Some Content Driven by Thumper Talk

Hey everyone, thought I would do something different. I don't have time to engage in the forums, but every now and then something  can get my attention. Here is a good one! Read the post first then, you can read my reply.  I did not post to TT, as I did not want to get caught up in the drama.

Thumper Talk Link

Hi guys this string was called to my attention by a friend, and I felt compelled to speak to some of the points.

There are a lot of details and variables being mentioned that all need in some way to be qualified. The case can be made in case “X” that a tuning aspect is not required, but without the qualifying details it would be needed for “Y”, and “Z”.

For me suspension design is not a one-time highly conditional variable. We need bikes to work better, broader, not more specific and more conditional. To have a set-up that a customer will be happy with over a broad range of conditions is the goal. Final disclaimer, while all my points are made to support my points, I am fully aware that one rider’s joy is another rider’s poison. Heck I have emailed back and forth with some members of this very conversation who feel the air fork is awesome! I’m not here to question one man’s judgement. What works for them works for them, but as a tuner who works with riders and other tuners the world over I can say I have a “perspective” about what the majority of riders will prefer.

So let’s discuss some details:

The Huck valve is not just a bottoming control device. It’s a way to alter the overall set-up so that it will allow for fewer compromises in the variables that relate ride quality, while still managing bottoming control effectively. I detect in the reading of the posts that some feel there is no compromise, that a “perfect set-up” nearly exists. So why would I need a Pro-Perch, or a Huck Valve. It does not exist in my opinion (this magical set-up), and it still does not even with a Huck Valve and a JBI perch, or N10Z set-up. We are all trying to improve the equation, by dividing work into more and more segments that can be optimized based on the volume and pressures or forces they regulate. To say that a Huck offers no benefit would be the equivalent, of saying that the 1990’s fork would not benefit from a midvalve. Don’t laugh in the late 90’s and early 2000’s I was on this very forum (and others) arguing with people about how a tuner can make a better fork performance with less compromise by using that part of the system, and some insisted that it was possible to do it all through the base valve. History would show the midvalve was the correct choice in further segmentation.

In regards to set-up.

Of course all aspects of the job need to be managed! If your fork is too soft, then a Huck Valve, Pro-perch, or XZY won’t make it better! Nor will it if your fork is too stiff or simply not optimized (all parts working together with an overall set-up in mind). So like all things to use it best, it requires an investment in time and understanding of its best use that is often not the result of a one-time test.

Pro Perch: is a great product that I had the privilege of contributing to in its development. I use it with many of my own professional level customers; it’s not best suited as a bottoming control. Its best application is as supplement to the midspeed compression damping, specifically with the ability to time itself independent of the top 1/3 of the stroke. So while it impacts bottoming control that’s not its ideal range of influence. Asking the ProPerch to do what the bottoming control device is designed to do would be like asking your needle clip in carb to richen the main. They impact each other, but they are not doing the same work.

Oil level:

It’s true, I don’t like air spring. The problem with the air spring is that it is highly progressive. As some have pointed out, air springs can impact the mid part of the stroke, making the fork firmer. They will claim that you use the forks air spring to support the fork in the middle and ok, I’m fine with that. But I ask rhetorically what happens when a rider is aggressively coming into a corner and hitting large bumps? What happens when this occurs as the rider is going down a hill?

Now ask yourself what is happening to that very force each 10mm? Pressure is a function of volume right? So early on nothing is happening but later the gas pressure rise is occurring at an exponential rate. Quickly, because the volume change is accelerating with respect to linear rate of fork compression, the small boost to the force in the middle that supports the rider becomes a massive force (By the 2/3rd of the stroke). What happens when you’re hitting the bumps now?

Visualize a track and some bumps in the middle of a long straight. Picture 2 bikes, one tuned by tuner X, and the tuner Z, you can see the swagger of 2 tuners talking about their magic settings and how well they work over the bumps. We might look at the same bumps and talk about valve area, and what they used for mid valve lift and these are all very valid points, and we will likely not talk about the air spring. Because at this point the air spring is not a factor, the fork is in the top ½ and it won’t really have an impact. Now the two showmen result in a dead heat, each performing well. But as the bikes and riders leave the straight and enter the corner into a downhill with braking bumps what happens next may illustrate my point. Brakes are applied, the bikes own weight transfers further forward, and guess what, tuner x ran a lower oil volume, but tuner z, did not. He ran a high one. Tuner z’s bike is harsh. Why? How? The bumps are no bigger than the ones on the straight! It’s pretty simple, the fork is a sum of the forces and we have an exponential force in the air spring. Whenever anything is multiplying what starts low can end up huge and that detail is only aggravated as the fork uses travel. So simply put, air spring can become the largest single force in the system. Bigger than friction, the main spring and the valving combined and it’s highly dependent on position! Need examples? SSS KYB fork verse PSF, or TAC, or even the commonly held position about the WP 4CS, that’s air spring driven midstroke harshness! Valving is not exponential! It can deliver a strong force at relative low speed and only modestly more later, but pressure as function of volume only increases! Stiffening the low speed might help by delaying arrival in a deeper position, but you will also increase transfer of energy to the rider in the exchange, and it might be a better option, but it won’t compete with a well-balanced set-up in wide range of conditions with nothing radically progressive in the 50%-85% range.

I hope this at least clarifies my position, and intent with respect to what I designed my parts to do and how we approach tuning with them.

Thanks for reading.

Jer