The keys to a fast - but comfortable road suspension setup?

[MiddayGun]

So I'll preface this question by admitting that my taste in suspension is probably the opposite of most, when people modify their cars, they generally want, lower, stiffer, etc, which to a point is fine, but for me at least, this can often ruin a cars road manners.

To the point then, I have an old 4th generation Honda Civic, not a daily, its a summer & weekend car, but it does get used a lot in summer, I drive it mostly on the road, but I do go on 4-5 track days a year. Its a pretty good handling car from stock with fully independant suspension all around, and a curb weight of around 900kg. (Well 990 if you include the driver!)

I used to own a Honda Accord Type R, and as I recall that used to be very comfortable to drive daily, but when you pushed on, it handled extremely well, not too much body roll, but it absorbed the bumps of a UK country lane really well. Because you could push on quite hard without ever feeling that the car was going to be thrown off course.

In this car, not so much, I find it quite crashy (short sharp bumps send a jar through the car that makes me wince) and while on smooth roads with bumps that aren't harsh, its very composed and quite, but as soon as you get it down a back road, it feels like you're being thrown all over the place, difficult to go quick and not fun, mentally wearing as well.

I'm trying to find a good compromise setup, the car came with BC BR Coilovers, 10kg/mm up front and 5kg/mm in the rear, and polybushed all around. It was very crashy, and the springs were far too stiff for the road. Plus the front was too sprung compared to the rear, so it felt quite understeery.
I then tried switching to some standard lowering springs. Eibach Pro, which are about 5kg/mm up front and 3.8kg/mm rear (progressive), combined with some KYB AGX shocks, I also 'un-polybushed' the suspension arms for some Hard Race bushes which are harder rubber than stock, but still rubber.

Its much better but but still reacts very fast to the smallest of bumps, still makes loud bangs while going over harsh bumps and still gets thrown all over the road, just not as much.

So before I spend any more money, I want to apply a bit more science to the process, try and work out where the suspension is defficient now, and what I can do to improve it.

So yeah, does anyone have any tips, or can point me in the direction of some good reading on the subject? I basically want to move in the direction of having a car that's comfortable and fast on the road, that I can still take on track and have fun. Rather than what I have now, which is good on track, but hard work on all but the smoothest of roads.

[Hawkshaw]

Suspension and steering design - how to make a car ride and handle well, and "feel" just right, is a fascinating business once you get into it

This may be not what you want to hear, but I think you should start off by putting the car back to standard - or as near standard suspension as you can get - and that includes wheels and tyres. Only then will you have a base line to work from - Honda's designers probably knew what they were doing and it might have been fairly okay to start with.

You are right to get rid of the polybushes. They do not suit every type of suspension. Rubber bushes are used for good reasons, compliance is sometimes necessary, and they are a complex subject in themselves.

At this point somebody is going to say: "Yeah I hear what you are saying, but....."

[trevalvole]

I suspect that Hawkshaw is right. As the car currently reacts to even small bumps, may be the damping is too hard? From a quick Google, your KYB AGX dampers appear to be adjustable. Have you tried adjusting them, as even if they are currently on the softest setting and adjusting them makes the ride harsher, then at least you could conclude that you might need some softer dampers?

[GreenV8S]

I've seen several cars set up by people why tried to make it feel more sporty by stiffening up the dampers, and that produces the symptoms you describe. It's the wrong way to do it. Using the dampers to try to control pitch and roll transients can lead to them being set far too hard. The springs are there to absorb the road input. The dampers are there to control the rebound and should be set to the softest setting that will do that.

If the dampers are worn, this can also make them feel very harsh and produce bangs as air bubbles go through the valves.

[MiddayGun]

Hawkshaw said:

Suspension and steering design - how to make a car ride and handle well, and "feel" just right, is a fascinating business once you get into it

This may be not what you want to hear, but I think you should start off by putting the car back to standard - or as near standard suspension as you can get - and that includes wheels and tyres. Only then will you have a base line to work from - Honda's designers probably knew what they were doing and it might have been fairly okay to start with.

I've certainly considered it, the main thing that is putting me off right now is that standard suspension is hard to find.
Obviously any original parts are over 30 years old now, Honda no longer supplies springs & shocks.

And the aftermarket for standard springs is a minefield, spring manufacturers love to claim that x y and z car is supported, but then you find its wrong, especially since Brexit as well, the parts I can find have reduced. (Autodoc FR for example, you can still get a complete stock exhaust system, in the UK they can't get it any more)

Possibly I will have to get them from RockAuto or somewhere as the Americans seem to support older cars for much longer.

Wheels and tyres, they came standard 14" wheels, its currently on 16s, but they aren't super low profiles.
15s are the lowest I could go as there is a brake upgrade in the future, and it won't fit under small wheels.

trevalvole said:

I suspect that Hawkshaw is right. As the car currently reacts to even small bumps, may be the damping is too hard? From a quick Google, your KYB AGX dampers appear to be adjustable. Have you tried adjusting them, as even if they are currently on the softest setting and adjusting them makes the ride harsher, then at least you could conclude that you might need some softer dampers?

Yeah I spent a good bit of time playing around, on track and on the road, they only offer 4 levels of adjustment, and I think its rebound only.
I actually find that I need to run them on or 1 below the max setting, otherwise when the car hits a big bump, the suspension will bounce a few times, so possibly they are not damping enough for my car.


Are there any recommended books / articles on the subject that might be worth reading?
Most the stuff I find when I search is aimed at building a race car.

[Hawkshaw]

If you haven't read it yet, I would suggest Allan Staniforth's Race and Rally Car Source Book - as per title, not mainly about road cars, but very readable, informative, and plenty of good information on a whole range of technical subjects.

[GreenV8S]

'How to make your car handle' by Fred Puhn is another recommended one.

[MiddayGun]

Thanks, I'll look them up.

[shirt]

i'd go with the lotus approach - a stiff chassis, softly sprung. look at the chris harris 911k video tracking shots, the car squats, dives and rolls. no denying its quick and grippy, but its the spring rates that makes it comfortable/useable.