Chainring size ( diameter )

Each link is 1/2",
that means 1/2" between the centres of each tooth,
42 teeth, 21 inches around.
Diameter, divide 21 inchec by Pi, 3.1418,
that will give the diameter at the centre of the chain,
add on half an inch for the top of the teeth. 🙂

Lets see how many more opinions we get, while I measure them for you. 😄

A Mountain Bike I moded earlier: http://www.cyclingforums.com/t363004.html

OK, a little difficult without a caliper, so give me some tolerence here, I used a plastic ruler:
42t = 175mm
48t = 200mm
50t don't have one
52t = 218mm
53t = 225mm

yaquaman1 said:

Can anyone help me figure out the diameter of the following chainrings: 42, 50, 52, and 53? I am looking at doing some modifications to my bike for better offroad / trail ( distance riding on hardpack) the bike is a Proflex 856.

Thank You

From a practical point, if you just want to know which 130BCD chainring combination can be swapped for a 104BCD crank, then a 52/39 with a 118mm ISIS (possibly, the BB spindle you already have ... instead of the "normal" 113mm ISIS spindle for a ROAD double) will probably clear the chainstays -- it does on my hardtail.

A 53t chainring is shy of about 1/8" larger in diameter than a 52t chainring ... so, clearance could be really iffy.

gclark8 said:

Each link is 1/2",
that means 1/2" between the centres of each tooth,
42 teeth, 21 inches around.
Diameter, divide 21 inchec by Pi, 3.1418,
that will give the diameter at the centre of the chain,
add on half an inch for the top of the teeth. 🙂

Lets see how many more opinions we get, while I measure them for you. 😄

A Mountain Bike I moded earlier: cyclingforums.comt363004.htmlOpen ↗

OK, a little difficult without a caliper, so give me some tolerence here, I used a plastic ruler:
42t = 175mm
48t = 200mm
50t don't have one
52t = 218mm
53t = 225mm

Each link includes the part which runs on the inside of the larger width part. Each part is 1/2", 1 link is 1 inch I am pretty sure. Half link chains are in existence. I just built a single speed MTB and had to use a half link because of the 1/2" too long/short problem