The LF needs to go up 0.3125 and the RF needs to go down the same amount. You can lower the cross weight to help on tacky tracks. - can make your car dive like a dump truck or a block of wood on ice. . To keep things clear I call this added weight Wedge Delta 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 even thought my excel spreadsheet calculated it's recommended corner weights to achieve 50% cross weight. 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. . can help us get our setup right with less testing. 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. 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 . Andy Hollis does this. [Up] [HarnessInstall] [WingInstall] [RemoveA/C] [OilCooler] [FireSuppress] [CutoffSwitch] [RaceExhaust] [Differential] [CornerBalance] [CatchCan] [RollCenters] [FrontBumpSteer] [Alignment] [ShockTuning] [Aerodynamics] [CatRemove]. g) Oval track and road racers use slightly different vocabularies to describe the adjustments made to their cars and the effects these adjustments have on the car's handling. These tell us all we need to know about the setup relative to the weight distribution. To find RF weight: Splash = 2-3 gallons, 1/2 can = 5-6 gallons, 1 can = 11-12 gallons, 1 1/2 cans = 17-18 gallons, 2 cans = full tank. Then measure from the lower wheel rim edge up to a spot on the fender on a piece of masking tape. Before putting your car on the scales you need to power up stiff springs on your coil overs. I had to do this with my truck. of the scale to take a reading. Right Rear weight: < Enter your corner weights in pounds or kilos and click 'Calculate'. You can estimate your car's center of gravity retract the right rear tire which puts more weight on the Left Rear and If you get the car neutral in left turns, it oversteers in right turns. For road racing and autocrossing, the ideal left weight percentage is 50 percent. You can also use this technique when adjusting your alignment and 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. I'm off by 0.1% (see numbers on left side of the spreadsheet). oval racing world and is simply another word for Cross Weight. you run on the track. I Some engines are used in two different classes with the only change being exhaust system. I saved a copy of the spreadsheet for each I've actually lowered a miata a decent amount just by forcing the bushings around. I was surprised how much these high rate More wedge means that the car will likely understeer more in a left turn. Both of these items will impact the cross weight of the car, and therefore they are important in the corner weighting process. Equal weight on each front wheel, same on the rear. lot of force to the suspension. center of gravity (CG) height by using this page: So we turn the RF adjuster up (to lower that corner) 2.5 turns and the LF down (to raise that corner) 2.5 turns. 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. When I drive down a strait road the I can clearly feel that the drivers side is heavier over bumps expansion joints and dips and the like. My left rear is something like 150lbs heavier than the right rear, with both fronts even at ~740lbs each on a 2425lb FWD car. I sometimes watch in frustration as teams struggle to set the corner weights and ride heights on their cars. 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. Additionally, it is much more difficult to change rear percentage much, since rear weight is mostly a design function. 4. 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. One of the most important aspects of car setup is the static weight distribution and the cross-weight percentage. 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. Using dead struts and lots of bearings will help. 2. Road racers can take a page out of the oval racing book and This is the arm length divided by the distance from the shock mount to the inner pivot line, squared. This will pitch the vehicle's. Thanks for posting this. Disconnect the shocks, when possible, and the anti-roll bars. 14. They kept saying that it would go anywhere on the track and anywhere they pointed it. Check your tire pressure and bump it up to the hot pressure Since the front and rear shocks are of different lengths you Adding more rebound to the car will make the car more stable on rougher tracks. That method keeps the ride heights close to the same. I always thought it was the other way, shock travel was increased in order to have more movement for better control over the suspension? In the old days when we ran close to equal springs at the front and at the rear, we could just put one round in the RF and one out of the LF, one in the LR and one out of the RR to put cross into the car. (adsbygoogle = window.adsbygoogle || []).push({}); If you prefer Microsoft Excel a Corner Weight spreadsheet is available for download here The nose weight is simple to remember the tricky ones are - cross and left side adjustments. For information on corner I don't like the lower weight ratings and plastic scale pads of proform. So, we are not reinventing the wheel here, just refining the process. And if you hold the inside wheel so it can't spin, the outside wheel will turn 400rpm. 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. This adds pressure to that end of the car just like putting the paper wedge underneath the table leg. another. The coiloversare typically mounted parallel to the centerline above the driver footwell. I recommend you start with your car at your desired ride First the tires. You cannot change the left or rear percentages by jacking weight around in the car, although this will change cross-weight. 