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Zeroed G-1 – a radical shift in mountain bike engineering

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May 6, 2011

The Zerode G-1 mountain bike incorporates a mid-bike-mounted internal geared hub

The Zerode G-1 mountain bike incorporates a mid-bike-mounted internal geared hub

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It wasn't all that long ago that things like air-sprung shocks and hydraulic disc brakes were just being introduced on mountain bikes. Since then, we've heard about electronic and hydraulic shifting, microprocessor-controlled shock forks, and continuously-variable sealed gearing systems. What's next? Well, how about a bike with two chains and no derailleurs that is claimed to be better than a traditional MTB in four key areas? According to its New Zealand designers, that's what the Zerode G-1 is.

Shifting

The first and freakiest thing one notices about the dual-suspension downhill bike is its drivetrain. Instead of the usual single chain reaching from the chainrings directly back to the cassette, it has two – one goes from the single chainring up to a midships-mounted Shimano Alfine internal geared hub, then another goes from that back to the rear hub. On a normal internally-geared bike, the Alfine would be the rear hub.

So why choose this set-up?

First of all, there are several good reasons to be using a mechanism like the Alfine, regardless of its location. For starters, it's much less fragile than a rear derailleur, and is relatively unaffected by mud and gravel. It can also shift easily under full chain load, or even when the bike is stopped. Additionally, chains will last longer, as they don't have to slide up and down a series of sprockets.

There are also a few reasons why internal geared hubs aren't more commonly used on mountain bikes, one of them being that the axles of such hubs typically aren't as strong as those of conventional hubs – but when not mounted on the wheel as is the case with the Zerode G-1, high axle strength isn't crucial. They can also be a little heavier, but more on that later.

The Zerode G-1 mountain bike incorporates a mid-bike-mounted internal geared hub, which is...

Handling

By locating the gearbox in the frame's main triangle, Zerode has taken the weight of the shifting system and moved it from the back of the bike to the middle. Centralizing the weight like this is said to improve handling, and is something that motorcycle and automobile designers likewise try to do.

The Zerode G-1 mountain bike incorporates a mid-bike-mounted internal geared hub, which is...

Suspension

The G-1's unusual layout is also designed to deliver better rear suspension performance, as the weight of the gearing system has been moved from the unsprung rear swingarm to the frame – in other words, the part of the bike that moves up and down when going over rough terrain is lighter.

This isn't the first time that such a strategy has been employed on a bicycle. A similar setup was used on the GT iT1, for example, which incorporated a mid-mounted Shimano Nexus internal geared hub.

The Zerode G-1 mountain bike incorporates a mid-bike-mounted internal geared hub, which is...

Pedaling efficiency

A common problem on suspension mountain bikes is a phenomenon known as "pedal bob," in which some of the energy that the rider delivers to the crankset is wasted by causing the suspension to bob up and down. This can be remedied by manually locking out the suspension, although this leaves riders constantly having to choose between pedaling efficiency and shock absorption. Since they didn't have to design the G-1 around a single continuous chainline, the folks at Zerode were able to give it an unusually-high rear pivot point, which they claim eliminates pedal bob while leaving the suspension active.

"By applying MTB variables to motorcycle theory, I could find a pivot point that would result in a chassis that you can pedal without bob," the company's Rob Metz told us. "In a nutshell, using a high pivot allows the compressive effect of weight transfer to be balanced by other effects/forces within the suspension. With a 'normal' derailleur system you are a lot more restricted in available pivot positions, and bob is minimized by using chain force to restrict suspension movement under pedaling, or shocks which do a similar thing. Generally these methods of reducing bob hinder suspension performance. With the high pivot you can achieve this elegant balance of effects/forces and get a bonus of a rearward axle path which significantly improves bump absorption on large bumps."

The Zerode G-1 mountain bike incorporates a mid-bike-mounted internal geared hub, which is...

The G-1 is currently the only bike Zerode makes, with the first production frames having been completed just this February. Metz said that the gearbox does add some weight, but that he's convinced the gains in performance offset it. Although precise figures on complete bike and/or frame weight aren't available, he did tell us that through the selection of lightweight components, some riders have gotten their G-1s down to about 16.5 kg (36.5 lbs). He added that a less hefty trail bike is presently in the prototype stage.

Prospective early-adopters can buy a G-1 frameset – including gearbox, shifter, shock, chain tensioner and sprockets – via the Zerode website, for about US$3,600.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
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6 Comments

Sick bikes. I have ridden one and it IS that good.

Chris Martin
6th May, 2011 @ 10:14 pm PDT

I want one!

Lee Dilkes
9th May, 2011 @ 02:44 am PDT

This has been done before a couple of times, there was the GT as aforementioned, but the Honda G-box was always super pimp I thought...

http://www.bikeradar.com/news/article/honda-gearbox-revealed-12941/

And here's another...

http://mikelevy.pinkbike.com/blog/jezken-gearbox.html

My biggest issue with them is that they generally make it a pain to take your rear wheel on/off or change your chain and maintain chain tension, a traditional rear mech (with an anti-chain slap tensioner) make all that super-easy.

PeetEngineer
9th May, 2011 @ 07:26 am PDT

Good NZ engineering again...just a correction to the article...internal gear hubs cannot be shifted under full load...the best part of them is anyway the ability to shift gears without having to pedal...

Almoto
29th May, 2011 @ 11:18 am PDT

Hey great article, just to clarify a few points:

The main advantage with the Zerode is the suspension pivot location. This alone makes it different from the low pivot gearbox bikes like the Honda and Jezken.

Derailleur bikes pivots are placed so they are inline with the chainring so the chain pull doesn't actuate the suspension. With the high pivot the rear wheel can follow a rearward path. This lets the bike carry speed better in the rough, and makes the bike feel super stable. You just have to try one to understand.

The rear wheel on the Zerode is really simple to remove and replace. It has a standard 150x12 rear hub and a chain tensioner which makes it as simple as a derailleur bike.

Also you can shift gears under full load, it just takes half a revolution of the cranks to shift instead of instantly when pedaling normally or stationary.

I have had my Zerode since february 2010

Jason Marsh
27th September, 2011 @ 06:43 am PDT

Has anybody ridden this thing UP a hill? I'm curious how it compares. All the promo pictures show it going downhill.

Collosus
6th June, 2012 @ 08:10 pm PDT
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