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OneUp Components was one of the first companies that started to offer aftermarket conversion kits for existing components, such as a 42T range-extender replacement cassette cog, a narrow-wide chainring, or the clever RAD cage that helps modified cassettes play nicer with Shimano derailleurs. Well, the company has now turned its attention to DH, and is launching what appears to be a nifty way to convert an existing cassette into a DH-specific "block".

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OneUp Components DH Block Highlights

  • 9 speed MTB cassettes convert to 6 speed DH
  • 10/11 speed MTB cassettes convert to 7 speed DH
  • 2 tooth jumps through the majority of the cassette with 11-36T base cassette
  • 11-25 to 11-21 range depending on base cassette
  • Possibility to shift through your entire cassette in only 2 shifts
  • Weight: 40g
  • Colours: green or black
  • MSRP: $45 USD

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The OneUp DH Block replaces the 3 biggest sprockets of an existing cassette with a spacer that also functions as a spoke guard. Depending on which cassette you convert from, you are left with the top 6 or 7 sprockets with close to identical jumps between gears when compared to SRAM's X01DH Mini Block cassette. As with the other products from OneUp, the idea here is to offer a cost-effective alternative to specific solutions from the two big drivetrain players. As an example, the aforementioned X01DH cassette costs $300, whereas you could convert a $50 Shimano SLX cassette and end up with almost the same gearing.

Looking closer, a typical Shimano 11-36 conversation would yield the following ratios: 11-13-15-17-19-21-24. The ratios of SRAM's X01DH by comparison are: 10-12-14-16-18-21-24. The major difference between the two have to do with the 10t sprocket found on the SRAM block. The smaller sprocket creates a bigger range in the cassette, but more importantly allows the use of a smaller chainring to achieve the same development in the tallest gear. On the flipside, running a 10t small sprocket is only possible on an XD-driver equipped hub, which may mean replacing the wheel or at a minimum converting the hub for many riders. Much as is the case when extending the range of a traditional cassette by using a range-extender cog, the DH Block conversion gets you 90% of the way in return for a lower cost.

OneUp Components DH Block Compatibility Chart (click to enlarge)

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Setup

There are 2 different ways to set up a derailleur to take full advantage of the DH Block-equipped cassette. The compatibility chart above indicates which one applies to which derailleur.

Standard Setup

  1. Ensure the high limit screw and cable tension is correct
  2. Turn the low limit screw in until the shifter can no longer shift into the 8th position

Alternate Setup

  1. Untighten the RD cable clamp and completely release all cable tension.
  2. With a chain installed adjust your High limit, so that the upper pulley wheel is directly beneath the smallest sprocket.
  3. You cannot use the Low limit screw to set a Low limit position for your RD. You must rely on the shifter position.
  4. Shift into the 3rd shifter position, wind the barrel adjuster on your shifter fully in (clockwise), then wind it out 2 full turns (anticlockwise). Now tighten the cable clamp on you RD and adjust your cable tension as you would normally.

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Riders have been "hacking" their drive trains for a long time already, and the recent proliferation of range-extenders show that many are willing to put up with slightly compromised performance to get access to modern drive train tech at a fraction of the cost. We would have to test the DH Block conversions before we pronounce an opinion, but it certainly looks like OneUp have once again productized a "hack" to provide a suitable solution for many gravity riders looking to ditch their road cassettes.

For more information, head on over to www.oneupcomponents.com.

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