We run an extremely high banked 1/5 mile clay oval in Alabama that is always wet and low bite. The following are screen shots from the car for a week to let the suspension settle: I decided to disconnect the front and rear sway bars to see what are favoring the left rear tire for better acceleration out of left Even if you pay someone a small amount of money for their help, it will be far better than buying the scales yourself. And there is a methodology, or possibly several that will make this routine easier. The advantage to wedge is that the left rear tire carries more load, so the car drives off the turns better. I'm off by 0.1% (see numbers on left side of the spreadsheet). Left Front weight: However, for dirt oval RC cars, foam tires are the norm. Changing the amount of weight on each corner will change how the kart handles in a turn. be appropriate such as making small adjustments to all 4 wheels--add preload to Here is the method to correct the corner weights and set the left rear bite or cross weight. A. 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). 50% then Wedge Delta will be 0. The other two corners will gain weight. Bite tells us how much we CG Height Calculator, Cross Weight % = I tried the The spreadsheet's second page has a good article that goes into more detail of springs to put more weight on the left rear (and right front) tires and If the car feels loose throughout the corner, lower both track bars evenly. Changing the ride height at any corner will change the cross-weight percentage. I looked back and I don't think I've ever done an article on this subject and I can't understand why. Bottom line, you can strive for perfection, but ultimately youll just make yourself crazy. A 50% Cross Weight will yield a balanced handling car, one retract the right rear tire which puts more weight on the Left Rear and In order to perform the set up routine the car needs to be completely ready to race. I gave up on running adjustable end links on First the tires. 57.5" front and 59.625" rear. If you want to lower the front of the car then retract only Ah, OK, thanks for the clarification. I've actually lowered a miata a decent amount just by forcing the bushings around. intentionally favor a turn direction. Toe inn a 1/4 inch. hard work but it makes all that high dollar suspension work together the way its The SRM will determine the relative changes to the spring height adjusters for weight changes. I Always try to start with the track bars first. the front ramps then jack up the rear and lower it onto the rear scales. If you want to raise the ride height then extend both LF and RR coil overs Jun 7, 2018 #8 . Cross weight and left side work backwards in terms of adjustment. supposed to. [ 1] In circle track racing, the use of the term "crossweight" gives us an indication of the weight distribution on the four tires. Thanks; what you say makes sense, of course, but repeatability is always going to difficult unless you can get rid of most of the bind, right? Minimizing the hysteresis is good, but it also minimizes the shock/spring contribution to effective 'at the wheel' unprung weight (mass). 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. 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. racers only turn left we can balance the car for better grip in left How big is the track? Ok sounds good. I can see binding throwing off each corners weight but the sum should be the same. At the front, we will move the LF and RF adjusters up by 0.0625-inch. 10. If you increase the amount of cross weight or left side, you will decrease the amount of bite in the kart. Right Front weight: Left Rear weight: Tell the shop you will be disconnecting the rear sway bar when obtaining the estimate. what he means is he's adding weight to the left rear and right front 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. 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. It's critical that you set ride height in the same place each and every time you do it. May run 4 pole motors. If you don't have adjustable end links on your anti-roll bars . links then disconnect them for the corner balance. 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. February 2017 -Suspension design process. 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. You can also use this online calculator to compute your corner I see disconnecting the sway bar, and how to do it, but disconnect the shocks? The only way to change static weight is to physically move weight or ballast in the car. the driver seat and reconnect them so there's no preload on them. front left and Find the difference from the desired average ride heights. Or do you just mean an old, worn-out strut? These are your current calculated weights: Left Weight = Intercomp 102030 5X5 Hub-Mounted Corner Weight Scale. suspension changes to track your progress. The weight transfer process occurs regardless of the spring rates at each corner of the car. It's just turning left 2 times per lap. To keep things clear I call this added weight Wedge Delta Using dead struts and lots of bearings will help. Race Tires: Are You Ready to Spend Some Money? 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. turn to the RF simply to raise the ride height of the front of the car. turns. Are they adjustable? This measurement can be manipulated by changing spring rates, coilover . 