My latest love-hate bike: the Genesis Onyx 29″ beach cruiser

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May 252013



I have been on a quest for my entire adult life to find a bike that I really like. I did manage to find it a couple of times.

Once was a yellow completely generic no-name mountain bike, no suspension, 7 back gears and 2 front. Very primitive by modern standards. I liked it because I was able to get it adjusted to fit me just right. Also because both the front and rear brakes (center-pull, but not V-brakes) worked all the time without squeaking or needing my attention. The bike had a heavy steel frame, and was essentially indestructible. So of course, as these things often go, once I got it exactly how I liked it, with good tire liners, bright lights, and everything just so, someone stole it. Bye, yellow bike. You were the best.

The other bike I loved was a Bianchi road bike. It was that weird pale green Bianchi color, had a sexy-sounding Italian name, and had a price tag that I couldn’t really afford. I’ve bought used cars for less than that bike. But it was worth the price. It was a wonderful bike. Effortlessly fast. Everything on it just worked. No futzing, no drama, it just went quick and smooth, braked hard and sure, and made riding really fun. Except for the tiny hard leather seat, but I got used to that. And my constant worry about theft every time I rode it to work. I never got used to that. So, the Bianchi became a weekend bike, and I bought another cheap generic no-name mountain bike for commuting. Over time, I got very un-used to the hard little leather saddle. Eventually, the Bianchi became That Dusty Bike With The Flat Tires. I gave it to a friend who fixed it up and rode it happily for several years, then he passed it on to another friend who really needed a way to get to work, and who is still riding it–fast, silent, and with a huge grin–to this day. So I’m pretty happy with how things worked out.

The new mountain bike was similar to the yellow one, except it was blue and it never was quite as good as the yellow one. The brakes squeaked sometimes. I could never get the seat height just right. It constantly needed some part or another replaced. Eventually, it was stolen too. I wasn’t terribly upset.

I went through a series of other bikes, a couple of fancy mountain bikes, a heavy-duty industrial bike, and a recumbent. I liked all of them in some ways, didn’t like them in others, and really hated at least one thing or another on every single one of them. The comfy recliner-on-wheels recumbent was probably my favorite, except for two things: On hills the combination of a long sloppy drivetrain and no way to “stand” on the pedals made for a real annoyance; it was possible to “spin” pedal the bike up a hill, but it wasn’t fun. It had a really long wheelbase, which made sharp turns on city sidewalk corners a complete hassle–and not just to me, but to the other riders who had to navigate around my land yacht. It ended up that the frame of that recumbent model had a flawed design and would eventually break. By the time mine did, I was already an ex-recumbent rider in my head, and was happy to say goodbye to it.

I burnt out on bicycling, and lost interest in it. Then one day I stumbled across an internet forum where people were describing how they modified their Onyx beach cruisers. There were lots of pictures, and the bikes looked really cool–all gloss black with white trim. One post included a link to the bike at WalMart. I couldn’t believe it–the Onyx was only $150. And it had a ton of rave reviews. That sounded like my kind of bike–both good and cheap. So I went to my local WalMart and checked one out. I rode it around the store a little, and loved it. The bike was huge, but it rolled like a breeze and was surprisingly comfy. I was ready to buy it. But having been burned by impulse buys in the past, I decided to think about it and come back the next day. As luck would have it, when I returned the display model had been sold, and they didn’t expect more in stock for at least a week, probably two. I didn’t want to wait that long, so I started checking nearby WalMarts, Craigslist, then eBay. Where I found drichard45 selling them for $120, including shipping. Sounded sketchy, but the reviews were good. So, I rolled the dice and bought one. It arrived in less than a week, brand new, still in the original box.


Assembly And First Ride

The bike needed a bit of assembly: I had to attach the handlebars, then put on the fenders, seat, water bottle cage, and reflectors. The front wheel’s axle was overtightened, so I got out the wrenches and got it just right so it spun smoothly with no wobble. The bright-white chain was very lightly greased, so I added a bit more grease. Overall, it took about an hour to assemble, maybe a little longer.

Then it was off for the first real ride, and I totally fell in love. The Onyx is unbelievably easy to pedal. It rides very smoothly for a bike without any suspension. It’s surprisingly fast for a single-speed beach cruiser. The tires and frame are so big that I feel like a kid riding it (though I can put my feet flat on the ground when straddling the bike’s upper bar). Basically, it’s a hoot. It’s fun.

The coaster brake gets the job done, but takes a bit of getting used to. Also, I’m thinking about maybe adding a front brake. It’s weird to not have that immediate stopping power that a good front brake provides, and I still grab for the nonexistent brake levers anytime I need to stop fast. On the other hand, it’s nice to not have brakes that squeak or need adjusting.



