22 March 2014

Monkey Ride: Neil’s Surly Krampus 29+ Mountain Bike with SuspensionFork, Belt Drive, and Rohloff SPEEDHUB 500/14

Neil built this Surly Krampus after test riding Tyler's Krampus and others we've built for customers and realizing that he needed one of his own. Naturally, he chose a Rohloff SPEEDHUB 500/14 and Gates Carbon Drive belt system for the drivetrain. The bike was finished just before Neil and Phil drove north for the Seattle Bicycle Expo, and Neil took it out for its first rides on the famed trails of the Pacific Northwest. The Krampus proved to be a very capable trail bike, with the oversize tires, stable handling, suspension fork, and dropper seatpost making for a fun all-mountain hardtail that is well suited to Neil's riding style.

We've put together quite a few Krampus builds for customers using the stock steel fork that comes with the frames, but most of these builds have had a touring or commuting focus, where the rigid fork is appropriate. The 3" wide tires that these bikes use provide some minor suspension that smooths out bumpy roads, but Neil wanted his own bike to be tailored towards more aggressive mountain biking where a suspension fork is a must - similar to the Krampus we built for the Interbike trade show: a durable ride capable of hitting jumps, rock gardens, and tight, twisty trails with ease.

Currently, there are no suspension forks available that are specifically designed with enough tire clearance to fit Surly's 29x3" Knard tires. The Fox fork that we used for our Interbike project bike had just barely enough clearance under the arch upon initial setup with low tire pressure, but after inflating the tires to a higher pressure they stretched and the front tire rubbed the crown.

Fortunately, Neil had a couple of Maverick’s DUC 32 forks in his spare parts collection, which work just fine with the larger tires. The inverted dual-crown design doesn't have an arch that the tire can contact and is internally adjustable to limit the travel so the tire doesn't hit the crown at full compression. With some custom parts from Ethan at The Flow Zone, who is the guru of all things Maverick, the fork travel was set to 100mm and the air volume was reduced to provide an appropriate spring rate. Ethan's floating piston was also added to the damper to prevent oil cavitation for more consistent damping.

The Maverick forks were always very tuneable, and Ethan's upgrade parts make them even more so. Unfortunately, Maverick closed their doors at the beginning of 2013, so the forks are only available on eBay or Craig's List. However, MRP has a soon-to-be-released model called the Stage, which was designed to clear a 3" tire and will be available with longer travel settings. Look for a future post on this fork.

In its stock format, Surly’s Krampus frame is not compatible with the Gates Carbon Drive system, so the first thing we did when we got the frame was to send it to a local framebuilder to get a tube splitter installed so the belt could be inserted into the rear triangle. We also had all the cable guides removed from the frame and re-attached triple-cable guides onto the downtube and chainstay for routing the Rohloff SPEEDHUB cables. Single cable guides were also installed along the lower right side of the top tube for routing the dropper seatpost controller cable. When the modifications were done, we sent the frame to our local powdercoater for a candy blue paint job.

For the wheel builds, we used Surly’s Rabbit Hole rims, which are 50mm wide single-wall rims to accommodate Surly's 29x3" Knard tires with cutouts in the rim bed to save weight.  These were laced up to a black Rohloff SPEEDHUB in the rear and a Hope Pro 2 EVO hub up front.  Hope's hubs can be easily reconfigured to work with a variety of axle options, including the 24mm built-in axle that Marvick's forks use.

One of the biggest advantages of the Rohloff SPEEDHUB is the fact that it can be ridden in extreme conditions and requires little-to-no maintenance. Because all of the shifting components are housed inside the hubshell, they are not exposed or susceptible to being broken or damaged from rough trails or wet or dirty conditions. This claim was certainly put to the test during the wet, muddy Pacific Northwest rides that were encountered on the trip to the Seattle Bike Expo. The SPEEDHUB and Gates Carbon Drive combo performed very reliably in these conditions - Neil was able to put the bike back on the car after a hard ride, with no thought given to maintenance, and have it ready to go at the next stop.

