| **Newbee question on gearing** | chskin
*May 22, 2003 12:12 PM* | | Hi
How does 42*23 or 39*23 apply to gearing? What are the numbers all about?
Thanks
Craig |
| **re: Newbee question on gearing** | ClydeTri
*May 22, 2003 12:17 PM* | | the number of teeth in a chainring...42 and 23 .....you will also see similiar numbers for the rear cogset, such as 11-22, showing the smallest and largest number of teeth... |
| **re: Newbee question on gearing** | Dave Hickey
*May 22, 2003 12:28 PM* | | The 42 x 23 are the number of teeth on the front and rear gears respectively. Gear inches is the distance your bike will travel for 1 complete revolution of the crank.
Assuming you're using 700c wheels, Using a 42x23 gearing, your bike will travel 49.3 inches for every revolution of the crank. 39 x 23, will result in 45.8 inches. |
| **Well this is completely wrong** | Kerry
*May 22, 2003 5:31 PM* | | I'm sure you just mis-spoke Dave, but gear inches is the "equivalent diameter of the wheel" not the distance traveled per revolution of the cranks. Gear inches = front/rear times wheel diameter. To get the distance traveled per crank revolution (called development), you would multiply gear inches by Pi (3.14). |
| **Kerry, you are correct.. my bad nm** | Dave Hickey
*May 22, 2003 5:57 PM* | | |
| **Here's a site for you** | coonass
*May 22, 2003 1:34 PM* | | http://www.panix.com/~jbarrm/cycal/cycal.30f.html
Enter your values and see the differences. |
| **good God guys, spare the newbie the gear inch stuff** | BergMann
*May 23, 2003 6:38 AM* | | If you live near anywhere with any hills at all, get the 39*23. In general, the smaller 39 ring will give you a wider gearing range. I like to pair it with a 53 front (vs. the traditional 52 tooth big ring) to spread the range a little more.
Spin up the hill, hammer back down!
Gear inches are a one way to quantify exactly what sort of gearing a given chainring/cog combination will produce vis-a-vis another.
I for one don't even bother with the extra math: I just calculate gear ratios (divide chainring by cog size e.g. both a 52/26 and a 48/24 combo give you a gear ratio of 2:1) to get a grasp on how new cog or ring sizes will compare with what I am riding now. |
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