Is it possible to make a single speed dual suspension mountain bike?

Question

the rear suspension is 4-6 inches

Answer 1

Absolutely.  MTBR turned a Specialized (not sure if it was an Enduro or an FSR) into one last year with great results.  Depending on the design of your rear linkage, you may have to fiddle quite a bit to get things working properly, but it's definitely doable.  

I'm in the camp that says, "why bother?", though.  I have a singlespeed road bike, and I think it's superior for things like bmx, dirt jumps, and trials riding....but on dirt?  Got made gears for a reason.   :o)

Answer 2

Um, it IS possible by replacing the rear derailleur with a chain tensioner, lacing a hub the proper width and putting a single cog on but why would you want to?

If you think about it, thats what BMX is for.

Answer 3

Yup, it's perfectly possible. You can get a pretty cheap single speed conversion get online and any bike store should be able to make the conversion for you.

It takes a few tools that you may or may not want to invest in yourself to do it like a lockring/cassette tool.

Sheldon Brown actually has a great tutorial on how to do that. I converted my dual suspension ride that way and I love it. Haven't looked back. It's definitely a lot less muck to clean from my bike at the end of the day.

I've also included another great resource for SS MTB riders and a link for the naysayers to read.

Answer 4

Unless the pivot point is the bottom bracket you can't. Because most suspensions will change the length of the effective chainstay length.

Check out Kona's A (pronounced 'Ah') it was designed as single speed full suspension.

I couldn't find reference to it on their site, they made it a few years ago, then sold them as frameset only for a time.