OHLINS TUNING GUIDE
OVERVIEW: WHAT THIS GUIDE COVERS
This guide pertains to Öhlins ‘Road and Track’ kits, Öhlins ‘Dedicated Track’ kits, and 3DM Motorsport ‘TrackDay Series’ kits.
Suspensions are VERY complex. Please note this guide is intended to be a BASIC tuning guide and covers information at a relatively high level. Just like there are several ways to brew coffee, there are several ways to setup suspensions. It is ultimately the drivers responsibility to figure out what works best for them.
- Understanding how the dampers work
- Setting up ride height
- Adjusting the clicker knobs
- Documenting your setup and changes
UNDERSTANDING HOW THE DAMPERS WORK
It is important to understand WHAT the shocks (dampers) are doing in order to understand how to make changes to the handling characteristics of your car.
Dampers create force to control the springs and the dynamics of the suspension/chassis. When the suspension moves we measure it by velocity. When the suspension compresses it is called “Bump” and when the suspension droops it is called “Rebound”. Turning causes the car to roll (outside tire compresses and the inside tire droops) and this is typically a low velocity occurrence of the suspension (aka low speed). Hitting a bump or curb is typically a high velocity occurrence (high speed).
So the more adjustment knobs the better right? The tendency is to want a damper that has a knob for every function… low speed rebound, low speed compression, and high speed rebound/compression so we can fine tune but unfortunately its not that easy. We see it over and over and over again where people install complex dampers, get lost with knob turning and end up NEVER adjusting them ever again. The best laid plans get derailed by complexity. Its important to keep it simple and keep good notes.
Öhlins dampers are competitive, not complicated. They are setup out of the box with force curves oriented to YOUR car and towards performance driving. The clicker predominantly adjusts low speed rebound (the most important) and low speed compression is matched as necessary. This low speed adjustment helps dial in the “dynamic balance” of the car, in other words, how the car reacts when you turn. It also helps dial in grip through the turn by keeping the tire contact patch optimal over small undulations and ripples in the pavement. The Dual Flow Valve (DFV) replaces the need for high speed adjustments, it allows the damper to soak up bumps without upsetting the car and lets the tire return to the ground quickly.
What about range of adjustment? There are typically two different use cases for aftermarket dampers and their adjustments: combo street/track cars, and dedicated track cars. It sounds enticing to buy a damper that can control a large range of spring rates to encompass multiple use cases but this approach is a major compromise. They typically end up with a small adjustment range for the springs you settle on limiting your adjustability and tuning capabilities from track to track. Everyone is a little bit different, or perhaps a lot different, which is why Öhlins offers two distinct kits, the ‘Road and Track’ and ‘Dedicated Track’, each of which are capable of handling a window of spring rates for their particular use case. No need to have your dampers re-valved if you want to make small spring changes to suit your driving style or car setup.
SETTING UP THE RIDE HEIGHT
Before setting up your ride height, we suggest reviewing the RIDE HEIGHT ADJUSTMENT article.
Set the spring pre-load first
In this article we will go over ride height and how it is one of the most critical settings on a suspension with respect to shock travel. Ride height also affects suspension geometry as well, which we will discuss in a future article. First, let's discuss a few basic topics related to ride height: bump, rebound, stroke travel and spring pre-load.
IMPORTANT TERMS TO UNDERSTAND
Bump: The compression of the suspension in relation to the chassis. Bump occurs when the suspension is compressed either from chassis roll, which occurs on the "outside" suspension, or a physical bump on the road surface pushing the suspension up.
Rebound: The extension of the suspension in relation to the chassis. Rebound occurs when the suspension is extended either from chassis roll, which occurs on the "inside" suspension, or the wheel returning to the ground after being compressed from hitting a bump in the road surface.
Stroke: The amount of distance the damper can move through rebound and bump. Total stroke distance is measured from full rebound to full bump. This is an important measurement because at ride height, we need to have sufficient travel for both bump and rebound.
RIDE HEIGHT VERSUS DAMPER STROKE POSITION
Let's say we have a scenario where the damper has a total stroke of 5 inches...
Ideally we want the damper to be compressed roughly half way at ride height allowing for approximately 2.5" of bump travel and 2.5" of rebound travel. How much it compresses will be determined by the weight of the vehicle and the spring rate. Other factors such as motion ration, bushing spring rate also play a factor. With a road and/or track car the spring rates are typically soft enough to allow sufficient compression. However, on a racecar you will have a high spring rate and a light car which may not compress the damper sufficiently. There are ways to design the spring package around this which we will cover in a future article.
However, what if we have an ideal ride height but the damper compresses 4 inches where you only have 1" of bump travel and 4" of rebound? This is VERY common with typical dampers and is not good as you will bottom out frequently which will cause handling problems and potentially damage your suspension. (See bump stop section below for more details) The only solution is to raise the spring perch or add spring spacers but unfortunately our ride height will then be too high.
IDEAL RIDE HEIGHT ADJUSTMENT METHOD
It is possible to adjust ride height without using the spring perch. Instead of changing the ride height with the spring perch, with Ohlins you can change the location of the mounting point of the suspension on the damper itself. Damper stroke position problem solved! With this method, you can now precisely set the stroke position using a combination of spring height and spring perch location. Then precisely set ride height with the location of where the suspension mounts to the damper. Win Win. Now we can get into more advanced suspension setup such as corner weight adjustment, bump stops, etc.