F.A.Q. Read Here *FIRST*

All over the world, Nissan products are involved in road racing, track days, time attack and autocross.
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F.A.Q. Read Here *FIRST*

Postby Joe » Thu Aug 25, 2005 9:08 am

Welcome to the Road Racing/Autocross forum, In this thread im gonna post a small list of rules and some of the general questions a newbie may have. This thread isnt finished so please point out errors or anything you would like to see added by replying.

- This forum is for discussion of sanctioned racing/high performance driving events. please keep talk of street and illegal racing out of here. it will not be tolerated.

- Most important rule is to SEARCH AND USE THIS FAQ! I will continually update it with the most common questions and answers.

All FAQ's can be found on this page, also linking them directly (will open in new window)


Road Racing/HPDE

Suspension 101

Suspension 102 under construction

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Re: F.A.Q. Read Here *FIRST* (Kamin)

Postby Joe » Thu Aug 25, 2005 9:08 am

AUTOCROSSAll information posted on http://www.7thgencivic.com/for...33268 thanks to user "robbclark1"

1) What is Autocross?2) How do I become involved in autocross?3) What do I have to do to my car to compete?4) What happens the day of the race?

1) What is Autocross?Autocross, also known as SOLO 2, is a timed motor sport within the SCCA (Sport Car Club of America), usually held in big open lots. Drivers navigate a safe course, outlined by cones, one at a time. Rather than retype all this useful information, the San Francisco and Washington DC SCCA’s along with tirerack have set up FAQs that they use. It is a general outline of Autocross, Autocross Classes, and the SCCA.

Usefull Linkshttp://www.tirerack.com/featur...k.htmhttp://w ... novice.htm

2) How do I become involved in autocross?

The first thing you want to do is go to the SCCA website http://www.scca.org and find your local region’s website. That will have all the info you need on local races. Most places can register you for a race online in a few weeks to a month in advance. Register early because they usually fill up quickly. Fees vary but are generally around $25-35 for the day.

3) What do I have to do to my car to compete?Nothing. You can race STOCK! There is nothing that says you have to modify your car to compete in Autocross. A car need only be road worthy, and free of lose contents. Although autocrossing is generally very safe, and conducted in an open area at relatively low speed, helmets are required. Most modern motorcycle helmets meet the required standard, and free loaners are often available. You do not need to spend a dime on the car to autocross it. Modifying it is simply a choice to improve the car as you improve with it.

Some people suggest getting to know how your car handles in its stock form then if you choose to modify it, add a single part at a time so that you can learn how the car responds each time. As far as the suspension goes, the stock setup can take the punishment. There is absolutely no need to alter anything to go out and run. Later on, you can upgrade things, provided you keep a close eye on compliance to the rules. They can get tricky and nit-picky if you're not careful with what you buy. Your modifying should be gradual...no need to drop $2000 all at once. I've slowly added things over the year and will continue to add through next year. It helps to slowly get used to the car getting stiffer, rather than all of a sudden.

Before you start modifying your car, pick a class you would want to race in, where you would feel comfortable. If you want to race stock, the rules are set up to separate you into classes so that you can be competitive. They would not put a corvette against a civic, now would they?

Civics, non-Si, are in H Stock (HS), if not modified, against cars like base Sentras, Focuses, and Protégés.

Beyond stock classes, most people with common modifications will end up in Street Touring S or X (STS/STX). STS is probably the biggest classification for tuners. It allows mostly bolt-ons, suspension work, and bodywork. This is a highly competive class, where the weapon of choice is usually the Falken Azenis or Kumho MX tire, however most common street tires are acceptable in this class. If you are planning on buying tires, and have autocrossing in mind, research should be conducted before making any major tire purchase. Generally small, light wheels (15/16” etc.) are preferable.

If your car is ridiculously modified you will find yourself in street modified (SM). This is basically a street legal free-for-all. Internal engine work, turbos, swaps, big brake upgrades, CF hoods/trunks, gutting the interior/weight reduction, etc, you will be bumped to Street Modified (SM). SM is where a lot of “big boys” race so be careful what you do to your car. You don’t want to be moved to SM just because of a CF hood.

If you find yourself on the bubble between classes, go for the lower one. If the only mod you have is an intake, take it out and use the stock one, run HS. You'll be better off until you can get the car a little more modified and you get better at finding the car's limit. If you're seriously setting the car up for autocross, then the rules to keep yourself out of SM should be in your mind. Keep the car in STS unless you've got big plans for a K20 or turbo setup. You will find that STS usually draws the largest crowd and is mostly the compact/tuner crowd. So bragging rights are up for grabs. And it doesn't matter who can put their foot through the floor and shift gears. It really is who is the better driver.

