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I'm trying to figure out the viability of a project to suspend bicycles from the garage ceiling. What I don't know, however, is how much to worry about the bearing capacity of wood screws to hold a pulley, fairlead, or other device to guide the rope down the wall. An example is something like http://www.ronstan.com/marine/product.asp?ProdNo=RF188 or http://www.landfallnavigation.com/har472.html, which I assume I can mount with a hanger bolt of some sort.

Anyway -- let's each bike maxes out at about 30 pounds, which will be a little higher while hoisting. What's the best way to attach something like the pulleys to a stud or rafter? My worry is that this is the worst kind of loading scenario -- basically perpendicular to the stud. I can't find any info online about what I can expect from standard screws in framing lumber, though. Would it be necessary to knock out a bit of drywall and attach this kind of stuff to a smallish (maybe 4" wide) panel of plywood? That way I could spread the load across more fasteners in the framing.

If this is a better fit for another SE site, let me know. Engineering seems a lot more exotic than this kind of question...

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  • You appear to be asking about a screw's shearing strength as opposed to its tensile strength. Some screws have great shearing strength while having terrible tensile strength, and vice versa. In either case, just about any screw ought to be able to hold a 30-lb bicycle. – BillDOe Apr 24 '16 at 20:12
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    I wouldn't agree that "...just about any screw..." would work. While something with a 1/4" shank would probably work, why not upgrade to 3/8"? – Aloysius Defenestrate Apr 24 '16 at 21:36
  • I was thinking of a bike hanger, so I googled it to find an image... man, there SOOO may bike hangers; lot's of DIY designs too! – Ben Welborn Apr 25 '16 at 17:06
  • There are definitely a ton of options, but unfortunately I've got some weird clearance constraints based on the available space and the location of the garage door, so the off-the-shelf kits (and most of the DIY ones) aren't quite viable. – moxen May 21 '16 at 18:38
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If you used a set of simple pulleys similar to these:

enter image description here

And then used 5/16" type screw eyes that were inserted into studs or ceiling joists using the proper sized pilot holes:

enter image description here

This should lead to strong and robust bike hoist system.

Open the loop of the screw eye with the aid of a vice to hook the pulley on. Then squeeze the eye shut again using the vice. For pulleys that do not have swivel tops you can set the right direction for rope travel by how you orient the eye when screwing it into the stud.

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    Or for ease of service, use a shackle in between. There are cheap screw gate D shackles available. – Chris H Apr 25 '16 at 7:04
  • So let's say that I've got the bike in the center of the garage, and the eye hook is on the side of the garage, where the wall meets the ceiling. I'm assuming that I'd want to drill the pilot at a 45-degree angle up and into the wall, right? And, would something around 5/16" going to be enough to tie off to? I'm more concerned about the screw in shear where the tie-off is, rather than the pulley connection. – moxen May 21 '16 at 18:52
  • I think you are way over thinking this. Put the screw eye straight into the wall stud or the ceiling joist. The directional strain on the hook will easily adjust itself due to the eye loop. I had suggested the 5/16" size because of the relative ease of opening the loop to put the pulley on but you could go to 3/8" size to gain way more strength and then use the screw gate shackle as suggested by @ChrisH to attach the pulley to the screw eye. If you are concerned about the ease of hoisting the bike into place read up on how you can arrange (continued) – Michael Karas♦ May 21 '16 at 21:28
  • (continued from above) the pulleys and ropes to halve the hoisting effort at the expense of needing to pull twice as much rope length. – Michael Karas♦ May 21 '16 at 21:30
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With regard to expectations for screws, perpendicular strength is usually the weakness. It's difficult to answer a question like what's the weakest screw that will work well when I'm pulling on it. Even if you had some specifications, interpreting the information into reality is not pretty. The length of time over which force is applied, area of the applied force, the measured shear strength of the screw, and stiffness of the wood are just some of the factors involved with answering whether xyz screw hold up a bike (but for how long).

The answer is repeated measurement. Experience and familiarity with materials (and seeing things that have failed in time) is what (some) people here have. The best answer is a good recommendation from someone who has enough experience and intelligence to make a judgement. Engineers rely on a lot of numbers and a lot of uncertainty. Their job is primarily balancing safety with price; the good ones also rely on experience and familiarity.

I agree that a 5/16" eye screw and the recommended pulleys should work fine. The $34 Harken Carbo Cam II Kit sounds like a fun toy.

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  • I'll definitely agree that the cam kit is overkill for the task at hand. The main problem is that viability of the project demands that other, less mechanically-inclined household members can easily hoist and tie off the bikes ;) But, I think the 5/16" screw is close enough to the answer I need (and I agree that there are too many variables to reasonably estimate here; I just don't have the domain expertise to make an educated guess, even with a large-ish safety factor). – moxen May 21 '16 at 18:33

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