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of the scale to take a reading. Always record the cross-weights and ride heights for reference at the race track in case changes are needed. Weight can be moved around at the track to fine tune the handling characteristics of the chassis. 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. 19. the scales. . (corner weights) instead of moving shims above / below spindle? I had the same question. Oval Track. bite, a negative value means the Right Rear is favored. Speaking of springs, it's a good idea The left weight percentage is found by adding the LF weight to the LR weight and dividing the sum by the total weight. Since the front and rear shocks are of different lengths you The ride heights are critical to the geometry settings on the car and the static weights help determine where our loads end up on the track in the turns. I gave up on running adjustable end links on be appropriate such as making small adjustments to all 4 wheels--add preload to So let's study ride heights first. For Oval guys I suggest talking to your local kart shop who knows the tracks you run on for a suggested starting point. They're made by Proform, and are quite a bit less expensive than the ones made by Intercomp, but they got good reviews. Corner weighting your car is That is what you need to read on the spring rate fixture at installed shock length. Finding The BBSS Front Spring Pre-Loading as Left Rear Bite + Right Front Bite. The car should be at minimum weight, using ballast as needed to make the proper weight. On the other hand, it drives really, REALLY good for being setup by this idiot behind the keyboard, and I really don't wanna spoil a good setup by chasing after a perfect setup at least not yet. To find LF weight: I mainly run the 3/8. To favor right turns, put more weight on the To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. adjustment so I have a history of each adjustment. RC Dirt Oval Basic Setup & Tuning Guide (21.5, dirt oval, GFRP, Custom Works, Purpose Built) - YouTube 0:00 / 43:10 Dirt Oval Setup & Tuning Tutorials RC Dirt Oval Basic Setup &. height and the shocks set to the exact same spring perch height If your car has coil over adjustable shocks you should consider you raise the rear of the car 10 inches or more and re-weigh it. Cross-weight percentage compares the diagonal weight totals to the car's total weight. . It also helps when shaking the car to take the bind out of the linkages. For asphalt, on the flatter tracks, corner entry is enhanced when running a softer right front spring. If we remember, or record this number, then we can easily make changes in the future to get to our intended crossweight percent fast and easy. 12. you weigh and adjust. need to roll the car back and forth a few inches several times, being careful Still, it is a worthwhile goal to strive for 50 percent left-side weight. Changing the amount of weight on each corner will change how the kart handles in a turn. oval racing world and is simply another word for Cross Weight. Iretighten them after I've made all my adjustments. Any corner weight adjustments that you make will impact the alignment of your car. Bounce the car at each corner to free the suspension from any bind, then roll the car onto the scales. 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. right swapped). the same time. and have shocks available for all forms of racing - dirt and asphalt sprint cars, dirt and asphalt . 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. When working with static weight distribution, we use two percentages to analyze the car's corner weights: Left weight percentage and rear weight percentage. This measurement can be manipulated by changing spring rates, coilover . That is because all of the points move together. the scales and zero them with no weight on them. I weigh 220. It changed the wheel weights by 10 pounds at each wheel: I finally went too far when I took two turns off the Right Front (went To do this you need to enter a corner at the car's limit of adhesion and then peel off the throttle aggressively. [Up] [CornerBalanceCalculator] [CGHeightCalculator], This calculator takes your car's four wheel weights and calculates current Right Rear = Oval racers favor left turns so they typically desire more weight on the right front and left rear tires. Ideal weight percentages: Front - 43-45% Left - 53-56% Cross - 52-54% What do these numbers mean? Astrut with its innards removed? Since oval Now that we have established the ride heights, our weights could be anywhere. The suspension of the racecar uses the same general theory and needs to be adjusted so that the car is stable. Unsure about autox. Plus it sounds like street and autocross pressures are about the same stagger front to rear, so it really shouldn't have a noteworthy impact. Bite tells us how much we 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. 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. should have their spring perches in the same spot and your left rear and right Maybe there's some sort of bind in the scales. It is best to get 50 percent left-side weight when possible. can help us get our setup right with less testing. I see disconnecting the sway bar, and how to do it, but disconnect the shocks? Also double check that the Brake pedal is soft, spongy and/or long before the car is run: Air in the system - bleed brakes. 2. ride heights after every change. Or am I missing something? With an oval track car turning to the left, weight will transfer from the inside to the outside. 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. I 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. The left rear link angles are less critical because that corner moves much less than the right side on asphalt cars. Today's oval lowered onto the scales the tires will need to spread out to unbind the Today, dirt late model racers are using cutting-edge tools to pinpoint where gains can be made based on hard data. 8 Read the ride heights as they exist. Move ballast first, since it's easier. Keep in mind the stiffer your springs the However, many cars cannot make the 50 percent left-side weight percentage due to driver offset. First some baselines. 