If you have modifications to your car, you must place yourself in the correct class. Be sure to read the rules very carefully before doing anything. There are lots of ways to trip over them. If you are in doubt of a modification complying with the rules check with the local SCCA and ask them if you don't understand what the rulebook says. General rule is that if it doesn't specify it in the book, you CANNOT do it.

Rules and Classifications

While no modifications are necessary, many people enjoy modding their cars. Lists of important modifications vary. Most people agree that a good set of lightweight rims and sticky tires are the best mods you can do. After that a full set of coilovers or adjustable shocks with springs are good. As a general rule of all tuning, struts should always be upgraded before, or at the same time as springs. Spring changes alone are generally a poor choice. Other suspension modifications include sway bars, strut bars, poly bushings, roll cages, floor bars, among many others. Engine modifications are also allowed and can be varied. Parts include cold air intakes, full exhaust systems, swaps, turbos, superchargers, headwork, block work, etc.It is up to YOU to decide what you want your car to do and research the parts you think will get you to that point! You should consider the impact a mod will have on your class rating as simple mods may move you into highly competitivee classes THERE IS NO PERFECT SETUP!!

4) What happens the day of the race?Well you show up, ON TIME, or early! Find out when check in for your heat is on your local website. The first thing you want to do is go to the registration booth so they know you are there. They will give you a worker assignment (fixing cones etc for 1 race) and explain to you what to do. Next, prepare your car to pass tech. If you are changing anything before the race, you must arrive extra early, and do it before tech. To pass tech your wheels must on tight, there can’t be anything loose in your car, you must take out your floor mat, every aftermarket part is secure, your front windows must be down and you must have your run number somewhere on your car. Your battery should also be tight, and your numbers should be highly legible, and 10-12 inches in size. Printouts generally work, as does shoe polish. There might be more or less depending on the race officials. There is more information in the links above.

Most races will have a novice coordinator who will make the whole experience much less intimidating for you. Often the novice coordinator can pair you up with an experienced driver who can ride along with you and give you some tips on a volunteer basis.

ANDY'S TOP TEN AUTOX DRIVING TIPSBy Andy Hollis(Andy is a multiple National Solo Champion and an instructor for the Evolution Solo School)

Originally posted on Miata.Net

[Just got back from a weekend of teaching Evolution schools and thought I'd share some stuff that I must have said a thousand times.]

1] Position first, then speed. Positioning the car perfectly is more important than trying to attain the highest potential speed. For example, you will drop more time by correctly positioning the car nearer to slalom cones than you will by adding 1 or 2 MPH in speed. Same with sweepers (tight line). Same with 90-degree turns (use all of the track). Also, position is a prerequisite for speed. If you are not in the correct place, you will not be able go faster. Or at least not for very long!

2] Turn earlier...and less. To go faster, the arc you are running must be bigger. A bigger arc requires less steering. To make a bigger arc that is centered in the same place, the arc must start sooner (turn earlier).

3] Brake earlier...and less. Waiting until the last possible second approaching a turn and then dropping anchor at precisely the correct place so that the desired entry speed is reached exactly as you come to the turn-in point is quite difficult to execute consistently. Especially when you consider that you get no practice runs on the course, and the surface changes on every run, and you aren't likely to be in exactly the same position with the same approach speed on every run, etc. Better to start braking a little earlier to give some margin of error. And by braking less you can either add or subtract braking effort as you close in on the turn-in point. This will make you consistent and smooth.

4] Lift early instead of braking later. Continuing with the philosophy of #3, when you need to reduce speed only a moderate amount, try an early lift of the throttle instead of a later push of the brake. This is less upsetting to the car, is easier to do and thus more consistent, and allows for more precise placement entering the maneuver (remember #1 above).

5] Easier to add speed in a turn than to get rid of it. If you are under the limit, a slight push of the right foot will get you more speed with no additional side effects. On the other hand, if you are too fast and the tires have begun slipping, you can only reduce throttle and wait until the tires turn enough of that excess energy into smoke and heat. Don't use your tires as brakes!

6] Use your right foot to modulate car position in constant radius turns, not the steering wheel. In a steady state turn, once you have established the correct steering input to maintain that arc, lifting the throttle slightly will let the car tuck in closer to the inside cones. Conversely, slightly increasing the throttle will push the car out a bit farther to avoid inside cones. It is much easier to make small corrections in position with slight variations in the tires' slip angle (that's what you are doing with the throttle) than with the steering wheel.

