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I have a Jamis TAXI cruiser bike. See https://www.jamisbikes.com/bikes/recreation/cruisers/taxi/.

Note the description "Forged alloy crank with 44T compact disc chainring".

If I needed to replace a worn chainring, can it be separated from the crank? How is the chainring mounted to the crank? Is there some type of threaded adapter that secures the chainring to the crank? chainring closeup

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  • The pictures on the web site are all taken from the drive train side and from there it looks like the chainring is somehow mounted directly onto the cranks. Could you make some close-up photos of the cranks and chainring from the other side so that we can check whether there is some bolted mount?
    – Benedikt Bauer
    Commented Sep 13 at 4:49
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    From the pictures it seems unlikely the chainring is removable. But you can of course remove and replace the crankset, should the need arise.
    – Burki
    Commented Sep 13 at 7:20
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    Not replaceable
    – Noise
    Commented Sep 13 at 7:21
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    Since you already have the bike, please take a couple of close up photos of both sides of the chainring-plate. Use lots of light, and perhaps even put the bike upside down to get a good angle. Then edit the pictures into your question.
    – Criggie ♦
    Commented Sep 13 at 12:06
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    I added a picture. As suggested in one of the comments, it does appear the chainring is bound to the crank. THANKS for all of your help!
    – Old Grouch
    Commented Sep 17 at 19:13

4 Answers 4

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I have found these photos using google image search.

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There appears to be no spider or bolts or rivets of any sort. Therefore the chainring seems to be integrated with the bottom bracket axle and perhaps that's why they call it "forged"

What's curious is that the crank arms themselves clearly have a central bolt but no pinch bolts, so there is a square taper or something like octalink holding the cranks to the axle.

To give you an idea of quality - the 16" and 20" bikes clearly have a one-piece ashtabula crank, a hallmark of a budget bike.

Also, these bikes have one coaster brake and that's it. If anything fails in the transmission, you've got no brake left. Not ideal, permitted in the US but not legal in other developed nations. Given you already own the bike, be aware of its limitations and the consequences of failure of the chain etc.

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    Forging is a common way to manufacture the crank arms. I believe square taper bottom brackets are more a common technology for mid-budget bikes than a curiosity.
    – ojs
    Commented Sep 13 at 14:02
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    Here’s an example of how the chainrings are swaged together with the cranks: i.redd.it/aumcrta2ew8b1.jpg Note that the aluminum from the cranks has been smushed into that star shape, acting like a massive rivet.
    – MaplePanda
    Commented Sep 14 at 8:27
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    @MaplePanda that's worthy of an answer by itself - based on that, likely OP would need a complete new crankset when teh chainriing teeth are worn. However, the chainring is likely to be steel and will probably go 50,000 km before it needs replacement. These beach cruisers probably won't go 1,000 km over their entire lives.
    – Criggie ♦
    Commented Sep 14 at 10:56
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    @Criggie Suggestion acknowledged :)
    – MaplePanda
    Commented Sep 15 at 16:51
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It appears from the photo that is a typical squared tapered crank arm. The images of similar pieces on line all show welds attaching the sprocket to the arm. In the Jamis image the welds are not visible. It could be possible that there is a nut similar to a BMX/beach Cruiser crank arm. The fact that so little information is given (no brand name) I would assume it is welded as the production cost is less than a threaded arn.

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    Usually cheap cranksets have the chainring riveted or swaged to the crank arm, not welded—welding steel to aluminum doesn’t work well and welding is more expensive anyways.
    – MaplePanda
    Commented Sep 13 at 13:59
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    @MaplePanda Isn't it all steel in cheap bikes?
    – Vladimir F Героям слава
    Commented Sep 13 at 14:32
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    @VladimirFГероямслава Note the description of “forged alloy crank”. I would imagine that’s aluminum? And if you look at the picture of the bike in the link, it looks like aluminum too.
    – MaplePanda
    Commented Sep 14 at 8:20
  • @MaplePanda OK, you meant the crank arms to be aluminium? I do not have an issue with that. I did not believe the chainring would be an aluminium one.
    – Vladimir F Героям слава
    Commented Sep 15 at 18:23
  • @VladimirFГероямслава Oh yeah the chainring is almost certainly steel. I was trying to imply that with "welding steel to aluminum" but maybe I should have made that more clear.
    – MaplePanda
    Commented Sep 15 at 19:32
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I cannot find a definitive answer to this as all the Jamis documents just describe it as a forged crank, however it looks very like a square taper crank to me, and the Jamis catalogue (pdf) describes it as a 170mm crank which is a standard size.

That means you can buy a square taper crank and a chainring of whatever size you want reasonably cheaply. There are two types of square taper crank but almost all cheap bikes use the JIS standard and that's what you'll get unless the description specifically states otherwise. As usual Sheldon Brown has a comprehensive article on this if you want any more information.

I have done precisely this mod to one of my bicycles and the results are described in my answer to Can I (easily) change this chainring? In fact I've done it several times to convert my bikes to a single narrow wide chainring. The only problem I've had was on one bike the new chainring was a couple of millimetres out of the perfect alignment with the rear gearset and I fixed that by using some spacers between the chainring and the crankset.

If you want to do the swap yourself you should find it straight forward. You will need a crank puller but they are very cheap, and you'll find lots of videos on YouTube explaining how to do it. Ask here if you want any more details.

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  • I deleted the comments because after the edit they were not fitting anymore.
    – Willeke ♦
    Commented Sep 14 at 19:40
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I'll expand a little on my comment under Criggie's answer. This is more or less what you'd see if you removed your cranks:

An example of a swaged crankset

You may think that the star-shaped pattern is a tool fitting for chainring installation and removal, but that is not the case. It's just an artifact from the swaging process used to permanently attach the chainring to the crank arm. Essentially, the crank arm's relatively malleable aluminum is deformed with a large hammer/press machine to more or less rivet the two parts together. This is permanent--not only would it be a major hassle to even try disassembling this interface, replacement chainrings are not available for sale and it's probably not worth your time trying to transplant them from a different crankset. As Criggie mentioned though, being a steel chainring, it is likely to last a very long time, and in all honesty the entire crankset is probably cheaper than a fancier replaceable chainring on its own.

Do not confuse this pattern with the removable lockring used on Shimano 12 speed cranks, for example. These are threaded and use a bottom bracket tool-style tool fitting for installation and removal:

A close up of the lockring used with Shimano direct mount chainrings

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