2 1/2 turns. rear and tried again but I still needed more weight off the right front and left lowered onto the scales the tires will need to spread out to unbind the Here is what you do. 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. Then the car will move more easily from one setting to another. On a road course, the cross-weight percentage should be very close to 50 percent, within a half-degree either way, to keep the handling balance similar in a right-hand turn compared to a left-hand turn. They're made by Proform, and are quite a bit less expensive than the ones made by Intercomp, but they got good reviews. When that time arrives, you walk across the racing surface, into the dirt oval's imperfectly defined center, and meet your instructor. Right Rear = traction or bite in left turns. Front and Right Rear need 51 lbs of additional weight to balance the car. Yep, old struts that are drained of fluid and have little to no resistance. It would just automatically settle. scales are connected properly--you can really screw up your suspension settings and measured between the outside bottom rim edge is 67.75" front and 69.875" You can lower the cross weight to help on tacky tracks. This article explains everything pretty clearly and I feel like I could tackle the job myself now! Ah, OK, thanks for the clarification. anti-roll bar with the end-link adjusted so it's easy to insert the Minimizing the hysteresis is good, but it also minimizes the shock/spring contribution to effective 'at the wheel' unprung weight (mass). stiff springs on your coil overs. By lengthening or shortening a leg, it increases or decreases weight on the other legs. 45. Moving weight to the front of the kart will provide more front-end grip. So 2.5" springs and experimenting is the way to go- I think I know that much.. . To properly corner weight the car, it is necessary to add weight to the driver's seat which is approximately equal to the weight of the driver (or have the driver sit in the car). The nose weight is simple to remember the tricky ones are - cross and left side adjustments. I lowered the left rear spring perch 1 1/4 turn and put it on Find the difference from the desired average ride heights. At the time Honda was still favoring their home market I reckon. To favor right turns, put more weight on the For the teams that are running very soft front coilover springs, you will have a very difficult time moving the adjustment ring with your shocks in the car because of the high amount of pre-load on the spring. My starting cross weight was 50.6%, I was off 7lbs If the car understeers or oversteers in only one direction, check the cross-weight percentage. Choose your ride heights before you measure and/or redesign your front geometry and then maintain those chosen ride heights. The total weight will ALWAYS be correct unless you can find some way to suspend gravity, if you can let me know. For asphalt, on the flatter tracks, corner entry is enhanced when running a softer right front spring. Since each side at each end will usually have different rate springs, the amount we change the spring height adjusters will differ side to side. 2) Stagger: Stagger is how much bigger the right side tires are compared to the left side tires. The only way to change the static weight distribution percentages is to physically move weight around in the car. To maintain the ride heights, we also must reduce weight or preload at the LF and RR springs. about 1/8" of wheel movement) to reduce the weight on the right front and left to get a balanced diagonal weight on the tires. Today's oval Use those racing internet forums, and dont be timid about asking for some assistance! The Circle Track Analyzer is a computer program that simulates most any car you can design, racing on most any size oval track. difference that made. the front ramps then jack up the rear and lower it onto the rear scales. The SRM will determine the relative changes to the spring height adjusters for weight changes. I recommend adding an eighth or slightly more to the lowest corner just to make sure you pass tech. then leave them connected. For our example, we use LF 4.00, RF 4.50, LR 4.50, RR 5.00. 5. document your current ride heights and your coil over changes each time 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. Ok sounds good. 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. 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 turns to the Right Rear: I still needed more weight on the LF and RR so I added +4 to the LF: I still needed more so I added +2 to the RR and drove the The following weights are with the front Comptech adjustable How would you makesomething like that? not to push it off the scales, to unload the suspension (as the car is in the driver's seat to load the suspension. Wheelbase: 9.5" min, 11.5" max Maximum width: 10.250" Minimum weight: 57.0 oz All cars must have 4-wheel independent suspension, single speed transmissions only. 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. - can make your car dive like a dump truck or a block of wood on ice. This gets very tedious, given the number of iterations it typically takes to get the corner weights right. Remember that this is a sample car, so don't use these numbers, but do use this method. Check static weight before working on cross-weight. split the adjustment between all four wheels--extend the LF and RR 1 1/4 turns So as long as you are draining the fluid from your shocks, also remove or cut away the seals. First the tires. track are left turns then having more weight on the Right Front and Left Rear Front + Left Rear) - (Left Front + Right Rear) and tells us how much Keeping track of Bite and I painstakingly leveled the scales and marked their locations In oval racing you always run more weight on the LR. you weigh and adjust. In our example we will be using the same method with corrections for different rate springs. works well. Basically, I don't see much of a relationship between 'static' corner weighing via adjusting spring length and the addressing of fundamental L/R weight imbalance as those difference are what drive suspension and mass motions when moving. You need a nice, flat and level surface for the scales. 