7] Unwind the wheel, then add power. If the car is using all of the tire's tractive capacity to corner, there is none left for additional acceleration. At corner exit, as you unwind the wheel, you make some available. If you do not unwind the wheel, the tire will start to slide and the car will push out (see #6 above).

8] Attack the back. For slaloms (also applicable to most offsets), getting close to the cones is critical for quick times (see #1). To get close, we must move the car less, which means bigger arcs. Bigger arcs come from less steering and require earlier turning (see #2). Now for the fun part... When you go by a slalom cone and start turning the steering wheel back the other way, when does the car start to actually change direction? Answer: When the wheel crosses the center point (Not when you first start turning back!) How long does that take? If you are smooth, it takes .25 - .5 seconds. Now, how long is a typical person's reaction time? Answer: about .5 seconds. Finally, how long does it take to go between slalom cones? Answer: Typically on the order of 1 second. Given all of that, your brain must make the decision to begin turning the steering wheel back the other way just *before* you go by the previous cone!!

Since this is a mental issue, a good visualization technique to get used to this is to think about trying to run over the back side of each slalom cone with the inside rear tire of the car. To hit it with the rear tire (and not the front), the car must be arcing well before the cone and the arc must be shallow. Attack the back!

9] Hands follow the eyes, car follows the hands. 'Nuf said.

10] Scan ahead, don't stare. Keep the eyes moving. Looking ahead does not mean staring ahead. Your eyes must be constantly moving forward and back, and sometimes left and right. Glance forward, glance back. Your brain can only operate on the information you give it.

Bonus Tip: Don't forget the stuff in between the marked maneuvers! Too often we think of a course as series of discrete maneuvers. There is typically more to be gained or lost in the areas that are in between. Pay special attention to the places where there are no cones

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Re: F.A.Q. Read Here *FIRST* (Kamin)

Postby Joe » Thu Aug 25, 2005 9:35 am

Road Racing/HPDE (High Performance Driver EducationSpecial thanks to kb58 from Honda-Tech for this information

The organizations below run driving events called an "HPDE" (High Performance Driving Experience,") or "time-trial." This is where you can take your stock or modified street car on a real road-racing track and drive as fast as you want in a safe environment. You'll see all kinds of cars, from Mini's, dune-buggies on slicks, Cobras, to Hondas, Toyotas, to Ferraris. It's great fun to go out with your buddies and see "what's what." You can show up with just about anything; turbos, oversize tires, NOS, big brakes; it's all welcome, unlike at SCCA events where you'd get reclassed or banned.

Consider what it costs to build up a decent drag race car and driving for 10-13 seconds at a time. Now consider spending about the same amount (or less if you leave it near stock) and driving in 3-5, 20 minutes sessions in one day! That's what you get to do at HPDEs, and no tickets! A pretty good deal if you figure driving time / money spent.

Requirements are usually (but not always) better seatbelts, helmet, cotton clothes, 18 years old or older, and that's about it. More safety equipment is a good idea (roll cage) but usually not required. Since you will be driving fast for quite a while, it is strongly suggested you check your tires, bleed the brakes, and check the pads before you go.

There is no official scoring other then recording your lap times. Costs (see last paragraph too) differ widely, from $200-$300 per weekend depending on the event, but for that cost you get a lot of track time. If that's too expensive, some tracks offer mid-week "test days" where you pay a reduced fee of $100-$200. Of course since testing sessions are for testing there is no timing, nothing is organized, but you get less of a crowd and you can do your own thing. Keep in mind though that the costs above only get you on the track. To be fair don't forget a motel, food, gas, tire and brake wear. It can be an expensive weekend if you don't watch things.

While a HPDE is not true wheel-to-wheel racing you still have to be careful. Passing is usually (but not always) restricted to straightaways which keeps MOST accidents from happening, but it won't prevent you from "doing yourself in" by dropping a wheel off and overcorrecting. Occasionally people do ball up their cars. Is this your only car, driving it to work or school? Also consider most insurance companies will not insure damages incurred at a timed event. Can you deal with the consequences and responsibility if you break it? If the answer is yes, read on.

Again, this is not true road-racing. If you want to get into the real thing, start at http://www.scca.org And note all the above is "in general." Contact your local HPDE organizer to get their exact rules.

