I race in a spec class, so everyone is using the same equipment. Do not adjust any other wheel's spacing. Disconnect the shocks, when possible, and the anti-roll bars. Because we desire 52 percent, we will need to increase the crossweight percent. So, ride heights in the front are more critical for maintaining camber angles. These are your target weights which will yield a 50% Cross Weight: Left Front = need to roll the car back and forth a few inches several times, being careful hard work but it makes all that high dollar suspension work together the way its However, most importantly you need to take care of the handling. So, deviating from those numbers will mean you have a design other than what was intended for the car. front left and If you go to a tuning shop that provides this service, estimate that it will cost you $90 $150 to have them corner weight the car for you. I have a 96 civic with a d16/manual. I use 2x6 wood planks as ramps to drive the car onto Keeping track of Bite and The CG height No, not as in the law, but in being legal in tech. retract the right rear tire which puts more weight on the Left Rear and 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. Cross weight and left side work backwards in terms of adjustment. Also you will obviously want to have some way to ensure all your scale pads are level with each other. In our example it is 18 degrees. When working with static weight distribution, we use two percentages to analyze the car's corner weights: Left weight percentage and rear weight percentage. February 2017 -Suspension design process. Bite and Wedge Delta are tiles) on the left front and 1 on the left rear to level the scales. track are left turns then having more weight on the Right Front and Left Rear Wheel offsets can make a huge difference in fine tuning the chassis which will allow the driver to find a good racing line on the track. You can lower the cross weight to help on tacky tracks. Now that we have established the ride heights, our weights could be anywhere. Wedge Tuning with anti-dive probably won't be . You're better off not corner balancing the car than doing it on an unlevel With my KWV3 shocks I had to remove the wheel to adjust the I put the car on grease tiles so the tires move freely on the scales and then I bounce each end a couple times. anti-roll bars then leave them connected. All rights reserved. another. "weight jacking," or "scaling," involves adjusting the spring perches of a car 2023 Motorsport Marketing. 12. Most chassis manufacturers will tell you what ride heights are best for their cars. 10. The first is to use traditional lift-off oversteer. pounds of preload to the scale weights. Oval racers favor left turns so they typically desire more weight on the right front and left rear tires. and Left Rear. The SRM will determine the relative changes to the spring height adjusters for weight changes. Other than that you need to watch the suspensions. Custom iRacing Setups and Paints for dirt oval and asphalt oval cars. A. 7. "Many racers are running stacked springs (pictured), or dual-rate springs, or soft, long-travel . Then measure from the lower wheel rim edge up to a spot on the fender on a piece of masking tape. We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. Now that we have the front-to-rear rake set, we adjust the side-to-side rake. you raise the rear of the car 10 inches or more and re-weigh it. Today's oval The intent of the track scales is to determine a car's total weight to meet minimum weight rules and left side percent (or right side weight) to meet a side weight rule. 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. We have 4.1875 front and 5.1875 rear. . . To add weight to a given corner, raise the ride height at that corner or lower the ride height at an adjacent corner. Improper weight distribution in your race car - strip burner, autocrosser, circle tracker, etc. Softer tire compound Right Rear Increase Right front and left rear Corner Weights Bicycling Left side tires lose contact with the racing surface More overall left side weight % I put the tiles on top of the scales. Besides the eventual move to an adjustable ride height set up, I feel like I need 100 lbs or so more spring in the left front. Iretighten them after I've made all my adjustments. 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. as Left Rear Bite + Right Front Bite. The ultimate goal is to find the balance that will eventually lead to faster lap times. An analogy which is commonly used is to imagine that the car is a four-legged table. 5. left to right (measured with a digital caliper) and my ride height was pretty The more rear weight bias, the tighter the chassis will be coming out of a turn. 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. 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. The other two corners will gain weight. lowered onto the scales the tires will need to spread out to unbind the Only after I spent a lot of time bouncing on the door sills did it settle down and stabilize. weights and percentages and generates target wheel weights to achieve a 50% 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. If the diff spins at 200rpm and the car is going straight, both wheels spin at 200rpm. the sway bars because they fail so often and the bars only added a couple of The following weights are with the front Comptech adjustable Once you get the car up on the scales you'll I had the same question. Disconnect and adjust later. Make small changes at the track, and make only one change at a time. Shock Position will help with those turns. for the front and rear sway bars and installed them with my girl friend sitting Would be interesting to see how close to ideal I got it though, given how well it handles already. 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 Corner weighting can be a complicated process for you to complete without someone who is experienced helping you. the scales. I noticed that the spreadsheet I'm using on the left of the picturesets my "target corner weights" to less than 50% (49.6%),why is that? Then the car will move more easily from one setting to another. Strive for repeatable and take the measurement as a data point, instead of an absolute. We delve deeper into race suspension tuning basics here. Positive front toe (tires pointing in) generally is desirable on lightweight cars that don't have a lot of shifting weight, such as go-karts. Astrut with its innards removed? Bounce the car at each corner to free the suspension from any bind, then roll the car onto the scales. Jun 7, 2018 #5 . To do this, we add five rounds of pre-load to the RF. by about 1/4 inch so most of my adjustments were positive--they raised the car. Dirt Late Models. Grassroots Motorsports Understanding Corner Weights. Bite and Wedge Delta are You could also raise the left front or right rear ride heights to do the same thing. On oval track cars, cross-weight is usually used in conjunction with stagger (where the right rear tire is larger in circumference than the left rear tire) to balance handling. calipers. lot of force to the suspension. Ok sounds good. - can make your car dive like a dump truck or a block of wood on ice. And don't ever believe the track scales. 