I'm tired of just asking opinions and would like to be able to research and find out what suspension would be best for my own needs. Could someone please identify and explain the major components of a suspension? What I need to be looking for in terms of quality? What do the different types of adjustments actually do in terms of car setup? Pretend I'm dumb. Thanks in advance.

 

Check out "How to make your car handle" by Fred Puhn. It's 19 years old, but not much has changed about how handling works. Or just go to a library and xerox all of chapter 1. It explains camber, tow, slip angle, different suspension arm designs, friction formulas, and all that good interesting stuff.
-Dan

 

Thanks.

 

THANK YOU BIG PHAT R

Well here is a first contribution to the FAQ page... <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emsmile.gif" BORDER="0"> It was not written by me, but I feel the content is valid and have edited it with regards to this board.

Understanding Vehicle Dynamics

Before we start we have to have an explanation of common vehicle dynamics terms. We had better understand the common ways to describe the different aspects of vehicle dynamics before we even turn a wrench, so here we go:

<u>Friction circle</u>: This is basically a vehicles performance envelope. It's expressed in lateral G’s, accelerating and braking G’s. When graphed, the friction circle looks like an egg with the X axis lateral G’s and the Y access braking and accelerating G’s.
<u>Understeer</u>: This is when, at the limit of vehicle traction, the front of the car slides first before the rear. Race car drivers call this "push". This is the way that many cars come set up to behave from the factory as it is the most predictable for average drivers (like the Type R). The crash mode for understeer is that when the limit of adhesion is exceeded, the car will plow strait ahead off the road nose first. This is not the fast way to have your car set up, but is best if you are an inexperienced driver. When the car understeers you should regain control if you let off the gas, unless of course you run out of road first. (That is what air bags are for.) It is not efficient for extracting maximum lateral G’s because the car will dynamically use the front tires excessively for turning, overloading them while the rear tires basically just hold the back of the car up - scrubbing off significant speed. Front wheel drive cars tend to exhibit understeer as the final terminal mode of balance.
<u>Oversteer</u>: This is when, at the limit of vehicle traction, the rear of the car slides first before the front. Race car drivers call this "loose". The rest of us call this "spinning out", "spinning a shitty", "doing a brodie" or even crashing. The final crash mode of oversteer is backwards, tail first into the woods or in the worst case spinning round and round with the driver as a helpless passenger. Since the infamous days of Ralph Nader and the Corvair, most auto manufactures avoid oversteer like the plague. Oversteer is difficult for an inexperienced driver to handle because recovery requires judicious use of countersteering and throttle feathering to control; fine motor skills that only some of us can deal with. Although oversteer looks neat and macho it is really a slow way to drive except in maybe pro-rally on the dirt . Oversteer is slow on the pavement because hanging the tail out bleeds off a great deal of speed going through a corner. Conserving the momentum is the fast way around as turn.
<u>Neutral</u>: This is the fast way around a turn where all four wheels slide evenly. Since the total friction circle traction of each tire is being used, all the available grip that the tires have is being put to the ground. Racers call this "drifting". This not to be mistaken for the idiotic Japanese Option Magazine video stuff which makes a mockery of proper driving technique. Neutral is the fast way around a corner most of the time. Neutral is also the hardest handling mode to achieve for the suspension tuner.
<u>Polar Moment of Inertia</u>: Or PMI as we will refer to it, is a description of how a cars mass is distributed along the length of the vehicle. A car with a high PMI is like a rear engine, rear drive car like a Porsche 911 or a front engine, front wheel drive car like our beloved Type R, same thing only the poles are different, so to speak. A car with a low PMI would be a mid engine car like a Boxster. Low PMI cars have most of their mass about the middle, high PMI cars have the mass at one end or another. Low PMI cars are the easiest to get a neutral balance out of due to the balanced, centralized mass. High PMI cars like to oversteer, in the case of the 911 or understeer like our cars. To get a feel for this phenomena, hold a bowling ball in one hand and rotate it back and forth by twisting your wrist. Now get a set of dumbbells of the same weight, grab the middle of the bar and do the same thing. Bet the bowling ball wants to rotate easier right? Guess what type of car will be easier to get neutral!
<u>Slip Angle</u>: This is the wonderful thing that allows us to tune our cars suspensions despite the design limitations caused by the PMI. Proper manipulation of slip angle is the great equalizer and is what suspension tuning is all about. Slip angle is the difference in which a cars wheels are pointed vs the angle that the tires contact patch is placed on the road. The main thing that affects slip angle is the manipulation of the individual load placed on each wheel while cornering. This is the key for suspension tuning. A front wheel drive car has most of the weight on the front wheels. So the front wheels run at higher slip angles and develop understeer. Conversly the same for a rear wheel drive, rear engine car developing oversteer. That is also a reason why a mid engine car with equally loaded tires will be more or less neutral. Slip angles, weight distribution and PMI are the main factors in how a vehicle will handle.
Because Type Rs are front heavy, front tire overloaded, front wheel drive cars, does that mean that we are condemned to econobox hell for driving fun? Heck no! By design we can not change the basic layout of our cars to significantly change the PMI or weight distribution but we can sure tweek the slip angles of the tires to achieve world class handling out of our killer compact sport transportation units.

