With the inception of the 1x drivetrain, Sram not only ditched the front derailleur and invented the narrow-wide chainring, but also introduced a 10-42T wide-range cassette with their new 11-speed groupsets that engages on a newly designed XD freehub. The new freehub standard became necessary to use a cassette with a smaller 10 teeth cog that offered a sufficient gear range to compensate for the lack of a second chainring.
The 10-42T cassette has a gear range of 420% and roughly covered the spread of Sram’s previous 2×10-Speed MTB drivetrains using smaller 11x36T cassettes. Since the 10-42T cassettes were rather huge Sram started machining them as one piece from steel to keep the weight low. Ultimately, they became even lighter than their smaller 11-36T cassettes. The gear range of the new 1x drivetrain was sufficient for mountain bikes, but is not for the newborn category of Gravel bike.
Riding Gravel is rarely endless miles of scenic undulating roads with a coarse (gravelly!) surface as our homepage photo may suggest. Gravel riding is mostly XC mountain biking interspersed with road riding and fire road climbing! At least here in SoCal. The wide range of terrain requires a wide range of gears leaning towards climbing. You want to keep spinning up steep hills while hauling your bikepacking gear and you want to be able to crank up a 25+% ramp when racing a technical gravel grinder. And on the other side of the cassette, you also don’t want to spin out every time the road points downwards and see the competition pedalling away, or when you desperately try to beat the closing hours of your most favourite brewery. Ride responsibly!
What are the limitations of a traditional 11-Speed 1x Gravel drivetrain?
When Sram came out with their 11-Speed Gravel groupsets and moved the 1x MTB technology over to Gravel bikes the default gearing option was 42T x 10-42T or sometimes 42T x 11-36T. This rather tough and narrow-ranged gearing proved pretty useless for most riders unless they were Pro athletes or racing CX, respectively. While you can now go smaller with direct mount chainrings the Sram Force 1/Rival 1/Apex 1 groupsets initially came with a 5-bolt BCD 110 spider cranksets only allowing a 34T as the smallest chainring. That wasn’t small enough for uncompromised Trail riding and you were already spinning out on downhills and flat roads.
Sram stopped short again when they first introduced the wireless electronic 12-Speed AXS eTap Red/Force 1x groupsets by offering 10-33/36T cassettes and 36, 38, 40, 42, 44, 46 and 48T chainrings only. You could argue, that these groupsets are made exclusively for Road bikes, however, you can find plenty of Gravel bikes specced with them as well. For more on this see below.
How to increase the gear range of your 11- or 12-Speed 1x Gravel drivetrain?
Grow a Mullet! Business in the front, party in the back. Mullet drivetrains combine MTB or modified Gravel rear derailleurs and MTB cassettes (the party!) with Road shift levers (the business!) to increase the gear range of your 1x groupset.
What does a Mullet conversion do for you?
In our shop we offer preconfigured Garbaruk Mullet conversion kits (the party!) that increase the gear range of your existing drivetrain from 420% to 500%. This is simply done by swapping the 10-42T cassette with a 10-50T Garbaruk 11-Speed cassette and modifying your rear derailleur. It will also save you from changing chainrings every time you plan a different adventure.
Let’s assume you have been running the default 42T x 10-42T Sram 11-Speed Gravel setup. Keeping the chainring size unchanged, a 42T x 10-50T Garbaruk drivetrain gives you the same climbing gear as a change to a 34T chainring (–> 34T x 11-42T), but with the advantage that you can keep pedaling when the trail or road points downwards. Same if you are running a 30T x 10-42T Sram 11-Speed setup geared towards climbing, now you can pick a 36T chainring for a 36T x 10-50T Garbaruk drivetrain and not lose any “climbability”, but gain a lot of “spinability”.
Compared to 2x drivetrains, a 36T x 10-50T Garbaruk drivetrain is equivalent to an older Sram X9 10-Speed 39/26T x 11-36T, or a 32 x 10-50T Garbaruk drivetrain is equivalent to a Shimano XT 11-Speed 36/26T x 11-42T. All have an enormous range, great for all kinds of climbing, riding and descending. But by picking the 1x drivetrain, you will save a significant amount of weight omitting a shifter, a front derailleur, a chainring and getting a much lighter cassette despite its bigger size.
We used the Bicycle Gear Calculator on ritzelrechner.de and plugged in the parameters from a buddy who rides a Salsa Cutthroat to make these comparisons. Click on the graphs and play with the settings, it is fun!
Mechanical 11-Speed Mullet: the Garabaruk Conversion Kit
By nplus2 cycles | May 16th, 2021. Garbaruk Mullet Conversion Kit in purple-black-purple.
This kit is the “party” and increases the gear range of your existing Sram 11-Speed 1x drivetrain to make your Gravel bike a true trail companion. Keep spinning uphill and pedalling downhill. This kit includes a superlight Garbaruk 10-50T 11-Speed Cassette, a Garbaruk Rear Derailleur Cage and a Garbaruk Rear Derailleur Pulley Set.
Pros:
- Increased 500% gear range.
- Resulting drivetrain is lighter and more efficient.
- Many color options to choose from adding lots of bling.
- Budget-friendly: cassette, cage and pulley kit only sets you back $375.
