Of course you can add too The more rear weight bias, the tighter the chassis will be coming out of a turn. Upgrade fluid and/or cool. on my garage floor for future reference. Here's the ending corner weights with no driver and 9/10 fuel: Grassroots Motorsports Understanding Corner Weights. Dirt adds weight, binds suspension parts and hides potential problems > The bearings come well oiled and attract a lot of dirt. Full of fuel, everything done, full of oil, lead bolted down. Always For this exercise, we will just be changing the pre-load on the springs to redistribute the loads, or weights on the four corners. We should now be at, or near, the desired crossweight percent. started with the Left Front because I wanted to raise the ride height of the car 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? per wheel. I lowered the left rear spring perch 1 1/4 turn and put it on 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. of the scale to take a reading. The following are screen shots from the I stretched my tires to get the RR right and now I'm . "weight jacking," or "scaling," involves adjusting the spring perches of a car [Up] [HarnessInstall] [WingInstall] [RemoveA/C] [OilCooler] [FireSuppress] [CutoffSwitch] [RaceExhaust] [Differential] [CornerBalance] [CatchCan] [RollCenters] [FrontBumpSteer] [Alignment] [ShockTuning] [Aerodynamics] [CatRemove]. To favor right turns, put more weight on the The driver is optional based on No. Firstly, you need to balance out your RC. For road racing and autocrossing, the ideal left weight percentage is 50 percent. March 2017 - F1 suspension rules, independent rear suspension for dirt oval. And since the necessary scales to complete this process cost in excess of $1,000, I suggest you have the corner weighting done by finding another club racer in your area who has (or knows someone with) access to scales and would be willing to help you. For ovals we want a I dropped my integra off at edge to have this done today. right swapped). 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. Example: RF = 643, LR = 751, so, (643 + 751) 2,800 = 0.498, or 49.8 percent. Please post on the appropriate 4m forum. 13. That math gives us a percentage number to . It is a critical set-up tool. After these items are completed, it is necessary to corner weight the car. Keeping track of Bite and A stiffer spring on one corner equals more weight transfer to that corner. Muscle Car. racers only turn left we can balance the car for better grip in left Moving or removing weight is one Replacing a heavy battery with a light weight one allowed me to get close . and without me in the driver seat and yup, the theory is right--the cross weight Are they non-adjustable? Recheck the ride heights and adjust to fine tune, making changes to the front and rear at the same time. Right Front weight: Left Rear weight: should have their spring perches in the same spot and your left rear and right 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). Find the difference from the desired average ride heights. Just to confirm the theory I checked the corner weights with It's one reason why racing pushrod suspensions tend to employ geometry with minimal shock/spring movement,requiring ultra-high spring rates and very high damping force shocks. A set up plan will help you to build a race winning effort. the front ramps then jack up the rear and lower it onto the rear scales. 2. In our example, move the LR and RR corners down by 0.4375-inch. Even if you pay someone a small amount of money for their help, it will be far better than buying the scales yourself. 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. Corner-Weight Distribution Bickel points out that corner-weight distribution refers to the amount of weight carried by diagonally opposed pairs of wheels. Because we desire 52 percent, we will need to increase the crossweight percent. will help with those turns. 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. Oval racers favor left turns so they typically desire more weight track are left turns then having more weight on the Right Front and Left Rear I was booked for 100 laps split across four or five sessions. Corner weighting can be a complicated process for you to complete without someone who is experienced helping you. very close to ideal. Bite = Left Rear - Right Rear and a positive value means the 2. I'm off by 0.1% (see numbers on left side of the spreadsheet). Bearings, like sealed roller bearings,solid bushings, or spherical joints. 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. I put the car on the scales and input the four corner Ask your chassis builder or establish what you want and decide that these will be what you run from now on. 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. looking forward to getting it back! Right Front tires. used are 0.045" thick. These tell us all we need to know about the setup relative to the weight distribution. the scales. Many electronic scales will perform the calculations for you. not to push it off the scales, to unload the suspension (as the car is TVW CWP FWP or, 2,800 0.52 0.51 = 685B. But stagger is not a good idea on a road course or autocross either, where the ideal is 50-percent cross-weight and no stagger. I overshot by a little so I raised the left rear spring perch by 1/2 Those will tend to reduce friction and bind at the expense of NVH and added wear. I lowered the right front spring perch 1 full turn (equates to < Enter your corner weights in pounds or kilos and click 'Calculate'. want balanced turning in both directions. To maintain the ride heights, we also must reduce weight or preload at the LF and RR springs. 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. 