Reader’s Ride(s) – Nathin’s Custom ERB Fat-bike

Nathin recently sent me a teaser photo of a VERY interesting fat-bike and now has this report on a customized ERB frame that was converted to take a 5″ fat-bike tire! Check it out!


So, I used to race for ERB racing for a number of years and used their bike platform for many 24hr endurance and WORS Races. I love the bike and it’s served me well. I have a number of them one setup 1×11 with a front shock and another SS 650b. I had a spare frame laying around and I thought about trying to have someone redue the back end to take a 5″ Fatbike wheel. Last year I really got into the Fatbike scene and raced in a number of winter and summer Fatbike races. For a bigger guy ( Clydesdale) a Fatbike really feels at home. I really don’t even ride my other bikes much anymore. That is what really pushed me to get the bike made. I wanted to try something different with the frame and have a one of a kind bike.


It really was an experimental project as I had no idea what kind of geometry I would end up with or how well everything would work, but I talked to Dave at Wiseman Frameworks and he agreed to do the build for me with the understanding this was just an experimental project. I had already machined some of the peices but he had a lot of trial & error to figure things out to match things up and fit the HUGE 5″ 2XL tire into the rear. I am amazed at what he came up with. Not only did he fit the tire in but it’s still got some extra room.

One thing we didn’t expect was the tire height. Dave did his best to keep things tight and matched up some of the previous geometry. I am sure he would have loved to do the whole build instead of just the rear to have more control of the lines. We matched the 5″ rear with an ICT 150 fork to go with a 5″ on both ends. It made the whole bike a little tall but this is mostly designed to be a Snowbike. The extra height won’t really be an issue.


Dave’s artistry with the rear S bends and clean welds on the rear is really impressive.

erb-fat-bike-2The rear will also break away to take a belt drive down the road if I decide. Cool stuff!


We painted the fork to match the rear. It’s a very similar look to the original, which I think is very cool look.

I have only had a handful of rides so far but so far the bike is really impressive! The tires have Huge traction. The wheelbase is tight so it climbs and accelerates really well especially out of the saddle. It turns well and does a decent job in the tight stuff. The more you slow down the more you feel the extra height on the tires. But for a snow bike most of the riding is not going to be that tight. The Big tires really roll over logs and obstacles well, and at speed they help keep things feel pretty stable.


The whole premise of the ERB (Energy Return Bike) is that it has an active spring that allows the bike to return some of the energy you put into the pedals back into forward momentum at the dead spot in your pedal stroke. It is sort of an inchworm type effect. In reality, it is a very subtle effect that is felt most when climbing or in a big gear.

It is somewhat like a oval chainring in that it helps you push a little bigger gear than you would normally. Also, just like the oval rings it has its fair share of doubter’s and scoffers. I think the bike design has some great engineering that has been real world tested on dynamo’s that prove the benefits.But it is a subtle difference that is not going to make up for poor training or the like. Another benefit of the design is it is active and lengthens the wheelbase slightly when you compressed so it makes the bike more stable as you stand to encounter bumps and speed sections. The bike acts like a rigid bike overall –  you really have to pay attention to feel the active spring but as a Snowbike I think it will be a great mix as I am often pushing hard and climbing on the Fatbike.

Overall, I think the bike was really a great project. I am super happy with the way it feels and rides. Dave’s part of the bike is spectacular and the whole thing turned out awesome! It’s a true one of a kind!


I’d like to give a shout out to Area 251 Bikes! They built up the bike for me and he also laced up the sick looking wheels. Zack does a great job and was stoked about doing the build for me!

Other tidbits:

  • ERB frame with custom rear conversion by Wiseman Frameworks.
  • ICT 150 fork
  • Fatlab Hubs 197/150 TA
  • Xtreme Warrior rims – Ti spokes.
  • Chris King headset
  • Thompson Seatpost
  • XT Shadow Shifter /Derailleur
  • 11-36 1180 SRAM cassette
  • 26t Race Face
  • Race Face Cinch crank & BB
  • Hope Mono Mini – Disc Brakes& Rotors
  • Silver braided hose lines.
  • XCR stem
  • Race Face silver 740 riser bars.
  • Vee Snowshoe2XL tires.
  • Eggbeater Candy SL
  • Approx weight: 32.5lb (w/tubes)


If you have a fat-bike that you modified or built up yourself that you are proud of, let me know. Just shoot me a note at! You may see your rig in a Reader’s Ride(s) feature!

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