Mountain Biking - Chainring adapter/spider for cassette body? Singlespeed cog

My search skills have failed me :(.

I'm trying to find out if anyone makes an adapter or "spider" to use an inner chainring as a singlespeed cog on a Shimano cassette body / freehub. I understand that the usual solution is to run a smaller ring in front, but there is a minimum size I can use in front and still clear the brake. I could hack up an old cassette, but it would be nice to have a cleaner solution for using larger cogs.

My current setup 34x24 is functional, but I'd like a bit lower gearing for steep sections that I now have to walk.

This may be one of those stupid questions, thanks for humoring me :).

What do you mean by "still clear the brake"? If you have disc brakes, the disc is on the other side of the wheel. If you have V-brakes or cantilevers they are on top. Since most bikes were designed with 32 teeth middle rings in mind, you should be able to swap the 34 for a 32. But in the end, why would you go any lower? Even on a 29er, 34/24 is so low that you'll spin like crazy on any flat sections.

Lemme get this straight... you wanna use a chainring as a single speed cog? Don't think that's gonna happen, although I've never tried it.

What kind of clearance problems are you having when you say it has to clear the brake. Do you have a chainstay mounted U-brake or roller cam brake? Even then the calipers shouldn't extend past the chainstays.

Agree with Thor29, 34/24 is already hella low. Do they have super steep long climbs in VA? When you go SS you'll inevitably walk some short steep sections, it's part of the deal.

Your post isn't stupid as much as it is confusing.

Thanks for the replies.


What do you mean by "still clear the brake"?
It is an under-the-chainstay u-brake. Here are two photos that may help. Setup is 34x23 with a tensioner pulling the chain down. Without the tensioner the chain hits the brake.

http://img.photobucket.com/albums/v472/n1np/Specialized/Specialized_HardRock_011.jpg

http://img.photobucket.com/albums/v472/n1np/Specialized/Specialized_HardRock_014.jpg


Do they have super steep long climbs in VA? When you go SS you'll inevitably walk some short steep sections, it's part of the deal.

Yes, long steep climbs and really no flat sections where I ride. It's all crank uphill, then coast downhill riding the brakes all the way (same on a geared bike). I do expect to have to walk some, even on a geared bike with 24x28 low gear I have to push some places.

Only way to possibly do it is to carefully measure the rear 34 gear you are using and then spot weld a steel front chainring onto the gear perfectly centered.
It'd still be wonky with all the stresses placed on it though. Good luck

Hmm... clearance seems tight down there. Are you getting noticeable chain slap with your current setup? What kind of tensioner are you using?

Perhaps go with a larger chainring and cog for a bit more clearance. Rennen make both larger rings (up to 50t) and cogs (up to 25t) so you can find your gearing. Need more clearance? Push your chainline outboard. Use the large chainring on your crankset and push the cog out. Dunno how much this will really help your issue. Just a thought...

Perhaps go with a larger chainring and cog for a bit more clearance.
Yes, that is what I was hoping to do.


Rennen make both larger rings (up to 50t) and cogs (up to 25t) so you can find your gearing.
I already have a Rennen 24T cog, but was hoping to go to 28t without hacking up an old cassette.


Push your chainline outboard. Use the large chainring on your crankset and push the cog out.
Good suggestion, but I refuse to give up my bash ring.

For now, I will go on the assumption that what I am looking for does not exist, enjoy the bike as-is, and try to grow some leg muscles :). Thanks again for humouring me :thumb:.