This graph shows the damping profile of a shock using a single orifice for its damping, the curve is exponential and has a rapid increase in damping at high shock movement speeds. You can vary the curve by choosing a different sized hole, but the curve is then fixed when on the road. I refereed to this as single rate but I should have said single orifice.
The issue with this setup is the steep curve at high speeds, if you have bumpy roads you pick a larger orifice but then lack damping on smooth surfaces. So which sized hole you choose is a compromise.
This is the Wibers and Nitron 3 set up, there are effectively 2 stages to the orifice hole, as the speed of deflection increases shims are forced open to increase the size of the hole and this removes the exponential rise in the damping forces.
This allows you to pick 2 damping curves, one for use on smooth roads and the second to kick in when the going gets rough. The first curve is as a single orifice but at the point the shims are forced open the effective size of the hole is increased and so the tall end of the curve is replaced by a lower rate of damping increase.
There are 3 types of VALVES, not holes, in any GOOD aftermarket shock, They are Progressive, Linear and Digressive.
Your artwork shows the damping curve to be Progressive, (green lines) something very rare to see in an Ohlins motorcycle product. Ohlins prefers a Linear valve for most MOTORCYCLE products.
With the curve you are showing, no wonder you need something to reduce damping.
This graph shows the three valves more the way they really are, not steep arcing lines.
AccuTune Off-Road’s Experience: Our Founder and author of this article, Ryan Raker, has been designing, tuning, and manufacturing shocks with digressive, linear and progressive damping curves since 2001. During that time he used state of the art shock dyno’s to design and/or tune premium shocks...
accutuneoffroad.com
When I use these terms, Progressive, Linear, Digressive, it is in discussing the design of the valve, as I think is the case with most suspension people. Of course you can use the terms anyway you want.
When talking about a shock or fork that uses a mechanism, that reduces the amount of damping when a higher load is applied such as a bump, that task, as you describe it here is done by a blow off valve, uncommon in a rear shock, very common in a front fork, there the type most used is referred to as a mid valve.
The reason it is used in a fork is due to brake dive, when you are using the brake hard, the front suspension travel is being used up, now when you hit a bump, it is transfered to the rider, this is reduced by allowing the damping to be reduced by the Midvalve or blow off valve. The advantage of the midvalve is it is a shim stack that can be adjusted. We have had this available to us for 20 years.
The newer Ohlins cartridge kits, and they are always getting better, reduce the brake dive better than you an imagine.
Your top graph describing a HOLE metering oil, is what very inexpensive forks and shocks use, or very old.
We like to call those REALLY GOOD $10 shocks.
You Said "This is the Wibers and Nitron 3 set up, there are effectively 2 stages to the orifice hole, as the speed of deflection increases shims are forced open to increase the size of the hole and this removes the exponential rise in the damping forces."
Of course as the speed of Deflection increases the shims that control the damping are going to flex more and allow more oil to pass thru.
How is that "2 stages"? That is how every shock with a valve and shim stack work, nothing special there.
Here is a link to Pictures of a Disassembled Nitron shock, (scroll down to see it) Looks very conventional to me.
www.bikehps.com