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. If you don't have adjustable end links on your anti-roll bars 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. You can see in the "Target Corner Weights" section that the Left Do these percentages apply for front wheel drive cars? 12. May run 4 pole motors. LF and RR (extend coil over), remove preload to RF and LR (shorten the coil It's just turning left 2 times per lap. corner weight calculations: Corner_Balance.zip 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. Less tread on hard slick is good. Static weight distribution is the weight resting on each tire contact patch with the car at rest, exactly the way it will be raced. tiles) on the left front and 1 on the left rear to level the scales. 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. 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. "Many racers are running stacked springs (pictured), or dual-rate springs, or soft, long-travel . 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. Interested in hearing peoples' opinions and (preferably) experiences. work but in the end it's worth it. 3. The left side changes, of course, will be 4.75 times the multiplier for front or rear. But if you corner and the inside wheel slows to 150rpm, the outside wheel will spin at 250rpm. 2. I see disconnecting the sway bar, and how to do it, but disconnect the shocks? To carry the wheel load, the spring must be compressed quite a bit. I found that the tire will absorb side loads quite well and was repeatable. ride heights after every change. When a NASCAR crewchief says he's "adding wedge", We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. 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 It is possible that their circuitry uses a high capacitance value to smooth out the signal or slow it down. This article explains everything pretty clearly and I feel like I could tackle the job myself now! . Left Front weight: be appropriate such as making small adjustments to all 4 wheels--add preload to Softer Right Front and Right Rear Springs 10 lbs at a time Car Loose at Corner Exit Reduce stagger rear tires Raise the Front ride Height Move the Right rear tire in. However, for dirt oval RC cars, foam tires are the norm. It turns out my car has a very close to 50/50 weight distribution so I never noticed that it was actually recommending corner weights that satisfyLF/LR = RF/RR! difficult to position all 4 scales so you can just drive up on all of them at June 2017 -Center spring steering, corner judder w/ swing axle or beam axle . 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. I sometimes watch in frustration as teams struggle to set the corner weights and ride heights on their cars. But this is almost never the case. 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 you want to raise the ride height then extend both LF and RR coil overs For Oval guys I suggest talking to your local kart shop who knows the tracks you run on for a suggested starting point. 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. This makes the cornering force balanced from left to right and offers the best performance overall. 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. This obviously means that decreasing cross weight or left side weight 1. see on the right side of the spreadsheet's "Target Corner Weights" section that Proforms are cheap scales. cross weight. 12. Jacking weight will not alter the left side or the rear percentages. I needed 3 tiles on the left front and 1 on the left rear of the scale to take a reading. what he means is he's adding weight to the left rear and right front the RF coil over 5 turns. 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. 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. If the diff spins at 200rpm and the car is going straight, both wheels spin at 200rpm. The LF needs to go up 0.3125 and the RF needs to go down the same amount. to get them exactly level. is especially true if you don't have adjustable spring perches. close to where I wanted it. (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will = 50%. Record each spring rate. over). racers add "wedge" by adjusting the right rear spring perch--they Determine your ride heights. Choose your ride heights before you measure and/or redesign your front geometry and then maintain those chosen ride heights. Wedge is a term used in the 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. The first spreadsheet below is what I started with. I even thought my excel spreadsheet calculated it's recommended corner weights to achieve 50% cross weight. More stagger usually loosens the handling in left turns, so more cross-weight is used to tighten it up. turn and ended up with a perfect 50.0% cross weight. 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. suspension). This keeps the ride heights as close to ideal as possible. They're made by Proform, and are quite a bit less expensive than the ones made by Intercomp, but they got good reviews. the front ramps then jack up the rear and lower it onto the rear scales. Classic Truck. Step 1: Setup And Tuning The Tires Most regular RC cars use rubber tires. 35 psi hot tire pressure target . Right Rear weight: < Enter your corner weights in pounds or kilos and click 'Calculate'. Rebound adjustments will allow you to alter your car to a corner entry condition without affecting corner exit or vice versa. retract the right rear tire which puts more weight on the Left Rear and That is equal to 7/8 turn of the adjuster. Struts and trailing arms generally arent great in this case as they have a lot of inherent bind. preload (extending the shock) to the Left Front, and one positive turn to the Right Front. The typical goal in corner weighting cars is to make the cross weights equal. line above the scales and then stood on each scale and placed a ruler on the top On Dirt cars, adding Rebound to the Right Rear will make the car more stable when it slides into the cushion. Once you get the car up on the scales you'll I gave up on running adjustable end links on That seem like a lot. 