Posted on Leave a comment

FZ-10 Stock Shock Technical Review

The jury has deliberated and the verdict is in on the shock. Meh. In fairness, it’s leaps and bounds beyond that of the ‘lesser’ FZ’s. By a long shot. But that shouldn’t be a surprise to anyone who hasn’t been living under a rock for the past three years.

First, the shock is identical externally to the R1 with one exception: The R1 has ride height adjustment while the FZ-10 does not. Despite what we’ve read in the press, the FZ-10 shock has the same spring according to our measurements. Both bikes use a spring that spec’d out at ~475-480 lb/in. Makes you wonder what they were thinking since the FZ has a heavier steel subframe, factory option luggage, and a greater probability of a pillion rider. Really – have you seen the R1’s seat? I’d rather walk.

Our prototype shock is being built next week, and we’ll start testing with a 550 lb/in spring rate for a 195 lb geared rider. Pro racers typically run 600-650 depending on the circuit and track conditions, so that should give you some perspective on how poorly sprung the bike is. So I’ll reiterate: if you weigh more than about 150 lbs in gear, the stock spring is too soft. And really, that weight is being generous. The pain you’re feeling on large bumps is the bike plowing into the bump stop as it bottoms out. A heavier spring will fix this issue.

The damping is another matter altogether. Penske ran the shock on the dyno yesterday for us.

The results are interesting. Well, maybe not since the performance is identical to the R1. But either way, there are some points that are worth mentioning. We’ve found a lot of people ‘feel’ something makes a difference, but the data doesn’t always support it. The placebo effect is real. Let this be our guide.

There’s a lot of stuff to make you cross-eyed here, so bear with me. I’ve left the image at full resolution and quality, so feel free to click on the image to zoom in.

  1. The range of adjustment is shown in the top/center. This highlights the range of adjustment you get and full open, full hard, and mid point on compression and rebound.
  2. The graph immediate to the left (still on top) is our spec for the FZ-09. This shock dyno curve was chosen to highlight a known ‘good’. Plus, the spring rate that shock was valved for is very similar to our target for an average weight FZ-10 rider.
  3. The next row down shows runs to highlight the variance that each adjustment affords. Low speed compression on left, rebound on right.
  4. The bottom three graphs show the high speed compression test. On the left, rebound was full soft, LSC was full hard. In center, both rebound and LSC were full hard. On right, both rebound and LSC were full soft.

Great. Translation?

  1. First, take notice of the rebound test plot on the center right. For those who are unfamiliar with these graphs, the positive sloping lines are compression and the negative sloping lines are rebound. Since the rebound adjustment was varied with run (4 click increase per run), you’d expect to see some increase in rebound damping on those negatively sloped lines. However, you’ll also notice that the compression curves varied as well. Why? Simple. The jet in the main piston effectively increases compression damping when rebound is increased. Conversely, compression damping is reduced as rebound is reduced. It’s important to note that the rebound adjuster’s effect on compression damping is actually greater than the LSC adjuster. It’s hard to explain without showing the internals, but take my word for it. The numbers don’t lie.
  2. Note the HSC runs across the bottom. You’ll see that the individual runs overlap on each sheet (six runs in total). This is because the HSC adjuster doesn’t actually do anything in the speed ranges we’re able to measure (10 in/s is pretty fast). As mentioned above, the rebound and LSC adjustments have a larger effect.
  3. Now, divert your gaze from the shape of the curves to the actual values at various shaft speeds. You’ll notice that the overall range of adjustment is limited and the magnitude is substantially less than the FZ-09 control shock.

Blah, blah, blah…are we done here? The take away is this:

Spring – too soft for most riders.
Rebound – sufficient range, but tied to the compression circuit.
High speed compression – minimal/no effect.
Low speed compression – works, but is overshadowed by the rebound adjustment.

Re-springing and revalving isn’t out of the question, but we’re still limited by the design of this shock. The relationship between rebound and compression won’t go away without substantial modifications.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.