Sorry I didn't know what sub topic to post this in. I hope this is ok to post in the general forum :-)

I'm working on an odd project for my kids. One of those mini-bmx bike things. I bought one in rough shape...it was missing the left crank. No big deal I figured, I could fix it...until I got i tried to order one.

So long story short, its a standard 68mm wide bottom bracket with a 3 pcs square tapered crank. The crank measure 127.5mm wide.

The crank arms are 89mm long with 28t sprocket. That's not impossible to find (I had to resort to aliexpress)...but the fact that the cranks are flared out is the issue. The bike has really wide rear wheels...like fat bike wide so the rear of the frame is extra wide.

I purchased a set of 89mm long cranks with 28t sprocket and it contacts the rear frame of the bike during the pedal stroke. The crank arms need to be about 3/8" wider to clear the frame. So i'm trying to find a solution to this and figured there must be some way...

I figured I could buy a wider crank for the 68mm bottom bracket. It's 127.5mm wide currently. But looks like that nothing wider is available.
-Are there things such as tapered crank extensions? Like something that slips over the existing square tapered crank and extends it wider???
-Or can I use a fat bike crank in my 68mm bottom bracket?

The easiest would be to find a set of 89mm flared cranks arms...but I literally can find zero. Does anyone know of flared cranks in 89mm crank length with a square taper?

Any suggestions would be greatly appreciated! Thank you!


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pictures?

Here's the thread that would get the best results - https://www.bikeforums.net/bicycle-mechanics/ - You can click on the red button on your original post and ask the Mods to move it

Help us, help you. More info helps with answers. What is the brand/model/year of the bike? Can you post pics of the bike and crank? Are there stamps or other labeling on the crank itself?

BMX bikes are a different beast entirely. Likewise their BB's are slightly different and generally come in three flavors (size/type). Don't let the small frame and toy like looks fool you. If you haven't already, I'd recommend you search specifically for BMX bottom brackets. Then look at the differences of the BB's and decide which you should have gotten along with cranks too.

Also realize that between the General Cycling Discussion , Bicycle Mechanics , BMX sub-forums, I feel you picked the least relevant and least perfect place to post this question.

I have not worked on a BMX before, but if it has a standard 68 mm wide bottom bracket shell, wouldn't installing a square tapered bottom bracket with a longer spindle be cheaper and easier than finding a crank with a specific length and sufficiently flared crank arms?

Maybe besides pictures the brand or model of the crankset/s you're dealing with.