Slacking Off- A Brief Study In Freecoaster Slack

Occasionally with a ‘job’ like this, I’ll be lucky enough to be sent parts to test by companies going through research and development stages of making new BMX components, my main qualification to do so is being able to throw a bike around while still being able to analyse a broken one better than simply saying ‘I fell and it broked!’
Then one day someone will pull a cruel joke and send you not one, but two types of freecoaster to test knowing full well how you feel about that kind of heresy and witchcraft… but with me being ever curious about new technologies emerging and not wanting to be left behind, I gladly accepted the task.
Trying out both clutch and pawl type freecoasters, I figured out that while the pawl type was the easiest to use, the clutch type was best for adjustability and thus, reliability (in the respect it won’t engage and throw you on your arse as easily when rolling backwards) due to being able to remove/ add slack spacers at will. This is something that can’t be done with a pawl type coaster without using a different clutch-disk or slack cam ring- depending on which brand you ride.  This is not to say that you are completely out of options when it comes to slack adjustability though; the following factors can also play a part in the time it takes your hub to engage;

Gearing.

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A higher gear ratio where a larger sprocket, or a smaller driver, is used so higher top speeds can be reached does so because a larger sprocket like a 27T-9T ratio for example, pulls more chain links over the driver with each pedal stroke than a smaller 25T sprocket pulls over a 9T driver; it works the same way that a single point on the outer edge of a vinyl record will move faster than a point in the middle despite it having the same number of revolutions per minute- except there’s a chain wrapped around it.  What this also does is reduce the time it takes for your rear hub to engage as chain gets pulled over your driver at a faster rate when your gear ratio is higher.  In the days of cassette hubs and freewheels (if you’ve been riding as long as some) this wasn’t so much of an issue but with freecoasters and fakie tricks coming back into popularity, it’s something that is of much greater importance.  If you’ve got steady legs and a desire to bomb it around at mach 10 then you could probably get away with something like 27 or 26T-9t but if you like a bit of room for error when moving your feet around while coasting backwards then maybe stick to a lower 25T-9T, no one likes a bruised arse.

Crank Arm Length.

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While 175mm tends to be the standard go-to length for BMX cranks they can usually range from around 165mm to 180mm depending on your height, riding style or personal preference so for arguments sake we’re just going to talk about the two extremes of long (eg. 180mm) and short (165mm).  If you imagine the crank in it’s engaged and disengaged position as well as the distance between the pedal spindles as a kind of triangle (as illustrated in the shoddy MSpaint diagram above) you can see that the red lines represent the set freecoaster slack angle but you can see that the slack effectively widens as the cranks get longer.  It’s worth noting that the difference is negligible but noticeable if you go between 165mm and 180mm cranks although virtually non-existent if you were running 175mm cranks to begin with, but you know, every little counts sometimes…

Chain Tension.

It’s pretty much common knowledge that freecoaster driver bearings really do not like tight chains but a loose chain can also artificially increase your freecoaster slack angle as well as help your bearings last longer.  Before your hub even starts to engage your legs have to make the chain tension enough to pull the chain over the driver to begin with so the slacker the chain; the slacker the angle, obvious enough.  But that also increases the likelihood of your bike sounding like a rusty bag of nails inside a biscuit tin so exercise restraint with that one kids.

While I’m sure all of the above is quite obvious to some older riders including the Bikeguide police, and I’m sure it’ll get picked apart in some way or another but the main point I want to make is that it’s not something that gets talked about a whole lot, especially to younger riders, despite being a big issue in BMX today. That said, if there are any points I’ve missed feel free to hit me up at oberzine@hotmail.com.

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