oldacura

Has anyone tried to integrate a Sram Eagle system to a tandem?

My understanding is that it is a 1 x 12 with a range of 10t - 50t.

It seems like this would solve a lot of range problems and completely eliminate a front derailleur. With a 48t or 50t chainring, one could get both a pretty high top end with a pretty low bottom end.

What compromises would be involved?

DeadGrandpa

I don't think 48x50 is low enough for me, at least if I have any hills at all. My mtb tandem has a 26/36 double on the front, 11-46 cassette. I have a 2nd wheelset for paved road riding and the low gear, 26x46, is not too low. The high gear, 36x11, is high enough for gravel but not enough for paved roads. 48x11 might be high enough, but I have an old road tandem with 60x12, and that seems like a good ratio for high gear on pavement.

1x11 or 1x12 works, more or less okay, for mtb and gravel, where you can dial in the low end of the gearing by changing the size of the front chain ring. This leaves you lacking a higher gear, but I seldom want to power downhill at max speed when I might hit a pothole or other obstacle. I find it safer to use the brakes and be able to maintain the helmet up/rubber down orientation.

reburns

oldacura

Our new tandem is 2x11 with a range of 5.6:1. This was about the widest range we could get in a 2x Di2. If we avoid big climbs, this works well enough for us.

Others on this forum are happy with a significantly narrower range.

mtseymour

The Sram Eagle (or the older 1x11 drivetrain) is very useful on a mtn tandem or mtn singles because it's virtually impossible to drop the chain on rough terrain, especially with a chain guide. It's also easier to find the right gear on rough terrain. A mtn biker is much busier than a road rider (pick the right line, shift weight, brake at the right time, absorb bumps, etc) that simplicity is a real plus. For instance, the left hand can control the dropper seat post while the right hand does all the shifting.

On a gravel or road tandem, the Eagle would be too expensive, and the gear jumps would be too big. For example, the Sram XG-1275 and XG-1299 (10-50T) cassettes retail for $220 and $450, respectively. By comparison, the Shimano Ultegra CS-R8000 cassette (11-32T) retails for $80.

I love my Sram 1x11 drivetrain on my mtn single, but have no interest in using it our road tandem or singles.

BTW, the Eagle is slightly noisier and slower than a 2x11 drivetrain (due to larger gear jumps).

bwebel

We could live with the gear range provided in a 10x50 rear cassette and a 48t or 50t front chainring, but could never live with the large gaps necessary for such a wide cassette. It would take probably a 16 cog rear cluster to make me happy with a 10x50 cassette.

merlinextraligh

Range really isn't a problem. With a 48 front chain ring, your top end is still as high as a 53/11, and you have below one to one gearing on the low end.

I agree that I don't think I'd like the gaps (preferring one tooth changes in higher ranges) but actually the gaps on the 10-50 aren't bad until you get to the bailout gears.

And compared to a 2x11 system with close to the same range (but slightly more limited, the jumps aren't that much bigger.

A 2x11 with 11-34 in the back and compact rings 50/34 gives you effectively 15 non redundant useful gears. The progreesion for those gears are mostly around 10-13 gear step( admittedly you could make those steps smaller in the mid range if yo made a double shift for every shift, but nobody shifts like that in the real world)
Compartiively the Eagle system gives 12 useful non redundant gears ( only 3 fewer) and steps typically between 13-17, not light years different.

oldacura

Merlin -

If you were to change to a 1x, you could have a close-ratio cassette for Florida and a wide range cassette when you go to hilly terrain. Do you see having a 1x drivetrain a benefit or just a "fad"?.

merlinextraligh

And compared to a 3x9 system that many people thought was just fine, the Eagle gives slightly better range, almost as many useful gears, and comparable gear steps.

i.e. typical mountain setup for a 9 speed triple 52/39/30 and 9 speed 11-34 gives you 13 useful non redundant gears and a top gear inch of 120, and a low gear inch of 24

Set up the Eagle with a 44 front chain ring, and you get 12 useful gears, top gear inch of 122, and the same bottom as the 3x9 at 24, and the gear steps are pretty close..


When you consider how many gears in a 2x or 3 x system are redundant, you can cover a wide range without outrageous gear steps on 1x12 with close to comparable gear steps because you get to use all 12 gears in a straight ahead one shift progression with no issues of cross chaining, cross over points and redundant gears.

merlinextraligh

We do that with the 2x11. Our everyday gearing iis 52/36 and 11/25., which is fine for us for moderate climbing.


We have an 11-36 for the back , but rarely use it.


Looking at the gear steps, the Eagle setup can cover the same range as the 11-36 setup, and the jumps are bigger but not all that bad..


I have 1x11 on my MTB. I think its more of an advantage on an MTB given that you don't have to worry about making a front shift under load on rough terrain when sudden changes in a single track trail present themselves. Even then, I'm not totally sold on 1x11 for a MTB. My current MTB gearing I need more top end, which would require a large chain ring, but then I'd have to also put on a larger rear cassette yo keep the low end where I need it. The new systems with 10 tooth small cogs help in that regard.