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. But this doesn't explain why the Vette's readings came in so well, while I had to jump up and down on my door sills quite a bit before my car's weight stabilized at its expected value. Here's the car with the same settings but empty: I took the newly corner balanced S2000 to a Summit Point Raceway Friday at Road racers are 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. Always record the cross-weights and ride heights for reference at the race track in case changes are needed. Most people find this out pretty quickly. "weight jacking," or "scaling," involves adjusting the spring perches of a car The springs OTOH exhibit little or no friction loss when compressed or extended. The left weight percentage is found by adding the LF weight to the LR weight and dividing the sum by the total weight. racers add "wedge" by adjusting the right rear spring perch--they It's critical that you set ride height in the same place each and every time you do it. knew I needed to put the car on the scales. Now that we understand why we need to maintain a set ride height, let's go through an example of how to set ride height. line above each scale and placed a ruler on the top Bite and Wedge Delta are . If you want to raise the ride height then extend both LF and RR coil overs 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. Record each spring rate. rear. 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. When looking at corner weighting, the cross weight (diagonal weight) is the most important component. important for cars with upgraded (stiffer) sway bars because they can exert a I've read all the info before, in various places, but it's good to have a refresher. They are never level. Corner weighting can be a complicated process for you to complete without someone who is experienced helping you. This measurement can be manipulated by changing spring rates, coilover . If you do have adjustable end links then disconnect Motor: 550 or 540 motors only. Cross weight and left side work backwards in terms of adjustment. Brake pads badly taper worn - replace. With the stock setup the car should have more grip turning the front wheels to measure caster. Many successful race teams use corner weighting to achieve the same F/R % on both sides equal, not cross weight. With the driver weight, the left side might move down 1/4-inch and the right side down 1/8-inch. 8 Read the ride heights as they exist. However, for dirt oval RC cars, foam tires are the norm. 1. front left and If you had a car with a fully rod-ended out suspension that frictionless and frictionless tires you wouldn't need to roll the car around or bounce it or anything. On an average workbench/table that's close to level, it's probably < 3g difference per corner, which is within the tolerance of stiction / binding in a touring car. . 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. And if you hold the inside wheel so it can't spin, the outside wheel will turn 400rpm. My left rear is something like 150lbs heavier than the right rear, with both fronts even at ~740lbs each on a 2425lb FWD car. Intercomp 102030 5X5 Hub-Mounted Corner Weight Scale. 3) Reverse stagger: The opposite of stagger when your left side tires are . coil over 5 turns. Plan to win in a repeatable fashion. I installed tires. 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. Add about 20% and slowly increase until your car turns when you let off the throttle in the middle of the corner without rolling out of the throttle. But this is almost never the case. For ovals we want a 4. rear. If you want to lower the ride height then retract both RF and That seem like a lot. 14. I was booked for 100 laps split across four or five sessions. If you don't have adjustable end links on your To find RF weight: Are they adjustable? Avoids a mess on scale pads and tires,prevents dirt fromcontaminating lube. things being equal). Grassroots Motorsports Understanding Corner Weights 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. Bottom line, you can strive for perfection, but ultimately youll just make yourself crazy. you run on the track. 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. The following are screen shots from the In any case, only make one spring change at a time and re-establish the ride height at that corner, then change the other spring(s). shifted by more than 1 pound after rolling the car on the scales. When a NASCAR crewchief says he's "adding wedge", Do these percentages apply for front wheel drive cars? Please post on the appropriate 4m forum. Get the numbers right and the percentages will follow. Forum Actions: Forum Statistics: Threads: 167; Posts: 1,367; Last Post: . Now that we understand the value in maintaining ride heights, just what heights do we want? Make sure under all conditions that you will have at least minimum ride heights. One of the most important aspects of racing is having a good handling balance. Wheel Offset Changes. Don't just blindly cross weight it thinking it's the "right" way. turns. Here's apoor mans way to reduce the effects of tire scrub/binding when the car is lowered onto the scale pads: Spray Pam into open bagto coat and lubethe inside, rub the bags between your hands to distribute. Of course you can add too very close to ideal. Calculator, I used these scales to weigh the car: Once the ride has been set, it's a simple operation to bring the corner weights to the predetermined values. retract the right rear tire which puts more weight on the Left Rear and lowered onto the scales the tires will need to spread out to unbind the That is why it gets tighter. 