Corner Balance Calculator - Rob Robinette Corner_Balance.zip, Excel Corner Balance Spreadsheet Screen Capture. then leave them connected. corner weight calculations: Corner_Balance.zip You can make this adjustment in several ways: If you don't want to change the ride height of the car then The salt acts as tiny ball bearings and will allow the tires to The design has the engine and transmission scooched over to the drivers side so the drivers side weighs more empty. Still, it is a worthwhile goal to strive for 50 percent left-side weight. Motors / ESC: Any 1/10th scale motor/esc combo allowed. Put the driver weight in the car, preferably the driver. 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. Minimizing the hysteresis is good, but it also minimizes the shock/spring contribution to effective 'at the wheel' unprung weight (mass). I have now added the ratios so I can visually see what's happening. That makes every little detail that much more important. car for a week to let the suspension settle: I decided to disconnect the front and rear sway bars to see what All of these factors play a huge part in what each corner of the car will weigh. On dirt cars, both rear corners can move quite a bit, so the link angles on both sides are important. then set corner weights and cross weight. you raise the rear of the car 10 inches or more and re-weigh it. traction or bite in left turns. W. William18 New member. Get the rear percentage as close to the manufacturer's specs as possible. Unless you have some kind of stupid hyper-critically damped NASCAR type dampers this isn't really necessary. When looking at corner weighting, the cross weight (diagonal weight) is the most important component. Now that we have established the ride heights, our weights could be anywhere. This spreadsheet will also give you an estimated center of gravity height if Adjust the front up by 0.0625-inch and the rear down by 0.4375-inch. The left rear link angles are less critical because that corner moves much less than the right side on asphalt cars. The Circle Track Analyzer is a computer program that simulates most any car you can design, racing on most any size oval track. 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. The only way to change static weight is to physically move weight or ballast in the car. Cross-weight percentage compares the diagonal weight totals to the car's total weight. If you want to lower the rear of the car then retract the LR 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. track are left turns then having more weight on the Right Front and Left Rear you don't use Microsoft Excel. If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. 6 Check your ride heights and make small adjustments for ride height and crossweight percentage if need be to finalize your setup. Left Rear tire is carrying more weight so it will get more traction and This is but one method and I encourage everyone to ask around and find a method that works for your type of car, this one may not be the most efficient. With the driver weight, the left side might move down 1/4-inch and the right side down 1/8-inch. I've spent an hour this afternoon trying to do corner weights "on the cheap" using our IKEA kitchen scale (cost - 15.99 a few years ago) and three wooden blocks cut to the same height as the scale (38mm). TVW - (RF + LF + LR) = 603. Similarly, dirt oval cars often represent crossweight as "bite", or weight on the left-rear tire relative to the right-rear tire. Hub stands are a great idea just for ease of access, but removing friction is an added benefit. If the driver lifts early but still has a fairly good amount of roll speed into the corner, there probably isn't much brake being used. In circle track racing, we often, and almost always, have different rate springs on each corner of the car. Other than that you need to watch the suspensions. Once you have established an ideal moment center design and the correct cambers through testing, you need to maintain those throughout your season. Just make sure none of them are flat or wildly overinflated. used cheap linoleum tiles (49 cents each at Home Depot) to shim two of my scales balance is complete put someone in the driver seat and reconnect the 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. How To Set Up RC Dirt Oval A Guide - Explained! When a NASCAR crewchief says he's "adding wedge", 6. To increase left-side weight, move weight as far to the left as possible. rear and tried again but I still needed more weight off the right front and left In our example it is 18 degrees. Motion Ratio of the lower control arm. Positive Caster is created when the caster line lands forward of the contact patch. Recheck air pressure often to assure ride heights stay consistent. Air up the tires as they will roll through tech. Motor: 550 or 540 motors only. I vary mine alot depending on conditions, so should I sayset them where I would at the beginning of an average day for autoX? to measure your new springs and put the longest spring in the left front--this Here are some setup tips that will help you really get the most of of your Slash: > Keep it clean. more important corner balancing becomes. %Right Weight = Caster creates stability as the geometry . need to roll the car back and forth a few inches several times, being careful 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. weights: Corner Weight Calculator if We had a good Miataset up for ST. Lay the bag flat onto the scale pad, partially open to vent, lower the car into the bag. We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. 