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Sram Eagle for tandems

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Old 09-13-18, 01:07 PM
  #26  
reburns
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I used the Sheldon Brown gear calculator to analyze the spacing in gear inches of my 3x9 drivetrain. The way I typically shift only uses the largest 3 or 4 cogs in the smallest ring, the largest 6 or 7 in the middle, and all but the largest in the big ring. So the way I usually shift has gear inch spacing from lowest to highest gear that looks like:
20.6, 23.4, 27, 31, 35.1, 40.5, 45.8, 52.7, 61, 70.2, 82.6, 93.6, 108, 127.6.

There are slightly different ratios also available to me, but mostly redundant with these 14 steps.

Eagle with a 48 tooth chainring looks like 25.9, 30.9, 36, 40.5, 46.3, 50.4, 61.7, 72, 81, 92.6, 108, 129.6.
With 46T ring: 24.8, 29.6, 34.5, 38.8, 44.4, 51.8, 59.1, 69, 77.6, 88.7, 103.5, 124.2. If I were to switch, this is the ring I would probably choose, which would mean giving up a little on the high end and a bit more (~20%) on the low end, but otherwise the spacing would probably be acceptable.
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Old 09-13-18, 01:53 PM
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Originally Posted by reburns View Post

Regarding total range (meaning difference between highest and lowest gears) of a 1X12, the numbers are pretty simple: just the ratio of the largest to smallest cog. For a 10-50 cassette, the range is 5. You can choose a larger chain ring that will give the desired high gear, or a smaller ring for a desired low gear, but the ratio is determined by the range of the cassette. Make sense?
Yes, but to get a wider range with your triple than offered by the eagle, you've got to go to a 26 inner chainring which is smaller than the 30 Co-Mo spec'd. So my point is the range on the Eagle is a wide as a standard triple setup. I never claimed you can't have wider range with a triple( albeit with some shifting tradeoffs going to bigger front ring shifts)

Your own post further down in the thread shows that the range for the Eagle is not that much smaller than with a triple and a 26 inner ring.
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Old 09-13-18, 06:49 PM
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Originally Posted by 124Spider View Post
I'm generally quite good with math of any sort, and graphs are usually easy for me to decipher.

Unfortunately, I have no idea what your charts are supposed to show; sorry

Mark
What the graph shows is while the general belief that a 1x would give an unacceptable too large gear ratio changes between gear changes, in actuality the change is actually no different than the smallest possible shift from ANY gear combination of a triple. What is the difference is the 1x does not offer the larger possible gear shifts from any gear combo of a triple.

i find this profound and unexpected.
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Old 09-13-18, 07:06 PM
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For performance riding on the road 1x is just to "gappy", especially at the top end. Going fast on flattish roads you want a reasonable selection of gears over 85". You spend quite a bit of time there and when working hard 15%+ jumps in gearing is the last thing you want.
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Old 09-13-18, 07:27 PM
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Originally Posted by Alcanbrad View Post


What the graph shows is while the general belief that a 1x would give an unacceptable too large gear ratio changes between gear changes, in actuality the change is actually no different than the smallest possible shift from ANY gear combination of a triple. What is the difference is the 1x does not offer the larger possible gear shifts from any gear combo of a triple.

i find this profound and unexpected.
I gathered that that was your interpretation of the data, but I could not make any sense of the data. Too bad....
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Old 09-14-18, 08:12 AM
  #31  
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Originally Posted by Dean V View Post
For performance riding on the road 1x is just to "gappy", especially at the top end. Going fast on flattish roads you want a reasonable selection of gears over 85". You spend quite a bit of time there and when working hard 15%+ jumps in gearing is the last thing you want.
I haven't run the numbers (like others have) but I would think the biggest jump would be the 11t - 10t jump. That would be only about 9%. Are there other jumps that are in the 15% range?

I now see that the Sram Eagle goes 10, 12, 14, 16, 18, 21, 24, 28, 32, 36, 42, 50

So the jump from 12t to 10t is almost 17%. My error.

Last edited by oldacura; 09-14-18 at 01:36 PM. Reason: new info
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Old 09-14-18, 09:37 AM
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There's a pretty handy tool for visually comparing the different drivetrain options discussed here (and nearly all others). Here's a link with it already setup to compare 44t x 10-50 12-speed to 53/39/30 x 11-34 9-speed.
Bicycle Gear Calculator

My tandem currently uses a 10-speed 11-42 cassette (usually with 52/34 chainrings), which has gaps very similar to the 12-speed 10-50 or 10-51 cassettes. It's manageable, but there are definitely times that I'd like closer spacing between the gears. Going to 1x12 would be less overall range and several ratios with wider gaps than our current setup.
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Old 09-14-18, 12:27 PM
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Originally Posted by OneIsAllYouNeed View Post
There's a pretty handy tool for visually comparing the different drivetrain options discussed here (and nearly all others). Here's a link with it already setup to compare 44t x 10-50 12-speed to 53/39/30 x 11-34 9-speed.
Bicycle Gear Calculator

My tandem currently uses a 10-speed 11-42 cassette (usually with 52/34 chainrings), which has gaps very similar to the 12-speed 10-50 or 10-51 cassettes. It's manageable, but there are definitely times that I'd like closer spacing between the gears. Going to 1x12 would be less overall range and several ratios with wider gaps than our current setup.
Thatís a great calculator, thanks!
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Old 09-17-18, 11:16 PM
  #34  
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Eagle sounds lovely to me for an upright road going tandem. I have a 24 speed Burley with slicks and itís hungrier for a top and bottom gear than my newer 1x11 MTB (30 & 11-42). With aggressive tires and suspension maybe you donít need the top end so much.

Eagle is available now at GX and NX level, it neednít be expensive. The cassette for NX is a terrifying monstrosity suitable for keeping canopies from blowing away at swap meets but it does its job great.
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Old 09-19-18, 09:16 AM
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Is there a tandem crank that will accept the Sram Eagle drivearm? The Eagle crank requires a BB30, PF30, or PFGXP bottom bracket.

For the SRAM Eagle, the rear wheel must use the dedicated XD Driver freehub body to mount the 11 or 12sp cassette. The NX will fit on a regular splined freehub (eg. Shimano 11sp).

Although the NX is more affordable than the XX1 and GX, it has a smaller gear range and is much heavier. The PG-1230 cassette is 11-50T (rather than 10-50T), and weighs 615g. By comparison, the Shimano R8000 Ultegra (11-32T) weighs about 240g.
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Old 09-20-18, 01:37 AM
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It's not really fair to compare the NX cassette to the Ultegra, I think. They're different animals. NX is equivalent to Deore level, two lower than XT/Ultegra. Shimano just left Deore stuck around y2010 tech level so there's no exact analogue. NX also has a steel chain ring - not especially trying to be light.

The Eagle chain rings look like they'll go on any crank that takes SRAM direct mount rings. If there isn't one of those for a tandem then it looks like Wolftooth claims nearly all their rings are Eagle compatible.
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