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. For information on corner Cross Weight % = cross weight. Teams that do not stay on top of these two setup phases will not only be inconsistent, they will struggle to find their way setup wise. 2023 Motorsport Marketing. You will have to repeat this every time you lower the car onto (adsbygoogle = window.adsbygoogle || []).push({}); If you prefer Microsoft Excel a Corner Weight spreadsheet is available for download here Left Rear tire is carrying more weight so it will get more traction and Are they non-adjustable? ride heights after every change. Calculate the average existing ride heights front and rear. are favoring the left rear tire for better acceleration out of left Set them to hot pressures is the norm as I understand it. Since I went to 800 front and 700lb rear springs over the winter I The last event in the rain i actually had the rears up to around 38. 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. If a setup sheet read as "30 pounds of bite", there would be 30 pounds more weight on the left-rear than the right-rear. Cross Weight or Wedge. % Wedge Delta will be 0 at 50% Wedge. Put the driver weight in the car, preferably the driver. To increase rear weight, move weight as far back as possible. We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. 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. On the one hand, I'd love to have my Supra corner weighted, just to see where it's at, see if there's room for improvement. Or do you just mean an old, worn-out strut? 9. I dont get this. Front + Left Rear) - (Left Front + Right Rear) and tells us how much it would help the car turn left and accelerate better. 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. Then move components like the battery or fuel cell. It will let you predict and understand the effects that various modifications have on handling, performance and lap times. you run on the track. To keep it clear in my head, I think of the car as a four-legged table sitting on a mattress. The spreadsheet's second page has a good article that goes into more detail of Dirt or asphalt? Oval racers favor left turns so they typically desire more weight 1 of the section on "Adjusting The Corner Weights," and that is 685. Currently, dirt car racing involves a left-hand weight measurement of 53.5-55, along with a wedge between 75-125 pounds. I plugged in a bunch of numbers into my calculator and it all checks out. You can also put two linoleum tiles with salt between them on Typically, a road racing car should have 50% Knowing those numbers will allow you to set and/or check your ride heights if the driver isn't around by adding the difference to the intended ride heights. 2 When you make a spring change, bring that corner back to the measured distance from the wheel rim to the fender mark by adjusting the spring height. Muscle Car. Left front weight + right rear weight = right front weight + left rear weight. 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. I 35 psi hot tire pressure target . camber angle of the wheels (-3.5 front, -3 rear). Bite = Left Rear - Right Rear and a positive value means the 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 If you shocks are working normally they are not worth worrying about. the RF coil over 5 turns. adjustment so I have a history of each adjustment. (I suppose cooking oil, motor oil, KY, or Astro-Glide would also work). We should now be at, or near, the desired crossweight percent. You can see the article here: I put the tiles on top of the scales. "This is called chassis pre-load. Free Download Chapter listings from. I still rolled the car back and forth a 3. So let's study ride heights first. Get it right and your car launches down the corner, hits that hard hairpin just right and holds the corner at full throttle. 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. I gave up on running adjustable end links on oval racing world and is simply another word for Cross Weight. 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. 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. 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. 19. more traction or bite in left turns. and have shocks available for all forms of racing - dirt and asphalt sprint cars, dirt and asphalt . 4. They kept saying that it would go anywhere on the track and anywhere they pointed it. Since this article still gets a bunch of traffic, just bumping it up. The weight transfer process occurs regardless of the spring rates at each corner of the car. The ultimate goal is to find the balance that will eventually lead to faster lap times. 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. scales. Crossweight is calculated by adding the RF and LR weights and then dividing that sum by the total weight. Funny. 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). Here is the method to correct the corner weights and set the left rear bite or cross weight. tank of gas, and no driver or passenger: Now here's the same stock S2000 with a 215lb driver in the seat: I was really surprised to see how far off the stock S2000 was In this example, we will adjust the crossweight percentage on a sample car with different rate springs. Keeping track of Bite and If most of the important turns on your Calculate the average front and rear desired ride heights. height and corner balance new springs. The design has the engine and transmission scooched over to the drivers side so the drivers side weighs more empty. 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. (TVW FWP) - RF = 743C. I put the car on grease tiles so the tires move freely on the scales and then I bounce each end a couple times. 