Neil selected a handful of other parts to add to the ergonomic comfort of the bike. Salsa’s Bend 2 bars provide plenty of backsweep to reduce strain on a rider’s wrists. ESI’s thick foam grips are cushy and absorb trail vibrations. SQ Lab’s 611 Active saddle features a flat shape that directs a rider’s weight to their sitbones and uses a rubber elastomer under the shell to allow the saddle to flex and give the rider a more round and efficient pedal stroke.

Neil’s Krampus project turned out to be a great success, and it has been riding very well so far. Read about the first rides on this bike in our recent ride report on the Cycle Monkey Tales blog, and see it it in action in our Northwest Trails Trip video. Also, look for it on the trails around the East Bay. If you would like to test ride one of our Krampuses or have us build one for you, contact us to see what we can put together for you!

Build Details:

• Frame: Surly Krampus
• Fork: Maverick DVC 32
• Headset: Hope
• Stem: Maverick Direct Mount
• Handlebar: Salsa Bend 2
• Shifter: Rohloff
• Grips: ESI foam
• Seatpost: X-Fusion Hilo
• Saddle: SQ Lab 611 Active
• Seat Clamp: Surly
• Front Hub: Hope Pro 2 EVO
• Rear hub: Rohloff SPEEDHUB 500/14
• Spokes: Sapim Race
• Nipples: Sapim Brass
• Rims: Surly Rabbit Hole
• Tires: Surly Knard
• Cranks: Race Face Deus
• Pedals: Shimano PD-M959
• Bottom Bracket: Race Face
• Chain ring: Gates Carbon Drive Belt Sprocket
• Rear Sprocket: Gates Carbon Drive Belt Sprocket
• Chain: Gates Carbon Drive Belt
• Brakes & Levers: Magura Louise Carbon
• Rotors: Magura Storm


  1. Neil, It looks like a touch of sealant has escaped from the bead in the fourth photo? Can you comment on your experience with tubeless systems for 29+, including the Rabbit Hole, Dually, Blunt35, etc. I've worked with both the RH and the Dually, and neither are simple tubeless candidates. Further, the 120tpi Knard is not a friendly tubeless tire, although it can be wrestled into submission. Thoughts?


    1. Hi Nicholas,

      Yes, the tubeless setup took a bit of work but was worthwhile. We had to cut a rim-wide strip of thin packing foam and tape it over the rim strip, with a full layer of Gorilla Tape on top of that. We then used a "ghetto tubeless" setup with a cut up 24" tire. The foam created a tight enough seal to inflate the tire.

      We have no experience with the Dually or Blunt 35 yet. We agree that the 120tpi Knard is not ideal, but it has done the job so far. We're definitely keeping an eye out for more 29+ tire options in the near future.

    2. The 120tpi Knards are amazingly thin, but we've set up several bikes with them on Rabbit Holes without too much trouble. Like with most tubeless setups, the key is building up the rim bed until the tire sits against it snugly. As Phil mentioned, we did this with a combination of foam, tape, and inner tube. It took a couple of test runs to get the thickness under the inner tube built up enough to seal well, but once we got there, the install was pretty straight forward. We always test the install without sealant first to make sure the fit is good. Otherwise, the tires are likely to burp.

  2. I have had luck with both a Blunt last year and 120 tpi Knard on a RH but it took several layers of gorilla tape and adding Stan's to get it to eventually hold for good.
    I just built a Dually up and with just one layer of tape it held air just fine, first time! A mix of Stan's and Slime may be the ticket. I really dig the new Dually rim for this reason alone.

    Neil, I'm surprised the belt drive ring fit up front on the Surly! No dimpling needed?

    I think the new inverted Rock Shox will fit a 3.0, really excited to try..

    1. I'm not surprised by your experience with the Velocity rims. We usually find that Blunts in all widths are pretty easy to setup. No experience with the Dually yet though.

      The Surly guys made some magic happen with their 29+ yoke. It's super thin around the sprocket area, so a 46T belt sprocket fits no problem, and is still quite stiff. The frame passed Rohloff's stiffness test easily.

      The new RS-1 fork looks like it will clear the large tire, but it costs nearly 50% more than the SID WC, so it will be out of reach for most people at nearly $2k!!! MRP's Stage fork should be shipping any time and will clear a 3" tire at a more modest, but still expensive $969.

  3. This comment has been removed by a blog administrator.