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. In our example, the front average is 4.25 and the rear is 4.75. This adds pressure to that end of the car just like putting the paper wedge underneath the table leg. This gets very tedious, given the number of iterations it typically takes to get the corner weights right. 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 If we are talking of weighing a stock type vehicle, not a lot can be done since there are no adjustable parts. PDF iRacing Set-up Guide Additionally, it is much more difficult to change rear percentage much, since rear weight is mostly a design function. 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. 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. in the driver's seat to load the suspension. 10. You will need to weight your vehicle on each tire to use this tool. 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. It also helps when shaking the car to take the bind out of the linkages. 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. 3. tire pressure RF 43 LF 35 RR 40 LR 35 psi. turn and ended up with a perfect 50.0% cross weight. Those will tend to reduce friction and bind at the expense of NVH and added wear. another. The following are screen shots from the adjustment so I have a history of each adjustment. Guess I have to try it. 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. Or maybe I read the post wrong. over I see disconnecting the sway bar, and how to do it, but disconnect the shocks? Record these. To find LF weight: If one leg is longer or shorter than the others, the table will rock and thus be unstable. At the right rear, a quarter-inch change in the height of the end of the link will change the angle and can make an asphalt car undriveable. Using dead strut inserts could be an option for cars with strut suspension. I created a Microsoft Excel spreadsheet do the following My car is a 1987 Honda CRX, set up according toITC class rules. turns. Use a load of fuel for where you you want the car balanced, either at the start of the race, the end of the race or an average between the two. As for setting the left side and right side equal, I understandthe reason why it might be best, but hard for me to picture how to adjust it. 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. bite, a negative value means the Right Rear is favored. A set up plan will help you to build a race winning effort. (CG) height by using this online calculator: CG Height right swapped). Use those racing internet forums, and dont be timid about asking for some assistance! Wheel Load-We have already determined the wheel load we desire in No. This is for a race prepped 1984 Audi 4000 quattro(2375lbs. 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. Move ballast first, since it's easier. To do this you need to enter a corner at the car's limit of adhesion and then peel off the throttle aggressively. shouldn't match the front to the rear but your left front and right front shocks Tell the shop you will be disconnecting the rear sway bar when obtaining the estimate. You cannot change the left or rear percentages by jacking weight around in the car, although this will change cross-weight. 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. Delta which is simply the difference between the two diagonal tire weights. Same goes for for swaybar endlinks. to get a balanced diagonal weight on the tires. Corner weighing will tell you how much overall mass your car has as well as the mass present at each wheel. 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. 3. You will have to repeat this every time you lower the car onto 13. front left and Always Check your tire pressure and bump it up to the hot pressure You need: 1. My track width with CE28 17" x 9" wheels Now that's pretty cool! ride heights after every change. Using dead struts and lots of bearings will help. In this example, we will adjust the crossweight percentage on a sample car with different rate springs. Get the numbers right and the percentages will follow. the scales and zero them with no weight on them. The cosine of 18 degrees is 0.95106, and that into 1.0 is 1.05146. If the car understeers or oversteers in only one direction, check the cross-weight percentage. not to push it off the scales, to unload the suspension (as the car is If the car feels loose throughout the corner, lower both track bars evenly. Brake pads badly taper worn - replace. If you moved only one point, then the problems begin. anti-roll bars then leave them connected. I usually mark an even inch and write that inch number on the tape. important for oval racers, especially on dirt ovals. A 50% Cross Weight will yield a balanced handling car, one How big is the track? 5 So, five rounds in the right-side springs (along with the corresponding Multiplier to the left-side springs) changes the crossweight percent by 5.6 percent, which is 1.12 percent per round, or 0.89 rounds per percent of crossweight. In oval racing you always run more weight on the LR. Typically, this adjustment will make the car tighter on corner entry or in the center, and a little looser on exit. The front is usually the lowest point on the car and most sanctions maintain a minimum ride height rule.
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