2 1/2 turns. If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. Moving weight to the front of the kart will provide more front-end grip. 5. A place where you can add in your Photo Galleries. balance is complete put someone in the driver seat and reconnect the 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? Maybe I'm over-thinking this, but I was amazed when I got my new scales, and let my car down on them for the first time. Rebound adjustments will allow you to alter your car to a corner entry condition without affecting corner exit or vice versa. Cross-weight percentage compares the diagonal weight totals to the car's total weight. It's a lot of Exhaust/Headers, Limited Slip Differentials and Fuel Injectors, Engine Dyno Tuning, Racing Wheels and Air Dam/Splitters, The Costs of Racing Personal Safety Equipment & the Racecar, Brake Pads, Fluid Routine Maintenance Timeline, Dealing with Cosmetic Bodywork: Painting the Racecar Interior. 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. To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. 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. First off, you must maintain the legal ride height to pass tech. Typically, this adjustment will make the car tighter on corner entry or in the center, and a little looser on exit. If your car has coil over adjustable shocks you should consider The situation isfrustrating. difference that made. I painstakingly leveled the scales and marked their locations positive Bite and positive Wedge Delta. Muscle Car. (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will be 50%. Unless you have some kind of stupid hyper-critically damped NASCAR type dampers this isn't really necessary. over Also double check that the May 2017 -Dirt late model pinning RF & heavy axle tube. 1 of the section on "Adjusting The Corner Weights," and that is 685. How would you makesomething like that? The vanilla neon setup would be SDK suspension (stock ACR, look at neon.org and figure out what you have) with 3.5 deg front camber, 1 to 1.5 rear, zero to 1/8" in toe front and rear. If you shocks are working normally they are not worth worrying about. I lowered the left rear spring perch 1 1/4 turn and put it on The left side changes, of course, will be 4.75 times the multiplier for front or rear. Raising the rear end will also provide a little more on-power grip by keeping more weight directly above the rear tires during acceleration. May run 4 pole motors. We also change the rear to correct the side-to-side rake by turning the RR adjuster up (to lower the corner) by 2.5 turns and the LR adjuster down (to raise that corner) by 2.5 turns. LR = left rear. Or do you just mean an old, worn-out strut? Cross Weight % = Firstly, you need to balance out your RC. 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. 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. Currently, dirt car racing involves a left-hand weight measurement of 53.5-55, along with a wedge between 75-125 pounds. tiles) on the left front and 1 on the left rear to level the scales. My car has solid/spherical bushings everywhere, so there should be very little bind from them. The outer rear tire drives "around" the outer front tire, allowing the chassis to efficiently turn into the corner because the rear tire (TVW FWP) - RF = 743C. They're made by Proform, and are quite a bit less expensive than the ones made by Intercomp, but they got good reviews. 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. Of course you can add too Even 1/8 inch difference will make a difference, especially if you have I needed 3 tiles on the left front and 1 on the left rear springs to put more weight on the left rear (and right front) tires and The front is usually the lowest point on the car and most sanctions maintain a minimum ride height rule. weights into the spreadsheet (the blue numbers in the left "Corner Weights" On a road course, the variety of corners require a wider range of performance; the setup needs to yield good speed through a fast kink and a slow hairpin. Lowering the cross weight does the opposite of raising the cross weight. In order to perform the set up routine the car needs to be completely ready to race. Delta which is simply the difference between the two diagonal tire weights. In circle track racing, we often, and almost always, have different rate springs on each corner of the car. Do not adjust any other wheel's spacing. used are 0.045" thick. In our example it is 18 degrees. which is simply the difference between the two diagonal tire weights. A 50% Cross Weight will yield a balanced handling car, one I needed 3 linoleum tiles (0.045" thick A jumbo ziploc bag prevents lube from escaping when not in use. 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. anti-roll bar with the end-link adjusted so it's easy to insert the Take the cosine of that angle, divide it into 1.0 and then square it, or multiply it by itself. 5 diameter stainless ball bearing on top of a 1" shortwell socket on the center of a floor Jack and jack the car up in the center of the rearend housing. At least for road racing. You will need to weight your vehicle on each tire to use this tool. To increase left-side weight, move weight as far to the left as possible. 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. about 1/8" of wheel movement) to reduce the weight on the right front and left 1) Tweak: Tweak is the amount of weight on the LR as opposed to the RR. You can use rubber tires on very specific tracks and seasons. I was booked for 100 laps split across four or five sessions. "Many racers are running stacked springs (pictured), or dual-rate springs, or soft, long-travel . Examine a modern push/pull rod suspension, particularly if it uses a crank link to transformthe The important thing to remember is that the laws of physics are the same whether you are racing on an oval or a rear should be the same. At the front, we will move the LF and RF adjusters up by 0.0625-inch. Open timing on motor and esc. To favor right turns, put more weight on the There are several ways race teams adjust corner weight. right swapped). 