August 21, 2012

Gravel Bike Build - Part 5

Return to Part 1

The Truvativ Elita 53 x 39 crankset is another part I have leftover from the old Giant road bike frame I sold a few years ago.  The Elita is a pretty decent crankset, anodized black aluminum and hollow forged, making it light and stiff.  Since I'm doing the 1x10 drivetrain, I don't need the 53 tooth outside ring.  I've read from several sources that single front rings have a problem with chains dropping off on bouncy or washboard roads. So I will install a lightweight aluminum chain guard to replace it.
To get the right guard you have to count the number of teeth in the chainring you will be using.  Mine is 39.  You also have to measure the Bolt Circle Diameter (BCD) of your crank.  Mine is 110 BCD.  There is a handy cheat sheet / measuring chart here

The guard I am using is made by BBG.  It is very well made, only 49 grams, machined from .0125 inch 5000 series aluminum and anodized black.  It comes with a lifetime guarantee for "bending or breaking no matter how you ride your bike". You'll see in the pics below that it ends up fitting perfectly.  Not bad for $14, and Made in America!

To remove the five chainring bolts from this style of crankset you need two hex keys, 5mm and 6mm.  These bolts are not your standard nut and bolt.  You have to insert one hex key from each side so they meet in the middle, then loosen them. 

Here's a good close up picture to show the bolts.  They are 2 pc, internal and external threads with internal hex recesses.  These bolts are another reason why the chainguard has to be added.  The grip length of the bolts only works for the thickness of two chainrings and crank.  Any change to that thickness would need new grip length bolts.  Adding the chainguard preserves that original thickness.

Rings removed

Reassemble with the new BBG part and a small dab of grease on each chainring bolt.

Torque each chainring bolt to 72 - 80 in lbs.

BBG chainguard installed.  Looks good.  The fit at all the crankset mating surfaces is perfect.  And more importantly the ring is flat and true.  There won't be any wobble while pedaling to interfere with the chain.

As a final check I laid out a short length of leftover 10 speed chain to check the clearance from 39 ring to BBG guard.  Looks like it is going to be perfect.

Some of the things I have been reading say that I will also need a chain keeper on the inside of my chainline.  I'm not sure yet if I will..  I'm thinking I will try it with just this outside ring first and see how it plays out.

Part 4                                                               Part 6


  1. I was going to ask how the chain knows not to fall off on the inside.

    1. It's called a chain keeper dude. It attaches to the frame and sticks out toward the crank.