Normally these events are announced months in advance and you must reserve a place ahead of time. In general, you are not allowed to just show up.

Notes:Racing can be very expensive; here's a thread on what it costs to go "real" roadracing: http://www.honda-tech.com/zero...age=1Granted this isn't an HPDE which will be less expensive; presumably you aren't blowing up high-strung racing engines, going though a set of pads each weekend, or buying a set of tires every event... but it can still be expensive.

Driving your car on a real track risks wrecking it, and possibly yourself. If you cannot afford to ball the car up, get out, and walk away and leave it there, rethink if you should really be doing this. Here's a thread on people's track accidents - it isn't if it can happen, but when: http://www.honda-tech.com/zerothread?id=1342480


Periodically amended to add the latest contributed links.

West:http://www.touringcarclub.comhttp://www ... erhill.com (street school)http://www.ncracing.orghttp://www.audic ... engate.org

Northwest:Pacific Raceways - http://www.pacificraceways.comBremerton Raceways - http://www.bremertonraceway.comhttp://w ... chool.com/ HPDE's at Pacific racewayshttp://www.irdc-racing.com/http://www.bmwacapo ... aceway.com

West...ish (Nevada, Utah)http://www.team.net/ivr/http://www.mill ... spark.com/

Midwest/North Central:http://www.cgimotorsports.comhttp://www ... ndex.shtml http://www.windycitybmw.com/home/http:/ ... t/"Compact auto timetrials", western slope of colorado 970-243-6620 Jerad

South:http://www.thedriversedge.net/http://www.rgvpca.org/ (south)http://www.edpracing.comhttp://www.cenl ... a-scca.org

Southwest (Texas/New Mexico):http://www.sandiamotorsports.comhttp:// ... racks.html

Southeast:http://www.morosomotorsportspark.com/ht ... portz.com/ (school)http://autox.carlc.com/ (auto-x)http://www.sebringraceway.com/ http://www.sfmreport.com/ Race Report for S. FloridaNASA Florida Regionhttp://www.safemotorsports.com/http://www.pboc ... -time.com/

East:http://www.trackschedule.comhttp://www. ... racepa.com

Way north... Canadahttp://www.clubdelta.ca/http://www.laps.cahttp ... decrew.com

National:http://www.mazdadrivers.comhttp://www.q ... .saac.com/

Racing Calenders:http://www.justracing.com/calendar.php

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Re: F.A.Q. Read Here *FIRST* (Kamin)

Postby Joe » Thu Aug 25, 2005 9:48 am

Suspension Tuning 101 (Basic information)Thanks again to robblark1 of 7thgenviciv.com

1) What do you want to do with your car?2) Vehicle Dynamics4) Camber/Caster/Toe3) Parts

1) What do you want to do with your car?It may be a simple question, but you have yourself this question before you start modifying your suspension. Do you just want to lower for show points, or do you want some serious suspension modifications so you can compete nationally? Before you slap on a performance suspension part, think about what it does and how it will allow you to move your car better. Sit back and think about it while you read up on suspension tuning.

2) Vehicle Dynamics

To get the maximum performance out of your car you have to first understand vehicle dynamics. Basically Vehicle dynamics are all of the things that affect the way your car handles, such as accelerating, braking, turning and various road surfaces and conditions. Most of this deals with weight transfer. When you accelerate, weight is transferred to the back, when you brake, weight goes to the front. And when you turn weight is transferred to the outside of the corner. The rest deals with your suspensions ability to keep the tires firmly planted on the ground and keeping the tire contact patch as large as possible.

a. WeightFrom every thing I’ve read, been told or seen work, how well a car handles is all about how well that car handles weight; as in where the weight is located in the car, where that weight gets transferred during cornering and how fast it gets transferred. Every thing you do to your car be it springs, shocks, or what not affects how the car handles its weight. Why is Weight so important to handling? Well that deals directly to how a tire makes traction. It’s a simple concept: the more weight on a tire, the more traction it will make. But this simple concept has a twist, and it goes: the amount of traction gained by increasing load decreases as more load gets placed on the tire. Meaning a tire with 100 lbs place on it will make 100lbs of traction, but a tire with 200 lbs on it will only make 180Lbs of traction a 10% loss. (This is an exaggeration but you get the idea). This concept of Diminishing returns brings up 2 truths.

