Tested: Progressive Suspension

WHEN I bought a 2010 Dyna Streetbob custom I was expecting my Harley to offer a plush ride. The Dyna is fitted with duel spring shocks on the rear.

What I did not expect was blown fork seals and a ride that that sent a spine shattering jolt up my back when I hit a bump in the road. After only a short ride I would get off the bike reaching for the painkillers. The bike felt and handled like a hard tail. I found myself picking a line around anything I thought might jolt and shudder the bike.

This was less than ideal as I have a lower spine fusion! I wondered how long the new toy would last before it was up for sale. I played around with the rear suspension settings but with little joy. The seat was a low profile designer seat and I thought changing that might help. I did not want a big thick seat as I felt it would spoil the line and look of the bike; it only took a couple of weeks riding to forsake the aesthetic option for something more practical.

The front end tended to dive under braking, I put this down to the blown seals and Harley handling. I have a larger 21 inch front wheel which did not hold the road very well and seemed to skip over smaller bumps.

I noticed a small oil patch on my garage floor but could not figure out where it came from. I then noticed some oil on the rear rim. Running my hand over the shock I found the source of the oil. I removed the lower shock bolts and the shock fell into three pieces on the floor with oil all over. I took the shock to a local dealer who said he had never seen a shock fail to that extent.

As the front forks were blown - and it’s always best to upgrade the front when you upgrade the rear - I ordered a Montotube fork kit.

The progressive Monotube was developed from sports bike R&D. This is a cartridge that features a gas charged monotube damper that runs in one fork and a custom tuned progressive fork spring that sits in the other fork. Progressive means the spring is wound with smaller gaps on the end then widen through the length of the spring. This helps iron out smaller bumps smoothly and the larger gaps sort out the bigger bumps. This makes for a smoother ride.

The kit replaces all the internal parts, uses far less oil with fewer service intervals.

I replaced the rear shocks with slightly lowered 444 Progressive shocks. They come in chrome or black. The black was a nice touch with my matt black bike. The 444 is the next best shock to the top of the range 970, the 970 has a high pressure gas monotube on the shock and I thought this would spoil the minimal look and style of the Dyna. The 444 comes with something they call Frequency Sensing Technology (FST) for its unique ability to dynamically adjust damping as you ride. This technology allows the shocks to sense the frequency of a bump and automatically adjust damping.

The shock has nitrogen charged hard anodised aluminium body, the deflective and FST valves sit inside the body and dynamically adjust the damping.

The 444 also feature the progressive rate spring, you have a choice of standard or heavy duty spring. You have the option of black or chrome finish. I went for the standard spring in black.

The shocks have a simple preload adjustment that you can do by hand. If you plan to carry a pillion you can just add a couple on turns on the adjuster.

The upgrades transformed the bike! The new fork kit almost eliminated the front dive.

The standard fork springs don’t offer adjustment; you can only add more oil or stronger springs. The kit offers adjustment options. A top mount threaded preload adjuster allows for fine tuning with a simple twist of the cap.

The front end feels connected to the road with more grip and control. The wheel does not skip over the small bumps now and when I ride over a man hole cover the front feels planted and secure. I don’t have to pick lines around man hole covers anymore.

The rear shocks offer a plush ride and the bike absorbs all the small bumps without you realising that they are even there. When I have hit a few bigger bumps I have not had that spine crunching jolt.

Overall, the bike has far more front and rear end stability and cornering is far better and much more fun to ride.  

444 Series shocks: Price: $624.95 (£403)

Monotube cartride kit: Price $399.95 (£258)