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Using a outer chainring on the inside?

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Using a outer chainring on the inside?

Old 02-22-07, 09:11 AM
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Using a outer chainring on the inside?

So I have a compact double, 50/36. In retrospect, I should've gotten a 52/42 or 52/39, because Michigan is SOOOOOOOOOO flat. Where I was used to biking (Western PA) was SOOOO hilly, but I digress.

In any case, my current usual speeds (19-24 MPH) and cadence (90 RPM, give or take) always have me cross-chaining my bike.



If I went to a 46 tooth inner ring, however, I would only cross chain above 23.1 or 24.9, depending upon your definition. That would mean that I would probably only need to shift the front derailler about twice (once in, once out) on the ride I go on most frequently, which is about two hours long.

So - has anyone put the outside chainring on the inner ring? The ramps would be all wrong, correct? How bad would the shifting be?
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Old 02-22-07, 09:53 AM
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Why not get, say, a 13-26 cassette, or something along those lines?
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Old 02-22-07, 10:40 AM
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I'll bet the CA central valley is flatter than Michigan.

It all depends on how fast you ride and what your most comfortable cadence is. For example, my "sweet spot" is about 95 rpms at around 18-19mph, if there's no wind and it's flat. So what I want are as many close ratios near that will give me 95 rpms at just above or just below 19mph.

So the perfect setup (which I've yet to find with a 9 speed) would give me gears that move me at 17, 18, 19, 20, and 21 mph at 95 rpms with as straight a chainline as possible.

Basically, if it's flat you want close ratios and not necessarily big gears. The big gears are for going downhill at 45 mph, which you probably don't need to do very often. Flatlanders basically use gears for the infinite variations in wind speed and direction.

I've found that 48-36 works well for me. I'm actually considering trying a 46-36 and that would give me even closer ratios.

Nice chart, btw. Numbers are pretty good. How did you calculate them?
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Old 02-22-07, 12:00 PM
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I agree with a previous poster - I'd fuss with the rear cassette before I'd fuss with a non-standard front arrangement. Beyond that, I remember doing all the spreadsheets when I moved from standard to compact cranks about a year ago, but out on the road, in the real world, all those decimal points and marginal differences became relatively unimportant in light of the other variables that entered into the equation, including: how I felt, who I was riding with, what kind of headwind I was dealing with, the grade I was facing, the cadence I was using, how many miles I was doing, etc., etc.
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Old 02-22-07, 12:11 PM
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I don't get it. Why don't you just stick 'er in the 50 for all your riding?

PS, I think for flatty flat flat riding, you want to have a tight cassette...
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Old 02-22-07, 07:55 PM
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Cassette won't work, because my one downhill I go ~40 MPH and I like it that way. I can barely do it in 50/11; I'm not that much of a spinner.

I can go 50 for all of my riding, but it gives some cross-chaining issues at the very brief uphills. I only need to go into the 50/19, but that still gives my derailler a couple of issues.
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Old 02-22-07, 07:56 PM
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Originally Posted by MrCjolsen
Nice chart, btw. Numbers are pretty good. How did you calculate them?
I stole the ratio for a 700c tire from Sheldon Brown's site. If you PM me your address I'll e-mail you the chart.
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Old 02-22-07, 08:10 PM
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I've done a 46 inner and 48 outer at different times in a similar flat terrain situationn. With a 48 outer I sometime cross chain quite a bit even 48-23 since I just don't bother to shift to the smaller ring. Also, even with the 1cm FD gap that I've had with the smaller front ring, shifting is just as bad, not any worse, as it was with a 1mm gap
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Old 02-22-07, 09:04 PM
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Originally Posted by ElJamoquio
snip…
So - has anyone put the outside chainring on the inner ring? The ramps would be all wrong, correct? How bad would the shifting be?
I think there might be a problem with the large chainring hitting the chain stay.

- Wil
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Old 02-22-07, 10:12 PM
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How would your FD work?
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Old 02-22-07, 10:42 PM
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modern inner chainring is desgined to be an inner chainring. An outer chainring used as an inner is not likely to shift as well.


