Understanding suspension | Upgrading your Triumph modern classic

The point of a motorcycle’s suspension is to both absorb the road’s imperfections and keep consistent traction with the asphalt.  But how does it work?

To understand the principles of suspension there are 2 different things to discuss: springs and damping.  The springs used in both front forks and in rear shocks are the same type of coil springs you would find in a pen or in a mattress, just much stronger.   What prevents the spring from continuously oscillating is the suspension’s damping characteristics.

Let’s look at a VERY simplified diagram how suspension works:

There are 3 main components in this image to pay attention to; the oil, the valve and the damper rod.  The valve is on the end of the damper rod and is pushed through the oil as the damper rod is moved up and down.

As we push the damper rod up into the shock we can see that oil is passing through the valve.  The rate at which this oil passes through the valve is determined by the size of the holes in the valve and by the viscosity of the oil.

The effect is the same in reverse for most stock shocks like those found on the Triumph Bonneville.  With shocks like these the rate at which the valve plunges through the oil is not adjustable nor can the oil be changed in order to get a different amount of damping from the shock.

Now let’s add the spring into the mix.  For every action (hitting a bump and the shock compressing) there is an equal but opposite reaction (the spring returning to its original length – rebounding).

Let’s discuss the Triumph modern classic line specifically.  The Bonneville, Scrambler and T100 have absolutely no adjustability while the Thruxton only has fork preload adjustability.  Preload is the amount of tension that is put onto the springs in order compensate for rider weight.  Our TTRNO Level 1 suspension package addresses the issue of preload adjustability and spring rate.

TTRNO’s Level 1 suspension kit for Triumph Modern Classics consists of:

• Preload adjustable front fork caps
• Progressive fork springs
• Hagon preload adjustable rear shocks

Preload adjustability is the first step in getting a motorcycle set up for you, but this Level 1 kit goes a step above by installing a spring with a progressive rate.  Let’s discuss spring rates…

The above spring is a standard flat-rate spring.  These springs are  used in stock applications because they are cheap to produce and easy to tune.  They work great for setting up a bike for the track, but are not ideal for a comfortable street ride.  That’s where the progressive springs come in…

Progressive springs are wound at a different rate throughout the length of the spring.  This allows for an increase in suspension “stiffness” as more force is applied.  On the road this allows for small bumps to be absorbed under a very light spring rate and more aggressive bumps to be controlled at a higher rate.  In other words, a soft ride without bottoming out.

Suspension level 1 price with parts and installation $920.

TTRNO’s Level 2 suspension kit for Triumph Modern Classics consists of:

• Preload adjustable front fork caps
• Rider weight specific flat-rate springs
• RaceTech Gold Valve front fork cartridge emulators
• Ohlins S36DR1L shocks

What makes Level 2’s components more advanced is the ability to adjust not only the spring preload but also the rebound damping.  Remember how damping is controlled by the valve on the damper rod?  Well, the rate at which the shock compresses and rebounds can be tuned by the size of the orifices in the valve.  RaceTech’s Gold Valve kit is able to tune both compression and rebound damping by both changing the size and shape of the valve orifices and by changing a series of shims that sit on both sides of the valve.  These shims help tune damping by their rate of deflection as fork oil passes them.  For simplicity’s sake I’ll leave it to RaceTech to explain the rest:  http://www.racetech.com/page/title/Emulators-How%20They%20Work.

The rear shocks for Level 2 are made by the world-famous Ohlins suspension company.  They are preload, rebound and height adjustable with larger and more advanced valves than those used in Level 1’s Hagon shocks.  Adjustability is externally done meaning that changes in road conditions can be tuned quickly and easily.

Suspension level 2 price with parts and installation $2,300.

TTRNO’s Level 3 suspension kit for Triumph Modern Classics consists of:

• Traxxion Dynamics AK-20 Axxion cartridge kit for front forks
• Rider weight specific flat-rate springs
• Ohlins S36PR1C1LB shocks

The set of components in Level 3 is all you need to make your suspension FULLY adjustable with preload, rebound and compression.  One of the largest advantages of the AK-20 cartridge kits is that rebound and compression damping can be externally controlled unlike that of the RaceTech Gold Valve kit.  This allows suspension tuning to be as simple as turning a few screws rather than taking apart the front forks.  Ohlins’ S36PR1C1LB shocks have an external “piggy back” reservoir to keep oil temperature and viscosity consistent.  All of the adjusters on these shocks are a simple turn of a knob with no need for difficult spanner wrenches and the damping control is so intricate that any and all traction characteristics can be tuned perfectly.  The amount of adjustability provided in this kit is the same as that of full factory race bikes and these components are by far the best on the market.  Take it from me, if you want the best suspension components on your Triumph Modern Classic, this is the kit!

Suspension level 3 price with parts and installation $3,900.

Maxwell Materne

2014 WERA Thruxton Cup National Champion