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Model X/Y bike rack loading issues

ArtK

Member
Jun 1, 2020
214
193
NYS
While this has been a source of debate since the MY hitch first came out, and while it is apparent that one can safely load 115 lbs. of bikes on this particular rack if you are simply storing them there, OP has shown that rigors of a bouncy trip exceeded this rack's capabilities at 115 lbs. Tesla needs to amend the weight limits as published for this rack, and to accept this rack back for full credit. Can't wait to hear about how they handle this. So sorry, @Berbinator , about your ruined vacation.
 

astrobill

Member
Oct 9, 2020
75
128
Washington, DC
While this has been a source of debate since the MY hitch first came out, and while it is apparent that one can safely load 115 lbs. of bikes on this particular rack if you are simply storing them there, OP has shown that rigors of a bouncy trip exceeded this rack's capabilities at 115 lbs. Tesla needs to amend the weight limits as published for this rack, and to accept this rack back for full credit. Can't wait to hear about how they handle this. So sorry, @Berbinator , about your ruined vacation

All:

The bikes in that image are largely loaded vertically, no? They're supposed to be horizontal. It's important enough that to help keep women's bikes horizontal on the racks that they sell snap-on crossbar adapters to correct for the diagonal frame on many women's bikes. I have one for my wife's bike.

Note: I use the Yakima Full Tilt rack on a Model Y. No issues thus far with three hybrid bikes and the weight of the crossbar adapter on long trips.

The center of mass of the bikes is higher relative to the "hitch line" the way he's got it loaded than if the bikes were in the recommended horizontal configuration. That alone might account for the problem here; I think the net torque on the hitch arm piece of the rack is higher because of the increased moment arm.

Also, the drag on the bike rack and stack in his photo is probably higher -- maybe significantly so! -- in that configuration than if horizontally loaded, in which case much more of the "bike rack and stack" total physical cross-section is blocked by the vehicle as it moves. The added drag in this case could increase torque on the rack and receiver, pushing it down and back more than typical. For a streamlined airflow design like a Tesla vehicle in motion, this could be a factor. The faster he drives, the more this additional drag is...and it increases geometrically with speed (as the squared of velocity, I think).

And thirdly, yes, we must ask if he drove on hard on particularly bumpy roads for this trip? The more/higher bumps, the higher the impulsive forces downward on the rack. Perhaps enough to exceed the rack's design margins in combination with the above two factors?

Side Note: Amateur bungee jumpers sometimes have their bungee cords fail because they jump from a location separate from where the cord is attached to the launch point. The net forces downward are higher in a swinging jump than from a purely vertical one -- and the bungee safety calculations they did are no longer applicable. Not exactly the same thing as here, with a potentially bumpy road affecting margins, but explains how assumptions and actual driving conditions can affect safety margins. Tesla, Yakima, Thule, etc....may not all account for these kinds of considerations.

R,
Bill
 

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BryWay

Member
Jul 1, 2018
52
68
San Francisco, CA
Sorry to hear about your experience with the Tesla-branded hitch. Hopefully the downward force didn't cause any damage to the mount / undercarriage itself. That whole situation sounded like a nightmare (considering transferring all belongings into rental, etc.).

Back in 2019, I did a lot of research before taking delivery of my 2019 MX to see if it'd be capable of supporting the weight of our two eBikes (which are heavy even without batteries attached) and noted the owner's manual specified a maximum of 120lbs of downward force -- vertical weight the hitch can support. Also noted total weight allotment would *include* the weight of whatever bike rack I connected to the hitch.

Having to balance strength vs weight, I decided against the Tesla-branded rack since it weighed a whopping 40lbs. If I'd bought that one, there'd be no way I could transport our two eBikes. So, I settled on the Saris Freedom 2 hitch. It only weighs 20 lbs, had great reviews, is sturdy, and being as light as it is, it leaves me 100 lbs for the two bikes. Our eBikes weigh exactly 48lbs each, so when it was all said and done, I had approximately 4lbs of margin, which allowed me to add a heavy-duty cable lock. We road trip frequently between San Francisco and Palm Springs (~500 miles each way) and have had no issues.

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