The bicycle is a Kent Genesis Onyx (or “ONEX” on the stickers on the bike) 29″ beach cruiser. It is very similar (identical?) to the Kent Shogun Stryker 29″ cruiser, but considerably cheaper. Genesis is a brand-name made exclusively for WalMart.

As is typical for beach cruisers, the Onyx has a chain guard and fenders (splash guards). It is a single-speed.

It has a pedal-operated coaster brake for the back wheel. It has no front brake, though there is a mounting hole on the front forks for caliper or V-brakes. There are no mounting holes on either the front wheel hub or the front fork for disc brakes. Similarly, there is a hole for mounting caliper or V-brakes on the back frame, but no support for disc brakes on the back wheel hub or frame.

The Onyx has a large, cushy seat and wide handlebars with hard-rubber grips at the ends.

The entire bike is black with the exception of the stickers, the chain, the insides of the pedals, and the water bottle holder, which are all bright white. Most of the bike is gloss black. It really does look cool. There are two rear reflectors, one on either side of the rear fender, and they look like little rocket exhausts. Very cute (and not at all like the standard reflector in the stock picture above) I personally don’t think that they’re big enough to be effective, but I added front and rear lights to my bike anyway, so for me it doesn’t matter if they are big enough or not.

The Onyx has a 3-piece crank, with 107mm long crank arms which attach to the bottom bracket via a spindle with tapered-square ends. The crank arms are held onto the spindle with 8mm-1mm “fine thread” x 16mm crank-arm bolts which thread into holes in the spindle. (More about this in the “Stuff I’ve Had To Replace” section below.)

The Onyx has 29″ wheels with 48 spokes per wheel, sturdy deep  V rims, and 29 x 2.125″ tires. These are “balloon” tires similar to the Schwalbe Big Apples. They take 40 PSI max, but are surprisingly firm at that pressure, and to my surprise don’t deflect or deform while riding. The inner tubes use the standard Schraeder valves (like a car, not the Presta valves like my Bianchi had), and the valve stems appear to be extra-long in order to poke far enough out of the V rims. Many reviewers have mentioned that their tubes went flat quickly, and that they had a hard time finding replacement tubes that had long enough valve stems.

From looking around a bit, it appears that Bontrager 425140 thorn-resistant 29″ x 2″ – 2.4″ inner tubes with 48mm (2″) Schraeder valves should work on the Onyx. Or Bontrager 425138 regular tubes–same specs as the 425140, but not thorn-resistant. Neither of these tubes are available through Amazon.


Stuff I’ve Chosen To Replace So Far


The first replacement was the pedals. The original pedals on the Onyx were of the “smooth block” style common on comfort bikes, and were unsurprisingly pretty cheaply made, mostly out of plastic. I prefer pedals that grip my shoes, and like steel pedals because they last forever. I replaced the originals with a standard set of steel mountain bike pedals: tough, cleated, and zero maintenance.


I next added a few parts: Front and back LED  safety lights, a black water bottle and matching cage (I thought the white cage looked weird), and a friendly “ding-dong” bike bell. Since the Onyx’s handlebars are 1″ diameter (instead of the usual 7/8″), the clamps for the lights and bell just barely fit, but they do fit. Some accessories that are designed to perfectly fit on standard bike handlebars may not have big enough clamps to fit on the Onyx.


Stuff I’ve Had To Replace So Far

(AKA the “hate” part of the love-hate relationship.) With the exception of the Bianchi, I’ve never bought a bike that didn’t need futzing, adjustments, and replacement of a few parts (usually the pedals). The Onyx is no different. Many on-line reviewers mentioned a variety of problems with their Onyxes. Given the $120 price tag, I was prepared to invest some time and money into getting everything fixed and solid. Still, I’ve only spent $200 total so far on my Onyx, including replacement parts and accessories.

One of the biggest frustrations with working on a bicycle is that they’re all so non-standardized. Even the ISO standards, which many–but far from all–modern bikes are built to are “multiple choice” standards. For example, there are at least 4 different non-interchangeable widths that an “ISO standard” bottom bracket could come in. And the way that an ISO standard crank arm is held on to an ISO standard bottom bracket spindle could be either via a bolt which threads into the crank arm, or via a nut which threads onto the outside of the spindle. Which width of bottom bracket does your bike use? You’ll need to measure it with a set of calipers to find out; the differences in widths are only a few mm. To replace that ISO standard bottom bracket, you’ll likely need two sets of tools: one set to remove the old bottom bracket, and a different set to install the new one. If your bike has a “standard” one-piece crank or follows the “BMX standard” or one of the other standards rather than ISO? You’ll need to buy an adapter to use an ISO bottom bracket on your bike, if one exists. The Onyx, like many modern bikes, pretty much kinda-sorta follows the ISO standards.

