bbarbulo

iTrader: (2)

Basic Suspension Operation:

On a car like the Civic, the vehicle's susp is designed with certain constrains in mind, like cost, comfort, NVH (noise, vibration, harshness), and probably in the last spot... performance. Now, somehow generations from 88-00 Civic got lucky and inherited Honda's world renowned double wishbone suspension. This particular setup has certain qualities that make it ideal for performance applications. For example, the double wishbone exhibits a geometry that allows the tire to change the dynamic camber as the suspension compresses under load. Secondly, the dbl wishbone has a tremendeous amount of wheel travel. Wheel travel is key to good handling, despite getting a bad rap due to body roll. Most ppl seem to think that if the car stays flat like an F1 car, that it must handle amazingly. This is simply not the case. In the real world of daily driving we deal with many obstacles like potholes, cracked up pavement and speed bumps. A suspension's job is to ensure through all these obstacle the tires remain in constant contact with the road. Ultimately, if the tire is not on the surface, it's not providing any grip. Ok, so now that the geometry is out of the way, let's talk components... shocks, springs, mounts, bumpstops, bushings.

Most commony changed "performance" component - springs. Rates from 50%-700% and anywhere inbetween stiffer springs are made available. There are two types of springs - linear and progressive rates. Liner means the spring is the same rate from uncompressed to fully compressed. Progressive means it starts out soft and gets harder the more it's compressed. This type is great for taking on small bumps and cracks in the road, but at the expense of retaining some body roll. Progressive is the preferred spring for street performance driving. As for the amount of drop, you want to retain the maximum wheel travel that you can afford because you want the spring to do the work, NOT the bump stop. If the wheel exceeds the wheel travel range, the shock body contacts the bump stop, creating an infinite spring rate (solid connection), usually sending the car into an understeer situation. So wheel travel is essential, meaning most of the wheel gap should stay. Slammed cars normally ride like ****, unless the geometry of the susp has been adjusted by way of custom a-arms or forks. How your car handles depends greatly on the springs, but how it rides AND how it handles is the responsibility of the shock!! The shock and spring rates must be matched in such a way that the body and wheel (unsprung weight) movement can be controlled by the shock.

The shocks/struts control the movement created by the spring... an undampened spring, sans frictional loss, would continue to undulate infinitely. That is why a car with **** shocks floats all over the highway or bounces after a bump. The shock is one of the key parts to contolling movemement of the wheel. Not all shocks are created equal, don't try to save money here - get the best component that you can afford! In terms of manufacturers, Bilstein>Koni>Tokico>KYB, but in terms of value (quality for price) it's Koni Yellow, Koni Red, KYB AGX, Bilstein TC sport, Tokico Illumina, KYB GR2, Tokico Blue (or I think they call it sport). This is just my opinion, not based on any scientific evidence or anything...use it as a guideline.

Bushings - ABSOLUTE KEY to solid and consistent results... the susp is made to push back against the chassis - the bushings are the interface between the two. Rubber is cheap and low NVH, BUT it's soft and breaks down under stress and ozone. Urethane is a far better alternative. Any car over 150,000 kms or 10 years can use a new set of bushings! Without these, any chassis improvements are a lost cause (like strut tower braces, roll cages, lower tie bars, etc.)

Sway bars - Great for fine tuning the balance of the car, but they are NOT meant to fix the way your car handles. Try to keep the front bar under 28 mm, and the rear 22mm and under. Stock 99-00 SiR bars are as far as I can remember 26 mm F and 14 mm R. An ITR 22 mm rear bar is a great addition to a car with a 26mm bar, but beware of the stress on the chassis and the radically altered balance (likely to oversteer!!).

Chassis improvements can be considered part of susp tuning, since the susp needs a solid platform to push agianst while working... so yeah strut bars can help... so can lower tie bars. But IMO, all you need is a solid stut bar (no flexible joints), and a Z10 radius arm. From what I can tell, Honda used something like a Z10 bar on the 1986 Prelude. Pricey - yes, but well worth every penny. For the rear, depends on whether you have a coupe, sedan or hatch... coupes and sedans are quite solid as is - the hatch needs help in the rear strut tower area. For lower tie bars, they are nice to have, they'll help rotation a little bit in tight turns - I like the Cusco units as well as Tanabe.

