Gear calculations

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03-01-2011, 04:56 PM
Catrin

Gear calculations

I am confused - but what is new about that? :o

I am trying to use Sheldon Brown's gear calculator to get an idea about how the gearing will differ between my Gunnar and my LHT.

My LHT has a 48-36-26 165mm crank with an 11-34 cassette.

My Gunner will have a 22-32-44 170mm crank with an 11-34 cassette.

When I look at the gear inches from Sheldon Brown's gear calculator for both bikes I get confused by the following:

LHT = the 23-34 gear gives me 19.9 gear inches

Gunner = the 44-34 gear gives me 33.6 gear inches

What is this actually telling me - that the Gunner, with the full mountain drive-train, will get me further in the easiest gear over the LHT granny gear? If I understand this correctly then I can make sense out of the rest of the table. I think....

I am not looking for a total understanding, just an idea of how to interpret the numbers I am seeing.
03-01-2011, 05:18 PM
OakLeaf

For some reason you have the numbers reversed from their usual configuration for the Gunnar but not for the Surly. Compare low gear to low gear and you'll see your mistake.
03-01-2011, 05:20 PM
indysteel

Quote:

Originally Posted by Catrin

I am confused - but what is new about that? :o

I am trying to use Sheldon Brown's gear calculator to get an idea about how the gearing will differ between my Gunnar and my LHT.

My LHT has a 48-36-26 165mm crank with an 11-34 cassette.

My Gunner will have a 22-32-44 170mm crank with an 11-34 cassette.

When I look at the gear inches from Sheldon Brown's gear calculator for both bikes I get confused by the following:

LHT = the 23-34 gear gives me 19.9 gear inches

Gunner = the 44-34 gear gives me 33.6 gear inches

What is this actually telling me - that the Gunner, with the full mountain drive-train, will get me further in the easiest gear over the LHT granny gear? If I understand this correctly then I can make sense out of the rest of the table. I think....

I am not looking for a total understanding, just an idea of how to interpret the numbers I am seeing.

I'm not sure what you're trying to compare, . Where did the 23 come from in the "23-34" referred to in your question? And why are you comparing it to the 44-34. That's the big chainring combined with your largest cog. That's comparing apples to oranges, it would appear.

The smallest gear you have on the LHT is a 26-34. The smallest gear you'll have on the Gunnar is a 22-34. I don't know how that translates in gear inches, but your Gunnar's smallest (easiest) gear is smaller than the smallest gear on your LHT. And both are darn small. The smallest gear on my bike is a 30-26.
03-01-2011, 05:22 PM
Catrin

Quote:

Originally Posted by OakLeaf

For some reason you have the numbers reversed from their usual configuration for the Gunnar but not for the Surly. Compare low gear to low gear and you'll see your mistake.

That was what was confusing me :) I got the numbers, in that order, for the crank from my parts-order list from my LBS and I wasn't sure which order was correct since they were opposite each other in how they were list (website for one, purchase order for the other)... I am so new to looking at the gear calculator that I wasn't sure if the big chainring was listed first or the smallest.

Now it makes sense - the gear inches for the SRAM drive- train is now 16.8 gear inches, smaller than the LHT as it should be.

IndySteel, that was a typo on my original post, thanks for pointing that out. I am just trying to figure out how to use the gear calculator and to have sort of an idea what I am looking at.
03-01-2011, 05:35 PM
indysteel

Just remember that the numbers refer to the number of teeth. So it logically follows that the biggest number refers to the biggest chainring, and vice versa.

And further remember that the bigger the number of teeth in a rear cog, the easier the gear.
03-01-2011, 05:39 PM
Catrin

Quote:

Originally Posted by indysteel

Just remember that the numbers refer to the number of teeth. So it logically follows that the biggest number refers to the biggest chainring, and vice versa.

And further remember that the bigger the number of teeth in a rear cog, the easier the gear.

Got it, and after playing with the gear calculator it actually helps - thanks!