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Single damper adjustments that control more than one factor

Suspension Tuning & Optimization

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Discussion and questions related to the course Suspension Tuning & Optimization

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I've gone through Damper Basics, and so far it seems like it seems like it's assumed that if you have an adjuster, it only adjust one aspect (eg low speed rebound) and the others are fixed and independent of that adjustment.

The coilovers I'm looking at (BC Racing BR series) have a single adjuster, but they say:

Linear Piston And Damping Curve

30-Clicks Of Simultaneous Compression/Rebound Adjustment

This seems to imply there is no knee (so know difference between low and high speed) and that the single adjuster affects both rebound and compression.

On a primarily road car, which aspects should I prioritize with my adjustment? Will prioritizing reaction to bumps and rough road (high speed) compromise the cornering aspects?


It all depends on the the valving in the dampers. When they say adjusts rebound / compression, you don't know whether this is more low-speed, high-speed, or somewhere in between. The only way to learn what the shocks will do is to put them on a damper dyno and test them with the various settings. Perhaps the manufacturer will provide that info for you.

Like most engineering optimizations, you need to change something and see if it's better, worse or the same. I would say that road holding (the feeling of grip and stability) should be emphasized in a road car. If your problem is with rough roads, then make changes that improve the road holding in those situations. If this compromises the road holding on transitions from braking to cornering, or cornering to acceleration -- then find out if they can be revalved to help this.

I will second David's comments - you really can't know unless you have the results from a Dyno run.

Typically, simultaneous rebound/compression adjustment just means there is unchecked flow through the piston bolt at low speed. Some dampers have a check valve on the adjuster circuit so it only affects rebound, but not all. A bi-directional adjuster circuit will often affect both compression and rebound but to varying degrees. Sometimes there will be little effect on compression, other times a noticeable effect on both. Sometimes very little change to either! In theory it should mostly control low speed damping but again it can have a large impact across the whole range or even more at high speed than low. It all depends on the exact design and valving of the shock so you need it dyno'd to know

As with David and Jono's comments, they would need to be dynoed in (preferably) all of the available positions to see how the response changes (or if it even does) to different positions.

My experiences with the BR Racing coil overs is that the differences between a single click are very minimal, and you usually need to make a change of 4 or more clicks to see a meaningful change. They are also non linear in their ratio of adjustment between the bump and rebound characteristics.

I have some dyno graphs from a set if these coils somewhere, as well as a set of the ER units as well, I'll see if I can find them, they would have been done a couple of laptops ago so it may be difficult to find them.

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