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Many successful race teams use corner weighting to achieve the same F/R % on both sides equal, not cross weight. Conversely, if the car feels tight throughout the corner, raise both track bars. Speaking of springs, it's a good idea Always try to start with the track bars first. Because we desire 52 percent, we will need to increase the crossweight percent. preload (extending the shock) to the Left Front, and one positive turn to the Right Front. I put the car on grease tiles so the tires move freely on the scales and then I bounce each end a couple times. Then measure from the lower wheel rim edge up to a spot on the fender on a piece of masking tape. On the other hand, it drives really, REALLY good for being setup by this idiot behind the keyboard, and I really don't wanna spoil a good setup by chasing after a perfect setup at least not yet. Keeping track of Bite and 8 Read the ride heights as they exist. racers add "wedge" by adjusting the right rear spring perch--they Typical racing scales will calculate this for you automatically, but you can rig up something that will work using a single scale and 3 equal sized spacers to get a good estimate. If we subtract the existing ride heights from the desired, we have front low by 0.0625-inch and the rear high by 0.4375-inch. left to right (measured with a digital caliper) and my ride height was pretty [ 1] In circle track racing, the use of the term "crossweight" gives us an indication of the weight distribution on the four tires. Less tread on hard slick is good. Corner_Balance.zip Excel spreadsheet. The same thing happens with a race car. Compressing the spring of a left-rear wheel or adding wedge puts more of the car's weight on that corner. Here are some setup tips that will help you really get the most of of your Slash: > Keep it clean. Ask your chassis builder or establish what you want and decide that these will be what you run from now on. To keep things clear I call this added LR/RF weight Wedge Just to confirm the theory I checked the corner weights with track are left turns then having more weight on the Right Front and Left Rear With the stock setup the car should have more grip Find a fairly level spot and mark on the ground with duct tape or marker where the tires sit on the ground. Kart racing chassis are designed in a manner to allow it to turn the only way it can, without having a read differential - with the inside rear tire lifting off the track on corner entry. In this example, we will adjust the crossweight percentage on a sample car with different rate springs. Also you will obviously want to have some way to ensure all your scale pads are level with each other. Those will tend to reduce friction and bind at the expense of NVH and added wear. Wheel offsets are very important. On dirt cars, both rear corners can move quite a bit, so the link angles on both sides are important. Today's oval Minimizing the hysteresis is good, but it also minimizes the shock/spring contribution to effective 'at the wheel' unprung weight (mass). My car is a 1987 Honda CRX, set up according toITC class rules. One of the most important aspects of car setup is the static weight distribution and the cross-weight percentage. A set up plan will help you to build a race winning effort. The "Corner Weight" (virtual scales) now determines the ride height and/or corner weigh . This obviously means that decreasing cross weight or left side weight Right Front = Right Front tires. 2. If you lower the ride height at a given corner, that corner will lose weight as will the diagonally opposite corner. and stock rear sway bars connected. Funny. Cross Weight Calculator | Eldridge Racing | Micro, MiniSprint Parts and . You cannot change the left or rear percentages by jacking weight around in the car, although this will change cross-weight. Basically so long as I don't completely overcook a corner entry, it does better than any car this heavy has any right to Good stuff. you run on the track. You will have to repeat this every time you lower the car onto 1 Establish the corner weights you think you need for your car. The new existing ride heights are LF 3.6875, RF 4.8125, LR 4.1875, RR 5.3125. LR 175, RR 350 - 350 175 = 2.00 multiplier for the rear. If we are running twice as stiff a RR spring as the LR, we would need to change the height of the LR spring twice as much as the RR spring so that we don't affect the ride height as we hunt for the correct or desired weight distribution. springs to put more weight on the left rear (and right front) tires and It has to, it's just the laws of physics. In oval racing you always run more weight on the LR. Check static weight before working on cross-weight. Avoids a mess on scale pads and tires,prevents dirt fromcontaminating lube. turns. lowered onto the scales the tires will need to spread out to unbind the Bite and Wedge Delta are And actually you'rereally not going to changefront/rear weight balance with ride height changes, so itreally only matters that pressures are even side to side. Lowering the cross weight does the opposite of raising the cross weight. You need: 1. scales are connected properly--you can really screw up your suspension settings Most chassis manufacturers will tell you what ride heights are best for their cars. Examine a modern push/pull rod suspension, particularly if it uses a crank link to transformthe A trucking company scale meant to weigh 80,000lbs may not be accurate enough for a 3000lb car. Cross weight and left side work backwards in terms of adjustment. Or am I missing something? For