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Your Ibis Trans–Fat

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Super sweet and good for you too.

Ibis Trans-Fat
Ibis bike underline

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Ibis bike underline

Our most versatile bike, the Tranny 29, just got a lot more versatile.

Introducing the limited edition Trans-Fat

The Trans-Fat utilizes the Tranny 29 front triangle, an all new rear triangle and a couple of clever bits to make it compatible with fat bike fitment standards.

Here are a few of the features, and check out the details tab for a lot more information.


  • 3.25 lb Carbon monocoque frame
  • Designed to work with 120mm forks
  • Works with 4" tires
  • Geared or Singlespeed compatible
  • Gates Carbon Belt Drive compatible
  • Internal routing for dropper posts
  • Clean, versatile multi-option internal cable routing
  • Tapered head tube (suitable for various Cane Creeks & Chris King InSet 3)
  • 100mm BSA thread bottom bracket (with provided BB92 adapters)
  • 177mm x 12mm Maxle rear axle
  • 160mm carbon fiber post mount rear brake mounts (we recommend 200mm/180mm rotors)
  • Headset: IS ZS44/28.6 | EC49/40
  • BB height w/ 4" Jumbo Jim tires: 315mm
  • Geometry measured with 531mm axle to crown fork and our 3mm crown race

Reviews / Awards

The Trans-Fat uses a Tranny 29 front end and a all new swingarm with a couple of custom pieces that allow you to do the transition from 29er hardtail to fat bike.

The Trans-Fat falls into the category of a very sporty fat bike. We use 4” tires on the Trans-Fat, which are considerably lighter and livelier than the 5” tires found on many fat bikes. We want the Trans-Fat to be responsive and fun, whether on sand, snow or dirt. The 4” tires let us put a much shorter than typical chainstay on the Trans-Fat. We’ve slackened the head tube a bit from the Tranny 29, so the bike isn’t twitchy, which is a common complaint of fat bikes our test crew has ridden.

The Trans-Fat is available three different guises:

  1. As a complete fat bike built with a our XT 1X kit and a RockShox Bluto fork
  2. As a frameset
  3. As a retrofit kit which will convert your existing Tranny 29 to a fat bike.

Trans-Fat Retrofit Kit

The Trans-Fat kit consists of:

  • An all-new swingarm that accepts 4” fat bike tires and a 177mm x 12mm Maxle through axle (SRAM standard)
  • 3mm thick crown race
  • BB adapters to fit 100mm BSA bottom bracket.

Note that you'll also need a few other things to complete your conversion, like at RockShox 120mm Bluto fork, a set of 4" fat bike wheels, a crank to fit on the 100mm BSA bottom bracket, and some warm clothing. Unless you're riding it on the beach, in which case, you'll need a speedo or bikini.

The Trans-Fat Retrofit kit has a US MSRP of $699.

Show/Hide the Geometry Overlay

Measurements with 120mm RockShox Bluto (531mm axle to crown)

Nominal Size   Medium Large X-Large
Seattube A 17” (432mm) 19” (483mm) 21” (533mm)
Toptube B 23” (584mm) 23.8” (605mm) 24.6” (625mm)
Headtube C 3.7” (94mm) 3.9” (100mm) 4.5” (115mm)
Chainstay D 452mm 452mm 452mm
Seat Angle E 72° 72° 72°
Head Angle F 70 ° 70° 70°
Wheelbase G 1097mm 1117mm 1149mm
Stack 630mm 636mm 651mm
Reach 379mm 400mm 424mm
Trail 80mm 80mm 80mm
BB Height (Jumbo Jim's) 315mm 315mm 315mm
Sizing Guide (height-inches) 5'4" - 5' 9" 5'9" - 6'2" 6' - 6'6"
Sizing Guide (height-cm) 163 - 175 175 - 188 183 - 198


  • Seat Post Diameter 31.6mm
  • Front Derailleur Just say no
  • Headset Mixed Tapered (1.5" EC49 lower, 1.125" ZS44 upper)
  • Bottom Bracket 100mm BSA
  • Rear Brake Post Mount 160mm
  • Rear Axle 177 x 12mm

Sorry, no build kit info for the Trans–Fat.

All action photography © James Adamson / Drop Media

If you live in snow country, you’re used to changing from your summer to winter tires on your car each year. The Trans Fat conversion is exactly like that, only completely different.

Summer to Winter

To move from Tranny 29 to Trans Fat, you need to first have a Trans Fat kit ($699), and a Bluto fork, or similar Fat Bike fork with 120mm of travel and an axle to crown of approximately 531mm. You’ll also need a set of 4” Fat Bike wheels and tires (177mm Rear Maxle)

Once you have that in hand, the process is simple.

  • Remove the wheels from your Tranny 29
  • Remove the swingarm and bottom bracket.
  • Remove the fork

Refer to our online instruction book if you have any questions.

  • To change the bottom bracket from the PF92 of the Tranny 29 to the 100BSA of the Trans-Fat, take the bb cups you removed from your Tranny 29 (provided you’re using the same spindle diameter). Install the bb cups into the provided adapters. Teflon tape or grease can be put on the threads of the bb cups. We don't want the adapters to spin in the frame, as that would erode the carbon and make a poor press fit. This is why we want you to put the bb cups into the adapters first. The adapters have indents that fit Park Tool HCW-17 (a fixed-gear lockring wrench). Tighten the adapters to a normal torque setting and press in the cups.
  • The adapters have 24mm of press depth and fit very firmly into the frame. In other words, they don't budge once installed properly.  Since we make the frame that the adapters fit into, we have total control of the frame ID and the adapter OD. The fit is excellent. No creak, no worries.
  • Install the swingarm, be sure to use carbon assembly paste on the mating surfaces of the slot machine. Refer to our instruction book page 29 for more info.
  • Assuming you’ll be building the bike geared and not single speed, tighten the Slot Machine to 25 N-m.
  • The final piece of the puzzle is to install the included 3mm crown race onto the fork, in order to get your geometry just right.
  • Now it’s time to reassemble the bike as normal, and hit the sand, snow or dirt.