SRAM X01 DH X-Horizon Rear Derailleur

Review by Ian Collins // Action Shots by Fred Robinson

Ever since downhill grew into its own discipline within mountain biking, riders have been tinkering and experimenting with their drivetrains, trying to optimize them for the demands associated with pointing bikes towards the bottom of the hill and all that comes along with it. This is in part due to the fact that manufacturers have neglected to build a specific group for the demands of DH. Until now.

SRAM recently released X01DH - a fully dedicated gravity drivetrain. Some parts are ground breaking, but in all fairness, some have been around and may seem like old news. The cranks are basically your standard carbon cranks that come with an XX1 group or were labeled as X0 DH in the past. What's most exciting are the derailleur and cassette. One of the major complaints with DH groups in the past was that they don't need 9, 10 or 11 gears and require too many shifts to get to the correct one. The new cassette is available as a 10-24 tooth 7 speed drivetrain that takes advantage the new XD driver system. Each time you shift a gear it jumps two teeth (as opposed to one) every time. No more double or triple shifting and “seeking” for the right gear. Another big thing is the X-Horizon derailleur – like the XX1 and X01 derailleur, it moves differently to derailleurs of the past and is a bit tougher and more reinforced. The shifter and chain are part of the group but nothing there stands out as glaringly different. Let's see how this group worked on the trails.

SRAM X01 DH Trigger Highlights

• SRAM 1X X-ACTUATION
• 7-speed
• Multi-adjustable trigger shifter
• MatchMaker X compatible
• ZERO LOSS Engagement
• Aluminum cover and adjustable forged aluminum pull lever
• Includes discrete clamp
• Colors: Red and Black
• MSRP: $143 USD

SRAM X01 DH Rear Derailleur (7-speed) Highlights

• X-HORIZON technology
• X-ACTUATION with more cable pull
• Two cage lengths for various applications, including abnormally long chain stay growth
• ROLLER BEARING CLUTCH with CAGE LOCK
• MSRP: $277 USD

SRAM X01 DH Crankset Highlights

• Carbon DH racing crank
• High strength alloy pedal lug
• 7075 CNC alloy single ring, 94 BCD, 30, 32, 34, 36, or 38 teeth
• Compatible with SRAM 1X 7- and 10-speed DH drivetrains
• MSRP: $315 - $347 USD

SRAM X01 DH 7-Speed MINI BLOCK Cassette Highlights

• Larger jumps between gears (10-12-14-16-18-21-24)
• Half as many shifts to get from 24-10 versus a normal 10-speed 26-11
• 10-tooth cog opens up high end and allows smaller chainrings for ground clearance
• More rear wheel clearance around spokes
• Currently fits any XD compatible wheel and driver body
• MSRP: $303 USD

Initial Impressions

When you first pull the parts out of the packaging and start getting them bolted up, you'll be impressed by the build quality. As per usual with SRAM - shift are crisp and snappy out of the box. As mentioned before, the cassette and derailleur stand out the most. Each cog (and the disc that prevents the chain from dropping into the spokes) are all machined from one piece of aluminum. It's sleek, black anodized, and just looks super clean.

The X horizon derailleur is sturdy and once set up it executes silently. The clutch style cage does a good job of preventing chain slap and damping drivetrain noise. The pulleys are narrow/wide, which prevents the chain from jumping around and keeps it cycling without hiccups.

The cranks are lightweight and well made. The ceramic bearings that grace their matching bottom bracket are a nice touch and bode well for longevity.

The shifter is feather weight and the action of the levers is light but decisive. The ergonomics of the levers are spot on, and the thumb paddle's positioning is adjustable.

The chain is just that sad part of a bike that's supposed to shut up and do it's job, and as expected, it did. The X-Sync ring with it's alternating thick/thin tooth profile finishes everything off and ensures that whether you run a chainguide or not, the chain will very likely stay put.