The easy way to tweek the slip angles are with anti-sway bars and springs. Shock absorbers, going against what people think that they do, are not really for changing the handling balance. Shocks mostly act as spring dampers and affect understeer/oversteer balance mostly only in transient (which is big word for a change from straight line travel to turning) maneuvers like initial turn-in and zig zaging around slalom cones.

Changing to heavier springs changes the slip angle differential by resisting the cars tendency to roll on the end of the car that they are installed on. The resistance of the heavier spring to compression causes more weight to be transferred to the outside wheel of the end of the car that they are installed on as the car tries to lean over in a corner. This causes that wheel to proportionally run at a higher slip angle than it normally would. If you put heavier than stock springs in the rear of your Type R while not changing the spring rate of the front, the car would tend to understeer less.

<u>Antisway bars</u> work in much the same way. Antisway bars are torsion bars attached to the cars chassis and are linked to the right and left control arms. Antisway bars offer resistance to independent side to side wheel movement. This is how these bars limit sway in the turns and hence their name. While limiting sway, the antisway bars also cause weight transfer to the outside wheels. By altering the diameter of the antisway bars or installing them where there were none before adds yet another chassis tuning element. If you were to increase the size of the rear antisway bar on an SE-R you would be increasing the amount of weight transfer to the outside rear wheel, thus causing it to run a bigger slip angle. This would give you more oversteer.

<u>Tire pressure </u>also can affect the slip angle. Higher pressures reduce the slip angle and lower pressures increase it. A great deal of suspension tuning can be done for free by adjusting the tires pressure.

<u>Alignment</u> also has a great deal of effect on a vehicles handling balance. Caster and camber affect how a tires contact patch is positioned on the ground by compensating for a tires tendency to flex and lift the inside tread while cornering, By helping keep the tread flat, these settings can increase or decrease the available friction circle traction on an end of a car thus affecting balance. Toe in or out can affect balance also by changing how a vehicle turns in.


Suspension adjustment--&gt;Affect on vehicle balance--&gt; Symptom of TOO MUCH adjustment

Front spring rate increase. More understeer .Terminal understeer, front of car hops in corners, excess wheelspin in FWD car

Front spring rate decrease. Less understeer. Too much oversteer, oversteer then understeer if spring is so soft that the car bottoms under lean, car bottom excessively with a jolting ride

Rear spring rate increase. More oversteer .Too much oversteer, hop in corners, twitchy

Rear spring rate decrease. Less oversteer. Car understeers, if way too soft car understeers then oversteers as car bottoms out under lean, car bottoms out excessively with a jolting ride

Front antisway bar stiffer. More understeer. Terminal understeer, Lifts inside front tire off the ground which can cause massive wheelspin, also not good for most effective tire usage as inside wheel is now doing nothing

Front antisway bar softer. Less understeer. Oversteer

Rear antisway bar stiffer. More oversteer. Big time oversteer, Can cause the inside rear tie to lift off the ground which is not two bad on a FWD car.

