Well Hung and Double Sprung

Updated 9 February 2010

During the initial 'wild-west' period of full suspension development, brands devised innovative solutions to trump their competitors and seduce the mountain biking public. The resultant imbroglio of diverse designs was utterly confusing. Some worked quite well, many were a disaster zone of flawed performance and high maintenance. The dust has now settled on these turbulent times, with the main players now evolving variations around two main threads: single pivot and the four bar linkage. So here's an (over) simplified summary of the generic full suspension designs. And to keep it really simple I've restricted my musings to XC and lightweight freeride bikes

Single Pivot

A basic swing arm attached to the frame at only one point.
Pros: A single grunty pivot for good reliability and minimal maintenance, the stiff rear end and relatively light, and you get good performance for modest price.
Cons: The pivot point placement determines its behaviour. Above the chain line causes the rear wheel to dig in as you pedal - better traction but locks out the suspension action. A lower pivot point retains active suspension under power but pulls the wheel away from the dirt - providing less traction. Choose your poison. A lock-out switch with a low pivot position is a tidy solution. Also, the single pivot and shock take the brunt of any sideways or twisting force, so long travel bikes require a heavier coil-spring shock.

Four Bar Linkage

A more sophisticated solution that includes 'horst link' and Virtual Pivot Point (VPP) variations.
Pros: The suspension is always active, ie. doesn't lock out under power and is less affected by braking.
Cons: All those pivots mean more maintenance and more to potentially go wrong on the trail. Anticipate a minor fiscal haemorrhage when replacing the multitude of sealed bearings every couple of years.

Show me the money

Before you rush out and buy the 'editor's choice' full suspension mount of your dreams take a moment to balance the ledger. Full suspension delivers a plush ride and lets you raise the bar on technical terrain. But you pay around a NZ$1000 premium over a comparable hard tail. It will weigh about 20% more and demand additional maintenance to keep the pivots good 'n' tight. That said, for most riders in most conditions, a lightweight full suspension bike is a good thing.

Travel, weight and price form an interdependent triangle. 100 to 125mm is the standard for cross country - and will weigh between 24lbs and 32lbs. An 'XT' spec'ed all day riding/occasional racing set-up should tip the scales at 28lb and lighten your wallet by upwards of NZ$4000. All-Mountain bikes typically provide 160mm travel with a weight range of 30-40lbs.

Platform shoes

The recent advent of stable platform rear shocks has revolutionised full suspension designs. When set up correctly (best to read the manual), these intelligent shocks provide a plush ride with minimal pedal induced bob. Combining this technology with simple designs has hugely reduced the price of full suspension bikes that really work and don't weigh a tonne. The shocks are so hugely popular that it is difficult to buy a bike with an old-school standard shock.

No Free Lunch

The cost of using stable platform shocks is the loss of fully active suspension. Dialling out pedal induced bob also prevents your shock from responding to small bumps - both when climbing and descending. Salvation comes in the form of the Virtual Pivot Point (VPP) - used on most models from Santa Cruz and Intense. They consistently rate at, or near, the top of gear tests conducted by magazines around the globe. Two links enable the rear axle path to follow a modified 'S' path. The mechanics are complex, but the result is fully active suspension without pedal induced bob. Regretfully VPP comes with caveats as well - a hefty price tag and extra pivots that require additional care.

Zen Pedalling

While manufacturers promise an absence of pedal induced bob, this will never be realised if you stomp on your pedals. The antidote is to pedal in smooth circles Grasshopper, while keeping your upper body nice and still. Check out Tech Tips: Lesson Four, Climb Like a Billy Goat

Here piggy piggy

It's unlikely you'll end up with a lemon if you stick to the established brands, but different models all have their relative advantages and compromises. Check out reviews on mtbr.com and talk to ya mates. Many shops and importers offer a test ride service. So once you've got your short list, thrash a few around some familiar track before breaking open the piggy bank.

May the force be with you.