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Tesla Model 3 Roof Rack – J-Bolt securing the rack snapped

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I received my Tesla roof rack last week and yesterday, one of the J-Bolt holding the rack snapped. In case someone asks, it was not due to overtightening as I was careful not to torque beyond 8 Nm (with proper torque tool).

This happened while I was in town with my cargo box on (empty), I found out because I could hear some rattling from the roof. Grateful it did not snap while I was on a road trip away, at high speed, with my cargo box full.

So, folks with Model 3 roof racks, be on the lookout for a suddenly rattling cross bar, one of your J-Bolt could have snapped. Hopefully Tesla will look over the QA of these little clips, as four of those is all that is preventing your cargo from taking off.

Now awaiting replacement part from Tesla. Hopefully it does not take too long.

DSCN0386.JPG
 
this is enough anecdotes for me to lose confidence that I will get solid J-clips. I wrote Tesla requesting a refund, given they are currently waiting on more stock.


--update--
got a response back. they processed the cancellation and refund.
 
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Calculating the odds of that .... :)

Good grief, why do they have to cheap out on everything? I took out some interior plastic bits the other day and they’re unbelievably flimsy. For me at least, this cheapness has been so freakin expensive so far ...

Doesn't really seem to be a "they cheaped out on it" problem. More just a poor design choice on how they cast the J brackets. I'm installing mine today so we'll see how they go...

the crossbars themselves seem super solid and everything else is great, it's unfortunate that just these little brackets seem to break under Tesla recommended torque. Also going to way under torque (compared to what they recommend)
 
Also going to way under torque (compared to what they recommend)

I wouldn’t even put a wrench on them at all. Just hand tighten them as much as you can and then use the key to lock the nuts into place. Hand tightening them made mine secure and very solid.

Then if you ever put a heavy load onto them it might be a good idea to go around and check the tightness on each corner, but intially with just bare bars I would hand tighten only. No need to tourqe them and deffenitly no need to put 8nm on them.
 
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I'm sure I'm over-simplifying it but it seems like someone loaded the metal into the machine in the wrong direction, so the grain of the metal is wrong for the direction the load is being put on it.

Tesla should likely issue a recall immediately for the batch these have come from before something bad happens.
 
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I've never seen one of those bolts because, among other reasons, I don't yet own a Model 3. I also am not a metallurgical engineer...but I do have a lot of real world experience with metals and with fasteners. And most importantly, with what happens to seemingly stout pieces of metals when loads are applied not in the directions for which they are designed.

So I am writing this only from having looked carefully at the photograph shown in Post #1. I am wondering if there may be a design flaw here; one that easily would be remedied by having that bolt-end notch made - counterintuitively enough - larger - at the base but possibly smaller in its upper portion.

Reasoning:
1. The j-bolt is created, obviously enough, by welding a bolt into a long notch of the J-shaped horizontal.
2. There is a deliberate gap remaining; absolutes don't matter but let's say it is because the notch is 22mm long and 20mm of bolt is inserted.
3. But also, the gap into which the 12mm bolt is inserted is, for ease of manuf'g, 12.5mm wide.

~~Again, those all are suppositions of size; absolutes don't matter but I think I can see that the pre-weld width of the notch is, on a relative basis, considerable~~

If this is the case then there can exist a manuf'g situation whereby the bolt is not perfectly parallel to the notch's sides and thus, during welding, its base abuts one side of the notch.

If that is the case, then when the J-bolt is tightened, yoyu can have stresses imparted in an enhanced fashion just to that corner-edge of the notch; rather than directly down the body of the J-bolt and thereafter into whatever slot the bolt is being emplaced.