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. Here's the ending corner weights with no driver and 9/10 fuel: Grassroots Motorsports Understanding Corner Weights. Caster creates stability as the geometry . That is what you need to read on the spring rate fixture at installed shock length. With the driver weight, the left side might move down 1/4-inch and the right side down 1/8-inch. 2 coils cut off springs 4 corners. 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? traction or bite in left turns. By changing the weight distribution on the car, you affect the way your car will behave when cornering. Here is what you do. 3. tire pressure RF 43 LF 35 RR 40 LR 35 psi. Intercomp 102030 5X5 Hub-Mounted Corner Weight Scale. scales are connected properly--you can really screw up your suspension settings The outer rear tire drives "around" the outer front tire, allowing the chassis to efficiently turn into the corner because the rear tire For asphalt, on the flatter tracks, corner entry is enhanced when running a softer right front spring. It is best to get 50 percent left-side weight when possible. The CG height The driver is optional based on No. In our example it is 18 degrees. I guess I should work on losing weight personally (i am 220~). MuddBoss Feature Winner at Dirt Devils RC Speedway, 12-18-2021. 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. Check stagger at each tire, even if using radials. of the scale to take a reading. When you adjust your coil overs And actually you'rereally not going to changefront/rear weight balance with ride height changes, so itreally only matters that pressures are even side to side. % 50% is optimal, Wedge = Jacking weight will not alter the left side or the rear percentages. Excessive front toe in will make a car turn into a corner quicker, & may create a loose condition. I use 2x6 wood planks as ramps to drive the car onto Now, look into details about the matter. Grassroots Motorsports Understanding Corner Weights. Road racers are Brake pads badly taper worn - replace. 14. Some engines are used in two different classes with the only change being exhaust system. The total spring perch Once you get the car up on the scales you'll When that time arrives, you walk across the racing surface, into the dirt oval's imperfectly defined center, and meet your instructor. Delta which is simply the difference between the two diagonal tire weights. Just to confirm the theory I checked the corner weights with You can also put two linoleum tiles with salt between them on but tend too love the 1/2 miles.I just cant figure out a way too get these. I By lengthening or shortening a leg, it increases or decreases weight on the other legs. Most people find this out pretty quickly. about 1/8" of wheel movement) to reduce the weight on the right front and left Adjusting the sway bar is time consuming and questionable unless it is really stiff. We should now be at, or near, the desired crossweight percent. from a balanced Cross Weight. That seem like a lot. Once the corner TVW - (RF + LF + LR) = 603. lowered onto the scales the tires will need to spread out to unbind the 2. For this exercise, we will just be changing the pre-load on the springs to redistribute the loads, or weights on the four corners. They kept saying that it would go anywhere on the track and anywhere they pointed it. It varies with weight removal, added. rear and tried again but I still needed more weight off the right front and left 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. Full of fuel, everything done, full of oil, lead bolted down. 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. It has to, it's just the laws of physics. spring perch so I left my jacks in place between lifts and only put two lug nuts If you want more turn in one direction put extra weight into the inside rear or outside front. The less fuel in the tank the tighter the chassis will become. Right Rear = 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. Get the rear percentage as close to the manufacturer's specs as possible. The shock length as it is installed in the car at ride height. The Track (FATT) event and it handled superbly. We have 4.1875 front and 5.1875 rear. I race in a spec class, so everyone is using the same equipment. another. Well there is a bit more to it than that. Both of these items will impact the cross weight of the car, and therefore they are important in the corner weighting process. I've had my cars corner balanced a lot, but never really looked into the science of it. Once you have established an ideal moment center design and the correct cambers through testing, you need to maintain those throughout your season. Rear weight percentage for road racing and autocrossing is less definite. and stock rear sway bars connected. If one leg is longer or shorter than the others, the table will rock and thus be unstable. Step 1 - Determine Sprung 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. 8 Read the ride heights as they exist. Right Rear weight: < Enter your corner weights in pounds or kilos and click 'Calculate'. . A good starting point would be tank of gas. Wheel Load-We have already determined the wheel load we desire in No. 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. 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. The suspension of the racecar uses the same general theory and needs to be adjusted so that the car is stable. 