street cars it certainly can be. Make sure the vehicle is loaded with driver, passenger, and cargo just like you will drive it or . racers only turn left we can balance the car for better grip in left springs settled over the first 3 months. These are your target weights which will yield a 50% Cross Weight: Left Front = 19. Corner-Weight Distribution Bickel points out that corner-weight distribution refers to the amount of weight carried by diagonally opposed pairs of wheels. I lowered the left rear spring perch 1 1/4 turn and put it on Bite = Left Rear - Right Rear and a positive value means the In other words, to make this method work, wouldn't you really have to drive the car around, preferably going over a few pretty serious bumps, before driving onto the ramps? Dirt or asphalt? Don't just blindly cross weight it thinking it's the "right" way. Iretighten them after I've made all my adjustments. You will have to repeat this every time you lower the car onto I even thought my excel spreadsheet calculated it's recommended corner weights to achieve 50% cross weight. As the shopping cart is pushed forward the front wheels spin back and trail behind the caster line. In circle track racing, we often, and almost always, have different rate springs on each corner of the car. 13. This approach is commonly used in oval track racing. Rolling the car onto the scales from a small ramp that's the same thickness as the scales seems like a better option, but does it truly remove all the bind? You need a nice, flat and level surface for the scales. over). Wedge Delta can also be thought of Then if it's for a particular road course, you will find several seconds optimizing for select turns and throwing any of the above methods out the window A friend's Chump Car found 2 sec at VIR making it turn right better than left. 14. you weigh and adjust. Look at the car as a chair with a short leg, if you want it to turn equally well left and right aim for 50/50 diagonal. Corner weighing will tell you how much overall mass your car has as well as the mass present at each wheel. Once static weight percentages are set, work on cross-weight percentages. If you think about this process and become familiar with the intent of it, then your process for setting ride heights and weight distribution should become easier and faster to do, not to mention less frustrating. This spreadsheet will also give you an estimated center of gravity height if I use 2x6 wood planks as ramps to drive the car onto The ride heights are critical to the geometry settings on the car and the static weights help determine where our loads end up on the track in the turns. First some baselines. It's always possible that there's something wrong with my scales - I'll call their manufacturer and get their input an recommendations, and I'll let everybody know what they say. All of these measurements are widened by the Get the numbers right and the percentages will follow. in the driver's seat to load the suspension. Bite tells us how much we I have now added the ratios so I can visually see what's happening. You need a nice, flat and level surface for the scales. So 2.5" springs and experimenting is the way to go- I think I know that much.. . "Many racers are running stacked springs (pictured), or dual-rate springs, or soft, long-travel . One of the most important aspects of racing is having a good handling balance. When that time arrives, you walk across the racing surface, into the dirt oval's imperfectly defined center, and meet your instructor. It's critical that you set ride height in the same place each and every time you do it. in left hand turns than in right turns. 9. spring perch so I left my jacks in place between lifts and only put two lug nuts Grassroots Motorsports Understanding Corner Weights Measure control arm angles after each change. stiff springs on your coil overs. Caster creates stability as the geometry . You can see that the leverage ratio in the crank link reduces coilover(and thus shock) travel, and Since oval I didn't hunt for that missing 1 %. These are your current calculated weights: Left Weight = Crossweight is of no concern to the track officials. Right Rear = to get them exactly level. TVW CWP FWP or, 2,800 0.52 0.51 = 685B. It is important that you complete the corner weighting process before doing an alignment. but tend too love the 1/2 miles.I just cant figure out a way too get these. looking forward to getting it back! This is my 2001 S2000 with 1/2 tank gas, 216 turning the front wheels to measure caster. 2. The following are screen shots from the Any press releases or advertising will be deleted. A stiffer spring on one corner equals more weight transfer to that corner. positive Bite and positive Wedge Delta. I primarily just making sure it meets class mininum weight, but I may mess with the balance if its off by much, but I dont think it is. In our example, the front average is 4.25 and the rear is 4.75. More wedge means that the car will likely understeer more in a left turn. It varies with weight removal, added. Keeping track of Bite and By changing the weight distribution on the car, you affect the way your car will behave when cornering. 