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Questions and answers about sports

Chainline calculation

5 min read

Asked by: Rhonda Cook

How do you find the correct chainline?

Chainline is the distance between the centerline of your frame and the average centerline of your chainring(s). For 1X this is easy – If the center of your chainring teeth is 49mm from the centerline of your frame then your chainline is 49mm. It gets slightly more difficult if you have multiple front chainrings.

How do you measure a bottom bracket chainline?


Quote from video: Part of the bottom bracket. So you get a caliper on it. And you measure it and then you take a look in this case it's 73. So well the most common sizes are 68 and 73.

How important is chainline on a single speed?

Chainline is important on all bicycle drivetrains but especially so on a one-speed. A perfect chainline is one in which the chainring and rear cog are in perfect alignment with each other and the chain takes a perfectly straight path from the chainring to the cog.

Why is chainline important?

The chainline is very important for several reasons: more efficient transmission; the less you bend the chain, the smaller the power loss; better function and less chance of the chain falling off the rings; less wear due to less friction; better function of the front derailleur; and quieter operation.

How is chainline fixed gear measured?

Quote from video: It it's because uh well measure and it just plain sucks. So I'm just gonna basically with the chain off and not touching any one of these bolts here all right you see what I'm doing here is I'm just

Which is better 1X or 3X crankset?

Gear range of different drivetrains:



In the above example of bikes with common drivetrains, the 1X bikes top out at 47 to 48KPH in their highest gear, while a 2X or 3X bike will offer 15-20% more speed, topping out at 56 to 57KPH.

What is chain line in bottom bracket?

The Ideal Chain Line



This measurement is the chain line. This is the engineering drawing for one of FIRST’s four direct mount cranks each offering a different chain line. The middle of the bottom bracket corresponds to the exact center of the bottom bracket shell which is also the frame’s geometric center.

How do I know what length bottom bracket I need?

To find out the size of bottom bracket needed, measure the inside of the bottom bracket shell in your frame, it will be 73mm, 70mm or 68mm. Some older frames may have Italian threaded bottom brackets, instead of the more modern English.

What chainline is super boost?

Super Boost Plus 157 uses the exis ng chain-line developed for DH bikes but uses standard trailbike BB widths and crank combinaYons to take 29” and Plus bike performance to the next level.

What is the best single speed gear ratio?

For flat places, a ratio of 2.6 to 3.0 is ideal for most people. The lower value of this range, with a cadence of 90 rpm, will allow us to ride around 30km/h, while the upper, 34km/h. If you’re just starting out on your adventure on a single speed or fixed gear bike, a gear ratio of around 2.7-2.8 will be ideal.

Do you need boost spacing for 12 speed?

If you are running 12 speed, the clearances are so small between chain and cassette that you MUST run a boost spaced chainring with a boost spaced bike. If you don’t, the chain will “tick” on the next bigger cog when in the smallest 2-3 cogs on the cassette.

What is boost on a crankset?

boost just refers to bikes that have a 148mm wide spacing between the dropouts for the rear hub, the Drivetrains are shifted outboard by 3mm. This may or may not affect the crank axle length depending on the bike and crank combo, In most case it has just resulted in wider q-factor cranks and not longer axles.

What is the Q factor on a bike?

Q-factor is the distance between the outside face of each crank arm at the point where the pedal attaches, while stance width is the distance between the centre of one pedal to the centre of the other.

How do you put chain lines on single speed?

Quote from video: To my chainring to the center of my chain ring and we're at let's say 50 51. And 1/2 let's say 52 millimeters. So that is my other number 52 millimeter – let's say to chain.

What is chain ring offset?

The offset of a ring is how much it is dished over from a standard flat chainring, it is used to achieve correct tyre/frame clearance and also to set the correct chainline.

What chainline is super boost?

Super Boost Plus 157 uses the exis ng chain-line developed for DH bikes but uses standard trailbike BB widths and crank combinaYons to take 29” and Plus bike performance to the next level.

What is the meaning of chain line?

Chainline is the angle of a bicycle chain relative to the centerline of the bicycle frame. A bicycle is said to have perfect chainline if the chain is parallel to the centerline of the frame, which means that the rear sprocket is directly behind the front chainring.

What is chain ring offset?

The offset of a ring is how much it is dished over from a standard flat chainring, it is used to achieve correct tyre/frame clearance and also to set the correct chainline.

What is the difference between boost and non boost crankset?

The only different between boost and non boost drivetrain kits is the crankset. The only different between a boost and non boost crankset is the chainring. You can swap a crankset from boost to non boost or vice versa just by installing a different chainring. Hope this is helpful!

What chainline is non-boost?

Non-boost or boost crankset really just means you need a chainring with the correct offset. For a 1x system it should be around 49mm chainline which means from the center of your BB to your chainring teeth should be about 49mm.

Can I use a non-boost crank on a boost bike?

I run non-boost rings/crank on my boost bikes because it slightly favors the lower gears where I do the large majority of my pedaling anyway. If there is sufficient clearance between the ring and chain stay and the chain and tire knobs, it’ll work well.