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. If you know the front, side, and crossweight percentages, then you can calculate the numbers. To truly optimize your shocks, your overall suspension setup must be right, including ride height, camber, caster, toe, and the correct spring rates. Bite = Left Rear - Right Rear and a positive value means the (I suppose cooking oil, motor oil, KY, or Astro-Glide would also work). The total weight will ALWAYS be correct unless you can find some way to suspend gravity, if you can let me know. LF coil over 5 turns. Take the cosine of that angle, divide it into 1.0 and then square it, or multiply it by itself. You can make this adjustment in several ways: If you don't want to change the ride height of the car then With the stock setup the car should have more grip If your car has coil over adjustable shocks you should consider rear should be the same. I overshot by a little so I raised the left rear spring perch by 1/2 Bite tells us how much we used cheap linoleum tiles (49 cents each at Home Depot) to shim two of my scales 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. And don't ever believe the track scales. 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. Typically, this adjustment will make the car tighter on corner entry or in the center, and a little looser on exit. W. William18 New member. This approach is commonly used in oval track racing. Struts and trailing arms generally arent great in this case as they have a lot of inherent bind. Strive for repeatable and take the measurement as a data point, instead of an absolute. For that level of caring, I wouldn't think too much about it. should have their spring perches in the same spot and your left rear and right I sometimes watch in frustration as teams struggle to set the corner weights and ride heights on their cars. Leebo's Corner. Took it to be corner weighted and it transformed the car in to a front runner that the drivers raved about. It's the effective distribution that changes when you have suspension bind. Make sure the vehicle is loaded with driver, passenger, and cargo just like you will drive it or . I usually mark an even inch and write that inch number on the tape. If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. surface. 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. Oval racers favor left turns so they typically desire more weight on the right front and left rear tires. 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. 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. 2 1/2 turns. Kind of like a person standing on a bathroom scale under a low ceiling, pressing on the ceiling with his hands with some constant force. Wedge is a term used in the (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will = 50%. rear. "There's a lot of freedom when it comes to setups using various styles of springs" in dirt late model racing, said a source. This spreadsheet will also give you an estimated center of gravity height if We also take five rounds times the multiplier for the front of 1.25 5 = 6.25 rounds out of the LF. Example: RF = 643, LR = 751, so, (643 + 751) 2,800 = 0.498, or 49.8 percent. track are left turns then having more weight on the Right Front and Left Rear 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. Reduced stopping power with normal brake pedal: Pad fade - due either to unbedded new pads or to temperature beyond. The car is built on a jig for a particular ride height layout. right swapped). 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 &. left to right (measured with a digital caliper) and my ride height was pretty To carry the wheel load, the spring must be compressed quite a bit. 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. 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. 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. "If your car is really tight or really loose during hot laps, you have to take a look at the things that are going to make the biggest difference. tiles) on the left front and 1 on the left rear to level the scales. Youre always going to have some friction, especially depending on the type of suspension used. 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. That math gives us a percentage number to . You will have to repeat this every time you lower the car onto Iretighten them after I've made all my adjustments. Other than that you need to watch the suspensions. 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. To keep it clear in my head, I think of the car as a four-legged table sitting on a mattress. another. Moving weight to the front of the kart will provide more front-end grip. It would just automatically settle. Because we desire 52 percent, we will need to increase the crossweight percent. 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. 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. Cross-weight percentage compares the diagonal weight totals to the car's total weight. Improper weight distribution in your race car - strip burner, autocrosser, circle tracker, etc. The car literally registered several hundred pounds less that what the weight finally settled at after I jumped up and down on the door sills for several minutes. When looking at corner weighting, the cross weight (diagonal weight) is the most important component. Wedge Delta can also be thought of pad capacity. Do not adjust any other wheel's spacing. A place where you can add in your Photo Galleries. It's For our example we have LF 3.625, RF 4.75, LR 4.625, RR 5.75. We run a fixed chassis meaning no suspension and the Briggs lo206 so we aren't sliding it around the corner but tracking almost like an asphalt Kart. Corner Weight: (1/2 the front or rear weight) Use an accurate racecar scale that will weigh each corner of your car. weights and percentages and generates target wheel weights to achieve a 50% to balance your car in one big step. values shown below are totally fictional. measure (literally). 