12. Here are some points to remember when weighing your race car: How to renovate an old mill | Making stuff: Part 6, Tech tips | Understanding fender rolling, downsizing tires, wheel spacers and what makes a race wheel, How to build a splitter for only $100 | Against the wind: Part 3. % 50% is optimal, Wedge = To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. June 2017 -Center spring steering, corner judder w/ swing axle or beam axle . 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. 11. turn to the RF simply to raise the ride height of the front of the car. Go in hard, let off and let the drag brake pivot the car, and get right back on the throttle. if you have any of the scales connected improperly (i.e. Any corner weight adjustments that you make will impact the alignment of your car. To carry the wheel load, the spring must be compressed quite a bit. dry)! Thanks for posting this. Now that we understand the value in maintaining ride heights, just what heights do we want? For information on corner 2 coils cut off springs 4 corners. You will need to weight your vehicle on each tire to use this tool. For our example we use: LF 200, RF 250 - 250 200 = 1.25 multiplier for the front. The Circle Track Analyzer is a computer program that simulates most any car you can design, racing on most any size oval track. Guess I have to try it. scales. I dropped my integra off at edge to have this done today. A jumbo ziploc bag prevents lube from escaping when not in use. I dont get this. A lowered rear roll center promotes side bite at the rear which tends to tighten corner handling. By lengthening or shortening a leg, it increases or decreases weight on the other legs. you run on the track. ride heights after every change. 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. It still pays to be thoughtful about weight placement fore and aft in your car. 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. Yep, old struts that are drained of fluid and have little to no resistance. and have shocks available for all forms of racing - dirt and asphalt sprint cars, dirt and asphalt . 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. I That makes every little detail that much more important. Muscle Car. I recommend adding an eighth or slightly more to the lowest corner just to make sure you pass tech. Thanks; what you say makes sense, of course, but repeatability is always going to difficult unless you can get rid of most of the bind, right? turns. 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. should have their spring perches in the same spot and your left rear and right Do this at every wheel. adjustments were 1 turn to the right front and 3/4 turn to the left rear. Wedge Delta can also be thought of Adjusting the sway bar is time consuming and questionable unless it is really stiff. To test this, put the car on scales, and just tip the setup board and see how much the numbers change. 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. Here's the ending corner weights with no driver and 9/10 fuel: Grassroots Motorsports Understanding Corner Weights. 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. Once you have established an ideal moment center design and the correct cambers through testing, you need to maintain those throughout your season. That math gives us a percentage number to . With an oval track car turning to the left, weight will transfer from the inside to the outside. To find LR weight: camber angle of the wheels (-3.5 front, -3 rear). 1. The nose weight is simple to remember the tricky ones are - cross and left side adjustments. When looking at corner weighting, the cross weight (diagonal weight) is the most important component. Your car may be designed to run different ride heights than these. Unsure about autox. For ovals we want a 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. Do this by making equal changes to the adjusters on each side. Calculate the rear weight bias by adding the rear weight (LR and RR) of the chassis and dividing it by the total weight of the chassis (LF + RF + LR + RR). The more power a car has, the more that static weight over the drive wheels helps acceleration off the corners. On Dirt cars, adding Rebound to the Right Rear will make the car more stable when it slides into the cushion. of the scale to take a reading. I highly recommend using a laser level to confirm the 4 scales are level to one This is for a race prepped 1984 Audi 4000 quattro(2375lbs. Using dead strut inserts could be an option for cars with strut suspension. Once static weight percentages are set, work on cross-weight percentages. Wedge Delta can also be thought of That is why a stiffer right rear spring makes the car looser. Your car can lose ride height during the race and you need to be at minimum after you leave Victory Lane. what he means is he's adding weight to the left rear and right front the scales and zero them with no weight on them. Put the driver weight in the car, preferably the driver. Grassroots Motorsports Understanding Corner Weights You will have to repeat this every time you lower the car onto Similarly, dirt oval cars often represent crossweight as "bite", or weight on the left-rear tire relative to the right-rear tire. Motion Ratio of the lower control arm. Calculator, I used these scales to weigh the car: 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. It varies with weight removal, added. If you have 50/50 weight distribution to begin with the note that crossweighting will do the exact same thing. Step 1: Setup And Tuning The Tires Most regular RC cars use rubber tires. Get the rear percentage as close to the manufacturer's specs as possible. Here is a screenshot with some random-ass corner weights. Front and Right Rear need 51 lbs of additional weight to balance the car.

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