Rear antisway bar softer. Less oversteer. Understeer

Front tire pressure higher. Less understeer. No traction as tire is crowned so more understeer, bad wheel spin, jarring ride, center of tires wears out

Front tire pressure lower. More understeer. Edges of tires wear quickly because tire is folding over, feels mushy, tires chunk because low pressure means more heat build up

Rear tire pressures higher. Less oversteer. No traction as tire is crowned so more oversteer, bad wheel spin on RWD cars, jarring ride, center of tire wears out

Rear tire pressures lower. More oversteer. Edges of tires wear quickly because tire is folding over and cupping upward, feels loose in back, tires chunk because low pressure means more heat build up

More negative camber (Front) Less understeer .Poor braking, car is road crown sensitive, twitchy, tires wear out on the inside edge

Positive camber (F) More understeer .Poor braking, car is road crown sensitive, twitchy, tires wear out on the outside edge You almost never want to have positive camber unless you are a dweeb

More negative camber (R).Less oversteer, more rear grip, less breakaway warning when limit is exceeded/-3 degrees. More oversteer, car feels twitchy in back, tires wear out on inside edge

More positive camber (R) More oversteer Car feels twichy in the back, tires wear out on outside edge

Ride height too low Car twitchy with unpredictable dynamics

Toe-in front. Car is stable while going straight. Turn in is average. Car has slow twichyness under braking, feels odd, kills the outside edge of tires.

Toe-in rear car is less likely to suddenly oversteer when throttle is lifted. Weird slow rocking movement in back, feels slow but still unstable, wears the outside edge of tires.

Toe-out front. Car turns in well, works pretty good in FWD cars as they tend to toe-in under load. Car is real twitchy under braking, car is very road crown sensitive, car wanders on straight road, kills inside edge of tires.

Toe-out rear. Helps the car rotate, useful on tight low speed courses and slalom events. Not to good for street driving, causes lift throttle oversteer, car makes violent side to side rocking motions in rear, tires wear more on insides .

 

THANK YOU BIG PHAT R

Basic Rules (again adapted from material from elsewhere - edited for content)

Here are some general basic rules if you want to improve your cars handling:

If you race in sanctioned competition, <u>read your rule book</u> before performing any modifications at all to your vehicle. It would be a pity to buy a fortune in trick parts only to have them declared illegal by an official. Beware of SCCA’s Street Prepared rules as many hot and popular street car mods would put you out of this class.

<u>Do not lower your car too much!</u> This perhaps is the number one no no. It is a symbol of a truly ignorant person with regards to suspension dynamics. Lowering looks really cool and can make a significant improvement to a cars cornering capability but going too low is detrimental to both handling and even safety. Going too low can cause bumpsteer, where the tie rods and control arms are traveling different arcs resulting in the wheels steering themselves with no steering wheel input. When a car is so low that the suspension bottoms under cornering loads, the end of the car that bottoms first will violently slide out. Super low guys are convinced that they are driving super touring cars but if you take them out on the track they will suck incredibly. Our Type Rs have a short travel suspension as it is and cannot take being lowered more than 1.5-2 inches at the most. So install some good springs such as Eibach, H&R or Ground Control and DO NOT CUT THEM MORE TO MAKE YOUR CAR LOWER. If you have the Ground Control springs do not adjust them to lower your car more than two inches except if you are going to compete in car shows where the car will be a stationary display. You want to maintain at least 1-3/4" of travel.