- True Mullet hack since you are likely converting and upgrading an existing drivetrain with minimal changes.
- Works for Sram Force 1, Rival 1 and Apex 1 Gravel, as well as Sram NX, GX, X01, XX1 MTB groupsets.
Cons:
- While shifting flawlessly, it may be experienced differently compared to the higher priced offerings from Sram and Shimano.
- Likely need a new (bigger?) chainring and (longer) chain as well. However, that applies to all Mullet conversions. Luckily, Garbaruk offers chainrings in matching colors for the vast majority of cranks as well.
Kit specs:
Cassette:
Gear range: 10-50T
Sprocket ratio: 10-12-14-16-19-22-26-30-36-42-50
Materials: hardened chromoly steel (body), 7075-T651 Aluminium (largest cog)
Weight: 317 grams (on our scale)
Compatibility: SRAM XD Freehub
RD Cage:
Material: 7075-T651 Aluminium
Weight: 44 grams (on our scale)
Compatibility: complete range of SRAM 11- and 12-Speed Type 2/2.1/3 Gravel/CX and MTB rear derailleurs: Force 1, Rival 1, Apex 1, and NX, GX, X01, XX1, as well as Eagle NX, GX Eagle, X1 Eagle, X01 Eagle, XX1 Eagle.
Check out our installation video.
RD Pulley Set:
Teeth: 12T+16T
Bearings: stainless steel or ceramic
Material: 7075-T651 Aluminium
Weight: 20 grams (on our scale)
Compatibility: Garbaruk Sram 11/12-Speed RD Cage
Two alternative Mullet conversions
Mechanical 11-Speed Mullet: a Sram derailleur chimera
Summary: Nice, innovative Mullet hack with some appreciated tinkering that uses a Sram XX1/X01/GX Eagle MTB rear derailleur modified with parts from a Sram Force 1/Rival 1 rear derailleur. Doesn’t break the bank if you can source used rear derailleurs. Still may end up with a Garbaruk 10-50T cassette due to the lack of wide-range alternatives though.
Pros:
- Increased 454-500% gear range.
- Relatively budget-friendly.
Cons:
- Need to source an 12-Speed Sram XX1/X01/GX Eagle rear derailleur AND an 11-Speed Sram Force 1/Rival 1 rear derailleur, if you are not converting an existing drivetrain.
- Only heavy wide-range cassettes (e.g. 11-50T) for a budget mullet available that may not give you a 500% gear range.
- Only higher priced Force 1/Rival 1 and GX/X01/XX1 rear derailleurs can be used for this modification.
- Likely need a new (bigger?) chainring and (longer) chain as well.
- Resulting drivetrain is heavier
Wireless electronic 12-Speed Mullet: Sram Etap AXS meets Eagle AXS
Summary: If you are looking for the crème de la crème of Mullet drivetrains look no further than the pairing of Sram’s Red/Force eTap AXS Road shifters with XX1/X01 Eagle AXS MTB Derailleur*. The setup is relatively simple and gives you a trail-capable Gravel bike with the latest wireless electronic 12-Speed shifting that is suited better for competition than bikepacking however.
Pros:
- Latest wireless electronic 12-speed drivetrain technology.
- Increased 520% gear range (10-52T).
- Staying within the Sram family not voiding any warranty or OCDness.
- Absolute dream build potential.
Cons:
- Need to decide if you want to eat the next month or grow this Mullet.
- Rather a mullet built than a conversion or hack making it an expensive project.
- Currently, Shift levers, rear derailleur and cassette will cost you at least $1585 (MSRP), or $1150 (MSRP) for the rear derailleur, the cassette and the chain (!) if you are converting an existing Road AXS eTap drivetrain.
- Can’t use SRAM’s innovative Flattop Road chain technology, you have to use an Eagle chain.
- Likely need a new (bigger?) chainring and (longer) chain as well, if you are converting an existing setup.
- Batteries that need to be kept charged are not the best option for remote bikepacking adventures.
*In the near future a more budget-friendly Mullet combining Sram’s Rival AXS and GX Eagle AXS could become available.
The Verdict.
We love the Garbaruk Mullet because of its simplicity and unbeatable optics. It offers a true budget-friendly Mullet hack perfect for the entire range of Gravel riding from bikepacking to racing. You only need to make minimal changes to your existing 11-speed 1x drivetrain and the resulting drivetrain has an increased 500% gear range, better drivetrain efficiency and is lighter than your previous setup.
You can find cheaper solutions to increase the gear range of your drivetrain, but they will likely be heavier and have less than 500% gear range extension. Not to mention, they won’t have the pretty looks of the Garbaruk conversion.
On the other side of the spectrum, the latest and greatest wireless electronic 12-speed Sram AXS groupsets let you mix and match their Road and Mountain drivetrains to create the most advanced Mullet drivetrain out there. But this innovative drivetrain comes with a hefty price tag and is actually very hard to come by these days. In addition our outdoorsy and remote bikepacking adventure heart is not completely beating in sync with the idea of charging a rear derailleur while out in the boonies for days. But that’s more the purist in us, a crisis can be likely averted by taking a spare battery and making sure everything is fully charge on the day of your departure.
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