakes. And two of the four brake magnets were dead. So I completely rewired it, including new lights as the original ones dripped like Inspector Clouseau's nose. And, I re-packed the wheel bearings.
That set me to wondering what it would cost to have my own. A bit of research told me that a used trailer in good shape sells for about 75% of a new one. And I'd already spent more than that on other's trailers.
But a bit more research determined that there are (IIRC) 3500 lb axles, 5500 lb axles, and 7000 lb axles. It was pretty obvious that two 3500 lb axles weren't going to be enough when I was playing with vehicles that weigh ~6000 lbs and the trailer weighs at least 2000 lbs.
Ahh! Maybe 5500 lb axles will do? And, they will if you get the load centered over the axles. But, you are supposed to have ~10% tongue weight, which means the load has to be biased forward, so it would be very easy to overload the front tires/axle.
Given that, I went with 7000 lb axles. The trailer cost very little more than it would have with lighter axles, and I have the peace of mind that I'm not likely to overload it. And when towing through the night, as we did bringing Big Blue back, that is huge.
Gary, AKA "Gary fellow":
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Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI
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However, we have a luncheon after church today and perhaps I'll get a chance to ask him about them then.