<u>Buy and install matched components from a single manufacture.</u> For instance do not put H&R front springs in with Eibach rear or a Suspension Techniques front bar with a TMC rear. Suspension manufactures usually offer these parts as a tuned set with rates, etc. made to match each other. So unless you really know what you are doing don’t mix and match. Good stuff for our cars is made by Eibach, H&R, Mugen, Spoon, TEIN, Ground Control and Comptech.
If you are using high performance springs, try to wait until you can afford the shocks also. Performance springs store more potential energy when they are compressed. They need a shock with more rebound damping to keep the car from bouncing all over the place after you hit a bump. Really good shocks like Koni or GAB’s are adjustable so you can tune your shocks to the springs. Performance springs with stock shocks usually feel floaty on high speed undulations. I find that that feels a little spooky. Performance spring’s quicker rebound characteristics also seems to wear out stock shocks quickly making them get super floaty. I prefer Bilsteins because of their auto adjustability and durability.

Limiting body roll is good. Our Type R’s sit high, and have fairly soft springs from the factory. They roll quite a bit. Install stiff springs and swaybars with matching shocks, and lower the car to a reasonable level. Limiting roll keeps the weight from transferring excessively, allowing the inside tires to work more in a turn. Limiting roll also helps keep the car from bottoming in a turn and keeps the car out of the bumpsteer zone. Type Rs like ours do gain some negative camber under roll either so limiting roll helps keep the tires from folding over.

<u>Having adjustably is good.</u> Having the ability to adjust shocks, camber and toe is very useful when trying to extract G’s from your car. On a showroom stock racer optimizing the alignment and tire pressures alone can make the car corner a lot better and have faster lap times. As front camber is not adjustable on our cars (unless you purchase a kit) it is important to make it so. Mugen and Skunk make high quality camber kits. These will slightly harshen your ride but will sharpen turn in due to the elimination of squishy rubber with metal bearings. Rear camber adjustably is not critical on most FWD cars. If you are racing Solo II stock class or Showroom stock and don’t want to cheat, you can get about ½ degree more negative camber by loosening all of the suspension bolts and having someone hold the wheel in the negative position while you retighten everything. No one currently makes an adjustable set of antisway bars for our cars but Ground Control can make you some custom ones if you are willing to send them your car for a few weeks. In fact, it would be no problem for just about any decent race shop to whip some up.

<u>Align your suspension and optimize your tire pressures.</u> In the previous paragraph, I said that alignment and tire pressures can make a huge difference. IT IS TRUE! If you are poor, you can still make big improvements in your cars grip by just playing with tires pressures and the car’s alignment. Try the poor boy technique and dial in some front negative camber, increase the front tire pressure, decrease the rear and set your toe. Boy will you see a difference. Try to find a place that does racing alignments near your house as alignment is where people really get ripped off as it is almost never done correctly. Most hacks just throw a car on the rack and if it falls somewhere within in the wide factory specs, don’t touch a thing. What you need is a blueprint type alignment where the suspension is adjusted exactly to spec. Most repair shop dorks don’t understand this and will argue and tell you that that is not necessary. A race prep shop will understand. When your car is aligned, it should be done with your weight in the drivers seat and with the technician bouncing the car after every adjustment to settle the suspension. Set your tire pressure before you take the car in. Remember that you must realign the car if you lower it!

<u>Cut your bumpstops</u>. It is important to cut the rubber bumpstops on your shock shafts to get a little more wheel travel out of lowered suspensions. Cut an inch or one segment out of the front and rear ones. Do not go crazy and remove the bumpstops or cut off more than half of them away. That can cause the suspension to bottom out possibly breaking it. If the car suddenly gets real bouncy, that is what probably happened. The only solution is to get new shocks.

If you are racing, <u>run R compound tires on the widest wheels that will fit.</u> These tires can get more that 2 seconds for every 30 seconds on a slalom course or 3 seconds for every minute on a road course. These tires usually have a vestigial tread and a really short tread life so you don’t want to run these as a daily driver tire. Also R type tires only have about 10 good heat cycles in them so their stickiness will decline quickly in daily use, leaving you with a fast wearing, not so sticky tire.

