no with the trailer you are only applying a pure vertical load to the towbar. The position of the trailer wheels affects the amount of vertical load applied but there is never any torque
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Exceeding maximum weight on towbar when using cycle rack
- Thread starter Peteski
- Start date
no with the trailer you are only applying a pure vertical load to the towbar. The position of the trailer wheels affects the amount of vertical load applied but there is never any torque
Ruffles
Member
I wonder how Tesla assumes you are driving with the bikes attached when they calculated the load? I know I drive so slow it ticks off the old people when I have the bikes on because the last thing I want is scratches/dents on the X or the bikes.
Okay that's a good data point. Over twice the stated limit! I don't think I'd push it that far myself, but good to know it can handle it.
Probably assume normal driving. The unknown is how bumpy the roads are. I would take it very easy over any bumps or crests to minimise excess loading. But on a smooth road I would just drive at normal speed.
Only in the static case. Once you accelerate, brake, or corner the vertical displacement of the COG is critical.
Yeah that's true but just keeping this simple for the sake of confusion between applying a direct vertical load vs a torque load to the towbar while static. The dynamic load will be a vector of vertical, horizontal and longitudinal forces and torque.
Right. I think for the bike rack, the dynamic torque is the critical factor. Especially given the needed tolerance in the adapter mount which leads to wobbling/ shock loading under oscillating loading conditions.
Ohmman's trailering thread with a weight distribution hitch is the extreme case of loading (it ruined the adapter, but never detached).
I think you are probably right. I'm not worried about the actual bike rack failing as it's rated to carry 60 kg worth of bikes and we'll always be comfortably under that even with 4 x 13 kg full-suspension mountain bikes.
So my only worry is potentially damaging the towbar mounting on the car, with its relatively low 54 kg max nose weight rating. If the nose weight rating was 80 kg or more, then I could confidently use the full rack load capability. But right now if I take the stated 54 kg limit seriously, I'm limited to carrying only 2 full sized bikes plus 1 kids bike. I expect it will be okay to exceed that load (like the guy with the motorbike!) if I don't drive too aggressively.
The weak point is definitely not your bike rack (more likely Bosal adapter attachment).
From a pure physics point of view:
Your rack is pretty low profile, have you run the numbers for 500 lbs at a hitch ball vs your load/ distance? Spec is 500 pounds at 8 inches from pin (not adapter) to ball, if pin to adapter is 4", then total lever arm is 12", If the max distance on the rack is less than 36" from the adapter, the load capacity would be 166 lbs.
Okay this is great info. I have a UK/Euro adaptor that plugs directly into the Model X receiver (not the 2" square adaptor you guys have in the US). So the adaptor goes straight from the receiver on the car to a ball with nothing else in-between. The bike rack mounts directly onto the ball. I'll take some measurements of the overhang tomorrow and see how it works out compared to the 500 lbs at 12".
I suspect that the low bike weight rating is related to the goofy Bosal hitch. It may allow Tesla to readily accommodate the hitch / receiver requirements in different countries but does not seem to handle high torque loads well from the forum postings I’ve seen. If you were in the US you could easily put on a welded 1 piece receiver hitch that could better handle 4 bikes but that’s not U.K. legal from what I can tell.
Nice bike btw, my wife who grew up in the Thames Valley, loves hers!
Nice bike btw, my wife who grew up in the Thames Valley, loves hers!
Thanks. I’ve just been reading an old thread that backs up your theory. I’ll keep a very close eye out for any play developing in the hitch/receiver. Fitted as new there is zero play in my assembly and it attached and released with minimal effort, unlike some of the demonstration videos I’ve seen! I wonder if the parts have been upgraded along the way? Mine feels rock solid at this point, so that’s encouraging.
Cheers, yes my wife loves her Juliana. My Specialized Enduro up front is a nice bike too, but I do think the Juliana/Santa Cruz frame design is a little better. I’m really looking forward to hitting some decent trails with the X over summer.
when I hung a 4 bike rack on the hitch on my prius I was worried about how much it 'bounced'... so I bought some of those 'clip' straps that are used on the trunk-mount bike racks. Now, after I load the bikes, I attach the straps from the rack to the trunk seam and apply a 'preload'. seems to make everything happier. Has anyone tried that here?
I.m.o., there's plenty of natural flex in the Thule rack itself to absorb vertical oscillations from bumps and such. I have the heavier Swing version and I can see the vertical motion when going over bumps or speed bumps.
It doesn't matter how much flex there is in the rack, all the loads are still reacted through the tow bar. In fact a very flexible rack boinging up and down undamped would make matters worse, not better.
Have not tried, but if you can preload the Bosal (or any hitch) enough that it doesn't bang back and forth, that seems like a good thing.
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