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. Cross weighting is crap for road courses and only applies to turning one direction OR if the car is about 50/50 F/R weight to begin with. The spreadsheet's second page has a good article that goes into more detail of Drag Racing. Choose your ride heights before you measure and/or redesign your front geometry and then maintain those chosen ride heights. Because we desire 52 percent, we will need to increase the crossweight percent. If the car feels loose throughout the corner, lower both track bars evenly. that turns equally well in both directions. I looked back and I don't think I've ever done an article on this subject and I can't understand why. are favoring the left rear tire for better acceleration out of left March 2017 - F1 suspension rules, independent rear suspension for dirt oval. That is equal to 7/8 turn of the adjuster. All 4 scales must be within 1/8 of an inch. To add weight to a given corner, raise the ride height at that corner or lower the ride height at an adjacent corner. Keeping track of Bite and "Many racers are running stacked springs (pictured), or dual-rate springs, or soft, long-travel . One of the most important aspects of racing is having a good handling balance. The weight transfer process occurs regardless of the spring rates at each corner of the car. The crossweight percent will have changed to, say 55.4 percent. Mudboss Setup #3 - Traxxas Slash transmission setup and diff oil for oval racing Oval RC 216K subscribers Subscribe 812 Share 51K views 2 years ago #diff #setup #mudboss Traxxas Slash. In our example we will be using the same method with corrections for different rate springs. 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. Record each spring rate. Moving or removing weight is one Replacing a heavy battery with a light weight one allowed me to get close . 14. That makes every little detail that much more important. Muscle Car. I put the tiles on top of the scales. looking forward to getting it back! 2. You will have to repeat this every time you lower the car onto Recheck air pressure often to assure ride heights stay consistent. Additionally, it is much more difficult to change rear percentage much, since rear weight is mostly a design function. 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. Dirt or asphalt? Doing the multiplication to square that number, we get 1.1056. Also you will obviously want to have some way to ensure all your scale pads are level with each other. Scale Type: . Right Rear. supposed to. 35 psi hot tire pressure target . I found that the tire will absorb side loads quite well and was repeatable. 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. Moving weight to the front of the kart will provide more front-end grip. used cheap linoleum tiles (49 cents each at Home Depot) to shim two of my scales You can make this adjustment in several ways: If you don't want to change the ride height of the car then Bite and Wedge Delta are This is the arm length divided by the distance from the shock mount to the inner pivot line, squared. Same goes for for swaybar endlinks. If you know the front, side, and crossweight percentages, then you can calculate the numbers. On Dirt cars, adding Rebound to the Right Rear will make the car more stable when it slides into the cushion. It was a good car. positive Bite and positive Wedge Delta. There are legal issues too at the front. This was my first adjustment: Four turns of positive coil I will say that if I'm starting on a fresh setup, or the car has been lowered, or I find myself making massive spring perch changes, then I will loosen all of the suspension bolts so that the bushings can relax and find their new happy place. An analogy which is commonly used is to imagine that the car is a four-legged table. Forum Actions: Forum Statistics: Threads: 167; Posts: 1,367; Last Post: . positive Bite and positive Wedge Delta. Beyond that, if your bushingsand other parts bind on the scales then they're also going to bind out on the road, so who cares? retract the right rear tire which puts more weight on the Left Rear and Finding these values and maintaining them is at the top of the list for being consistent in your racing effort. - can make your car dive like a dump truck or a block of wood on ice. 45. Would be interesting to see how close to ideal I got it though, given how well it handles already. 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 % lb driver, no passenger, spare tire removed, soft top up, Magnaflow mufflers (-20lbs), Braille When a NASCAR crewchief says he's "adding wedge", The new existing ride heights are LF 3.6875, RF 4.8125, LR 4.1875, RR 5.3125. You could also raise the left front or right rear ride heights to do the same thing. suspension). Road racers are balancing see my corner balance how-to and "two linoleum tiles & salt" technique to allow the tires to slide on the scales hard work but it makes all that high dollar suspension work together the way its . important for oval racers, especially on dirt ovals. To properly corner weight the car, it is necessary to add weight to the drivers seat which is approximately equal to the weight of the driver (or have the driver sit in the car). Step 1 - Determine Sprung Weight. Check your tire pressure and bump it up to the hot pressure 13. Raising the rear end will also provide a little more on-power grip by keeping more weight directly above the rear tires during acceleration. Open timing on motor and esc. One of the most important aspects of car setup is the static weight distribution and the cross-weight percentage. To maintain the ride heights, we also must reduce weight or preload at the LF and RR springs. I plugged in a bunch of numbers into my calculator and it all checks out. 1 of the section on "Adjusting The Corner Weights," and that is 685. Most chassis manufacturers will tell you what ride heights are best for their cars. We were racing dirt oval about a month ago, and then I tried this scale system . 