Put a 12-25 on the back, and just keep it in the big ring
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Old 02-23-07, 12:35 AM
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Your 50-36 has 110 bcd cranks, right? Then a 44 or 46 from an old mtb crankset would work as long as it clears the chainstay. Also, try to get rings designed for a 9 speed chain.
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Old 02-23-07, 12:42 AM
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Hi ElJamoquio-

How long is the downhill that you would have to sacrifice top-gearing if you altered the cassette? The reason I say this is because if it's only a quarter-mile slope, it's not the end of the world. If it is a ten-mile descent, that would be very impactful. My feeling is that it is MUCH cheaper and easier to finetune the cassette rather than playing with chainring swaps.

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Old 02-23-07, 01:19 AM
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1) The big chain ring on the inside position would be bad. Think circular saw action on your chainstay.

2) Why not just keep it in the big ring?

You should be able to go all the way up your 18t on your 50t chainring without really "cross chaining". Just as you should be able to go down to your 13t with ease on your 36t chainring. Also, by putting the 46t chainring on instead of the 36t, you're limiting your gear ratios severely. Which is kind of against the compact crank school of thought.

My real question is this: why are you even using your small chainring? In the Midwest, for the most part, unless theres a avg. 20mph+ headwind (very common, sadly) or I'm warming up, I never touch the small ring.
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Old 02-23-07, 06:42 AM
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Originally Posted by Blue Jays
Hi ElJamoquio-

How long is the downhill that you would have to sacrifice top-gearing if you altered the cassette? The reason I say this is because if it's only a quarter-mile slope, it's not the end of the world. If it is a ten-mile descent, that would be very impactful. My feeling is that it is MUCH cheaper and easier to finetune the cassette rather than playing with chainring swaps.

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I don't think it's cheaper, but it's definitely easier to swap the cassette. It *is* only about a quarter-mile, but it's my favorite part of my ride, so I wasn't particularly fond of giving it up.
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Old 02-23-07, 06:45 AM
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Originally Posted by Duke of Kent
My real question is this: why are you even using your small chainring? In the Midwest, for the most part, unless theres a avg. 20mph+ headwind (very common, sadly) or I'm warming up, I never touch the small ring.
You do still have to protect for wind. 90% of the time, and almost 100% of the time, I'm in the big ring. A lot of time is in the big/second or third smallest combo, and I don't think that's optimal.
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Old 02-23-07, 06:46 AM
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Originally Posted by merlinextraligh
modern inner chainring is desgined to be an inner chainring. An outer chainring used as an inner is not likely to shift as well.

Put a 12-25 on the back, and just keep it in the big ring
I might end up just putting on a 12-25 or something similar; but I'm not really worried about the shifting, because I shift the big ring very infrequently.
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Old 02-23-07, 06:50 AM
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Originally Posted by Wil Davis
I think there might be a problem with the large chainring hitting the chain stay.

- Wil
There's a bit of clearance there on my bike. I wouldn't guarantee it without a test fit, but it looks like my 50 toother would fit in there.
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Old 02-23-07, 06:51 AM
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Originally Posted by MrCjolsen
Your 50-36 has 110 bcd cranks, right? Then a 44 or 46 from an old mtb crankset would work as long as it clears the chainstay. Also, try to get rings designed for a 9 speed chain.
Now *that* is a good idea, especially because I already have a MTB sitting right next to my road bike. I could try it out for free, minus my time. Thanks!
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Old 02-23-07, 06:52 AM
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Originally Posted by rufvelo
I've done a 46 inner and 48 outer at different times in a similar flat terrain situationn. With a 48 outer I sometime cross chain quite a bit even 48-23 since I just don't bother to shift to the smaller ring. Also, even with the 1cm FD gap that I've had with the smaller front ring, shifting is just as bad, not any worse, as it was with a 1mm gap
Yeah, I'm not very thrilled with FD's, which is part of the reason for this discussion.
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Old 02-23-07, 07:29 AM
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If the cassette doesn't do it, it might just make sense to dump the compact and get a regular road double... it's what you need at the end of the day. If you ever need more low end, you can put a wider cassette on the back, but in the meantime a 52-42 or 52-39 would solve your problem without any Frankensteining of the drivetrain.
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