j0hhhhn

Hi all

A couple of weeks ago I bought the Nashbar Hounder Single-Speed Bike for my 15-yr-old son. It seemed to be well reviewed, and many reviews mentioned a flip-flop hub, but the bike I received is a fixed gear (no coasting). (Looking closer at the description I can see now that this is what I should have expected!)

I am overall happy with the purchase, but would like to change it from a fixie to a single-speed that coasts. I am not well versed in bike mechanics (if you haven't already guessed), but I gather I need to take off the fixed-gear cog and replace it by a freewheel. But I don't know anything else beyond that, and I don't want to buy the wrong part.

Can anyone recommend the part I need to buy? And perhaps a freewheel tool, if necessary? Is it recommended to keep the number of teeth the same (16)?

Here are some photos of the rear hub as it is now, can you tell from these which part or parts would do the trick?





Thanks!

striknein

Any single-speed freewheel would work. I recommend shimano mx-30's for an affordable, reliable option.

You don't need a tool to install a freewheel, but you do need one to remove it. Park's FR-6 will do the job for most BMX freewheels. To install, remove the wheel, grease the hub threads on the side of the axle opposite the currently-installed fixed cog, spin the freewheel onto the threads, and flip the wheel. If you go with the same tooth count as the fixed cog, you don't even need to break the chain.

A higher tooth count in the rear will make for an easier time pedaling, at the cost of max speed. It looks like the wheel axle is already pretty far forward in the track ends though, which may prevent you from being able to install a larger freewheel. If you do go bigger, you may need a longer chain as well.

Make sure a rear brake is installed when going single speed. It's much better to have it and not need it than to need it and not have it.

JanMM

It looks as if the other side of the hub is threaded for screwing on a freewheel.
(Pics of upside-down bike are disorienting me.)
Attach single speed freewheel and flip the wheel/hub. If the cog size is the same, tension should be ok with current chain.
Lots of info:
Singlespeed Bicycle Conversions

HillRider

A "flip-flop" hub means it's threaded on both sides and usually fitted with a fixed cog on one side and a single speed freewheel on the other. You remove the wheel and turn it around to use the side you want.

Jeff Wills

As other said- you need a single-speed freewheel. BMX shops will have what you need, or you can order from my favorite online supplier:
https://www.universalcycles.com/shop...p?category=403

Retro Grouch 

Well, there's a little more to it than the previous posters have indicated.

1. Measure the diameter of the threads on the side opposite the fixed gear side. Freewheels commonly come in 2 different sizes. One is roughly 29 mm diameter, one is roughly 35 mm diameter.

2. Now look at your chain. It's probably 1/8" wide (that's the common single speed width) but 3/32" also exist. Make sure your freewheel matches.

3. Finally number of teeth: If you get the exact same number you won't have to worry about chain length.

j0hhhhn

Awesome info! So glad I won't have to take off the fixed cog after all, it will be a lot easier on me to use the threads on the other side of the hub. So apparently the hub on this bike is still strictly speaking a "flip-flop hub", because it's threaded on both sides, and they used to ship this bike with the freewheel attached, but no longer.

There are already brakes on the front and back, so I am good there.

I went ahead and measured the diameter of the threads, they are very nearly 35 mm in diameter. I assume this is the standard/default size? I don't see any mention of diameters when shopping for parts.

I am not confident in my ability to distinguish between the 1/8" vs 3/32" chain, so I sent a note to nashbar asking them to clarify.

Just looked closer at the specs for the bike listed on the nashbar website and it identifies the chain as "CHAIN KMC Z410", which according to google is 1/8". So I went ahead and ordered this Shimano SF-1200 freewheel with 16 teeth. Hopefully this will do the job!

striknein

29mm freewheels and hubs are very uncommon, so much so that you rarely see them mentioned.

Retro Grouch 

Do you really think so? I'm thinking they're the majority.

striknein

There may have been a few BMX flip-flop hubs back in the 80s and 90s that accepted a 29mm freewheel, but 24tpi/1.37" became the de facto standard at least 30 years ago. You certainly wouldn't find smaller threads on a wheel belonging to a bike unboxed less than a month ago.

Retro Grouch 

I've worked on a LOT of kids BMX bikes. Almost all of them used the 29 mm size. Last month I needed to buy a replacement freewheel for my grandson's bike and none of the local shops had a 35 mm freewheel in stock. Lots of 29 mm freewheels.

All that I was really saying to the OP is that it's prudent to measure rather than to guess.

Jeff Wills

It's actually 30mm x 1mm... this is the "metric BMX" thread used on flip-flop BMX hubs. It allowed a smaller freewheel- 14 and 15 teeth where the standard thread freewheel only allows 16 teeth.

Traditional Thread-on Freewheels

j0hhhhn

Just a followup to say thanks to all for the advice, the freewheel went on without a hitch. Success!