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. 6 Check your ride heights and make small adjustments for ride height and crossweight percentage if need be to finalize your setup. traction or bite in left turns. First the tires. Oval racers favor left turns so they typically desire more weight You've mentioned "dead struts" a couple of times - what do you mean by that? weights: Corner Weight Calculator if If we are talking of weighing a stock type vehicle, not a lot can be done since there are no adjustable parts. Caster and Caster split can be adjusted to find more speed and stability. If you want more turn in one direction put extra weight into the inside rear or outside front. A. You should read the spring preload amount. racers only turn left we can balance the car for better grip in left Yep, old struts that are drained of fluid and have little to no resistance. But this is almost never the case. Now that the car has the correct ride heights and weight distribution for your setup, you need to make sure those don't change at the track. The important thing to remember is that the laws of physics are the same whether you are racing on an oval or a 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). cross weight. Right Front tires. which is simply the difference between the two diagonal tire weights. Once you get the car up on the scales you'll 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. end-link into the anti-roll bar's hole. , = change needed to get to target weight, Cross Weight = However, for dirt oval RC cars, foam tires are the norm. 4. Road racers can take a page out of the oval racing book and Tuning with anti-dive probably won't be . preload (extending the shock) to the Left Front, and one positive turn to the Right Front. Delta is equal to (Right That is why it gets tighter. Improper weight distribution in your race car - strip burner, autocrosser, circle tracker, etc. 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. If most of the important turns on your 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. decided to try 5 turns total of spring perch movement to balance the car. 10. it would help the car turn left and accelerate better. to get them exactly level. the scales. Air up the tires as they will roll through tech. , Left Rear = A. I was surprised how much these high rate LR coil overs 2 1/2 turns. Or maybe I read the post wrong. balance is complete put someone in the driver seat and reconnect the springs settled over the first 3 months. When looking at corner weighting, the cross weight (diagonal weight) is the most important component. tires. The SRM will determine the relative changes to the spring height adjusters for weight changes. 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. I sometimes watch in frustration as teams struggle to set the corner weights and ride heights on their cars. MuddBoss Feature Winner at Dirt Devils RC Speedway, 12-18-2021. I needed 3 linoleum tiles (0.045" thick does not change when a driver is added. More stagger usually loosens the handling in left turns, so more cross-weight is used to tighten it up. You need: 1. Make sure the floor is perfectly level; use shims under the scale pads if needed. When a NASCAR crewchief says he's "adding wedge", Corner Weight Calculator This is used to calculate the corner weight and Wedge. over). you don't use Microsoft Excel. Adjustable end links are more started with the Left Front because I wanted to raise the ride height of the car Here is a screenshot with some random-ass corner weights. Then the car will move more easily from one setting to another. Here is what you do. Disconnect the sway bar. I use 2x6 wood planks as ramps to drive the car onto When that time arrives, you walk across the racing surface, into the dirt oval's imperfectly defined center, and meet your instructor. scales are connected properly--you can really screw up your suspension settings and Left Rear. The springs OTOH exhibit little or no friction loss when compressed or extended. 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. You can drop the front end slightly or raise the rear end for more aggressive turn-in. LR = left rear. By lengthening or shortening a leg, it increases or decreases weight on the other legs. I always thought it was the other way, shock travel was increased in order to have more movement for better control over the suspension? Yeah generally its the same stagger 9/10 times. Then just leave them attached. Take the cosine of that angle, divide it into 1.0 and then square it, or multiply it by itself. works well. I use 2x6 wood planks as ramps to drive the car onto the driver seat and reconnect them so there's no preload on them. Here is the method to correct the corner weights and set the left rear bite or cross weight. and stock rear sway bars connected. rear. I've read all the info before, in various places, but it's good to have a refresher. 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. 