<u>Don’t over tire or wheel your car.</u> Our cars will go the fastest and handle best with the widest, lightest 15 inch wheel that will fit. 16, 17 and 18 inch wheels which look radical, really slow the car down because they are heavy and the bigger diameter screws up the gear ratio. There are few R type tires out yet in these big plus sizes to my knowledge yet either. The widest tire that you should run unless you have a turbo or some other ungodly power is a 205. Wider tires will result in more drag that our relatively low power engines can accelerate. A 205/50-15 works well in most cases and a wide variety of R compound tires are available in this size. The maximum rim width that the Type R can run is 7 inches with a 43-50 mm offset. Since this always comes up, the bolt circle measurement on our wheels is 5x114.3 mm. The competition wheels that impress me the most are the Spoon and Mugen wheels. These wheel are forged so it can be much thinner than a cast type wheel. It weighs like 11 lbs which is twice as light as a regular wheel. Any forged or semi-forged wheel under 13 lbs is great. Remember that 1 lb on the wheel is worth about 10 on the car due to the wheels rotational inertia.

<u>Tire pressures rise considerably during a run/race.</u> Take notes of your tire pressures before and after every run so you can start with a cold pressure that will increase to your desired hot pressure during a run. Bleed your tire pressure down after every run to keep it constant.

 

THANK YOU BIG PHAT R

How to adjust your suspension

The previous discussion involved basic concepts and principles of suspension design theory. These principles work pretty well for most driving styles (as well as most of the good drivers that I have worked with) and preferences. Your preference could be different. To find the optimal settings for your personnel suspension set-up there are a few tricks that you can do to make the process less painful and quicker.

To adjust your suspension you need a just a few simple things.

<u>First you need a good, accurate tire pressure gauge. </u>A gauge with a bleeder valve is very useful. Gauges like this can be purchased at just about any racers supply house for about 20 bucks. Don’t waste your money on those expensive electronic gauges. Those are slow to use and never come with bleeder valves.

The next bit of stuff to have is a <u>compressed air tank </u>for adjusting tire pressures. Tracks almost never have a handy air tank. I got my tank from Sears for about 50 bucks. Fill it at a gas station or use your home air compressor before heading out. Make sure the tank you buy has a safety relief valve so you don’t blow the crap out of your self if you leave the tank in your hot car during lunch or something.

A <u>digital tire pyrometer</u> is very important. Get one with a wire bead probe. These are used for measuring tire temperature differentials across the tread which is a good tool for judging whether your tires pressures and alignment settings are right. You can get one of these at any racers supply house for 50 to 200 bucks. If you don’t want to shell out the bucks for this, bring a bottle of white out with you.
A notepad and pen are critical also. With so many adjustment parameters it is important to try to write everything down as you will never remember it all.
When at the track, first note your initial settings including the air pressure. Write it all down. Paint a stripe of white out on your tire’s sidewalls going down to the tread. It helps if you have someone do all these things for you as it gets pretty hectic when you are trying to get ready to run. Go out and drive the car, making mental notes on how it handles, what you like and what you dislike. When you pit or when your run is over, immediately measure your tire temperatures. You only have a few seconds to do this as the temperatures drop quickly. If the course is clockwise, measure the left side of the car first starting with the left front. If it is counterclockwise, measure the right side first starting on the right front. You want to measure the treads temperature in three places, the outside, the middle and the inside. Push the wire of the bead probe slightly into the rubber for the most accurate measurement. Measure all the tires quickly and be sure to write it all down. Next measure and record the tires pressure quickly before the tires have a chance to cool much. Look at the white out stripe that you made. It is there to indicate if your tires are rolling onto the sidewalls. The stripe should not be worn past the rounded corner of the tread- sidewall junction.