1. A lighter car is inherently more maneuverable then a heavy car.2. Weight transfer is bad for handling.

The first one is easy to explain. We’ll use our overly exaggerated tires as examples and put them on 2 cars. Car A weighs 400LBS evenly distributed between all 4 tires, car B weighs 800LBS also evenly distributed between all 4 tires. So using the tire above, car A will be producing 800LBS of traction where car B will be making 1520LBS of traction. What this means is that although car B is making more traction, Car A is making proportionately more traction Vs its weight. (Car A is making 200% traction Vs. Weight, were car B is making 190% traction Vs. weight).

The second truth is a bit more complex. We will use Car B as our example here. Car B is making 1520 LBS of traction when it’s not cornering. When the car turns, weight gets transferred from the inside tires to the outside tires, so lets say 100 LBS came off of each inside tire. Now the 2 outside tires have 300LBS on them each, were the inside tires only have 100 lbs each. With 300lbs on the out side tires they are making 510lbs of traction a 30% loss (1020 total LBS) and the inside tires are making 200 LBS each (400 LBS) so now the total traction being made is only 1420 LBS Vs the 1520Lbs it was making before it turned. This is overly exaggerated for clarity, but the concept remains.So with these truths comes the reasoning that getting rid of weight and stopping weight transfer is a good thing.

b. TractionOk you now know how weight affects traction, but what exactly is “traction”. Traction is the tires ability to grip the road, and a tire only has so much traction. Tires make traction though friction between the rubber molecules at the tire contact patch and the road surface. And as discussed before, traction increases as vertical load on the tire increases, which is why aerodynamic down force works so well. Lastly, a tire will make more traction if the entire contact patch is equally loaded. There are 5 characteristics that affect traction. 1. Basic tire design and construction. 2. Sidewall rigidity. 3. Tread rubber compound. 4. Tread design. And 5. Tire size. Of these characteristics we only have a choice of Tire size, compound and Tread design. We can also control the tires pressure, camber, toe in/out and camber change [Camber Change is the number of degrees of camber that wheels lose or gain from static (down the straightaway) to dynamic (in the middle of the turns) chassis attitude.]

http://www.sentra.net/tech/garage/suspension.php has a large chart demonstrating what happens when you change certain parts and settings!!! Read it carefully.

3) Camber/Caster/ToeCamber, caster, and toe are all changes to the way your wheels and tires come in contact with the ground. Most factory cars have some negative camber in the rear set. Most owners’ manuals will tell you OEM specs of camber, caster and toe. These settings can become moved by driving, hit potholes, racing, etc. This is why you get an alignment every so often. Alignment shops will return your car to factory or near factory settings.They affect vehicle dynamics greatly if fine-tuned. Each car is different so you will have to play with the sittings to get the desired results. General rule of thumb is that some negative camber and some toe out will help handling, but the amounts will vary. So please don’t think that leaving your tires at –2 degrees camber all the time will help you! By changing the camber, caster and toe, you WILL ruin your tires faster. They take more stress and take the corners harder so it is suggested that you don’t run with “race” settings on the street if you can prevent it. You will be buying tires every month. Parts like Camber or caster plates allow for quick changing of the camber or caster for race days.

http://www.artsautomotive.com/...y.htmh ... n...31519/

WheelsYou know those shiny things holding your tires on. Some people call them rims, but that’s just a throw back to the 50's and 60's when all wheels were steel and to dress them up people put chrome rims on them to make them look pretty. Ok enough of the history lesson, up sized wheels can both help and hinder handling. They help by replacing large areas of flexible rubber with relatively inflexible metal. This can significantly reduce wheel/tire deflection in cornering (i.e. it stops the tire from bending to maximize the tires contact patch). Alloy wheels also help to cool your brakes, they are like big heat sinks helping reduce the risk of brake fade under hard braking, that and most alloy wheels are more open then stock thus letting more air in to cool the brakes down. If they are light enough, they can improve acceleration and braking.

TiresDollar for dollar a good set of tires will boost you cornering abilities more then any other part. Performance tires aren’t cheep, but cost less then high performance tires, which in turn are cheaper then Ultra high performance tires. Race compound tires, surprisingly, can cost less then Ultra high performance tires, however you must consider the cost per mile. Ultra high performance tires, while offering the best traction for street tires, wear the quickest of all street tires. (Approx 20,000 miles.) Race compound tires can be found in many DOT legal treads (Meaning that they are legal to use on the street) and if driven lightly may last you 10,000 miles. Race compound DOT tires make gobs of traction, in the dry. When it's wet out forget it. You may as well have bald tires on ice. So think about where and when you intend to use a tire, then pick the right one for your needs. For those who intend to race, 1/4 mile or Autocross/Track Days, I highly recommend getting a second set of wheels and tires. Race compound tires while extremely fun on the street will not last long and can be dangerous in the rain.

