Gears & Gadgets: 2x10 Drivetrains for Public Safety Use

Gears & Gadgets:  November 2014
Drivetrains

Gears & Gadgets is intended to provide IPMBA members with tips for properly maintaining their bikes and conducting emergency field repairs.  I will also discuss current technological trends in mountain biking, and how they may be beneficial to Public Safety Cycling.  Contributed by Jared Williams.

Since the last installment of Gears and Gadgets focused on keeping drivetrains clean and operating smoothly, I thought I’d touch on the current drivetrain technology found on the latest and greatest mountain bikes.

First off, let me start with a little terminology.  Many people still refer to drivetrains as “27-speed” or “30-speed.”  This old terminology comes from the old 10-speeds of yesteryear.  They refer to the total number of possible gear combinations – i.e., three gears up front, and 7, 8, 9, or 10 in the back (for example, three gears in front x nine in the back would be a “27-speed”).  Well, sorry folks, but not all of these gear combinations are actually possible (remember “cross-chain” from your class?), and several of them are repeating/identical gear ratios.  The correct method of referring to current drivetrains is 3X10, 2X 10, etc. 

A Little History

In the past few years, mountain bike drivetrains have undergone some significant changes.  Just a few years ago, a triple chain-ring drivetrain was standard on all mountain bikes.  3X10 and 3X9 combinations were standard equipment, because that’s the way it had always been done.  But just across the bike store were those sleek and shiny road bikes, with their fancy 2X9 and 2X10 drivetrains. 

Without going into too much detail, a 2X10 drivetrain generally had substantial performance benefits over their 3X10 brethren.  The reason for this was better chain alignment, fewer issues with cross-chaining, and smoother shifting from the front derailleur.  Someone realized that there was no reason we couldn’t throw a 2X10 drivetrain on a mountain bike and reap the same benefits. 

Just a few short years ago, 2X10 drivetrains by SRAM and Shimano started showing up on high end mountain bikes.  As this technology trickled down, it became far more common on mid-level mountain bikes.  Mountain bikers soon began reaping the benefits of a more efficient double-ring drivetrain.  Some people worried that giving up the “granny gear” in the front would lead to more difficulty on steep climbs.  This was properly accounted for by adjusting the cassette to allow for larger gearing.

In addition to the 2X10 setup, the SRAM type-2 and the Shimano Shaddow-plus rear derailleurs were introduced.  Both derailleurs operated on basically the same concept:  adding a clutch mechanism that kept the chain pulled taut.  This clutch kept the rear derailleur’s fore-aft movement to a minimum, significantly reducing dropped chains and chain slap on the chain stay in rough sections of the trail.

The most recent drivetrain technology is a 1X10 or 1X11 setup, where there is only one gear up front (no front derailleur) and 10 or 11 in the rear.  These systems are generally suited best for downhill or racing.  They are not going to be a system with enough diversity for the average mountain biker.  I personally have been testing one for a period of time and I don’t believe it has a place (right now) in public safety cycling.

The Public Safety Cyclist Drivetrain

I would venture to guess that 99.9% of public safety bicycles these days are running a triple-ring drivetrain.  I know there are plenty of variances for the rear cassette, ranging anywhere from 7-10 gears. 

As I discussed above, a triple ring drivetrain generally has repeating gear ratios and cross-chaining issues.  So, a 3X10 drivetrain does not have 30 actual useable gear combinations; it likely has in the neighborhood of 20 actual useable and unique combinations.  Furthermore, a 3X10 drivetrain can be tedious to keep properly adjusted.  As a former bike shop wrench and current bike-team mechanic, I know all too well how much of a pain this can be. 

In my experience, teaching novice riders to use a triple-ring drivetrain can be difficult.  “Should I be in the middle ring?  Should I be in the granny ring?”  It is not uncommon to see students attempting slow speed maneuvers or powering up a hill in the large chain ring, even after I’ve reminded them about proper gear selection.  Having more options can actually hinder a student’s ability to grasp the concept of proper gear selection.

I understand wanting to have the “granny-gear.”  It allows super-low gearing for those tough hills, especially if there is a lot of equipment to haul around (such as EMS).  But, with the current available 11-36 tooth cassettes, low gearing is not difficult to achieve.  Triple chain-ring designs have traditionally offered a maximum low-gear cassette range of 30 or 32 teeth.

I recently converted my personal bike to a 1X10 drivetrain, including a 30-tooth chain ring and a 42-tooth low cassette gear.  Much like the reports I have reviewed, I have found the 1X10 drivetrain to have significant benefits over a 2X10, for the purpose I am using it.  With that being said, I don’t think a 1X10 or 1X11 drivetrain is ideal for public safety use.

I do believe a 2X10 drivetrain would have significant benefits over a triple-ring drivetrain for police cycling.  The simplicity and maintenance of the system have significant benefits over the triple ring setup.  There is only a minor loss of the low-end gearing, and in my opinion, it is insignificant. 

That said, I believe a triple-ring setup still carries benefits for EMS cyclists, who have to carry significantly heavier loads.  For EMS cyclists in hilly areas, the low gearing of a triple-ring is hard to beat. 

My department recently purchased two Trek Stache 7 mountain bikes that sport a 2X10 drivetrain.  While I have only had the bike for a short time, I have already noticed significant shifting performance over the 3X10 drivetrain I was previously riding on.  I have not noticed any lack of gearing or felt like I couldn’t turn a low enough gear up a hill.  Additionally, the SRAM X9 type-2 rear derailleur has significantly reduced chain slap and dropped chains while ascending and descending stairs.

The next time you are looking to purchase a new bicycle or update the components of your existing fleet, you owe it to yourself to consider a 2X10 drivetrain. 

If you have any questions, or suggestions for future topics, please feel free to email me at jared.williams@ci.tacoma.wa.us.

Jared is currently a Community Liaison Officer for the Tacoma Police Department.  He loves to tinker, and can often be found obsessing of the mechanical state of his bicycles.  Jared is the owner and operator of Piggies On Wheels, LLC, which exists for the purpose of public safety bicycle education.  To learn more, go to https://www.facebook.com/PiggiesOnWheels.

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