how strong are the roof bars?? - Nissan Xterra Forum
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#1 Old 01-25-2013, 02:28 PM
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how strong are the roof bars??

hey... im about to get a 2002 Xterra, and i plan on building a camping vehicle that is equally well suited for some mild offroad as well as for highway driving and pulling a boat... i camp a lot, and these camping trips can be up to 4 days, and besides all the camping equipment, we carry a lot of climbing equipment as well... so the first mod i want to do is a homemade roof rack to increase the space... i have been thinking about fixing it to the original roof bars with 4 U bolts, one on each corner...

do the roof bars are strong enough to hold a rack and equipment?? the rack will be very light, but once ready for camping it can be quite heavy, with the backpacks full of equipment, ice chests, and supplies... i would try to put the heaviest equipment inside, but the rack would get some weight as well...

will it hold?? i dont want it to tear the bars from the roof, i dont even know how they are hel to the roof yet... i have seen pictures of roof racks with spare tires, ice chests, and stuff, but im not sure how they are fixed to the truck...
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#2 Old 01-25-2013, 03:46 PM
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Pretty sure they say the weight rating right on them. It's around 140lbs total if I remember correctly.

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#3 Old 01-25-2013, 03:54 PM
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thanx... i think i saw the weight rating of the small basket it has at the front of the rails, but i dont remember if it also had the total weight... 140 lbs would be fine, its almost 65 kg, and i guess the rack will weight 5 kg at most...

so 4 U bolts would be fine??
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#4 Old 01-25-2013, 04:08 PM
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I would anticipate 4 U-bolts being fine. Just make sure the hardware is tightened properly...and use lock tite on the threads to keep them secure.

I haven't seen your design or anything, so it's hard to tell where it would fail...but my guess would be not at the U-bolts


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32" Cooper Discoverer ATP | Lokked and Dropped Front Diff |2.125" Lift Shackles | 3" UCA's | 3" Bils | 2" BL | TC IAB | Bandit 4x4 Idler Arm Bushings | Custom Bumpers | Shrock Sliders | RSB Delete | Snorkel | Cobra 19 DX III CB | 4' Firefly

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How To: < Remove Rear Sway Bar > < PML > < Re-Index Torsion Bars > < Lokk and Drop >
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#5 Old 01-26-2013, 11:09 AM
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thank you!!

i plan on building it of such a size that it fits inside the roof bars, so it wont be very high... im not much of designing on paper, i just think about the design, and once everything fits in my head, i build it... i have built front and rear bumpers for my jeep, rock sliders, 2 cargo baskets, toolbox, and several other things, and i rarely draw anything.... so i guess i will be taking pictures of the builds for the How To forum but i wont upload sketches or drawings beforehand...
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#6 Old 01-26-2013, 09:39 PM
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i went to test drive my future Xterra today and i noticed the rails say "max 120 lbs"... i think its enough for my needs anyways....
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#7 Old 01-27-2013, 05:49 AM
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Thats what it says, but my 250lb brother stood on mine to retrieve something up in a tree and the only bowed a little

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#8 Old 01-27-2013, 09:36 AM
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here is a secret from the world of engineering:

Factor of safety...or the "factor of ignorance"

When designing something and determining a max allowable load...the rating is often anywhere from 20-50% on the conservative side...and often failure criteria is not always a catastrophic failure...IE a bowing tube on the rack, or a certain angle of deflection that is allowed. Also...if that 250 pound brother was distributed to the entire roof rack, by a basket bolted at various locations...the load is even easier to carry by the roof rack.

If that 120 max load seems maybe borderline for your needs or on the low side, rest assured if you are at 150 pounds or 160 or even 200...if that weight is in a basket that is resting on the roof rails and distributing the weight to multiple points on the roof rack, you are probably in no danger

That being said, if you think you may be on the heavy side of the max load rating, having 6 or 8 u bolts distributing the weight even more so each section of the rack holds less weight will mitigate the heavier load. Depending on your design, u bolts will probably be enough in the sense the u bolts wont break, but you don't want the middle of the basket to sag under the weight either! That is where the 6-8 U-bolts would help out the most


2004 Xterra 4X4

32" Cooper Discoverer ATP | Lokked and Dropped Front Diff |2.125" Lift Shackles | 3" UCA's | 3" Bils | 2" BL | TC IAB | Bandit 4x4 Idler Arm Bushings | Custom Bumpers | Shrock Sliders | RSB Delete | Snorkel | Cobra 19 DX III CB | 4' Firefly

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How To: < Remove Rear Sway Bar > < PML > < Re-Index Torsion Bars > < Lokk and Drop >

Last edited by robcarync; 01-27-2013 at 09:41 AM.
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#9 Old 01-27-2013, 11:11 AM
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Quote:
Originally Posted by robcarync View Post
here is a secret from the world of engineering:

Factor of safety...or the "factor of ignorance"

When designing something and determining a max allowable load...the rating is often anywhere from 20-50% on the conservative side...and often failure criteria is not always a catastrophic failure...IE a bowing tube on the rack, or a certain angle of deflection that is allowed. Also...if that 250 pound brother was distributed to the entire roof rack, by a basket bolted at various locations...the load is even easier to carry by the roof rack.

If that 120 max load seems maybe borderline for your needs or on the low side, rest assured if you are at 150 pounds or 160 or even 200...if that weight is in a basket that is resting on the roof rails and distributing the weight to multiple points on the roof rack, you are probably in no danger

That being said, if you think you may be on the heavy side of the max load rating, having 6 or 8 u bolts distributing the weight even more so each section of the rack holds less weight will mitigate the heavier load. Depending on your design, u bolts will probably be enough in the sense the u bolts wont break, but you don't want the middle of the basket to sag under the weight either! That is where the 6-8 U-bolts would help out the most

so true...

since im planning on building the rack of such a size that it sits inside the roof rails, it will be more or less square, so it would be small... thats why i had considered 4 U bolts only.... but if i decide to build it on top of the rails, it would be bigger, and maybe 8 bolts would be better, or at least 6, 3 per side....
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#10 Old 01-27-2013, 12:30 PM
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Oh I see...so a square type basket in between the side to side rails?

I was thinking of a rack with no cross members, and a large basket in between the long front to back rails...the entire length of the roof type of thing

But that is where your design comes into play...the stock roof rack will be able to do what you need it to do


2004 Xterra 4X4

32" Cooper Discoverer ATP | Lokked and Dropped Front Diff |2.125" Lift Shackles | 3" UCA's | 3" Bils | 2" BL | TC IAB | Bandit 4x4 Idler Arm Bushings | Custom Bumpers | Shrock Sliders | RSB Delete | Snorkel | Cobra 19 DX III CB | 4' Firefly

Building my X


How To: < Remove Rear Sway Bar > < PML > < Re-Index Torsion Bars > < Lokk and Drop >
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