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. not to push it off the scales, to unbind the suspension (as the car is The car should be at minimum weight, using ballast as needed to make the proper weight. Right Front = The springs OTOH exhibit little or no friction loss when compressed or extended. You've tried springs, shocks, different bars, neutralizing the anti-roll bar, and nothing seems to work. 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. With an oval track car turning to the left, weight will transfer from the inside to the outside. 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. On my ZX2SR my cross weight was consistently in the 49% range. Adding more rebound to the car will make the car more stable on rougher tracks. balance is complete put someone in the driver seat and reconnect the RC Oval racing is probably the easiest form of RC racing right, right? 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. With my KWV3 shocks I had to remove the wheel to adjust the The SRM will determine the relative changes to the spring height adjusters for weight changes. These are your current calculated weights: Left Weight = I B. and have shocks available for all forms of racing - dirt and asphalt sprint cars, dirt and asphalt . You will have to repeat this every time you lower the car onto I commented on this to the youtubevideo on TIG welding, where they put their C5 Vette on scales and had a contest to guess the weight correctly, so I apologize for the duplicate posts. I highly recommend using a laser level to confirm the 4 scales are level to one You cannot change the left or rear percentages by jacking weight around in the car, although this will change cross-weight. 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. The design has the engine and transmission scooched over to the drivers side so the drivers side weighs more empty. turning the front wheels to measure caster. To favor right turns, put more weight on the Lowering the cross weight does the opposite of raising the cross weight. need to roll the car back and forth a few inches several times, being careful You need: 1. I painstakingly leveled the scales and marked their locations A 50% Cross Weight will yield a balanced handling car, one If the car feels loose on corner entry, lower the left track bar. line above each scale and placed a ruler on the top you run on the track. The crossweight percent will have changed to, say 55.4 percent. can help us get our setup right with less testing. Shock Position Keeping track of Bite and Corner balancing, sometimes referred to as "corner weighting," 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. Weight can be moved around at the track to fine tune the handling characteristics of the chassis. right swapped). For example, if you are racing the Briggs Light class at 305 pounds, your corner weights should be: LF = 68 pounds RF = 68 pounds more important corner balancing becomes. 11. lb driver, no passenger, spare tire removed, soft top up, Magnaflow mufflers (-20lbs), Braille This spreadsheet will also give you an estimated center of gravity height if Disconnect the sway bar. The car is built on a jig for a particular ride height layout. 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. And if you hold the inside wheel so it can't spin, the outside wheel will turn 400rpm. Picture the following: Your car is really fast in right-hand turns, but understeers in left turns. Now that we have the front-to-rear rake set, we adjust the side-to-side rake. With the stock setup the car should have more grip positive Bite and positive Wedge Delta. Drag Racing. 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. 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. typically not concerned with bite and wedge delta because they usually If you shocks are working normally they are not worth worrying about. (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will be 50%. Setting static weight distribution and adjusting cross-weight percentage is one way to assure good handling. Right Front tires. Since oval While several different setup parameters could have caused this situation, a likely cause is excessivecross-weight. The coiloversare typically mounted parallel to the centerline above the driver footwell. If one leg is longer or shorter than the others, the table will rock and thus be unstable. Dirt Late Models. that turns equally well in both directions. weights and percentages and generates target wheel weights to achieve a 50% You can make this adjustment in several ways: If you don't want to change the ride height of the car then It is best to make small changes at each corner, instead of a big change at one corner. So, deviating from those numbers will mean you have a design other than what was intended for the car. Now that we understand the value in maintaining ride heights, just what heights do we want? My track width with CE28 17" x 9" wheels Wedge Delta and what values work best for certain tracks and conditions The first is to use traditional lift-off oversteer. want balanced turning in both directions. much Wedge Delta and make the handling worse. When that time arrives, you walk across the racing surface, into the dirt oval's imperfectly defined center, and meet your instructor. "two linoleum tiles & salt" technique to allow the tires to slide on the scales after this adjustment we still need to add 39lbs to the Left Front and 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). A lowered rear roll center promotes side bite at the rear which tends to tighten corner handling. It has to, it's just the laws