SRAM 1x Drivetrain

A recent Trike Asylum blog entry entitled Eulogy to the Front Derailleur inspired me to do a little more thorough investigation of SRAM’s challenge to the front derailleur.  Steve gathered a couple of pretty funny videos on the topic, it’s worth checking out the link.

Of course it’s possible to eliminate the front derailleur with various internally geared hubs, but SRAM’s 1x technology is unique in that it achieves the same thing by subtracting complexity from the system instead of adding it.  It does this by combining a super-wide 10-50 tooth 12-speed rear cassette with a single front chainring.  Is it the right technology for a recumbent trike?

I’ll try to answer that question by comparing it to what I consider the best alternative—Shimano Di2 and Schlumpf.  SRAM’s 1x is currently among their finest drivetrain solutions; in my opinion Di2 is Shimano’s.  With Di2, additional gearing is necessary to achieve reasonable range.  I chose the Schlumpf Speed Drive because, like 1x, it eliminates the front derailleur and shifter.  I don’t include SRAM’s eTap electronic shift technology in the comparison because it isn’t compatible with 1x.

 

Range and Percent Change

The first question is whether it has adequate gear range for a recumbent.  For me it does,  so 1x is is still in the running.

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SRAM 1x

 

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Shimano Di2 and Schlumpf Speed Drive

Cost and Weight

SRAM comes out slightly ahead on both counts, about 600g lighter and $300 cheaper than Shimano / Schlumpf.  However take these numbers, especially for SRAM, with a grain of salt.

Shimano/Schlumpf Weight Cost SRAM Weight Cost
Ultegra Di2 RD-6870 GS Rear Derailleur, Alfine SW-S705 Shifter, Alfine SC-705 Display, SM-BTR2 Battery, E-Tube cable, Junction Box 415g $745 X01 Eagle Type 3 12-speed rear derailleur 252g $222
XX1 Eagle grip shift 103g $150
Schlumpf Speed Drive and crank arms 1080g $699 X01 DM crankset GXP 540g $350
11-speed Shimano HG600 chain (x3) 640g $60 PC-X01 Eagle chain (x3) 750g $180
Shimano 105 CS-5800 11-speed 11-32 Cassette 309g $50 XG-1295 Eagle 10-50 12-speed cassette 268g $360
White Industries CLD-11 rear hub, 135mm, 11-speed 265g $295 American Classic Rear Disc 225 Hub Mountain 135mm QR 32h Black with XD Driver (SRAM XX1 225g $260
Total 2709g $1849 Total 2138g $1522

 

Everything Else

Both solutions eliminate the front derailleur and shifter.  Both make it really easy to shift gearing up or down to accommodate any size of drive wheel.  Here’s how they compare for everything else.

Feature Comparison Advantage
IGH Internally geared hubs are an engineering marvel and a great solution to a number of drivetrain problems.  But if you could eliminate an IGH without sacrificing any functionality, would you do it?  Of course you would. SRAM
Chainring That complicated and expensive IGH buys you a dramatically smaller front chainring.  34 vs. 52 teeth. Shimano/Schlumpf
Performance The primary measures of drivetrain performance are shifting speed and accuracy.  I don’t have experience with the SRAM “rolling thunder” technology, which should be an improvement over the standard SRAM twist shifters I’ve used.  But it still uses mechanical cables.  Based on the dramatic improvement I saw going from mechanical to electronic shift, I’m going out on a limb here. Shimano
Chain drop The long, unwieldy recumbent chain is inherently prone to dropping the chain off the chainring.   Without a front derailleur, chain drop is more common because the derailleur cage isn’t there to prevent it.   Higher-end mountain derailleurs employ a clutch to prevent the chain from slipping backward, which (I’m told) helps prevent chain drop.  Since Ultegra is a road groupset, it doesn’t have a clutch.  Of course the low-tech way of preventing chain drop is to slap a trouser/bash guard on both sides of the chain ring. SRAM
Maintenance Periodic cable lube and/or replacement vs. an overnight charge, in the same maintenance interval.  No contest. Shimano
Ergonomics I used to think a well design twist shifter, like the new SRAM “rolling thunder” shifters might be, would be the ultimate for a trike with upright handlebars.  After using the Alfine pushbutton shifters I no longer think so.   In the front, pushing a button with your heal to shift the Schlumpf is certainly less ergonomic than doing nothing at all.  But the advantage of the Alfine shifter is so much greater than the disadvantage of the Schlumpf, I’m giving this one to Shimano. Shimano
Longevity The jury is still out on longevity of a Di2 battery, but in general I consider occasional battery replacement a wash with occasional shifter replacement.  But given Di2 longevity is still an unknown to me, I’ll give this one to SRAM. SRAM
Noise In overdrive, the Schlumpf makes some noise.  I suspect Di2 will make less noise than 1x, but derailleur noise is less overall than the Schlumpf noise. SRAM
Aesthetics Electronic shift makes it easy to run cabling inside tubes or taped to the frame for an extremely clean install.  A smaller front chainring looks better in my opinion.  And the Alfine gear display is a nice touch. Shimano
Weather No mechanical cables means performance unhindered by water and sludge getting into the cables.  And no frozen gears in the winter. Shimano
Complexity Mechanical cables, no battery, and external gearing are certainly less complex. SRAM
Gear range The 1x drivetrain has slightly wider range than the Shimano/Speed Drive.  I’m not sure it’s enough to matter, and the Schlumpf High Speed Drive will provide a huge increase in range over the 1x. Shimano/Schlumpf
% change The % jump between gears is 8-14 for Shimano/Schlumpf and 13-20 for 1x.  I’m not sure I’d notice, but roadies/racers will certainly prefer the smaller jump. Shimano/Schlumpf
Maturity The 10-50 tooth 1x system isn’t available until June this year.  Di2 and Schlumpf have been around many years. Shimano/Schlumpf
Weight See table above SRAM
Price See table above SRAM

Conclusion

SRAM’s 1x technology is a viable option for a tadpole recumbent trike, which surprises me a bit.  Until I looked, I didn’t think the range would be wide enough.  It won’t be for some trikers, just as the Di2/Speed Drive combination I’m running won’t be.  For me, as soon as someone pulls off similar 1x technology with electronic shift, I’ll be back in the market.  Until then I won’t give up my Di2.

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One thought on “SRAM 1x Drivetrain

  1. Ron Richings

    Being a ‘belt and suspenders’ kind of guy, I would probably put a double or tripe crankset on the front, but with fairly narrow difference in the chainring teeth – eg. 24/28 – 34 – 40 or whatever might fit and be within a range that the rear derailleur could handle. But perhaps no front derailleur, particularly if there is no mounting post/frame piece. Just move the chain by hand if different range needed for a significant period. I am coming at this from the perspective of a touring/utility rider. Sometimes really low gears are just what is needed.

    Liked by 1 person

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