To me, the bigger issues with 1x are the weight of the huge rear cassettes ( my assumption is a total 1x system can actually be heavier than a 2x); the aesthetics of an insanely large rear cassette, the wear of the big cogs if you make them out of Ti to save weight, the inefficiency of the small 10 tooth cog.


I haven't ridden my 1x enough yet to really come to a conclusion how well I like it, and whether any of the above is an issue in practice.

merlinextraligh

We do that with the 2x11. Our everyday gearing iis 52/36 and 11/25., which is fine for us for moderate climbing.


We have an 11-36 for the back , but rarely use it.


Looking at the gear steps, the Eagle setup can cover the same range, and the jumps are bigger but not all that bad..


I have 1x11 on my MTB. I think its more of an advantage on an MTB given that you don't have to worry about making a front shift under load on rough terrain when sudden changes in a single track trail present themselves. Even then, I'm not totally sold on 1x11 for a MTB. My current MTB gearing I need more top end, which would require a large chain ring, but then I'd have to also put on a larger rear cassette yo keep the low end where I need it. The new systems with 10 tooth small cogs help in that regard.


To me, the bigger issues with 1x are the weight of the huge rear cassettes ( my assumption is a total 1x system can actually be heavier than a 2x); the aesthetics of an insanely large rear cassette, the wear of the big cogs if you make them out of Ti to save weight, the inefficiency of the small 10 tooth cog.


I haven't ridden my 1x yet to really come to a conclusion how well I like it, and whether any of the above is an issue in practice.

merlinextraligh

If you have what would have been typical straight from the factory gearing on your Trek or Co-Mo, I bet you an Eagle 10-50 with the right front chain ring actually can give you the same or better range. Se my example above.

oldacura

Never thought of the weight of a huge cassette but it is probably quite a lot. With respect to the aesthetics, I agree - the huge cassette looks pretty weird (but I could get used to it).

Our road tandem we have a 2x11 Di2: 52t-34t up front and 11t-40t in the rear. I've gotten used to riding it as a 1x on the big ring unless I think we are going to be climbing below about 10 mph for a while. Then we drop down to the small ring but I have to let my stoker know because the drop takes a second or so where there is no resistance. We don't ride big hills like we used to so I don't need to use the front derailleur as often. So it is kind of a 1x with a bailout.

merlinextraligh

my assumption about weight appears to be wrong. If your willing to pay for the expensive cassette it only weighs 368 grams which is lighter than standard Sram 11-36. Even if you go with the "bargian" GX Eagle at $215 , it's only 75 grams heavier, which is presumably offset by losing the front derailleur, wires or cables, and a presumably lighter brake lever with no shifter in it.

124Spider

+1

Our tandem has a range of 6.3, and on any ride with any hills (that mostly doesn't include railtrails, but includes most everything else), we use all of them. I really value having the close-ratio gearing that a 3x9 gives, also.

My half-bike has a range of only 3.7, and that's fine for me riding it by myself, on any ride I've taken yet (which includes some serious hills). But riding a CF single bike, for me, is a completely different experience than riding a steel tandem; we need those low gears (and all of them).

Mark

reburns

bwebel

But we aren't choosing between a 9 speed cluster with a triple and a 12 speed with a single ring; the gear steps on the 12 speed 10x50t are massive compared to an 11 speed 11x32t cassette. It's fine if those gaps don't matter to you, but there is a huge difference to me between 10-12-14-16-18-21-24-28-32-36-42-50 and 11-12-13-14-16-18-20-22-25-28-32. I would far rather have a front derailleur and the close gaps than the huge gaps and a single chainring.

oldacura

I would think that a progressive range from high to low without a big step in the middle has some real advantages. Relatively large steps between gears may be objectionable to some but OK for others.

I would guess that some or all of the big tandem builders would have considered this (and maybe rejected it for this very reason).

Not sure how Sram does a 10 tooth cog. 11 teeth was the smallest standard for a long time.

merlinextraligh

merlinextraligh

reburns

Alcanbrad

I have been following this thread with some interest. I too feel somewhat passionately that I want the "fine tuning" of a triple and do not want large jumps in gear range. On the other hand, I am forever seeming to be futzing with my triple shifting performance and eliminating that agita has some appeal.

So I took my current 3x10 drive train, calculated the gear inches for each combination, then sorted the list from smallest gear inches to largest gear inches. Then I made the assumption that all shifts were one at a time. In other words, whenever I shift, it is discretely either the rear or the front, but never both in the same shift. Then I calculated the delta (change) in gear inches for every gear change possible (i.e. pick any gear combination, then calculate the difference in gear inches for all possible gear changes from that gear. I did the same thing for a hypothetical Eagle 48 x 10-50. I then looked at the gear inches for both set ups and roughly overlaid the gear combinations giving me the following:




(E1 is Eagle 50, E2 = Eagle 42 and so one, S1 = Small 32, S2 = small 28, .... M1 = middle 32, M2 = middle 28, .... and L1 = Large 32 and so on)

I also plotted the gear inches for each and convinced myself, as mentioned in the thread several times, that the Eagle will give about the same low and high end as my triple.