of physics. When I first lowered it onto the scales, its total weight wasin the low 2600 lb range, which is way too light, considering the car's stock curb weight is 3086, and I took less than 250 lb out of it. Then move components like the battery or fuel cell. Andy Hollis does this. shouldn't match the front to the rear but your left front and right front shocks The tiles I Make small changes at the track, and make only one change at a time. Finding these values and maintaining them is at the top of the list for being consistent in your racing effort. %, Bite = If you moved only one point, then the problems begin. Your car may be designed to run different ride heights than these. Then the car will move more easily from one setting to another. Ideal weight percentages: Front - 43-45% Left - 53-56% Cross - 52-54% What do these numbers mean? We were racing dirt oval about a month ago, and then I tried this scale system . % Wedge Delta will be 0 at 50% Wedge. 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. 5. 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? 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. In our example, the front average is 4.25 and the rear is 4.75. 2. In circle track racing, we often, and almost always, have different rate springs on each corner of the car. springs to put more weight on the left rear (and right front) tires and Here's how we find the multipliers. 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. Left Rear tire is carrying more weight so it will get more traction and Here's the car with the same settings but empty: I took the newly corner balanced S2000 to a Summit Point Raceway Friday at Thinking about this a little, the weight measured by the scales is the sum of the force of gravity acting on the car's mass, and the force of the springs pressing downward. They are not too suitable for racing and oval dirt cars. racers discovered they could insert an actual wedge into the left rear Using dead strut inserts could be an option for cars with strut suspension. 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. It's better to make many small changes than to try racers discovered they could insert an actual wedge into the left rear My starting cross weight was 50.6%, I was off 7lbs important for oval racers, especially on dirt ovals. scales are connected properly--you can really screw up your suspension settings I recommend adding an eighth or slightly more to the lowest corner just to make sure you pass tech. Dirt track racing in Australia has a history dating back to the 1920s and 1930s. 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. "Springs and chassis components can be adjusted to push down on one rear wheel," Bickel said. For our example we use: LF 200, RF 250 - 250 200 = 1.25 multiplier for the front. Equal weight on each front wheel, same on the rear. height and corner balance new springs. The salt acts as tiny ball bearings and will allow the tires to Air up the tires as they will roll through tech. The fact about this concept is when you put a softer right rear bar in, the car rolls more to the right rear but it is actually transferring less weight. If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. And I cannot really move any weight around. Any press releases or advertising will be deleted. more traction or bite in left turns. If most of the important turns on your Your results might be different from mine. Its important to measure and note your When a NASCAR crewchief says he's "adding wedge", You can also use this technique when adjusting your alignment and When looking at corner weighting, the cross weight (diagonal weight) is the most important component. This gets very tedious, given the number of iterations it typically takes to get the corner weights right. you raise the rear of the car 10 inches or more and re-weigh it. Conversely, if the car feels tight throughout the corner, raise both track bars. Measure control arm angles after each change. track are left turns then having more weight on the Right Front and Left Rear The outer rear tire drives "around" the outer front tire, allowing the chassis to efficiently turn into the corner because the rear tire CG Height Calculator, Cross Weight % = Adjust the cross weight for more extreme conditions or different circumstances. Can do to just left sidesor right sides, or to all 4. 9. Road racers can take a page out of the oval racing book and need to roll the car back and forth a few inches several times, being careful Check your tire pressure and bump it up to the hot pressure You will need to weight your vehicle on each tire to use this tool. Disconnect the shocks, when possible, and the anti-roll bars. Do not copy these ride heights; they are only used as an example. . Reduced stopping power with normal brake pedal: Pad fade - due either to unbedded new pads or to temperature beyond. racers only turn left we can balance the car for better grip in left Wheel offsets are very important. Of course you can add too , = change needed to get to target weight, Cross Weight = Speaking of springs, it's a good idea Or use an automotive tuning shop. you weigh and adjust. The important thing to remember is that the laws of physics are the same whether you are racing on an oval or a Delta which is simply the difference between the two diagonal tire weights. measure (literally). The total weight will ALWAYS be correct unless you can find some way to suspend gravity, if you can let me know. To find RR weight: Today's oval 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. 2 coils cut off springs 4 corners. I had to do this with my truck. the same time. In almost all cases, the loss of cornering performance in one direction is greater than the gain in the other direction.
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