Anyone have any questions, ask away... or if you wanna correct me or add something, please post!

bbarbulo

iTrader: (2)

this is open so ppl can add to it if need be... I'll be deleting useless posts

imported_gatherer

Spring rates are a fun topic....

some definitions that some people get all mixed up when I talk to them will help here.

understeer - this condition is caused when you turn the wheel to go in another direction and you continue to go in the direction you were heading in(the car does not turn). Honda's are commonly set up with this condition, because the engineers think it's easier for the common person to control.

oversteer - this condition is when you turn the wheel and the back end of the car "steps out" rotating you faster then you had intended .... it's one of the prime ingredients in fish tailing and drifting.

ok spring rates. commonly for street driving most people get progressively rated springs (see Bbarbulo's post for definition) and these work great however most manufacturers like to stick to the standard honda set which is stiffer in the front and softer in the rear. there is nothing wrong with this but you must understand that it will not completely correct the understeer thats in hondas. The common thought is honda put stiff in the front because of the wieght of the engine... while yes the engine does cause a unbalance in the wieght from front to back it is still possible to get springs rated high enough to handle the load and get even stiffer ones in the rear to create a closer to neutral handling charateristics. but hey if it's for daily driving this isn't needed since out of the box packages are good enough.

for track linear rated springs are the best. reason why is because they never change as the spring compresses and decompresses. This results in the car being more predictable. ussually custom spring rates are used here. ussually with 350 to 500 lbs/in in the front and for the rear from 450 to 1000+ lbs/in. while this may seem like something fun to do because it would create tons of oversteer it also raises the NVH factor (nice term bbarbulo ).

now some useful information. provided that you change only one thing at a time, the change you make will move the handling more towards oversteer or understeer. assume everything else stays the same except the change. here it is:

increase in front spring rates ----------> more understeer
decrease in front spring rates ---------> more oversteer
increase in rear spring rates -----------> more oversteer
decrease in rear spring rates ----------> more understeer

bbarbulo... care to make your other tutorials sticky too?

bbarbulo

iTrader: (2)

thanks for that addition gatherer!!

I would like to just clarify:

increase in front spring rates ----------> more understeer
decrease in front spring rates ---------> less understeer - until you hit the bumpstops, in which case understeer prevails
increase in rear spring rates -----------> more oversteer
decrease in rear spring rates ----------> more understeer

This can also be applied to sway bars, stiffer end slides out first... so when you upgrade the rear bar, the rear end will rotate more easily.

gatherer, there will be a bunch of these stickes made up for educational purposes as I feel like writing them. If anyone cares to write up a mini-me, any swap experiences, etc.... I'll gladly put them up... eventually to be moved into the Perf/Susp archive.

imported_gatherer

yes your right about sway bars ... but my doesn't have any...

anyways yes sway bars (correct me if wrong I don't have any )

increase front diameter -------> increase understeer
decrease front diameter ------> increase oversteer
increase rear diameter --------> increase oversteer
decrease rear diameter -------> increase understeer

with bump stops your correct if the front get hit you understeer ... if the rear hits you oversteer.... (and you'll ussually do so in a very spectatular way since it throws the control to the far end of the spectrum)

the spectrum of steer (as I call it)

|-----------------------------|------------------------------|
Understeer Neutral oversteer

so remember when you change something to move in a desired direction you might not move all the way to the effect you want ... but you will move closer too it.... so if you have terrible huge gobs of oversteer and you change the front spring rates to get more understeer. well you might not throw yourself all the way to the other side of the Neutral line. it all depends on the quantity of the change. if you move from 300 to 900 lbs/in you'll get a bigger reaction then if you moved from 300 to 500 lbs/in.

as for swap experiences just get Dented DX to post the picture of me he has

Brett

How would you setup your handling to be neutral, minimal under or oversteer when pushed? Wouldn't that be the optimal goal?

Blue Dream

there is no ultamate goal IE:

just depends on what you are doing with the car..

autox?
1/4 mile?
rally?

all have different setups, and require different combinations to acheive desired goals.


preloading bars, larger rear sway's, larger front sways, not using fronts...

bbarbulo

iTrader: (2)

For street use, it's simple... Koni Yellow, Eibach Pro, ES bushings, Si front sway bar, Progress adjustable rear sway bar, ITR front strut tower brace, Cusco lower front brace, and Cusco rear lower brace... the Yellow shocks and Progress adjustable bar will allow you to dial in exactly how much neutral handling you want according to your driving needs. Cuz some ppl like to brake early and come out on the gas, and some ppl (like me) like to go into the corner hot and lift off halfway to rotate. So our setups would be diff't according to our style. If you just want to do it by way of changing springs, you'd have to get custom spring rates done, I'd say 100 lbs more in the rear than what out-of-the-box ProKit comes with, but that's a guess, you'd have to experiment with it.

Brett

Rotate around the corners, You do that on the street? That is something that i need to learn how to do. Actually im interested in going to the autox next year so neutral handling is not my goal. What would be the difference in setup then? Also, would configuring your car for ultimate autox handling take away from the stability of the car on the highway?

MPR

Again...personally don't agree with everything, but some very good info.