Sheared screws on my Prinsu Rack

That's great. I removed a screw by hand and the head snapped off. I don't wanna touch the others, but I'm now wondering if I should try so I can get some freebies.

 

Once one broke I took the whole thing apart and all but one had a snapped bolt . It took a few weeks to get them but it’s worth it

 

Is that TNUTZ extrusion basically an OEM replacement? Because $20 is way cheaper than $75 for a brand new one. I have a set of awning brackets that would fit on this crossbar, but I don't know if it would fit since it is not OEM. I am very much considering this one.

 

Have you tried a drill bit and easy out?

 

If you flex the side rail out to get the crossbar with the broken screws out, these can be helpful in backing headless screws out of stuff.

$28 VAMPLIERS 7.5" Vise Grip Heavy Duty Locking Pliers with Screw Extractor Curved Jaws. Professional Grade. Secure Hold, Quick Release. Grip & Remove Stripped/Stuck Screws in seconds.

https://www.amazon.com/VAMPLIERS-EXTRACTION-Stripped-Specialty-VT-003-7LP/dp/B07NH9XWJW/

Also, when the crossbar is out, heating the whole area will expand the aluminum faster than the steel screw, and should break any corrosion pretty well. Don't go much above 300-400F though or you'll de-temper the aluminum and lose most of the strength at the end of that piece.

For putting new hardware back in, I've been told by multiple mechanics that anti-sieze is OK to use with aluminum now, and with a standard extrusion being a lot easier to replace than an engine block, the risk/reward for using it is pretty favorable if it's actually not OK.

 

This thread seems like the appropriate place to ask, because I haven't had much luck elsewhere. I've always been concerned about the design of Prinsu styled racks, where any load on top is carried by the side plates of the rack, or ultimately the handful of small threaded bolts holding the load bars to the side plates. I'm not very knowledgeable about bolt shear strength, but considering the mismatching of metal from the rack and hardware, and the issues it seems to be causing, is anyone else concerned about heavy loads up top (say a RTT, load of 12' lumber, etc). I've always wanted to utilize the rack to hang a hammock, but have heard horror stories of people ripping off their stock racks on vehicles doing that, so never have. Assuming mismatched metals weren't at play, what would the shear strength be of these sized bolts, especially if side loading a hammock or something?

 

I would not hang a hammock off one. It’s what 3/16 aluminum? It’s going to bend with a 150+lb person pulling sideways and down at an angle off it. Maybe if you attached the hammock near one of the mounts but otherwise no way.

see example
https://www.tacomaworld.com/threads/bent-prinsu-rack.610781/

 

Yes. It's 99% the same product. There was one, minor, cosmetic difference between my stock Prinsu ones and the ones I got from TNUTZ but for the life of me I can't exactly remember what it was. Fitment and the extrusion dimensions are identical so all accessories will fit just as they did before.

 

This is the answer I need, thank you so much! I will probably go by myself a replacement crossbar from TNUTZ just so as long as the dimensions and fitment match OEM. Did you also end up replacing all of your torx bolts, and if so, did you buy them from TNUTZ? Link please? I am not at all impressed with the torx bolts that came with Prinsu as they have sheared and rusted.

 

Did you install yours with thread locker or antiseize? I believe this is the root cause of the issue. I think if you used one of those that there probably would not have been any corrosion or shearing. I bought mine second hand and the previous owner didn't use any

I had to look up my order... when I ordered mine I added on the screws they suggested. I didn't think about it at the time but when it arrived I realized the hardware was silver and didn't match. I didn't want it to stand out because I'm picky like that. So, I ended up spending more money than I'd like on some stainless steel black oxide hardware from McMaster.



I bought enough to replace all of my hardware (not just on the replacement crossbars) but that then puts you in the predicament of having to remove the other hardware, which means you might shear another screw and then need to buy another replacement crossbar. Ugh. So I just left well enough alone. For now.

 

That is precisely my worry... and I would also be OCD about not matching screws, and would 100% purchase the black oxide ones. I appreciate you posting those so I know which ones to purchase for myself! I did not use any thread locker or antiseize so you're probably right. I am still very relieved to know that there is a $20 alternative to the $75 OEM, that was hugely helpful! You have no idea. I truly appreciate that. I just need to order that and the additional hardware. Thank you!

 

Also, pretty sure I remembered what the difference was. I think the Prinsu crossbars are anodized AFTER they've been cut to length (perhaps also after they are tapped). The TNUTZ crossbars are anodized then cut to length. So the end of the Prinsu bars are black and the TNUTZ ones are raw aluminum.

 

IIRC the tnutz extrusion don’t have the widened out slots at the ends to allow usage of just any t bolt easily. Looks like tnutz sells their own t-bolt that doesn’t need the widened slots since its narrower.

 

Hanging a hammock laterally away from the rack is a very bad idea, but it might work to hang one with the strap running over the hood of the truck (if you have enough length in the line); those side rails aren't going to be strong for lateral load but should be able to handle quite a bit if the load axis is along the length of the truck. The best way to hang one end of a hammock off the truck would be to get a front bumper with one or more hoops on it, or to tie into a recovery shackle point on the front/rear (or one mounted in the hitch receiver).

Mounting a RTT will engage enough of the rack that its weight will be well-distributed, lots of people run them on these racks both on and off road without problems from what I've seen. hauling long lumber for short trips should be OK, but be a bit careful on bumps. Since long boards are likely to sag, they could end up concentrating their load at the front/rear crossbars unless they're strapped down tightly in the middle and/or stacked over a few sheets of 1/2-3/4" plywood or if you have a rack on both the cab and on the cap and keep the load supported close to both ends.

