Track Side Quick Reference - FMI Knowledge Base - FMI Racing preload (extending the shock) to the Left Front, and one positive turn to the Right Front. That method keeps the ride heights close to the same. springs to put more weight on the left rear (and right front) tires and . < Enter your corner weights in pounds or kilos and click 'Calculate'. The effect of shock rod seal frictionat the wheel will be reduced by the crank leverage ratio. If you have 50/50 weight distribution to begin with the note that crossweighting will do the exact same thing. adjustment so I have a history of each adjustment. Grassroots Motorsports Understanding Corner Weights. Put the driver weight in the car, preferably the driver. When working with static weight distribution, we use two percentages to analyze the car's corner weights: Left weight percentage and rear weight percentage. 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. You can The salt acts as tiny ball bearings and will allow the tires to (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will = 50%. 2023 Motorsport Marketing. Adjustable end links are more If the car understeers or oversteers in only one direction, check the cross-weight percentage. Grassroots Motorsports Understanding Corner Weights "two linoleum tiles & salt" technique to allow the tires to slide on the scales There are legal issues too at the front. Even 1/8 inch difference will make a difference, especially if you have However, most importantly you need to take care of the handling. unbalanced--it will turn better in one direction than in the other (all other how and why to corner balance a car. This gets very tedious, given the number of iterations it typically takes to get the corner weights right. 4 Establish the exact weight change in percent that a given spring height change will make and record that number. cross weight. McMaster-Carr adjustable end links You can drop the front end slightly or raise the rear end for more aggressive turn-in. Additionally, it is much more difficult to change rear percentage much, since rear weight is mostly a design function. Your ride heights determine your arm angles up front, as well as the cambers, and, to a lesser degree-excuse the pun-the caster angles. Once you have installed your coil-over suspension, mount the rims with the tires you will be racing with, and complete all other items that could impact the vehicles weight and placement of that weight. It was a good car. It's better to make many small changes than to try Use those racing internet forums, and dont be timid about asking for some assistance! We had a good Miataset up for ST. In the above example, to go from 52 percent to 50 percent cross-weight, try lowering the right front and the left rear one-half turn on the weight jack bolt or spring perch while raising the left front and right rear the same amount. Thanks for posting this. I made a 4-scale system for my off-road cars. 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. Other than that you need to watch the suspensions. In the example at the beginning of the article, this was the problem: a cross-weight percentage that was less than 50 percent, and probably off by at least two percent. I lowered the right front spring perch 1 full turn (equates to I installed dry)! My track width with CE28 17" x 9" wheels These are your current calculated weights: Total Weight = Front Weight = % Left Weight = % Right Weight = % Rear Weight = % Cross Weight = 50% is optimal Bite = Bite should be positive for oval racing Wedge = % Wedge Delta should be positive for oval racing To truly optimize your shocks, your overall suspension setup must be right, including ride height, camber, caster, toe, and the correct spring rates. 2. extra weight is on the left rear and right front tires which gives them more When looking at corner weighting, the cross weight (diagonal weight) is the most important component. Check your tire pressure and bump it up to the hot pressure The outer rear tire drives "around" the outer front tire, allowing the chassis to efficiently turn into the corner because the rear tire Once you have established an ideal moment center design and the correct cambers through testing, you need to maintain those throughout your season. Right Front tires. turns. To find LF weight: document your current ride heights and your coil over changes each time To get good accuracy easily make sure you get the low hanging fruit first like removing the friction between the tires and the scales so there is no bind. difficult to position all 4 scales so you can just drive up on all of them at PDF iRacing Set-up Guide Get the rear percentage as close to the manufacturer's specs as possible. I'm anxious to see what Proform says about my experience. Left Front weight: We delve deeper into race suspension tuning basics here. Carry some in your tool kit and buy tarus wheel studs if you want a dirt cheap slightly longer wheel stud to have more safety. Put the car on ride height blocks without the shocks in the car and then measure the shock length from center of bolt to center of bolt. Remember that there are several ways you can maintain ride heights at the track, with loaded spring length measurements, chassis to lower control arm or chassis to rear axle tube measurement are some of those. My left rear is something like 150lbs heavier than the right rear, with both fronts even at ~740lbs each on a 2425lb FWD car. These are your target weights which will yield a 50% Cross Weight: Left Front = not to push it off the scales, to unload the suspension (as the car is Always To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. Jacking weight will not alter the left side or the rear percentages. rear and tried again but I still needed more weight off the right front and left springs to put more weight on the left rear (and right front) tires and Also double check that the Take care that the car does not accidently slide off the scale pads. If you raise the ride height at a given corner (put a turn in or add a round of wedge), the weight on that corner will increase, as will the weight on the diagonally opposite corner. Now that we have established the ride heights, our weights could be anywhere. Remember that changes in stagger, tire pressures and springs will change the ride height and alter the cross-weight percentage. weights: Corner Weight Calculator if Examine a modern push/pull rod suspension, particularly if it uses a crank link to transformthe Here is what you do. The front will show close to 60%. decided to try 5 turns total of spring perch movement to balance the car. Cross-weight is also called wedge: If the percentage is over 50 percent, the car has wedge; if below 50 percent, the car has reverse wedge. I Wheel Offset Changes - Dirt Track Supply Drag Racing. positive Bite and positive Wedge Delta. It puts power down better, and any decent FWD car will be carrying a wheel in the air around a turn anyway, so by default the outside rear gets 100% weight transfer when it's being asked to turn anyway. 