On The Trail

Once we finally got out and started knocking out DH runs on this group we have to say we were floored. It really is everything we would want in a dedicated downhill drivetrain. Where do we begin? Let's start with the most boring bits and work our way towards the more exciting parts - the chain held up and proved to be strong and durable. As many consumers know by now, a narrow/wide chainring does an incredible job of keeping the chain on, and this was no exception. We experienced no drops with the addition of the chainguide. Some may consider eliminating the lower guide altogether in favor of less friction. The cranks, although lightweight were stiff and handled some rock deflections without issue.

Now to the juicy stuff – having the right gearing out back was a gift. We can't emphasize it enough, this is the best part. It was refreshing that the act of shifting was no longer cerebral. For the most part finding the right gear only took one click of a shifter (sometimes two), allowing us to focus more on riding and the trail ahead, especially given the fact that the actuation was so sharp and spot on. It really was a relief to not have to bang through 3-5 vague and messy gear changes to get the right ratio at a moment's notice.

Things That Could Be Improved

In our time spent on the group so far, we have absolutely zero complaints with how this system works. It is absolutely flawless. It's a bit of a pain that it requires a dedicated cassette that only works with an XD driver, but as more and more hub manufacturers get on board with the increasing popularity of SRAM's 11 speed trail group, there are really only a few fringe hubs that don't work with this system. Is that 1 tooth drop down from 11 teeth to 10 teeth a dire necessity? No. Could SRAM engineer a similar 11-25 tooth high end cassette in 2 tooth increments that isn't crazy expensive and would work with every normal freehub on the market? Yeah, they have the capacity to do so.

In reality, the only gripe here is the price of the whole system and the fact that you have to dedicate to it. In SRAM's defense, most downhillers are a bit particular and either commit to SRAM or Shimano. So, if you're building up a new DH bike, consider going full in - this stuff works incredibly well. Chances are you're going to be like all the other lemmings and jump on board with the new set of wheels anyway. In this scenario, having to buy a proprietary freehub isn't a big deal.

Long Term Durability

During the few months we spent on this system we experienced ZERO issues and the whole group has held up well despite more than a few unplanned moments of contact between the cranks and derailleur with some wayside boulders and other various trailside obstacles. At this point, our group is a little banged up (as expected after some rowdy DH fun), but still works as good as it did when we first bolted it up.

What's The Bottom Line?

Is this a bit of a luxury that comes at a price? Absolutely. Is it worth it? Depends on how much you love downhill and want to invest in your bike. If you don't mind spending a good chunk of dollars to attain top notch performance, and spend a great deal of time on a DH bike, indulge and no longer have to think about the act of shifting gears on your bike. Albeit expensive, X01DH is worth the money. This group absolutely rules. Just be cautious of smashing that rear derailleur...

It's also worth mentioning that if you wanted to build up a 4X, dual slalom, or slopestyle bike this group would also serve as the cream of the crop drivetrain choice. We're excited that SRAM finally gave gravity drivetrains the much needed tip of the hat they deserve and have been lacking for so long.

As with the 11-speed groups, it's very likely that the technology will “trickle down” to lower price points in the future. We'd certainly imagine SRAM could get enough OEM spec to justify doing so. As a side note, if you don't want to go full in, buy the shifter, derailleur, cassette and XD driver. We're reviewing the group as a whole here, but no one is forcing you to buy it as such. If you want performance on a budget, save a few bucks and buy aluminum cranks. SRAM also makes the derailleur available by itself for existing 10-speed users. Why upgrade from a clutched system? That horizontal derailleur movement is the key, and it really does make a remarkable difference on a DH bike.

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

About The Reviewer

Ian Collins grew up racing mountain bikes on the East Coast before moving to California in search of the never ending riding season. Although he's generally a fan of slick and steep riding conditions, Ian has gotten acclimated out west and loves its speed. Also an avid surfer, what's most important to him in a trail is flow. Known for being meticulous and borderline obsessive about bike setup, he aids in product development for local frame builder Turner Bikes when he's not out on a photo mission.