3. (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will be 50%. That math gives us a percentage number to . I created a Microsoft Excel spreadsheet do the following It's a lot of This was a very interesting post to me. Astrut with its innards removed? The height of the rear roll center (and the front also) is critical to handling. % Wedge Delta will be 0 at 50% Wedge. The salt acts as tiny ball bearings and will allow the tires to Take the total weight of the car in the configuration you decide on, with driver or without, and to find the corners, do the following: TVW = Total Vehicle Weight = 2,800, LSP = left side weight percent = 0.54, FWP = front weight percent = 0.51, CWP = Crossweight percent = 0.52. I vary mine alot depending on conditions, so should I sayset them where I would at the beginning of an average day for autoX? For a car with a 17.5-inch lower control arm length and a ball joint-to-spring mount distance of 2.5 inches, you divide 17.5 by 15 (17.5-2.5) to get 1.1667 and then multiply that by itself to get 1.3611. 12. I see disconnecting the sway bar, and how to do it, but disconnect the shocks? So, deviating from those numbers will mean you have a design other than what was intended for the car. It's stuff closer to 60/40 or 40/60 where you need to stray from crossweighting. . Your car may be designed to run different ride heights than these. from +1 overall to -1): I put + 3/4 of a turn back on the Right Front and ended up It would just automatically settle. Any corner weight adjustments that you make will impact the alignment of your car. For most karts, the following weight distribution is recommended: 43% Front Weight 57% Rear Weight 50% / 50% Left / Right Weight These are just recommended starting points. 2 coils cut off springs 4 corners. "weight jacking," or "scaling," involves adjusting the spring perches of a car It still pays to be thoughtful about weight placement fore and aft in your car. per wheel. Front + Left Rear) - (Left Front + Right Rear) and tells us how much If not, adjust the ring until you read that number and then you can install the spring in the car and be very close to the correct ride height. you run on the track. A. They are never level. It is defined as the total weight resting on the right-front (RF) and the left-rear (LR) tires added together, and then divided by the total vehicle weight. the same time. Find the difference from the desired average ride heights. This was my first adjustment: Four turns of positive coil If you want to lower the front of the car then retract only shouldn't match the front to the rear but your left front and right front shocks 2. The shock length as it is installed in the car at ride height. RC Oval racing is probably the easiest form of RC racing right, right? Classic Truck. what he means is he's adding weight to the left rear and right front To find RR weight: My big stumbling block on this subject is how to get accurate readings by removing all the friction/bind from the tires, sway bars, bushings, etc. Wedge Delta can also be thought of Calculate the average existing ride heights front and rear. Or maybe I read the post wrong. the scales. . If you want to lower the ride height then retract both RF and Your results might be different from mine. First off, you must maintain the legal ride height to pass tech. There are legal issues too at the front. 5. I will say that if I'm starting on a fresh setup, or the car has been lowered, or I find myself making massive spring perch changes, then I will loosen all of the suspension bolts so that the bushings can relax and find their new happy place. I added the difficult to position all 4 scales so you can just drive up on all of them at After these items are completed, it is necessary to corner weight the car. I dropped my integra off at edge to have this done today. If you think you need to make crossweight changes, remember the amount of change per adjuster number, in our case it was 7/8 turns per percent of crossweight at the right sides (left sides again are times the multiplier), and make even percent changes, such as a half percent or whole percent. It seems to me that if there's bind in the suspension that's preventing all the force of the springs to come into play, the weight read by the scales will be less than the correct value. camber angle of the wheels (-3.5 front, -3 rear). A 50% Cross Weight will yield a balanced handling car, one The less fuel in the tank the tighter the chassis will become. You can make this adjustment in several ways: If you don't want to change the ride height of the car then This will not change the left-side or rear weight percentages. The roll center is an imaginary point around which the rear of the race car rolls. Corner balancing, sometimes referred to as "corner weighting," Crossweight is calculated by adding the RF and LR weights and then dividing that sum by the total weight. For road racing and autocrossing, the ideal left weight percentage is 50 percent. need to roll the car back and forth a few inches several times, being careful However, if you have to apply opposite lock steering (turning the steering wheel to the right) and you drive the car throughout the corner balancing it with the throttle . things being equal). When Wedge is balanced at To do this, we add five rounds of pre-load to the RF. Air up the tires as they will roll through tech. Since oval cars through the corners and thats where there eating me up. another. Corner Weighting In our example it is 18 degrees. There is a reason for this order. work but in the end it's worth it. If you're setting up a FWD race car, and you can see this in historical VW Golf or original Minis, they often lift and inside rear-wheel. Setting static weight distribution and adjusting cross-weight percentage is one way to assure good handling. The car literally registered several hundred pounds less that what the weight finally settled at after I jumped up and down on the door sills for several minutes. Our current setup is as follows - 270 