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. I saved a copy of the spreadsheet for each 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. If the car understeers or oversteers in only one direction, check the cross-weight percentage. want balanced turning in both directions. (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will be 50%. In our example it is 18 degrees. Do this at every wheel. You can see the article here: I recommend you start with your car at your desired ride suspension changes to track your progress. by about 1/4 inch so most of my adjustments were positive--they raised the car. Hot Rod. Once the ride has been set, it's a simple operation to bring the corner weights to the predetermined values. My left rear is something like 150lbs heavier than the right rear, with both fronts even at ~740lbs each on a 2425lb FWD car. rear and tried again but I still needed more weight off the right front and left Calculate the average existing ride heights front and rear. racers discovered they could insert an actual wedge into the left rear Road racers can take a page out of the oval racing book and To carry the wheel load, the spring must be compressed quite a bit. Picture the following: Your car is really fast in right-hand turns, but understeers in left turns. Struts and trailing arms generally arent great in this case as they have a lot of inherent bind. I The height of the rear roll center (and the front also) is critical to handling. Rebound adjustments will allow you to alter your car to a corner entry condition without affecting corner exit or vice versa. We delve deeper into race suspension tuning basics here. Calculate the spring rate multiples. Check static weight before working on cross-weight. Excessive front toe in will make a car turn into a corner quicker, & may create a loose condition. A 50% Cross Weight will yield a balanced handling car, one 12. Check your tire pressure and bump it up to the hot pressure Setting static weight distribution and adjusting cross-weight percentage is one way to assure good handling. Some engines are used in two different classes with the only change being exhaust system. I was booked for 100 laps split across four or five sessions. I still rolled the car back and forth a However, most importantly you need to take care of the handling. extra weight is on the left rear and right front tires which gives them more Wheel Load-We have already determined the wheel load we desire in No. 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. 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. Example: RF = 643, LR = 751, so, (643 + 751) 2,800 = 0.498, or 49.8 percent. 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. Now with the steering straight ahead and both hands on the steering have your buddy record the . another. The shock length as it is installed in the car at ride height. My shocks are double adjustable, as many will be when at this level of prep. Cross weights can be changed by making ride height adjustments to the coil-over suspension by either winding the lower spring platform up or down. Wedge Delta and what values work best for certain tracks and conditions 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). and without me in the driver seat and yup, the theory is right--the cross weight If you don't want to change your ride height then a more balanced approach would After these items are completed, it is necessary to corner weight the car. 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. 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 the car feels loose on corner entry, lower the left track bar. While several different setup parameters could have caused this situation, a likely cause is excessivecross-weight. Disconnect and adjust later. I've actually lowered a miata a decent amount just by forcing the bushings around. Do not copy these ride heights; they are only used as an example. Motor: 550 or 540 motors only. I didn't hunt for that missing 1 %. shifted by more than 1 pound after rolling the car on the scales. At least for road racing. So, deviating from those numbers will mean you have a design other than what was intended for the car. I added the Taking the time and making the effort always pay dividends. Using dead struts and lots of bearings will help. then set corner weights and cross weight. Wheel Offset Changes. center of gravity (CG) height by using this page: This gets very tedious, given the number of iterations it typically takes to get the corner weights right. It's the effective distribution that changes when you have suspension bind. 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. I borrowed some scales to weigh my Terceltomorrow. Motors / ESC: Any 1/10th scale motor/esc combo allowed. Small angles can throw off your readings significantly. And what do you mean by "lots of bearings"? This approach is commonly used in oval track racing. 3. tire pressure RF 43 LF 35 RR 40 LR 35 psi. You can also use this online calculator to compute your corner Rolling the car onto the scales from a small ramp that's the same thickness as the scales seems like a better option, but does it truly remove all the bind? retract the right rear tire which puts more weight on the Left Rear and I highly recommend using a laser level to confirm the 4 scales are level to one First off, you must maintain the legal ride height to pass tech. You can estimate your car's center of gravity Avoids a mess on scale pads and tires,prevents dirt fromcontaminating lube. Once you have returned the wheel corresponding to the spring change back to its measurement, the other wheel measurements will be OK. 3. I lowered the right front spring perch 1 full turn (equates to stiff springs on your coil overs. 12. turn and ended up with a perfect 50.0% cross weight. Bite should be positive for oval racing, Wedge = Today's oval I'm not saying you get what you pay for with race scales but there is a reason I went with longacre. what he means is he's adding weight to the left rear and right front So as long as you are draining the fluid from your shocks, also remove or cut away the seals. The total spring perch 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. Other than that you need to watch the suspensions. I race in a spec class, so everyone is using the same equipment. 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. In April 2013 I corner balanced the S for the first time in 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. difficult to position all 4 scales so you can just drive up on all of them at Proforms are cheap scales. (TVW FWP) - RF = 743C. Bite = Left Rear - Right Rear and a positive value means the lowered onto the scales the tires will need to spread out to unbind the