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. On an average dirt track you will need to change tread and stagger at least once a night, due to changing conditions. the scales and zero them with no weight on them. Adjust the cross weight for more extreme conditions or different circumstances. Once the corner 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. Delta is equal to (Right This also coveys other advantages, the short shock travel means that it can be shorter and lighter. I sometimes watch in frustration as teams struggle to set the corner weights and ride heights on their cars. Other things to take into consideration are track conditions and weather changes. I dropped my integra off at edge to have this done today. There is work involved in going fast for the full race and racing other racers clean. Here's how we find the multipliers. Today's oval 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. what he means is he's adding weight to the left rear and right front If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. Hub stands are a great idea just for ease of access, but removing friction is an added benefit. important for oval racers, especially on dirt ovals. Remember that changes in stagger, tire pressures and springs will change the ride height and alter the cross-weight percentage. For example, if your initial setup is 52 percent cross-weight, and you want 50 percent cross-weight, lowering the right front or left rear corner will decrease cross-weight percentage. Search for: CG Height Calculator, Cross Weight % = On my ZX2SR my cross weight was consistently in the 49% range. May run 4 pole motors. To add weight to a given corner, raise the ride height at that corner or lower the ride height at an adjacent corner. used are 0.045" thick. This will pitch the vehicle's. (adsbygoogle = window.adsbygoogle || []).push({}); I still needed more weight on the Left Front and Right Rear so I added + 4 Drag Racing. 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. It's better to make many small changes than to try hard work but it makes all that high dollar suspension work together the way its intentionally favor a turn direction. The first is to use traditional lift-off oversteer. Shock Angle-measure the angle of the shock installed and at ride height. This was my first adjustment: Four turns of positive coil difficult to position all 4 scales so you can just drive up on all of them at February 2017 -Suspension design process. end-link into the anti-roll bar's hole. renting/borrowing/buying some scales and corner balancing your car. Disconnect the sway bar. Rebound adjustments will allow you to alter your car to a corner entry condition without affecting corner exit or vice versa. You can see in the "Target Corner Weights" section that the Left 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. I'm anxious to see what Proform says about my experience. Small angles can throw off your readings significantly. The other two corners will gain weight. This keeps the ride heights as close to ideal as possible. Oval Track. May 2017 -Dirt late model pinning RF & heavy axle tube. Now that we have established the ride heights, our weights could be anywhere. Wedge This obviously means that decreasing cross weight or left side weight Wedge Delta and what values work best for certain tracks and conditions Wheel Load-We have already determined the wheel load we desire in No. In almost all cases, the loss of cornering performance in one direction is greater than the gain in the other direction. Check stagger at each tire, even if using radials. Smaller will scrub less speed of if your not sideway threw the corner. 50% then Wedge Delta will be 0. Once you get the car up on the scales you'll [Up] [HarnessInstall] [WingInstall] [RemoveA/C] [OilCooler] [FireSuppress] [CutoffSwitch] [RaceExhaust] [Differential] [CornerBalance] [CatchCan] [RollCenters] [FrontBumpSteer] [Alignment] [ShockTuning] [Aerodynamics] [CatRemove]. Example: RF = 643, LR = 751, so, (643 + 751) 2,800 = 0.498, or 49.8 percent. The typical goal in corner weighting cars is to make the cross weights equal. Excessive front toe in will make a car turn into a corner quicker, & may create a loose condition. Even on a track with mostly right-hand turns, the problem in the left-hand turns costs a lot of time. The tiles I On Dirt cars, adding Rebound to the Right Rear will make the car more stable when it slides into the cushion. positive Bite and positive Wedge Delta. 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. Improper weight distribution in your race car - strip burner, autocrosser, circle tracker, etc. Or am I missing something? your scales. That is why a stiffer right rear spring makes the car looser. 2 coils cut off springs 4 corners. So if you have 60% on the front , you should have 30% on each front wheel. you don't use Microsoft Excel. For dual a-arm solutions, dead shocks can be used with springs and they can be built with much less bind out of the box. 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. the scales. I tried the "Springs and chassis components can be adjusted to push down on one rear wheel," Bickel said. 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. That is what you need to read on the spring rate fixture at installed shock length. If most of the important turns on your weights: Corner Weight Calculator if 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. 2. Doing the multiplication to square that number, we get 1.1056. If we are talking of weighing a stock type vehicle, not a lot can be done since there are no adjustable parts. that turns equally well in both directions. I vary mine alot depending on conditions, so should I sayset them where I would at the beginning of an average day for autoX? 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.