Suspension 101 Part 2 - Springs and dampers


Hi there! Nice writeup there,
From reading parts one and 2, ek9 have standard linear springs correct?
Linear front springs, progressive rears.

If I was going for a ( let's say cusco for example) only thing I'll be befitting is just the springs and dampers correct?

Cuscos are coilovers, although technically speaking basic springs and dampers are coilovers also. The term coilover is related to when cars with non concentric springs/dampes were fitted with concentric 'coil over damper' units, or even converted from say leaf springs to concentric coilsprings and dampers.

Since we have 'coilover' suspension as standard, in this context a 'coilover' is an all in one unit usually with built in height adjustment, but essentially it is still just a coil spring and a damper.
 
Which part of the spreadsheet to we enter the damping curve?

I haven't provided any spreadsheet?

You don't 'enter the curve', the inputs are;

Vehicle mass
Weight distribution
Unsprung weight
Spring rates
Motion ratios
Damping ratio

These produce the curve that you could then provide with your dampers to a damper specialist to have them valved correctly.
 
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This critical dampening ("CD") concept is speed dependant, right? CD at 80km/h versus CD at 140km/h on the same stretch of road be different, right?

Be interesting to know more about the internals / shim design/gas pressure & gas volume. - see Page 11 of the JRZ catalogue.

Page 11 (JRZ) - compression stack has a strong influence on the dampening force range of the blow off system.



"Deflective disc valving in Bilstein shocks eliminates the need for check valves and tiny coil springs that cause inconsistencies in shock valving"

Monotube dampers use a deflected disc-metering valve on each side of the piston to control both compression and rebound damping. Each valve is composed of a stack of springy steel disks, or shims

http://www.peterverdonedesigns.com/highspeed.htm
 

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Remember that compression (or bump-damping) occurs when the wheel contacts a bump and compresses, and rebound or tension damping occurs as the spring forces the shock or fork to extend. The fact that the compression velocity is forced by the size and shape of the bump means it sees a very wide range of velocities. Rebound, on the other hand, is largely controlled by the spring force and therefore sees a much smaller range of velocities. Typically, rebound may see one third of the velocity of compression. For this example, where compression sees 6 m/s, rebound may see 2 m/s. This means the transition to high-speed rebound damping might best be thought of, in this example, at around 0.2 m/s
 
If you are using a progressive stack with a gap shim in place, by making the gap shim thicker, the shock becomes softer - what really happens is the thicker (small diameter) gap shim lets the large shims deflect further before hitting the next line of progressive shims in the second stage stack, thus making the shock softer
 
nerds!!:blabla: JK this is really good info .. i have learned alot from this .. thanks

sticky???
 
One thing to bear in mind is that you almost always want the rear frequency higher than the fronts. This is so that when the car rides a bump, the rear settles quicker than the front, aiming to have both axles return to equilibrium at the same time. If the frequencies are the same you risk ending up with an uncontrollable front and back pitching which is neither pleasant for the occupants nor good for performance. General recommended split is about around 0.2 to 0.3hz for optimum ride comfort, you can then alter this according to the handling balance you want.



Can any one help me out with better understanding this?

Trying to select springs to help improve the ride as much as possible while still having the car be fun to drive on the road. It will never see any track time and I am to old to have a shitty riding car.

If I am reading this correctly the front to rear split needs to be at 0.2-0.3hz. But is this more important than the overall spring rate or is both the split and a lower spring rate equal for ride quality?

I am also having trouble with all of the numbers in the calculations above the quote. Can some one tell me what each letter is so I can do some calculations for myself?


Thanks!
 
The 'flat ride theory' is a very wide generalisation (incidentally seems to be used on a lot of coilover systems, good indication of shitty R&D being applied perhaps?). Typically used for RWD cars it works pretty well to get a balanced and well riding car. On a FWD it would create a pretty heavily understeering car, so we typically have a larger split to combat understeer, around 0.4 - 0.5 on the EK9 seems to work well. I have the front/rear frequencies at 1.16 and 1.57hz on the 9, although my motion ratios may be a little out.