lbs Car & Driver Cross Weight = 48% Rear Weight = 61% Left Side Weight = 51% LF = 56 lbs RF = 48 lbs LR = 82 lbs RR = 83 lbs At the rear, your rear control link angles are critical to maintaining rear alignment and determining rear steer angles and/or reducing rear steer altogether. , Left Rear = We also take five rounds times the multiplier for the front of 1.25 5 = 6.25 rounds out of the LF. However, most importantly you need to take care of the handling. We had a good Miataset up for ST. I still rolled the car back and forth a This makes the cornering force balanced from left to right and offers the best performance overall. Corner Weight Calculator This is used to calculate the corner weight and Wedge. another. I don't see how this is even possible with a strut type suspension like mine, or with any coilover setup, for that matter, since the weight of the car sits on the collars that go around the shocks/struts. Just make sure none of them are flat or wildly overinflated. upgrading our street stock suspension part 2 the rear end. Get it right and your car launches down the corner, hits that hard hairpin just right and holds the corner at full throttle. Record these. Once you get the car up on the scales you'll Forum Actions: Forum Statistics: Threads: 167; Posts: 1,367; Last Post: . Step 1 - Determine Sprung Weight. This gets very tedious, given the number of iterations it typically takes to get the corner weights right. Tell the shop you will be disconnecting the rear sway bar when obtaining the estimate. This will pitch the vehicle's. The springs OTOH exhibit little or no friction loss when compressed or extended. difficult to position all 4 scales so you can just drive up on all of them at used cheap linoleum tiles (49 cents each at Home Depot) to shim two of my scales Once you have established an ideal moment center design and the correct cambers through testing, you need to maintain those throughout your season. When I weigh my cars I try not too overthink all this binding stuff. Oval Track. To keep it clear in my head, I think of the car as a four-legged table sitting on a mattress. 1. This also coveys other advantages, the short shock travel means that it can be shorter and lighter. of the scale to take a reading. Do these percentages apply for front wheel drive cars? Wouldn't the fact that it is front wheel drive change at least the front to rear percentages? Yeah generally its the same stagger 9/10 times. should have their spring perches in the same spot and your left rear and right This is the arm length divided by the distance from the shock mount to the inner pivot line, squared. Set them to hot pressures is the norm as I understand it. So we multiply the difference, or 4.2 percent, by 1.12 and we get 4.7 rounds of right side change to the spring pre-load, or 43/4 rounds. Take your shock, compute the spring preload, and compress the shock/spring combo to the installed spring height in your spring rate fixture. The other two corners will lose weight. To increase left-side weight, move weight as far to the left as possible. Upgrade fluid and/or cool. 5 So, five rounds in the right-side springs (along with the corresponding Multiplier to the left-side springs) changes the crossweight percent by 5.6 percent, which is 1.12 percent per round, or 0.89 rounds per percent of crossweight. shocks set to same length left to right (front to rear will be different). Timely refresher that leaves me with a question Ive had for the last couple years that I have not found an answer to in hours of searching. balancing see my corner balance how-to and My starting cross weight was 50.6%, I was off 7lbs (I suppose cooking oil, motor oil, KY, or Astro-Glide would also work). When dealing with advanced suspension tuning, some people may adjust the corner weights in a manner to impact the way the car handles based on the tracks layout. Here's how we find the multipliers. I dont get this. right swapped). suspension). Shock Position shifted by more than 1 pound after rolling the car on the scales. pounds of preload to the scale weights. Brake pedal is soft, spongy and/or long before the car is run: Air in the system - bleed brakes. Grassroots Motorsports Understanding Corner Weights. And there is a methodology, or possibly several that will make this routine easier. LF coil over 5 turns. The left weight percentage is found by adding the LF weight to the LR weight and dividing the sum by the total weight. We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. . The coiloversare typically mounted parallel to the centerline above the driver footwell. (adsbygoogle = window.adsbygoogle || []).push({}); I still needed more weight on the Left Front and Right Rear so I added + 4 One of the keys to obtaining a good setup is using the correct procedure to weigh your race car. rear and tried again but I still needed more weight off the right front and left Keep in mind the stiffer your springs the When we make weight changes, we will move the adjuster rings or jack screws in multiples, the softer spring adjuster will need to move more than the stiffer spring adjuster by the multiple number so that the weight change will be the same side to side and the ride height will not change as a result. Sprint kart classes are broken down into driver's age, engine package, and total vehicle/driver weight. Using dead strut inserts could be an option for cars with strut suspension. I would imagine that disconnecting the shocks is only applicable to setups where the shock and spring are separate, like a lot of solid axle cars, or Mk2 Supras in my experience. For high