And - craaackkk


SOLUTION:

Create the notch (a) so that it bells out very slightly at its bottom - at least those last 2mm per my #2 above; and (b) so that the difference of width of the shaft and the bolt is effectively zero - thus the bolt always aligns perfectly perpendicular to the forces (or are they stresses?) that will occur in use.




~~~~~~~Eager to have a metallurgist/design engineer assess this analysis.~~~~~~
 
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Yikes. Fortunately my J-Bolts haven't snapped yet, but several clips were broken off or cracked on the plastic end caps when I received my rack. Reached out to Tesla for replacement caps and they sent me a whole new rack... which was even more broken. I could tell before even taking all the foam wrapping off. That was a month ago and they've been unresponsive to my emails trying to address it ever since :/ For the caps with intact clips the gap tolerances between the plastic cap and the metal rack are all over the place too.

Since I got two duds in a row, has anyone else had trouble with broken end cap clips?
 
Installed mine a few days ago, after reading this thread I decided to go check my bolts because I did hear a loud crack during my install but didn’t notice any damage and the rack still felt secure. Well after inspecting today I found the front left bolt was broken. I have been driving it for almost a week now and had no idea.
 
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I've never seen one of those bolts because, among other reasons, I don't yet own a Model 3. I also am not a metallurgical engineer...but I do have a lot of real world experience with metals and with fasteners. And most importantly, with what happens to seemingly stout pieces of metals when loads are applied not in the directions for which they are designed.

So I am writing this only from having looked carefully at the photograph shown in Post #1. I am wondering if there may be a design flaw here; one that easily would be remedied by having that bolt-end notch made - counterintuitively enough - larger - at the base but possibly smaller in its upper portion.

Reasoning:
1. The j-bolt is created, obviously enough, by welding a bolt into a long notch of the J-shaped horizontal.
2. There is a deliberate gap remaining; absolutes don't matter but let's say it is because the notch is 22mm long and 20mm of bolt is inserted.
3. But also, the gap into which the 12mm bolt is inserted is, for ease of manuf'g, 12.5mm wide.

~~Again, those all are suppositions of size; absolutes don't matter but I think I can see that the pre-weld width of the notch is, on a relative basis, considerable~~

If this is the case then there can exist a manuf'g situation whereby the bolt is not perfectly parallel to the notch's sides and thus, during welding, its base abuts one side of the notch.

If that is the case, then when the J-bolt is tightened, yoyu can have stresses imparted in an enhanced fashion just to that corner-edge of the notch; rather than directly down the body of the J-bolt and thereafter into whatever slot the bolt is being emplaced.

And - craaackkk


SOLUTION:

Create the notch (a) so that it bells out very slightly at its bottom - at least those last 2mm per my #2 above; and (b) so that the difference of width of the shaft and the bolt is effectively zero - thus the bolt always aligns perfectly perpendicular to the forces (or are they stresses?) that will occur in use.




~~~~~~~Eager to have a metallurgist/design engineer assess this analysis.~~~~~~

I can see this as being a possibility. On my broken bolt the threaded part looks like it was welded on slightly canted to one side meaning the J hook was probably making contact with the car on one corner and not evenly across the entire bottom of the hook.
 
Installed mine a few days ago, after reading this thread I decided to go check my bolts because I did hear a loud crack during my install but didn’t notice any damage and the rack still felt secure. Well after inspecting today I found the front left bolt was broken. I have been driving it for almost a week now and had no idea.

How did you check? Did you just uninstall the rack?
 
Doesn't really seem to be a "they cheaped out on it" problem. More just a poor design choice on how they cast the J brackets. I'm installing mine today so we'll see how they go...

the crossbars themselves seem super solid and everything else is great, it's unfortunate that just these little brackets seem to break under Tesla recommended torque. Also going to way under torque (compared to what they recommend)

Well, good thing the bars are solid. So then it’s 90% safe for anyone to drive behind a Tesla equipped with a rack ... close enough!
 
I wouldn’t even put a wrench on them at all. Just hand tighten them as much as you can and then use the key to lock the nuts into place. Hand tightening them made mine secure and very solid.

Then if you ever put a heavy load onto them it might be a good idea to go around and check the tightness on each corner, but intially with just bare bars I would hand tighten only. No need to tourqe them and deffenitly no need to put 8nm on them.
Tensile pre-load of bolts is often necessary to extended their fatigue life in application. So unless you've done some serious modeling or testing I don't think this is sound advice. https://www.asminternational.org/documents/10192/20564188/amp17208p18.pdf

It does appear there may be a manufacturing quality problem and/or design flaw in the 3's roof rack. Tesla needs to get on top of this.