The corrosion issues with the different metals involved will always lead to accelerated corrosion in the aluminum, probably the cross-bars where the steel threads make direct metal-to-metal contact over a significant area. The bolts won't lose shear strength to carry vertical loads, and with the length of bolt engagement with stock hardware the joints should be OK as well even with significant corrosion, but the rack itself doesn't have huge lateral strength against concentrated loads like attaching a hammock.

To run a hammock off to the side, the best way would be to use the hoop on an aftermarket front bumper, and the second best way would probably be don't do it, and the third best might be to put a 16-foot "tree saver" winching strap looped around the roof through the doors, with the "over" strap end fed through the loop in the "under" one and then clip the hammock line to the "over" loop with a heavy carabiner or shackle (watch the windows when raising/lowering the hammock, or just leave them open). I can't promise that won't damage anything, but it's probably the strongest way to engage and tie off to the roof of the truck.

 

Good call, you're correct. I now remember seeing that as well, wasn't sure what that was for though. Doesn't affect me as I am only using "drop in" style.

 

Wow, I wasn't expecting to see the side rails bend before the mounts ripping through the roof, but I suppose its good that it did for that person! I've always been against the idea of hanging a hammock from any brands roof rack, even though UpTop advertises a photo of it being done. As you both indicated, it just seems like a horrible idea. My best idea for using a hammock with roof rack has been the thought of girthing your hammock strap to the opposite side slider, running the strap over the top of the rack to the other side, and attaching hammock. All the weight would be pulling up on the slider, and equally distributing the weight of everything completely downwards across the entire width of the rack. I've not attempted it yet, but seems like it would work well. I think the only caution would be to use some padding under the straps so the side rails don't eat into them.

Thanks for the ideas though; definitely proves that aside from shear strength worries, side loading the rack/roof mounts is just a horrible idea altogether.

 

The problem with changing the strap angle like that is that at the corner where the strap turns down to get to the slider, you'll have the tension load in the strap (which is much higher than the weight in the hammock by a factor of anywhere from maybe 3x-100x depending on how tight the lines are pulled and how much sag is allowed with the hammock loaded. With the hammock tied off at the height of the roof on the truck on one side, it's unlikely that the 100x load would leave it in a useful spot, it can be tricky to fine-tune where the actual working load ends up coming in at. That kind of load would definitely dent the roof of a vehicle with no rack, and could possibly curl the upper edge of a prinsu-style rail inward; with the relatively sqare corners on those rack rails, it's possible that the rubbing inherent with the hammock moving around could start to cut into and fray the webbing of whatever straps you're using.

If you were to attach the hammock strap low on the support "leg" of the side rail where it's close to the installation bolt (or even actually tied to the spacer between the bolt and the "foot" of the rail, the loading into the installation bolt would be close to being pure shear load with little or no tension and a fairly small bending load which might be workable. The installation bolts for those racks are around 5/16 in (8mm) diameter, which even without being upgraded to grade 8 (or 10.9 for metric) can handle around 5000 lb in shear load; the weak point most of the time is the sheet metal around the mounting nuts flexing and allowing the nuts to pull out (which would still take probably thousands of pounds on the bolt), but that's not really a concern for an almost completely lateral load and setting the strap as low as possible minimizes the leverage which could effectively multiply a smaller applied load into a much larger working load.

 

Basically they don’t make the cross bars they are bought and added to the prinsu kits. Maybe they do some cutting but any own that is the correct length will work.

 

https://prinsu.com/product/prinsu-universal-utility-hook/
"This universal hook can be used to mount and attach all the accessories you might need out on the trail. Whether you are are anchoring your hammock or needing a tension line for your shelter this hook will withstand the elements."

So why are they saying you could hang a hammock off the side? $$$ grab?
Any recommendations on using a part of your vehicle as one of the hammock sides so you just need 1 tree?

 

The website is written by marketing/sales, and very few of these kinds of companies have an extensive engineering/analysis team on board.

I don't doubt that hook could hold up fine with a 250 lb weight hanging directly down from it, and probably would be able to hold up under the kind of load it would see supporting a hammock if it were solidly anchored into a wall or a large tree (put on with stainless steel lag screws). Where supporting a hammock gets tricky is that depending on how tight the support is strung, and what angle the lines "sag" to, the actual load on the ends can be much more than the amount of weight placed in the hammock.

Installed onto the rack as shown, with the hook at the end of a cross-bar, it's possible that the load could spread through enough of the rack to keep something from bending, but I don't know that I'd trust the stock cross-bar installation screws to hold up under that load (especially if they've been exposed to weather for a significant amount of time). If you could find a "10.9" or Grade 8 replacement (the bar extrusions are metric, but the thread taps in the ends might be 1/4") for those screws it might actually be OK for a skinny person to use a hammock hung off the side there. As a mechanical engineer with 25+ years experience doing Aerospace Structural analysis and weighing over 250 lb, I personally wouldn't trust it.

If you absolutely have to hang a hammock with one end tied off to your vehicle, the best place would be on a rock slider if you have one, or a light hoop mounted to a plate bumper. A recovery shackle might also work on either the front or rear, including one connected into the hitch receiver. If you have a bed rack, the front leg of that should be pretty solid.

It might be possible to tie off to one of the D-rings in the bottom of the bed, but I'd probably remove the tailgate to prevent it from possibly being damaged by contact with the strap (unless you have a gate reinforcement plate with a steel upper edge channel).