More compliant damping?
Discussion
I don't know whether to post this here or under the 'Technical' section, but here goes.
There exist a few cars that have a hard ride, namely Audis, a few Alfas etc. Is there a way to change the dampers on these cars for something more compliant? My understanding is that the springs control the ride height and the dampers generally the ride quality.
Has anyone found a specialist that can supply an alternative damper to get over the sometimes rock hard 'not suitable for bumpy British roads'?
Am I talking nonsense and we have to simply accept that lowered suspensions these days reduce travel and therefore necessitate a harder damper to compensate and I am trying to achieve the impossible?
There exist a few cars that have a hard ride, namely Audis, a few Alfas etc. Is there a way to change the dampers on these cars for something more compliant? My understanding is that the springs control the ride height and the dampers generally the ride quality.
Has anyone found a specialist that can supply an alternative damper to get over the sometimes rock hard 'not suitable for bumpy British roads'?
Am I talking nonsense and we have to simply accept that lowered suspensions these days reduce travel and therefore necessitate a harder damper to compensate and I am trying to achieve the impossible?
strummerville said:
My understanding is that the springs control the ride height and the dampers generally the ride ?
My understanding is that the springs are there to support the vehicle and to absorb wheel movements. The shock absorbers are there to control the spring oscillations.Too much damping and the springs are not permitted to fully absorb wheel movements, too little damping and the springs continue to oscillate after the wheel has stopped moving.
The ride height is set by the springs, but is a factor of spring length combined with spring rate.
Your assumptions are not quite correct. Springs have a length and a spring rate. The spring rate (in N/m) is the force required to change the length of the spring by a given amount, thus the force exerted by a spring is proportional to its displacement from its starting length.
Dampers exert a force proportional to the rate of change of displacement as the fluid/gas inside them is forced through constrictions. This can be the same in both directions or the constrictions can have valves so that the force is different in different directions.
The total force exerted is therefore the combination of the displacement of the wheel from its starting point and the rate of change (speed) of displacement. The feel of the suspension and its 'hardness' can therefore be affected by both the springs and the dampers but it is a complex relationship and the matching of the two components hugely affects how the suspension reacts to the road surface.
Dampers exert a force proportional to the rate of change of displacement as the fluid/gas inside them is forced through constrictions. This can be the same in both directions or the constrictions can have valves so that the force is different in different directions.
The total force exerted is therefore the combination of the displacement of the wheel from its starting point and the rate of change (speed) of displacement. The feel of the suspension and its 'hardness' can therefore be affected by both the springs and the dampers but it is a complex relationship and the matching of the two components hugely affects how the suspension reacts to the road surface.
It's both the spring and the damper that control ride comfort. Put simply, the spring absorbs the initial force when you hit a bump or change direction etc, and then the damper controls the movement thereafter - think spring = shock absorber and damper = control. Their roles do overlap though, as obviously the damper is connected to the spring when it compresses and extends. You can buy aftermarket springs and dampers for most cars, but they're generally to get things firmer for faster road or even track use, plus tuning the springs and dampers to each other and the car is quite a complex task requiring considerable skill to get right (Lotus do consultancy for other major manufacturers on this and have done for years - that's how hard it is). You can buy adjustable aftermarket dampers, and you may find some which may have settings more forgiving than your standard car, but I couldn't guarantee it and you'd need to do a bit of research.
Often manufacturers choose one setting for a range of wheel sizes and changing to the standard wheel size can work wonders. For example, I have an E90 BMW 320d on standard 16" wheels and the ride's fine, but people frequently complain about the ride on 17s or 18s with the same springs and dampers as my car. Equally, the M3 on its standard size wheels actually rides very well, because the springs and dampers were tuned for that wheel size.
There is another component in the suspension of your car, and that's the tyre sidewall. If you change from run flats (RFTs) to ordinary tyres, change to a tyre with a higher sidewall, or to a lesser extent tweak the pressures a bit (although you're probably already at the manufacturer's minimum recommended setting), you will effectively be softening the spring and damper combo that the sidewall provides in the system. It's common on BMWs to change the RFTs to standard tyres, but personally I think it degrades the ride and handling, which gives you an idea of how sensitive cars are to small adjustments. To give you an idea of how subjective it is though some people say it's the best thing they've ever done!...
So in summary, you could consider changing tyres or running lower pressures (still within the manufacture's recommendations though) as a cheap fix, but to be totally honest you might be better off choosing your car based on the ride and handling that you want.
Often manufacturers choose one setting for a range of wheel sizes and changing to the standard wheel size can work wonders. For example, I have an E90 BMW 320d on standard 16" wheels and the ride's fine, but people frequently complain about the ride on 17s or 18s with the same springs and dampers as my car. Equally, the M3 on its standard size wheels actually rides very well, because the springs and dampers were tuned for that wheel size.
There is another component in the suspension of your car, and that's the tyre sidewall. If you change from run flats (RFTs) to ordinary tyres, change to a tyre with a higher sidewall, or to a lesser extent tweak the pressures a bit (although you're probably already at the manufacturer's minimum recommended setting), you will effectively be softening the spring and damper combo that the sidewall provides in the system. It's common on BMWs to change the RFTs to standard tyres, but personally I think it degrades the ride and handling, which gives you an idea of how sensitive cars are to small adjustments. To give you an idea of how subjective it is though some people say it's the best thing they've ever done!...
So in summary, you could consider changing tyres or running lower pressures (still within the manufacture's recommendations though) as a cheap fix, but to be totally honest you might be better off choosing your car based on the ride and handling that you want.
Edited by RobM77 on Monday 3rd March 17:59
In my experience, almost all modern cars that try to be "sporty" are over-sprung for their dampers, so reducing spring rate while maintaining the same dampers is probably a viable way to improve both ride comfort and handling on a tight budget.
Reducing unsprung mass is often a more powerful way to improve both things though. Narrower tyres on smaller, lighter wheels can made an enormous difference.
Reducing unsprung mass is often a more powerful way to improve both things though. Narrower tyres on smaller, lighter wheels can made an enormous difference.
Thanks for the comments. I always wondered if you can 'tinker' with the valving of dampers to change their characteristics. I suppose the closest thing is a Nitron custom? www.nitron.co.uk
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