Deeo

I wanna get a real low gear ratio on my bike, and I've been thinking over some ways to achieve this. Either a really big sprocket on the rear wheel, or a small one in the front. Getting big cogs for the back wheel seems impossible, so I've been looking at the BMX style Splined cranks.

Now, a splined crank requires a splined bottom bracket. I have a "regular" bottom bracket with square ends. Would it be possible to switch out my old one for a BMX one?

Leebo

Regular low mt bike gears are 22 front 34 rear. Need lower that that?

Deeo

Nope, been looking at 25t fronts. Problem is, this is a SS bike, so there can only be one cog. That's why it's such a hassle to find individual ones.

well biked

Decide on how many gear inches you are shooting for and it will be possible to discuss what's possible and available.

hueyhoolihan

a very little research shows me that most, if not all, of the splined cranks use press-in bearings. unless there is an adapter available, you may be out of luck.

BTW, here's a pic of a VERY small front chainring on a splined BMX press-in bearing BB.


OP might want to post a thread to BMX forum.

DCB0

Great advice. We cannot know what is possible unless you indicate what type of bike, what wheels you have, etc, and what you consider to be a 'low' gear. As mentioned above, 22 tooth chainrings are common on mountain bikes, as are 34 and 36 tooth cogs. 22-36 is a low gear - so low it isn't really useful on most bikes unless you are going up a very steel hill or towing a trailer up a slightly less steel hill.

Also, I believe there are 'euro' bottom brackets that mount BMX cranks in English-threaded bottom bracket shells. I odn't know the details, though. It is something that some of the big mail-order places might have info one... I find niagara cycles has lots of BMX stuff.

Edit: Just looked at Niagara cycles and the smallest sprocket for bmx cranks is 25... I guess that it what you were talking about in your post above. Well without changing bottom brackets you can easily put a 22, 24, or 26 tooth small cog on a regular MTb crankset.

Edit 2: Here is a BMX crankset with a splined BB for threaed BB shell. If the crank exists, the bottom bracket must be available somewhere.

Deeo

Thanks for the info!

I'm checking out some cogs for the crank I've currently got. I'll make it work!

Humpy

Profile Racing makes several types of bottom brackets for their BMX cranks.

https://www.profileracing.com/estore/...bottombrackets