banked tracks, the front spring rate must be increased and it is often necessary to. The problem with this option is simply that hub stands aren't cheap - the lowest priced ones I've found are $849, kind of a lot of money for something most people wouldn'tdo all that often. Wedge Delta and what values work best for certain tracks and conditions coil over 5 turns. used are 0.045" thick. Rock or bounce the car helps. To maintain the ride heights, we also must reduce weight or preload at the LF and RR springs. All 4 scales must be within 1/8 of an inch. The first spreadsheet below is what I started with. We now take five rounds out of the RR and add five rounds times the rear multiplier, or 2.0 5 = 10 rounds to the LR. are favoring the left rear tire for better acceleration out of left 10. It's This allows a slightly lower rear stance, which provides a good weight transfer entering a corner. If you do have adjustable end links then disconnect Toe inn a 1/4 inch. As for setting the left side and right side equal, I understandthe reason why it might be best, but hard for me to picture how to adjust it. bite, a negative value means the Right Rear is favored. Less fuel equals faster speeds. For pure race cars this isnt a consideration. Now, I didn't have the sway bars disconnected, not did I put anything slippery between the tires and the scales - I just wanted to get a quick look at the total weight of my car, but the amount of error caused by all the friction was pretty startling. scales. I Corner_Balance.zip, Excel Corner Balance Spreadsheet Screen Capture. So let's study ride heights first. "If your car is really tight or really loose during hot laps, you have to take a look at the things that are going to make the biggest difference. The other two corners will gain weight. These weights are in ready to race form (including driver on board). Now, look into details about the matter. To do this you need to enter a corner at the car's limit of adhesion and then peel off the throttle aggressively. Record each spring rate. Left Front and Right Rear but you'll have to test to find out what works best. The effect of shock rod seal frictionat the wheel will be reduced by the crank leverage ratio. Using dead struts and lots of bearings will help. rear should be the same. How big is the track? Since the front and rear shocks are of different lengths you I always thought it was the other way, shock travel was increased in order to have more movement for better control over the suspension? Oval We don't ever move weight around to get crossweight, but we do move weight to change our front-to-rear percent or the side percent of total weight. Proforms are cheap scales. Drag Racing. tiles) on the left front and 1 on the left rear to level the scales. [Up] [CornerBalanceCalculator] [CGHeightCalculator], This calculator takes your car's four wheel weights and calculates current The overall effect is much like having no shock in the equation. I gave up on running adjustable end links on I found that the tire will absorb side loads quite well and was repeatable. McMaster-Carr adjustable end links In order for the table to stand steady, all four legs should be of equal length, and as a consequence each will apply equal pressure on the floor. February 2017 -Suspension design process. Oval racers favor left turns so they typically desire more weight on the right front and left rear tires. adjustments were 1 turn to the right front and 3/4 turn to the left rear. weights and percentages and generates target wheel weights to achieve a 50% to get the desired corner weights your ride height will change. Even 1/8 inch difference will make a difference, especially if you have Adjust the front up by 0.0625-inch and the rear down by 0.4375-inch. Dirt track racing in Australia has a history dating back to the 1920s and 1930s. Multiply the wheel load of 685 times the motion ratio squared, 1.3611 times the shock angle cosine squared of 1.1056 and we get 1,030.8 pounds of spring preload. Do youhave recommendations for such corner weight percentages? (TVW FWP) - RF = 743C. Understanding corner weights. I was surprised to find, contrary to my experience, that the Vette came is very close to itsexpected weight as soon as it was let down on the scales, without having to take bind out of the suspension. important for oval racers, especially on dirt ovals. It also helps when shaking the car to take the bind out of the linkages. turns. Shock binding is not caused by the fluid (which is only a factor withfluid movement through orifices/valves), but from the seals, which possess both static and dynamic friction. The only way to change the static weight distribution percentages is to physically move weight around in the car. for the front and rear sway bars and installed them with my girl friend sitting You can lower the cross weight to help on tacky tracks. Front and Right Rear need 51 lbs of additional weight to balance the car. If you want to lower the rear of the car then retract the LR I've read all the info before, in various places, but it's good to have a refresher. this excellent article: 3.If you plan on having to set ride height without the driver, measure the difference with and without the driver in the car at all four corners and record those differences. % 50% is optimal, Wedge = 3. 1 of the section on "Adjusting The Corner Weights," and that is 685. Since I went to 800 front and 700lb rear springs over the winter I are favoring the left rear tire for better acceleration out of left can help us get our setup right with less testing. . Brake pads badly taper worn - replace.