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. if you have any of the scales connected improperly (i.e. A trucking company scale meant to weigh 80,000lbs may not be accurate enough for a 3000lb car. the scales. close to where I wanted it. Finding these values and maintaining them is at the top of the list for being consistent in your racing effort. Prepare the car. We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. 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. Corner weighting can be a complicated process for you to complete without someone who is experienced helping you. 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. scales are connected properly--you can really screw up your suspension settings and stock rear sway bars connected. To make sure your spring changes don't upset your ride heights or crossweight percent, you need to mark your wheel spacing to the fenders. Basically - after you finish the set up routine, the car goes in the hauler. I The car should be at minimum weight, using ballast as needed to make the proper weight. You should also complete this process with approximately the amount of gas with which you will be racing. (i.e., if we move the RF adjuster two rounds, then we will move the LF adjuster 2.5 rounds.) But if you corner and the inside wheel slows to 150rpm, the outside wheel will spin at 250rpm. Static weight distribution is the weight resting on each tire contact patch with the car at rest, exactly the way it will be raced. right swapped). Make sure the vehicle is loaded with driver, passenger, and cargo just like you will drive it or . Make small changes at the track, and make only one change at a time. - Use blocks the same height as your scale pads to move the car off the scales to make adjustments. Why? Lay the bag flat onto the scale pad, partially open to vent, lower the car into the bag. For street cars it certainly can be. The new existing ride heights are LF 3.6875, RF 4.8125, LR 4.1875, RR 5.3125. So let's study ride heights first. 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. 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). There are many ways to corner balance a car. tires. I overshot by a little so I raised the left rear spring perch by 1/2 You could also raise the left front or right rear ride heights to do the same thing. The design has the engine and transmission scooched over to the drivers side so the drivers side weighs more empty. I see disconnecting the sway bar, and how to do it, but disconnect the shocks? 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. Dirt Late Models. racers add "wedge" by adjusting the right rear spring perch--they Do youhave recommendations for such corner weight percentages? dry)! 4m.net - The Most Opinionated Racing Message Board In The Universe. . 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's a box stock 2006 Honda S2000 with 5/8 of a spread when the car is lowered onto the scales. 6. Keep in mind the stiffer your springs the You can end-link into the anti-roll bar's hole. 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. values shown below are totally fictional. 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. Corner-Weight Distribution Bickel points out that corner-weight distribution refers to the amount of weight carried by diagonally opposed pairs of wheels. I had the same question. 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. scales are connected properly--you can really screw up your suspension settings MuddBoss Feature Winner at Dirt Devils RC Speedway, 12-18-2021. (CG) height by using this online calculator: CG Height There is work involved in going fast for the full race and racing other racers clean. I usually mark an even inch and write that inch number on the tape. for the front and rear sway bars and installed them with my girl friend sitting Recheck the ride heights and adjust to fine tune, making changes to the front and rear at the same time. Do these percentages apply for front wheel drive cars? Shock Position This was a very interesting post to me. Race Classes Whats Available and Acquiring a Racecar, Suspension, Glass Sunroof Replacement and Racing Seat and Harnesses, Fire System, Transponder, Rear View Mirror. bite, a negative value means the Right Rear is favored. We used to run about 1/8 of toe-in at the local tracks, and this helps the kart to cut through a corner easier in the center, where the steering is the greatest. Ask your chassis builder or establish what you want and decide that these will be what you run from now on. 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. Those will tend to reduce friction and bind at the expense of NVH and added wear. 57.5" front and 59.625" rear. Also you will obviously want to have some way to ensure all your scale pads are level with each other. 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. A set up plan will help you to build a race winning effort. 19. If you moved only one point, then the problems begin. If you want to lower the rear of the car then retract the LR 11. 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. To keep it clear in my head, I think of the car as a four-legged table sitting on a mattress. 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. 2023 Motorsport Marketing. Classic Truck. Using dead strut inserts could be an option for cars with strut suspension. We should now be at, or near, the desired crossweight percent. are favoring the left rear tire for better acceleration out of left 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 Now that we have the front-to-rear rake set, we adjust the side-to-side rake. I use 2x6 wood planks as ramps to drive the car onto Recheck air pressure often to assure ride heights stay consistent.
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