So then I plotted the min and max differences in down-shifts from each gear combination as well as the min and max differences in up-shifts for each. In the cases where there was only one possible down or up shift, I repeated the data. What I found was interesting. In just about every shifting case, the jump in gear inches for the 1x was about the same as the minimum of the possible jumps from the triple. You can see this in the graph with the black straight-ish lines being the Eagle, and the other lines being the triple:



What this suggests is that the 1x offers fairly consistent differences to the minimum possible with the triple. What we lose is the larger jumps possible with the triple. Thinking about it, as experienced cyclists we really don't always think about what gear we're in or the next gear we want to be in, we have an innate feeling of knowing whether we need to shift the front or rear next. The 1x setup strips that away and one would have to develop the feelings about how many shifts one needs to make to get to where one wants to be. That might not be so bad, but it could be problematic if the situation requires one to shift down many 10's of gear inches quickly.

I need to go back and check my work as I see some anomalies in the graph, but I think this is telling us that a 1x does not come with the penalty of large jumps but at the penalty of not being able to perform large jumps (in addition to having more choices of gear rations that are very close together).

I'm curious as to what folks think?

124Spider

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.

What would be a useful chart, I think, would be to show the gear ratios (either in inches or in front/rear) for each. Given that a 3x9 or 3x10 has about twice the gear ratios of the 1x14, it would seem likely, to me, that the 3x9 or 3x10 gives a far more nuanced ability to find the right gear, and (as you stated) it gives the ability to make a large shift (shifting the front ring) or a much smaller shift (shifting the rear); or even (with my brifters) choosing between downsshifting one, two or three rear gears.

I don't particularly enjoy the shifts that require simultaneous shifting of the front and the rear, so I certainly can appreciate the benefit of a truly linear gear-train. But I have a hard time believing that the Eagle has the same ability to have close-ratio shifting as a 3x9 or 3x10, which you seem to be suggesting.

Mark

oldacura

Very interesting analysis. I don't think in gear-inches (rather ratios) but I know gear-inches is the common language for detailed analysis.

Our old Co-Mo was a triple with a low end of 30t x 34t and a high end of 54t x 11t. When we ordered our new bike, folks on the forum convinced me that Di2 was the way to go. Once I accepted that, it limited us to a 2x drivetrain. I wanted to preserve as much of the range as possible. The new bike has a low end of 34t x 40t and a high end of 52t x 11t. This works OK. I ride the bike as a 1x on the big ring with a bailout to the small ring. I've decided to adopt the Full Sychro option with Di2 where one just shifts the rear and jumps up or down on the front at pre-determined points. I did this because when I shifted in the old-school manner, I often shifted the front at the wrong time and the jump was huge (52t down to 34t). My stoker did not like this. So, now with Full Synchro, the display will beep twice on the shift before it shifts the front derailleur. I know that this "cliff" is there and try to avoid it. Full Synchro makes a compensating shift of the rear of 1 - 3 gears (also pre-selected) but there is a delay of a second or so until the chain re-engages.

That is why the Eagle appealed to me. I could have almost as much range without the big cliff in the middle.

Nice analysis!

TCW2

Shimano XTR has the 10-51 12 speed cassette coming soon. With regard to Eagle, it's awesome - on my mountain bike (wife also loves hers on her Tallboy - she fancy). The X01 cassette weighs 353g on my scale. I first started with 1x10 Shimano gearing back in the day then incorporated Leonardi GL cassette expander (largest 3 cogs on an XT cassette up to 42t), then Wolftooth, etc. They worked well but the SRAM XX1/X01 10-42 11 speed was far superior; the wife now has those gears on her rigid Niner gravel/mtb bike. Eagle is a bit heavier but the 50t solves all sorts of issues especially in the big Colorado/Wyoming mountains. We Okie flatlanders need low gears, big time when doing real mountainous adventuring.

On a road tandem the larger Eagle jumps would likely get on my nerves. On an MTB/gravel tandem, no problem. I even confirmed gravel use with a SRAM X01 10-42 cassette/Force/Red 1X drivetrain on my single gravel bike. It is great and the jumps aren't noticeable. We currently run an 11 speed Shimano Ultegra 52/39 x 11-32 and even then the jumps sometime feel a little large. I may slap the 11-28 cassette on to compare.

Also, SRAM Eagle (and 11 speed equivalent) derailleurs aren't compatible with their road shifters. However a Rival/Force long cage can handle the 10-42 cassette. My medium Force even handles the 10-42 (Red shifters). Perhaps a solution has been released and I missed it? Good conversation!