4. I needed 3 tiles on the left front and 1 on the left rear 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. camber angle of the wheels (-3.5 front, -3 rear). You can change ride heights later on, but remember that your front moment center geometry will change and your rear geometry will also change, including link angles and pinion and third link angles, as well as rear alignment in some cases. This makes the cornering force balanced from left to right and offers the best performance overall. To help you, here is a method you can use to set the spring height on the shock using a spring rating fixture with coilover ends installed. Dirt oval racing tips/ Go karts - Don Terrill's Speed-Talk Granted, moment centers will stay fairly consistent with small movements of the chassis in dive and roll from the ride heights being off a little. Rock or bounce the car helps. 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? Check your tire pressure and bump it up to the hot pressure I put the tiles on top of the scales. To keep things clear I call this added weight Wedge Delta "There's a lot of freedom when it comes to setups using various styles of springs" in dirt late model racing, said a source. suspension changes to track your progress. How To Set Up RC Dirt Oval A Guide - Explained! Record each spring rate. TVW - (RF + LF + LR) = 603. A good starting point would be tank of gas. That is what you need to read on the spring rate fixture at installed shock length. Once you get the car up on the scales you'll 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. works well. The Circle Track Analyzer is a computer program that simulates most any car you can design, racing on most any size oval track. For ovals we want a (corner weights) instead of moving shims above / below spindle? How NASCAR Wedge Adjustments Work | HowStuffWorks corner weight calculations: Corner_Balance.zip Caster Creativity - JOES Racing Products To maintain the ride heights, we also must reduce weight or preload at the LF and RR springs. Delta which is simply the difference between the two diagonal tire weights. Hub stands are a great idea just for ease of access, but removing friction is an added benefit. Right Rear. Intercomp 102030 5X5 Hub-Mounted Corner Weight Scale. If we make equal and opposite changes to each side to change the ride heights and do both the front and rear together, then the process will move along faster. LR = left rear. Here are some setup tips that will help you really get the most of of your Slash: > Keep it clean. [Up] [CornerBalanceCalculator] [CGHeightCalculator], This calculator takes your car's four wheel weights and calculates current You would be amazed at how much bushing twist can contribute on your suspension. turns. If you lower the ride height at a given corner, that corner will lose weight as will the diagonally opposite corner. 50% then Wedge Delta will be 0. . In contrast, the corners on most ovals are super speedways are of a similar radius, and run within a very narrow range - closer to three-to-five miles an hour in difference. This measurement can be manipulated by changing spring rates, coilover . Now that the car has the correct ride heights and weight distribution for your setup, you need to make sure those don't change at the track. The first spreadsheet below is what I started with. This obviously means that decreasing cross weight or left side weight I'm off by 0.1% (see numbers on left side of the spreadsheet). to measure your new springs and put the longest spring in the left front--this The rear weight percentage is found in a similar manner: Add the LR and the RR weight together and divide the sum by the total weight. Battery: 2 cell lipo max "Many racers are running stacked springs (pictured), or dual-rate springs, or soft, long-travel . By lengthening or shortening a leg, it increases or decreases weight on the other legs. The crossweight percent will have changed to, say 55.4 percent. lb driver, no passenger, spare tire removed, soft top up, Magnaflow mufflers (-20lbs), Braille (TVW LSP) - LF = 769D. Can do to just left sidesor right sides, or to all 4. Measure control arm angles after each change. The third, and probably the best, option seems to be to invest in a set of hub stands, as this not only takes care of the bind issues via their built-in rollers, but it just makes the task of doing the alignment a lot simpler as well. For street cars it certainly can be. Take the cosine of that angle, divide it into 1.0 and then square it, or multiply it by itself. There is a reason for this order. As long as the tires have near "1 to 1 traction" with the ground, you should set up your race car like an asphalt car (see the Chassis Set-up At The Rear For Cornering page). These weights are in ready to race form (including driver on board). A lowered rear roll center promotes side bite at the rear which tends to tighten corner handling. If you are using scales as a base, level the scales with a long level, a long straight piece of tubing, square or round with a smaller level, or better yet, an instrument level such as a construction level. Make sure all of the weights are in the car including fuel, oil, battery, cooling water, hood, and so on, or weights that will simulate those. Dirt Late Models. You can see that the leverage ratio in the crank link reduces coilover(and thus shock) travel, and Yeah, I'm a little puzzled by my result when I let me car down on my new scales as well. W. William18 New member. want balanced turning in both directions. Step 1: Setup And Tuning The Tires Most regular RC cars use rubber tires. Right Rear weight: < Enter your corner weights in pounds or kilos and click 'Calculate'. 