PMK, all good points.
It's a BRP hitch. Tongue weight isn't excessive; about 45#. I'm estimating that 2 riders and luggage on the bike itself weigh about 450#. I should weigh the loaded trailer, but I'm estimating 400-450# there. So, total with 1050# for Spyder = 1950#
The trailer itself has a solar panel with lithium battery, 1 gallon of water, food and bedding, clothing, etc.
Unless 2dogs can come up with a better solution, I'm looking at about $500-600 for new back-plate, hubs, brakes and electric brake controller. Maybe more if i need bigger wheels, which in itself would create issues with the way the top unfolds and sits on the ground. I may be better off trying to lose carried weight but i don't see where that could be.
So, I'm focusing for now on a Spyder braking system upgrade, starting with a flush!
In my opinion, good choice on the hitch you chose.
Regarding the tongue weight you mentioned, while only 5 pounds over the designed and published rating, consider even more than just tongue weight. I am not going to mention correctly loading the trailer, there is plenty of videos showing why you must ensure adequate tongue weight.
In simple terms, the design of the Spyders trailer hitch is less than ideal, even enters into kind of poorly decided upon. Even aftermarket hitches suffer the same bad design. Yes, this relates to tongue weight limits. The Spyders hitch, when installed, becomes part of the rear suspension. The hitch is not isolated from the rear wheels movement over bumps. Therefore, every, or nearly every road imperfection or item rolled over is felt by the trailer after that force is transferred through the hitch. Unfortunately, the forces and loads induced can peak at a quite large amount. That 40 pound tongue weight design limit could easily see actual load of over 500 pounds, maybe even close to 1000 pounds depending on what the tire feels. Add to this, the hitch ball is well aft of the axle, further increasing the vertical linear movement of axle vs hitch ball. So a 10g load induced by a bump into the wheel assembly and axle is even greater load at the hitch ball.
For comparison, you use a carpenters hammer to drive a nail into lumber, but it is unlikely you would drive that same nail with a 5 pound sledge hammer. The added tongue weight is towards the sledge hammer effect.
It is kind of the same for folks that run those carrier basket setups. Loaded light they work, add weight and those similar loads I mentioned happen, plus there is bending moments and side load moments not experienced by pulling a trailer.
Some have attempted to design and build a frame mounted hitch for the Spyder. This would allow the rear wheel freedom of movement when needed to react while rolling. Unfortunately, there are no production hitches of this design I am aware of.
As time permits, when the weather cools a bit, I plan to modify our RT622 trailer to lessen considerably the induced forces I mentioned. You might consider researching if you can purchase a suspension style trailer tongue for your trailer. Possibly it already has that feature. If so awesome.
Regarding your quest for trailer brakes, no doubt noble and viable. Myself, I would be ok with oem parts if not worn. Regarding the brake fluid though, shop wisely and pay more for a brake fluid deemed compatible, having a higher wet boiling point than others.
I do not suggest upgrading to DOT 5.1 unless you are set up to flush and bleed at least 3 times per year. The Motul RBF 600 is excellent brake fluid, but does suffer from a crystal like separation that fouls the master cylinder cup seals. Even other 5.1 fluids in other applications have done similar.
Stick with DOT 4, but as mentioned, research wet boiling temp spec. Flush the Spyders brake system fully two times when initially swapping fluids. If you use a dealer to accomplish this task, you are pretty much at their hands as to what fluid they use. My guess is a lower cost product, purchased in bulk. Hopefully kept clean and not allowed to absorb moisture.
When I worked for Flight Safety International, they had an advertising catch phrase.
“The best safety device in any aircraft is a well trained crew”.
Similar might be applicable when Spyder riding, hauling that trailer that exceeds Can Ams published limits.
