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Bike Check: George Chapman's Zerode Taniwha - A Gearbox Bike Without the Gearbox

May 24, 2024
by Mike Kazimer  
George Chapman s Custom Zerode Taniwha

These days it's fairly common for slalom and speed & style competitors to take a trail bike and modify it for their specific needs, typically by running a smaller frame size than usual and switching to 27.5" wheels front and rear. George Chapman has taken things a step further with his Zerode Tanhiwha, which is usually sold with a Pinion 9-speed gearbox. There's not really any need for shifting during a slalom race, so George removed the gearbox and transformed the bike into a belt-driven singlespeed with some help from a Williams Racing Products bottom bracket.

Finding the right gear ratio took a fair bit of experimentation, and the build also involved getting out the angle grinder to make a new mounting plate for the chain tensioner. In this configuration, the Taniwha has 140mm of travel and a 150mm fork, although it would take a pretty massive impact to use all that travel given the bike's current setup - the fork's air pressure is maxed out, and the 600 lb spring is extra-stiff.

George Chapman s Custom Zerode Taniwha
Bike Details:
Frame: Zerode Taniwha, size small
Fork: Fox 38 / 150mm travel / max pressure
Shock: Fox DHX coil, 600 lb spring
Tires: Maxxis Minion DHF / Maxxis Ardent / max pressure
Brakes: Magura MT5 / 203mm rotors
Drivetrain: Belt drive singlespeed w/ WRP bottom bracket
Bars: Burgtec Ride High 50mm, 740mm wide
Stem: Burgtec, 42mm

George Chapman s Custom Zerode Taniwha
A 600 lb spring isn't plush, but it helps take the edge off bigger hits.

George Chapman s Custom Zerode Taniwha

George Chapman s Custom Zerode Taniwha
The Pinion gearbox has been removed to save weight and simplify things.

George Chapman s Custom Zerode Taniwha
A WRP bottom bracket and a custom mounting plate make this setup possible.

George Chapman s Custom Zerode Taniwha
Might be time to track down another chainring bolt.

George Chapman s Custom Zerode Taniwha
Factor hubs.

George Chapman s Custom Zerode Taniwha
George runs 203mm rotors front and rear so that he can still use the bike for park laps.

George Chapman s Custom Zerode Taniwha
A look at the non-driveside and the WRP bottom bracket setup.

George Chapman s Custom Zerode Taniwha
High bars make back flips easier (according to George), and there's enough brake housing for bar spins.

George Chapman s Custom Zerode Taniwha

George Chapman s Custom Zerode Taniwha
Conditions were a little soggy, but they dried out enough for slalom to go off smoothly.

Author Info:
mikekazimer avatar

Member since Feb 1, 2009
1,752 articles

  • 48 1
 While it's a cool idea; it's kinda like taking 3 left turns to make a right turn.
  • 32 0
 Didn’t UPS figure out it’s better (safer/cheaper) to take three right turns instead of a left?

Just sayin…
  • 7 0
 @cpscotti: I mean the fuel savings for the idle time at the left light is a little different than this, but yes..yes they did.
  • 11 0
 @cpscotti: Naw, a Kiwi on a Kiwi bike in Aussie, we drive on the left down here, so the left turns are more appropiate
  • 8 0
 some people are not ambi-turners
  • 2 0
 @mattmatthew: love the kid like a son
  • 24 1
 I want to see this for e bikes. Allowing an extension of life for old frames when the battery or motor dies, or for uplifts, or allowing you to take the bike on planes, or go for a pedal while the motors being warrantied
  • 6 0
 I reckon they should make whatever Martin Maes was running on that orbea non-e-wild publicly available
  • 13 0
 that's a crafty idea. there's lots of premium ebikes out there that'll be worth dirt once the drive components are unsupported. and the storage capacity of the unused downtubes would be great for bike camping setups.
  • 6 0
 i saw something similar the other day:
  • 2 0
 @90sMTBEnjoyer: including the new linkage rocker arm that gives it 200mm rear travel!
  • 17 0
 3 chainring bolts to save extra weight.
  • 1 0
 Well spotted
  • 12 0
 Inflation is screwing everyone.
  • 4 0
 You save weight and get the same effects of the Ochain without the $300 price tag.
  • 14 0
 Beltring bolts, if we're getting picky.
  • 8 1
 That’s just so damned cool.
  • 3 1
 Entirely logical.

If this fellow has backing from Zerode, (or, it's just simply what he's got to use for DS) , and doesn't want / need the gearbox, well a Hanger for a conventional BB is 'it'.

I've had a few people want an adaptor for my Pinion frames, so, I'm happy to oblige. Just pay me for it.

And, if I am all healed up in time for next years Old Bastards World Championships (again) at Cairns, well, I'll have a Hanger and d\Derailleur gear set up with me, in case my Pinion Carks it, if I don't have a spare Pinion GB at that time.

I'll check out WRP for these - I've enough work to do as it is, and if it's sold / is affordable, I'll refer people to them.
  • 10 0
 You wrote this comment without including any context of who you are or what you do or a link to what you do make….
  • 2 0
 You could easily do this with E bikes, optons for discontinued E bikes with no motor options or redundant batterys, parts etc, either bin or re cycle a perfectly good E frame or fit a geabox or conventional BB and cranks, perhaps make motor mounts as a standard then 3rd party manufactures could make mount plate adapters to allow us the choice to pick what we want.
  • 2 0
 Soooo... Basically it's a belt driven single speed bike, could it have been done with any "chain transmission" based bike by just converting the chainring and rear cog to belt friendly parts?
  • 3 0
 Whoa, reverse engineering…
  • 1 0
 Factor is dead. Long live Factor! They made some great products and while the name is gone you can still get that stuff rebranded from the parent companies Novatec/HT.
  • 2 0
 @xy9ine: You know what would make even more sense, just having a replacement motor and battery.
  • 1 0
 Why does he want to save weight. Everyone Lewis telling us heavy bikes are better
  • 2 1
 Why coil out back, I wonder?
  • 6 4
 Cause coils are rad noob! Less servicing too.
  • 1 0
 They're never 38s with a square arch.
  • 1 0
 a new storage bay or coffee grinder i hope.
  • 2 1
 This is extremely rad.

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