Gears? Getting rid of my 53/42T
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  1. #1
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    Gears? Getting rid of my 53/42T

    I'm looking to get a new crankset to complete a campy conversion. I have been on a 52/42 for the last month with an 11-28t cassette. I got a wheel with a 13-26t cassette (not wildly excited about the missing 12 cog, but it was free) on it that I will use on the campy set up and am now trying to decide which way to go with my crankset. I have used mostly compacts (50/34t) but after using the 52/42t crankset with the 11-28th cassette, I'm thinking that might be a bit much? Meaning, I'm doing pretty good with the current set up and I'm not totally bike fit yet. I go into the 28 cog every now and then for short periods and lately have been trying not to touch it at all. I do lots of climbing. And I would like to do some steeper climbs even still (current rides about about 8% average with up to 14% stretches).

    So, with a 39 small chainring and a 26 rear cog, will I be loosing some low end? I've looked at the sheldon brown's gear calculator and... I don't know if I really understand the results, or I don't trust my knowledge to interpret. the calculator says in my current setup the 42 ring and 28 cog gives me 39.4 gear inches. And my possible future setup it says the 39 ring and 26 cog will give me 64.1. So, from my research I thinking the 39 ring, 26 cog will be an easier gear on the climbs than the 42 ring, 28 cog. Is this correct. I've always just thought of gearing in simple terms of bigger front is higher and harder pedaling, smaller front lower gear and easier pedaling. But after researching my inherited 52/42 cranks, I'm not so sure. Its opened up a can of worms... all the options. Hope that made some sense.

    so can someone here set me straight? How do you interpret all these numbers? thanks in advance.

  2. #2
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    equivalent gears...

    I prefer a simple formula to compare gear ratios. Using your example, 28/42 x 39 = 26. Coincidentally, these gear ratios are exactly the same. A gear-inch chart should have told you the same thing.

    Gear inches is a meaningless number. It's just a gear ratio multiply by a constant.

    If you compare the ratios, it's 42/28 = 1.5 and 39/26 = 1.5.

    I also use percentages to compare gear ratios. An average cog shift is 8%, if the difference between two gear ratios is only 2%, it's too small to be of much concern.

    If you use a compact crank, you'll find that a 50/13 is not much top gear.

    13/50x52= 13.5 This means that a 50/13 is in between a 52/13 and a 52/14.

  3. #3
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    you're very mixed up, I'm sorry to say. Go read some more Sheldon.

    The math is simple, and if you think for a minute you'll realize you read something wrong. 42/28 is exactly the same ratio as 39/26.

    a bigger gear inch number is a harder gear.

    I've always just thought of gearing in simple terms of bigger front is higher and harder pedaling, smaller front lower gear and easier pedaling
    .

    You thought right, but that's only half of the formula. You have to remember that it goes the opposite way in the back.
    Last edited by JCavilia; 07-14-2010 at 12:05 PM.

  4. #4
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    thanks C-40, gear ratios does seem to make sense to me as oppossed to inches. looking at the a comparison of my current set up and the new one using this method, I can see that I am less that 2% difference on every cog. The Highest is obviously the biggest spread, but still barely under 2%. So I really shouldn't feel a big difference between the two setups. Nice to know. I would like to get a 12 cog still, I'm using that 11 a lot on descents. but I guess I'll limber up and go aero. Thanks for the help C-40, that was refreshingly simple.

  5. #5
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    ???

    Your previous top gear, if 52/11 is a lot more than 2% less than a 50/13. It's about 18% lower or more than two cog's worth.

  6. #6
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    yeah, I was only referencing the smaller rings, 42 vs. 39. I'm not going to go compact. The lower gears were my main concern. comparing 52 vs. 53 is even less of a difference as all are within 1% except the 11 and 12 cogs since I won't have those anymore.

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