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I have a Diamondback Outlook Omni 181 CL, bought it second hand for $40, and I'm not sure of the original parts. Recently I have been having trouble with the rear axle, the one it came with bent so I replaced it, and then next two bent. I don't do anything extreme, I ride ~6 miles a day, mostly on sidewalks. I'm tired of replacing the axle, I'm tempted to switch to a solid axle, as I currently have a hollow one for a quick release but I don't use that feature often. I don't know if the axles I have gotten are just bad or if there is some damage to the wheel that is causing the axle to bend, but I don't see any damage to the wheel.

One of the axles I have tried:

  • I had a front hub that kept bending axles. Finally figured out that the hub was bent, so that the cups on opposite ends were not parallel with each other. This caused the cones to "crawl" tighter until the axle would be stretched and distorted. So I bought a new wheel and have not had a problem since. – Daniel R Hicks Feb 9 at 2:10
  • Plain questions - how much do you weigh? Do you ride off curbs/kerbs? Do you ride through potholes? Do you carry a backpack or things on a carrier rack ? – Criggie Feb 9 at 6:44
  • I suspect th e bike is a Diamondback Outlook. The Omni is the brand of fork, and the 181 CL is its "volumetric displacement" which means little. – Criggie Feb 9 at 6:45
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    @Criggie I try not to go off curbs, or through potholes, and I do carry a backpack, anywhere from 5 - 20lbs (~2.3 - ~9.1kg) with me every day. – John Smith Feb 9 at 7:28
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Broken axles are an inherent feature of the 'freewheel' hub design. They happen because the load from wheel bearings is close to center, where it has more leverage than closer to axle ends. Newer 'freehub' cassette designs solve the problem with either having bearings inside the cassette close to axle end or with oversized axle.

The best option would be replacing the rear hub with a freehub type. The easiest way of doing this is replacing the entire rear wheel. If this is not an option, an original axle from known brand should be expected to last longer than random junk from Amazon or Aliexpress or at least have a warranty. A solid axle does not help, because the reason for breaking is tension from bending the axle. The tension is greatest at the surface of the axle, so solid interior does not help but the compression from quick release skewer slightly reduces it.

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  • How would I go about finding the right freehub, and what would that cost me? How can I find the original part? – John Smith Feb 9 at 7:26
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    Just google for 7 speed hub, and you will find plenty of information about hubs in general and fitting 7 speed cassette on modern hub. The hubs themselves don't cost much, but building one into wheel is manual work and will likely cost more than new rear wheel. For axle, quality freewheel hubs haven't been made in decades so the best bet would be to go to a bike shop that has been in business since at least 80s and ask them. – ojs Feb 9 at 10:25
  • @John Smith A new or used rear wheel with a freehub is the easiest and most economical route to take. Any correct sized wheel with a freehub marketed with any speed number(s) 7-9 will work. If the hub isn't 7 speed specific, a simple spacer is all that's required for it to take a 7 speed cassette. IMHO I'd favor acquiring a wheel with an 8, 9, 10 speed hub, which are more commonly for sale and are also ready if u choose to upgrade the number of speeds, use it on a different bike with more gears, and are more desirable to others if resold. – Jeff Feb 26 at 19:46
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The best option is to acquire a new rear wheel that is equipped with a more modern freehub that accepts cassette sprocket clusters. The freehub puts the bearings more outboard and that helps prevent bent axles because there now isn't such a long stretch of axle unsupported like is found in the right side of freewheel systems.

Your bike is likely a 2002 Diamondback Outlook. Possibly '03. In any case, new rear wheels with similar specs to your current--albeit with a freehub--are reasonably priced and the better deals include skewers and sometimes a cassette as well. Seven speed cassettes also are very reasonably priced. Here's what you presumably have for a rear wheel and here is the same model wheel only with a cassette hub. You can still use a seven speed cassette on this 8/9 speed hub with the addition of a spacer that slides on prior to the cassette. Please keep in mind you're not limited to this model (or that price point) of rear wheel. These links are examples illustrating the subject.

Many areas now have "bicycle coops" where good used parts can be obtained for very reduced prices. Same situation exists online in the form of e-stores and forums within sites like Facebook, so these are additional options to get a better wheel without spending more than you bought the bike for. Hope this helps.

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