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. Picture the following: Your car is really fast in right-hand turns, but understeers in left turns. 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. Because it's targeting LF/LR = RF/RR to equalize the left vs right handling characteristics. Open timing on motor and esc. You should also complete this process with approximately the amount of gas with which you will be racing. 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. 5. Bite tells us how much we You should read the spring preload amount. When you lower the panhard bar the rear roll center drops. Moving weight to the front of the kart will provide more front-end grip. Proforms are cheap scales. You need a nice, flat and level surface for the scales. The proper progression for these two parameters is to establish ride height first and then set the corner weights, which comes down to setting the crossweight. They kept saying that it would go anywhere on the track and anywhere they pointed it. LF coil over 5 turns. The angles are another way to set the suspension for the desired ride height and cross-weight percentage. Oval racers favor left turns so they typically desire more weight on the right front and left rear tires. Corner Balance Calculator - Rob Robinette Caster creates stability as the geometry . Some of the most popular engine packages are the Yamaha KT100S, Parilla Leopard, Honda CR125, Briggs L0206, Honda Clone, TaG (Touch and Go) and many more. LR 175, RR 350 - 350 175 = 2.00 multiplier for the rear. There is work involved in going fast for the full race and racing other racers clean. If you want to lower the ride height then retract both RF and What you're saying makes sense, but I can't explain why it took so long for my car to settle into its final weight reading. These are only average measurements, and they will differ depending on the particular model of car that you have and the tires it is using. If you have uneven mass on your wheels then your tyres will all have different levels of grip which can lead to an unpredictable car on circuit and make it corner faster in one direction than the other. racers discovered they could insert an actual wedge into the left rear Using dead struts and lots of bearings will help. Dirt Track Chassis Set-up At The Rear For Cornering - Auto-Ware I put the car on the scales and input the four corner This keeps the ride heights as close to ideal as possible. Only after I spent a lot of time bouncing on the door sills did it settle down and stabilize. Adjust the rear down by using the same method as in No. Step 1 - Determine Sprung Weight. this excellent article: Upgrade fluid and/or cool. In my situation, I have a lift, and I'd like to simply drop my car onto the scales, but it seems like that's the worst option as far as removing friction and bind. I use 2x6 wood planks as ramps to drive the car onto can help us get our setup right with less testing. 9. I even thought my excel spreadsheet calculated it's recommended corner weights to achieve 50% cross weight. If the car feels loose throughout the corner, lower both track bars evenly. Lowering the cross weight does the opposite of raising the cross weight. 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? Cross Weight or Wedge. The driver is optional based on No. Then the car will move more easily from one setting to another. split the adjustment between all four wheels--extend the LF and RR 1 1/4 turns (CG) height by using this online calculator: CG Height I see disconnecting the sway bar, and how to do it, but disconnect the shocks? One of the problems with cross-weight is that it will change the handling balance from a left to a right turn. Static weight distribution is the weight resting on each tire contact patch with the car at rest, exactly the way it will be raced. Adjusting the corner weights is how we establish the crossweight percent, or what is often referred to as the amount of bite, left rear weight, or wedge. These are your current calculated weights: Left Weight = I plugged in a bunch of numbers into my calculator and it all checks out. two years. Please post on the appropriate 4m forum. We will deal with preload on the bar later on. Now with the steering straight ahead and both hands on the steering have your buddy record the . rear. Its important to measure and note your Do this by making equal changes to the adjusters on each side. Other things to take into consideration are track conditions and weather changes. Brake pads badly taper worn - replace. will help with those turns. the scales. Ideal weight percentages: Front - 43-45% Left - 53-56% Cross - 52-54% What do these numbers mean? Or use an automotive tuning shop. 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. Strive for repeatable and take the measurement as a data point, instead of an absolute. Corner weighting your car is 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. but tend too love the 1/2 miles.I just cant figure out a way too get these. it would help the car turn left and accelerate better. weights into the spreadsheet (the blue numbers in the left "Corner Weights" Air up the tires as they will roll through tech. The following are screen shots from the If you shocks are working normally they are not worth worrying about. 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. Bearings, like sealed roller bearings,solid bushings, or spherical joints. We also take five rounds times the multiplier for the front of 1.25 5 = 6.25 rounds out of the LF. Keep in mind the stiffer your springs the another. If you don't have adjustable end links on your anti-roll bars I had the same question. you raise the rear of the car 10 inches or more and re-weigh it. be appropriate such as making small adjustments to all 4 wheels--add preload to To carry the wheel load, the spring must be compressed quite a bit. used cheap linoleum tiles (49 cents each at Home Depot) to shim two of my scales
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