Now review your notes and the recorded data. How did you like the way the car handled? Did it push? Was it loose? Was it perfect? Look at your temperature distributions across the tread. Ideally it should be about 10 degrees hotter on the inside than the outside with an even gradient across the tread. *This is usually only attainable on a race car with optimized suspension geometry.* On a street, production based car that is totally modified for adjustably, even temperatures across the tread may be possible and on a FWD car usually the outside will always be a bit higher. On a stock car you cannot usually get better than a 20 degree gradient. Anyway, the camber and pressures might need some adjustment to get an optimal temperature gradients out of the tires. If the temps are fairly even, it means you are using the whole tread of the tire to it’s fullest. You also want to get the average temps on the front and rear tires the same. That is not possible with a FWD production based car. A spread of 30-40 degrees is about the best that can be expected with the front tires running hotter than the rears.

<u>Modern R compound tires work the best at temperatures above 180-190 degrees.</u> At temperatures much above 220 degrees, most tires will start to chunk. To know the exact temp that your tire works best, call your tire manufactures tech line for advice. Watch for chunking on the outside edge of the tire, where it is most likely to be a problem with a FWD car. Like I said, play with your air pressures and camber to get the temps right and an even distribution to avoid chunking. Raising the tire pressure will reduce flexing and the tire will run cooler, lowering it will cause the tire to run hotter. Raising the pressure will cause the inside of the tread to run hotter and the edges cooler, lowering will make the outside edges hotter and the inside cooler.

Once you are using all of your tires tread properly, you can play with the balance. Look at the previously displayed chart to see all of the variables. Usually you want to play with swaybar and spring rates to balance the car. Toe settings are useful to get the car to turn in and rotate. Keep on monitoring the tire temps and pressures and note how changes affect the car. (BE SURE TO WRITE ALL CHANGES DOWN AND MAKE ONLY ONE CHANGE AT A TIME) In a few sessions you will be able to have a good grip on how to set your car up (bad pun).

On a stock car, about the only variables you can play with are tire pressures and toe. Adjust your pressures so the temp gradient is as even as possible across the tread. Since your adjustably is limited this will not be possible. Do not add so much pressure that the outside and middle of the tire are at the same temperature. At this point the tire is crowning with a bulge in the middle. This is not using the tire well. Tire pressures can be used to tune the balance. Try 2 psi increments as most good drivers can feel a difference in that. Remember to only adjust one thing at a time! Toe adjustments are very useful on the stock car also. A little front toe-out can help reduce push and get the car to turn in and set quicker. A little rear toe out can get the rear of a pushing car to rotate in tight turns.

If you don’t have a pyrometer, then use the white out sidewall stripe method to determine if the tire is rolling over excessively. If you adjust the tire pressure so it is only rolling just to the end of the rounded tread to sidewall juncture, then you are very close to the proper set up. Don’t be afraid of adding to much air as I have run up to 55 psi hot on the front tires of heavily understeering Showroom Stock cars with no ill side effects. In fact this is probably safer than allowing the tire to overheat and chunk. Just having the ability to play with the tire pressures at the track can give you a good edge over the typical slalom weekend warrior, at least in the beginners type classes. As you get better, you will have to master the art of suspension setup to remain competitive.

<u>Don’t be afraid to ask fast guys for help and advice but take it with a grain of salt. </u>Most of these people are helpful and friendly but every once and a while one of them will see you as a potential threat and will feed you misinformation so you will mess your set up all to hell. If someone’s advice seems the exact opposite of what I outlined here, be extra careful as this person could be snowing you.

My outline here is not the last word in suspension tuning. It is just meant to help explain things and to be a guide*** The final element is you***. You need to be able to make the car do what you want it to do. Don’t be afraid to experiment as long as it is under safe and controlled circumstances. Please experiment to get an idea what different settings do. Set your car wrong and know how that feels. Write everything down. Compare notes. Soon you will become a tweek master! Hopefully these hints will give you the winning edge and help guide your learning process.

And lastly - keep it off the streets - join an autocross club or driving school.

Peace
BPR

 

Copy and paste to file. Thanks alot. This is exactly what I needed.

 

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