The 0.2 - 0.3 split is not essential for ride comfort nessasarily, but what definately want to try and avoid is having front and rear frequencies the same, as this will result in the car pitching back and forwards after a bump. Having the rear slightly higher means it settles quicker, which given it hits a bump slightly later than the front wheels, means both axles should settle at roughly the same time.

f = (1 / 2 . π) . sqrt(K/M) Reads "Half of pi multiplied by the square root of K divided by M" where K equals spring rate at the wheel in N/m, M equals sprung mass on one corner in KG and pi equals roughly 3.142. Spring rate at the wheel is equal to spring rate multiplied by the motion ratio squared.

The overall spring rate will still have a bigger impact on the ride quality, but getting the wrong split could cause you and your passengers motion sickness, even with very low spring rates!
 
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Thanks. Equation make a lot more sense after a good night's sleep and I am not crossed eyed.

M=sprung mass

How do I figure out sprung mass for each corner? It is not simply the weight of the car divided by 4, correct? I am guessing the weight balance of the car is a factor?

Car is a 96 US hatchback with a B-series drive train and the entire suspension and brakes off a US SI coupe. I am guessing it weighs about 2400-2450 lbs.
 
I have it as 2555lbs for the EK4 hatchback, you need to apply the weight distribution between the axles, around 62%, divide the axle weight by two for the individual wheels then subtract the unsprung mass on each corner, which I have at around 27kg at the front and 31kg at the rear. None of those values are particularly accurate really but they are close enough to get you in the ballpark, which is good enough for general road/track/amatuer motorsport use.
 
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I love this thread but i have two comments.
For the motion ratio, I always thought the ek civics were closer to .8 in the rear due to a longer LCA compared to the EG/DC chassis.
When calculating the spring rate at the wheels, shouldn't the spring rate from the sway bars be added in?
 
I love this thread but i have two comments.
For the motion ratio, I always thought the ek civics were closer to .8 in the rear due to a longer LCA compared to the EG/DC chassis.

Motion ratio is a tricky one, I haven't actually measured it properly yet, the only way to do it properly is to measure the spring deflection for a set amount of wheel movement. It is not, as I have found out since starting this thread, sufficient to simply use the distances between the the pivot points on the LCA to calculate MR as the offset of the wheel from the steering axis does infact play a large part in determining it too, contrary to some 'reliable' sources... :angry:

When calculating the spring rate at the wheels, shouldn't the spring rate from the sway bars be added in?

As for wheel rate, you would be correct when talking about roll mode springing as the ARBs affect the total load at the tyre and so play a big part in determining the handling balance.

For heave and pitch mode, the roll bars have no effect, since it is this mode that we consider for the primary ride characteristics, we can exclude them from the wheel rate calculations. They come in afterwards when you need to determine load transfers and set the damper curves.
 
Yeah motion ratio is pretty hard to measure correctly. People have reported MR ranging from 0.7-0.9 for the rear of an ek.

Will you be doing a Suspension 101 part 3 which includes roll mode? I am very interested in it and would love to know how to add ARBs into the equation.
 
I would do, but tbh I haven't got the time at the moment. I wanted to do one on geometry and another on brakes (although according to a few people on Civiclife, I am a full blown retard on that subject...) as well as load transfer, and might get round to it one day, but it does take a lot of time.

Feel free to start a seperate thread on load transfer/roll mode if you are interested and I'll do my best to answer any questions you have. It's always good to have new technical theory threads up! :nice:
 
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another on brakes (although according to a few people on Civiclife, I am a full blown retard on that subject...)


Haha that thread is funny, some people don't understand the laws of physics and you could not have written it any clearer than you did.

I myself am still learning about it all with regards to getting the best out of my suspension, brakes etc.. so find your threads and links an interesting read !
 
Haha that thread is funny, some people don't understand the laws of physics and you could not have written it any clearer than you did.

I probably could have cleared it up a bit quicker, but my method of throwing a question out to get people to think about a particular point backfired big style. If nothing else, it was an amusing waste of an evening!

I myself am still learning about it all with regards to getting the best out of my suspension, brakes etc.. so find your threads and links an interesting read !

Glad to be of help. :))
 
Love these threads, so much to take in though.

I'll save it as a favorite and keep reading through it, maybe my brain will act like a sponge more that way.

Like I said Brilliant thread!
 
Do you know if the H&R race springs are progressive or linear,or is it the nuespeeds? i think i want to go linear, i bought koni yellows but need help choosing the springs.i dont mind a stiff ride, just trying to find out which spring is more performance rated
 
I don't know about either of those springs in particular I'm afraid.
 
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