Anyone ride/race BMX?

I think the key thing you need to consider here is chainline. Is this a proper bmx with a fixed freewheel location? If its is then whatever you do for the crankset needs to be the same chainline otherwise your going to introduce a potential new problem with the chain wanting to come off all the time because the cog and chainring are out of alignment.
You can measure the chainline of your current setup by measuring from the centerline of the seat tube to the top of chainring.
Measure the width of the bottom bracket, I don't know if bmx runs the same widths as mtb. That might stop you from being able to run a mtb crankset.
This is a good explanation https://www.supercrossbmx.com/blogs/news/centering-your-chain-alignment
 
Lost Kiwi said:
I think the key thing you need to consider here is chainline. Is this a proper bmx with a fixed freewheel location? If its is then whatever you do for the crankset needs to be the same chainline otherwise your going to introduce a potential new problem with the chain wanting to come off all the time because the cog and chainring are out of alignment.
You can measure the chainline of your current setup by measuring from the centerline of the seat tube to the top of chainring.
Measure the width of the bottom bracket, I don't know if bmx runs the same widths as mtb. That might stop you from being able to run a mtb crankset.
This is a good explanation https://www.supercrossbmx.com/blogs/news/centering-your-chain-alignment
Click to expand...

This was helpful - most of the generic 1x Aliexpress cranks seem to have the ability to mount the chainring on the inside or outside so you can dial in the chainline - I think they purposely make them one size fits all to fit road/mtb/bmx/hybrids. It's hard to tell if it would be OK though without actually mounting - I just rolled the dice and bought a $39 one that looked decent.

BB width seemed to be 68mm for this frame. I tried one BB spacer on the non-drive side but there was a tiny amount of side-to-side play. Added another and it's gone, although it seems like there's a tiny bit more drag than what I'm used to. I avoided putting a spacer on the drive side to keep the chain as straight as possible - pedaling around the neighborhood I don't notice the extra pedal width.

Switched the chainring to a 39T so now running 39x17, regular/traditional cruiser BMX track gearing. Feels like a big improvement, hopefully it makes a difference on the gate.

I was able to track down a 104BCD 4 bolt chainring for $25 from BRG.

https://www.brgstore.com/chainrings/203-insight-chainring-104mm.html

Chain super loose now, even all the way back in the dropouts. Removed a link, added a $5 1/8th-in master link and all seems good again. Hopefully this hodge podge 2 piece crankset lasts longer than the square taper one. I'm normally a "buy it and forget it" kind of rider but the 44T front was too hard to pedal and the square taper crank/bb was coming apart. It's been fun modifying this little ripper though.

Funny enough it comes with a bottle cage as you can see. Might throw on a fidloc one for summer neighborhood rides since it the mount is so minimal with the bottle removed.

I think I've put way more thought and ride time into this budget children's bike than anyone ever intended.

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Well.. not in 40 years. Me at 16 years old. I was pretty good at bunny hopping fire hydrants too but I did miss a low fence chain that was only 12-14 inches off the ground at one point. Ate sh$t on that one. I had a Mongoose bike with a flip flop rear wheel. I would ride against the wind down Knott street all the way to Huntington Beach PCH from Garden Grove. Then go south to Beach Blvd. and swap to a faster speed gear to catch the wind back home on Beach Blvd. bunny hopping onto the seats of bus benches along the way. I have a few pics at a local bike park in Westminster and Estero Beach, South Ensenada, Mexico where I was along with my buddy to ride where ever I chose. We rode miles into town late afternoon returning in the dark. No money. No lights. No extra tubes. No cell phones. Etc. 15 or so years old. I have a couple of pics if I can find them.

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I bought a Chase Edge XXL 20" race level BMX, a few weeks later seriously messed up my foot at Skypark and now a few months later back riding BMX. Figured I'd get the Gravity working again as a beater / neighborhood / friend bike. I've had continual issues of the wheel migrating forward, especially on hard starts. Dried double nutting the axle, safety wire, some improvised tensioners with long metric bolts and axle parts from Aliexpress, probably some other stuff. The weird forward facing dropouts presented some challenges since a regular horizontal dropout tensioner wouldn't work.

Here's what I cooked up. I used some Origin 8 fixie tensioners, a half-link to get the wheel farther back in the dropout (but not too far). V-brake is maxed out now but still functional.

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Danimal said:
Which is good for people like me that have no saw etc. And must say I can certainly use one.
Click to expand...
You don't own a hand saw or a drill? Report to the front desk and hand in your man card.

If you want, you can come and grab mine, I'm not using it at the moment. Although I should, still can't manual or wheelie to save myself but overall balance on the bike improved a lot.
 
Lost Kiwi said:
You don't own a hand saw or a drill? Report to the front desk and hand in your man card.

If you want, you can come and grab mine, I'm not using it at the moment. Although I should, still can't manual or wheelie to save myself but overall balance on the bike improved a lot.
Click to expand...

Oh I have a drill! It's nice and gets used once or twice a year. A saw, no don't have that, so I'll turn in half of my man card. :(
 
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