Handlebar Stem

After just two rides, the handlebars started getting “floppy”. The problem ended up not being with the handlebars themselves, but with the handlebar stem. It was designed to have an adjustment pivot in the middle, and the latching teeth that locked the pivot in place were completely stripped. I think this is because the teeth (and the entire stem) were made out of some very soft metal (aluminum?) that simply wasn’t strong enough to handle the stress that they had to take whenever I leaned hard on the handlebars.


I replaced the stem with a non-pivoting chromoly stem: 1 1/8″ x 135mm quill, 25.4mm handlebar clamp. These measurements might seem strange at first, but they are correct. If you take a tape measure to the stem, you’ll find that the quill (the part that goes down through the bike frame and attaches to the front fork tube) is 1″ diameter. Many bikes use 1″ handlebar stems. So, what’s with the 1 1/8″? Well, that’s bicycle measurements for you. The 1 1/8″ is actually the size of the tube that the quill will fit in. Or, the Onyx quill is 1 1/8″ nominal, aka 1″ diameter. The clamp’s 25.4mm is also 1″, which is the diameter of the Onyx’s handlebars. Chromoly is a type of steel that is fairly strong but also has a little give to it, so it is popular for bike parts. So, if you need to replace your Onyx handlebar stem, just make sure that the quill is 1 1/8″ diameter and the handlebar clamp is 25.4mm diameter. Taller riders might want to look for a stem longer than 135mm.

Here’s a similar (but shorter) handlebar stem on Amazon. I bought mine on eBay from seller bikemaui; it was cheaper overall and shipped quickly, but it was silver-colored rather than black. Meh, I don’t really care. It works great and is very strong.

Pedal Crank Retaining Bolt

The next problem was with the left pedal–it started feeling a little jerky, or hesitant as I was riding home one day. Shortly after that, it started feeling downright floppy. By that point, I was almost home, so I just walked the bike the rest of the way.

Once I looked at the bike carefully, I found that the left crank arm that connected the pedal to the rest of the bike (the bottom bracket, to be specific) was very loose. The pedal was screwed firmly into the crank, but the crank was not connected tightly to the bike. The only reason the crank had not completely fallen off was because the little plastic dust cover over the bolt that held the crank on had kept the bolt from falling out.

I figured that I hadn’t checked the tightness carefully enough when I first assembled the bike. I got out my wrenches and tightened up the bolt, good and snug.

By the time I got to work the next day, the bolt was completely loose again.

This time I took a careful look at the bolt. It was one that had a “lockwasher” built into the underside of the bolt cap (with little radial serrated “teeth”). Much like with the handlebar stem’s pivot, the lockwasher teeth on the bolt had completely worn down.

I fished around in my junk drawer and found a real lockwasher that fit the bolt, reassembled the crank, and tightened the bolt down. I took the bike for a 10 minute test ride. The bolt was loose again by the end of the ride. Gah. So, I got out the wrenches, tightened the bolt really good and snug… and the head of the bolt came right off. Huh. Now, I wasn’t invoking gorilla strength, I was using a small racheting  wrench and finger strength. No way should I have been able to break that bolt. But I did. Closer inspection revealed that the bolt was made out of very soft metal, possibly aluminum. Really?


After much searching of local stores, I finally found a replacement bolt at Menards (a midwestern hardware store chain). An 8mm-1.00 fine threaded x 20mm length hex cap machine screw. Unlike the Onyx’s original Mystery Metal bolt, the one from Menards is good old boring zinc-plated steel. Menards also had some 16mm length bolts. Since they were only 69 cents each, I bought a couple of both lengths. The 20mm ones are closer to the original bolt’s length, and seem to work better. I bought a spare of each length with the assumption that the bolt on the right crank will eventually come loose too.

I reassembled the crank with the new bolt and lockwasher, put some Loctite Red on the bolt just to be sure, and tightened the bolt down but good. So far, it’s holding just fine. Fingers crossed it stays that way.

Update 6/1/2013: Well, that held for 2 rides. I’m betting that the bottom bracket spindle is made out of Mystery Metal too, and is too soft to properly hold the new bolt. What to try next? I’m thinking to maybe swap out the entire bottom bracket and crank set. I haven’t ever done that before, and don’t have the tools. Plus, I have no idea what size the BB is, and surprisingly none of the online comments I’ve found from the many people who have modified their Onyxes and swapped out their BBs have mentioned what they replaced theirs with. I guess that for experienced bike modders, that’s an easy obvious thing? Somehow I doubt it. The other option is to just break out the JB Weld and fix it permanently. I’m not quite to that point yet.

Really, though, that’s a very small bolt for the job it needs to do. It’s smaller than the two bolts that hold the handlebars in the stem’s clamp. I’m not sure what people were thinking when they decided to use such a small bolt.