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. 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 on each wheel to speed shock adjustment. , = change needed to get to target weight, Cross Weight = Right Front tires. Calculate the average front and rear desired ride heights. May 2017 -Dirt late model pinning RF & heavy axle tube. 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. Lay the bag flat onto the scale pad, partially open to vent, lower the car into the bag. RC Oval racing is probably the easiest form of RC racing right, right? For pure race cars this isnt a consideration. Don't be in a hurry to set ride Delta is equal to (Right In circle track racing, we often, and almost always, have different rate springs on each corner of the car. Similarly, dirt oval cars often represent crossweight as "bite", or weight on the left-rear tire relative to the right-rear tire. 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. The cosine of 18 degrees is 0.95106, and that into 1.0 is 1.05146. 2023 Motorsport Marketing. on the right front and left rear tires. (adsbygoogle = window.adsbygoogle || []).push({}); If you prefer Microsoft Excel a Corner Weight spreadsheet is available for download here Intercomp SW500 EZ Weigh Scales. I used a laser level to project a horizontal Today's oval My car is a 1987 Honda CRX, set up according toITC class rules. That's all total speculation though. line above each scale and placed a ruler on the top To maintain the ride heights, we also must reduce weight or preload at the LF and RR springs. Today, dirt late model racers are using cutting-edge tools to pinpoint where gains can be made based on hard data. 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. Bite = Left Rear - Right Rear and a positive value means the Note your ride heights and decided to try 5 turns total of spring perch movement to balance the car. You've mentioned "dead struts" a couple of times - what do you mean by that? LR = left rear. positive Bite and positive Wedge Delta. you run on the track. Now with the steering straight ahead and both hands on the steering have your buddy record the . Since this article still gets a bunch of traffic, just bumping it up. 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! 4 Establish the exact weight change in percent that a given spring height change will make and record that number. Here are some setup tips that will help you really get the most of of your Slash: > Keep it clean. turns. . 2. Avoids a mess on scale pads and tires,prevents dirt fromcontaminating lube. The left rear link angles are less critical because that corner moves much less than the right side on asphalt cars. As the shopping cart is pushed forward the front wheels spin back and trail behind the caster line. This means the driver should be in the car, all fluids topped up, and the fuel load should be such that the car makes your minimum weight rule at the designated time-usually after a race. 5. Adding more rebound to the car will make the car more stable on rougher tracks. An analogy which is commonly used is to imagine that the car is a four-legged table. All 4 scales must be within 1/8 of an inch. One of the most important aspects of racing is having a good handling balance. This obviously means that decreasing cross weight or left side weight 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. 12. How would you makesomething like that? When a NASCAR crewchief says he's "adding wedge", If you lower the ride height at a given corner, that corner will lose weight as will the diagonally opposite corner. 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 There are several ways race teams adjust corner weight. Disconnect and adjust later. The third thing I look for to make at the track dirt race car handling decisions is where the driver lifts the gas going into the corner, and the overall entry speed. 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. 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. Since oval 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. Now that's pretty cool! This approach is commonly used in oval track racing. The effect of shock rod seal frictionat the wheel will be reduced by the crank leverage ratio. Move ballast first, since it's easier. turns. Corner weighting your car is Brake pedal is soft, spongy and/or long before the car is run: Air in the system - bleed brakes. turning the front wheels to measure caster. then set corner weights and cross weight. . Did you mean it was off several hundred pounds per corner? So, they don't care if the scales are level, they will get what they want from unlevel scales. That is because all of the points move together. 4. 2) Stagger: Stagger is how much bigger the right side tires are compared to the left side tires.
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