Hussnain Subhan

Hi Everyone... Saw a flip flop hub in a bike i had kept in my store for some time ...its my first time seeing one ...whats the actual purpose of the fixed cogs on one side of the hub ... Like are these useful in any ways ...

mrv 

The purpose is to have a fixed gear on one side and a free wheel on another.

The reason I set up my Surly that way is sometimes riding downhill fixed can wear a person out!

On a hilly ride I have the option to do a 2 minute wheel flip and I can coast the downhills… probably faster than two… but not trying to brag or anything…😏

RCMoeur 

Riding a fixed gear instead of freewheel serves multiple functions, in that it doesn't allow you to coast. The bike moves, the legs move.
If you have any minor imbalances or odd movements in your pedaling, it can point them out for correction.
If you have a tendency to "bounce" at high cadence, it can point this out.
It can help you develop the ability to be smooth at a wide range of cadences.
It can help develop a more fluid and "rounded" pedaling style.
It makes you mindful of your riding, in that forgetting you can't coast can activate "ejection seat" mode.
You can get really good at trackstanding.

All that being said, using the freewheel side is a nice occasional vacation from the discipline and rigor of the fixie side...

Also, I have a 17% hill in my neighborhood I have to ride to get in and out. I've learned that a brief 125 cadence downhill or 30 cadence uphill won't kill me.

JohnDThompson 

Or, to have a different gear ratio on each side. The length of your dropout slot will determine how much the sprocket tooth count can differ while still allowing appropriate chain tension. Fixed/fixed hubs were often used on British path racers.

veganbikes

The point of having a cog or freewheel is so you can propel your bicycle forward via pedaling, having another one on the other side allows you to have a different gear ratio to make it easier or harder to pedal by flipping your wheel over.

You can have double fixed, fixed or free wheel or double freewheel. I generally go double fixed because I can run either fixed cogs or freewheels without issue. I cannot run fixed gear cogs with their lockrings on a freewheel threading and you do want the lockring.

It doesn't mean you have to run two forms of gears back there but if you want to it is helpful.

Ruben_

How do you manage chain tension when using double fixed?

veganbikes

Same way with single fixed, If you are literally running two chains then you would want everything to be the same size and nothing would change if you are running single chain it would be the same thing though you wouldn't want to go with too huge of a difference so it works together.