Shocks & SpringsContrary to popular belief, shocks don’t actually absorb shocks, but rather they dampen vibrations. The springs actually absorb shocks over bumps and control body roll. The shocks control the oscillations of the springs, determining how fast the spring moves up and down. Stiffer shock rates slow spring movements, while a softer shock rate allows the spring to move faster. Shaft speeds. Shocks work mostly with in a range of about 3 inches per second to about 20 inches per second. The lower speeds come in to play during weight transfer when the body is rolling or pitching. The high speeds come in to play over bumps and ruts. A shock manufacturer can alter low-,medium-, and high-speed valving to control what the shock does in different situations. Low- and medium-speed valving are used to control how the shock influences handling. When a shock is user adjustable, it is usually the low-speed valving that can be altered. Springs, are the heart of the suspension system. Springs perform five critical jobs. First, they keep the chassis and suspension from bottoming out over bumps. Second, they control the tires over bumps. Third, they control body roll during cornering, chassis squat during acceleration, and chassis dive under braking. Fourth, the springs determine how the load on the tires shifts during braking, cornering, and acceleration. (this makes them a pivotal component in establishing the neutral handling balance of the car) Finally, the springs are the major factor in establishing the ride height of the chassis.

Anti-Rollbars/rollbars/swaybars ect.Anti-roll bars are quite possibly the best addition to cars since tires. They provide an excellent means for adjusting roll couple Distribution (Handling balance). They also control body roll, reducing camber change through corners. Of the two jobs that an Anti-Rollbar does, adjusting the Roll Couple Distribution is the MOST important. So just what is roll couple distribution? Simply put, roll couple distribution is the amount of roll resistance at the front of the car relative to the amount at the rear. Changing the roll couple distribution balance changes the handling balance of the car. This makes roll resistance changes the key to finding a perfect steady-state handling balance. Adjustable anti-rollbars allow fine-tuning of the roll couple distribution making setup much easier.

Strut/Tie bars/Roll cagesStrut bars are a chassis reinforcement made to reduce flex in the body of the car they are also known as Tie bars when struts are not present on the car. Roll cages main purpose is to protect the people in the car if the car were to flip over. Roll cages can also help to brace chassis flex and allow for safe 4-6 point harness attachment.

Polyurethane bushingsThe stock bushings are rubber which allow for soft and squishy contact. Poly ones are harder. By replacing the rubber bushings with poly bushings you will reduce ride comfort but you can affect things like weight transfer, steering, etc. There are many different types of rubber mounts in your car. Motor mounts are usually rubber and lessen the vibration the engine puts out. Changing to poly mounts, you will keep the engine more stable which will greatly help weight transfer, but you might feel the engine shake more. There are also control arm bushings. Control arm bushings are bushings that buffer some of the road vibration when you are driving. By changing the front ones you can increase steering response as well as weight transfer. The rears will help with weight transfer. There are other poly bushings you can get for the transmission, ball joints, sway bars, endlinks, tie rods, strut rods, etc. Energy Suspension and Prothane are two good bushing companies.

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Re: F.A.Q. Read Here *FIRST* (Kamin)

Postby Joe » Thu Aug 25, 2005 10:02 am

Suspension Tuning 102 (Advanced theory and tuning)

Big thanks to Mike Kojima for this information, he is a suspension god if there ever was one http://www.sentra.net/tech/garage/suspension.php

Advanced Vehicle and Handling Dynamics Friction circle: 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. Understeer: 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. 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 if you are a dork mode driver, you are probably better off with your car set like this(or a raw beginner, I did not mean to be insulting). 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. Even my uncoordinated evil twin sister could get that right, maybe. 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. Front wheel drive cars like ours tend to exhibit understeer as the final terminal mode of balance. Oversteer: 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 ****ty", "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 a dork (uh sorry, beginner) 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 pro-rally on the dirt which I don’t know too much about. Oversteer is slow on the pavement because hanging the tail out bleeds off a great deal of speed going through a corner. Unless you are in some sort of Option Magazine drift contest, conserving the momentum is the fast way around as turn. Neutral: 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 and the car possesses is being put to the ground. Racers call this "drifting". This not to be mistaken for the idiotic Japanese Option Magazine video/Stupid Street Magazine stuff that 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. Polar Moment of Inertia: 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 Sentra, 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! Slip Angle: 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. Conversely 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.

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