corner weights for dirt oval racing

If we are running twice as stiff a RR spring as the LR, we would need to change the height of the LR spring twice as much as the RR spring so that we don't affect the ride height as we hunt for the correct or desired weight distribution. Unsure about autox. 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. Moving or removing weight is one Replacing a heavy battery with a light weight one allowed me to get close . I have a 96 civic with a d16/manual. For example, if you are racing the Briggs Light class at 305 pounds, your corner weights should be: LF = 68 pounds RF = 68 pounds right swapped). Choose a level spot in your setup area. 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. Lay the bag flat onto the scale pad, partially open to vent, lower the car into the bag. 1) Tweak: Tweak is the amount of weight on the LR as opposed to the RR. For pure race cars this isnt a consideration. You can see that the leverage ratio in the crank link reduces coilover(and thus shock) travel, and Struts and trailing arms generally arent great in this case as they have a lot of inherent bind. Just make sure none of them are flat or wildly overinflated. The driver is optional based on No. Just to confirm the theory I checked the corner weights with 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. 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. Step 1: Setup And Tuning The Tires Most regular RC cars use rubber tires. Measure control arm angles after each change. Right Front = I run generally 34F/30R for the street and usually (again depending on the day) drop the fronts to around 30~ and the rears to 26 or 28. you raise the rear of the car 10 inches or more and re-weigh it. On an average dirt track you will need to change tread and stagger at least once a night, due to changing conditions. from a balanced Cross Weight. 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. 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. 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. Leebo's Corner. At the time Honda was still favoring their home market I reckon. Most chassis manufacturers will tell you what ride heights are best for their cars. Disconnect the sway bar. 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. [ 1] In circle track racing, the use of the term "crossweight" gives us an indication of the weight distribution on the four tires. 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. Weight can be moved around at the track to fine tune the handling characteristics of the chassis. Disconnect the shocks, when possible, and the anti-roll bars. each and retract the RF (Right Front) and LR 1 1/4 turns each. Now that's pretty cool! if you have any of the scales connected improperly (i.e. The design has the engine and transmission scooched over to the drivers side so the drivers side weighs more empty. Why? of its weight on the Left Front and Right Rear tires, and 50% on the Right Front Or do you just mean an old, worn-out strut? 2) Stagger: Stagger is how much bigger the right side tires are compared to the left side tires. Today's oval ride heights after every change. 1. Since oval You can see the article here: lowered onto the scales the tires will need to spread out to unbind the 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. Don't be in a hurry to set ride If you align your car prior to doing the corner weights, it will be necessary to verify the alignment again after the corner weighting is completed. height and corner balance new springs. A perfectly corner balanced car will handle the same when turning left and right, and will maximize the tire contact area on all four corners. 4. It's stiff springs on your coil overs. Bite tells us how much we (TVW LSP) - LF = 769D. As an autocrosser I've always thought that cross weight should be set at 50% and be done with it. Positive Caster is created when the caster line lands forward of the contact patch. Always record the cross-weights and ride heights for reference at the race track in case changes are needed. 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. intentionally favor a turn direction. Yeah, I'm a little puzzled by my result when I let me car down on my new scales as well. With the driver weight, the left side might move down 1/4-inch and the right side down 1/8-inch. Now that we understand the value in maintaining ride heights, just what heights do we want? Road racers are camber angle of the wheels (-3.5 front, -3 rear). Are they non-adjustable? Calculator, I used these scales to weigh the car: MuddBoss Feature Winner at Dirt Devils RC Speedway, 12-18-2021. unbalanced--it will turn better in one direction than in the other (all other 5.00 front 8.00 back aren't too big unless you can get by with smaller and not lose traction. Today, dirt late model racers are using cutting-edge tools to pinpoint where gains can be made based on hard data. Its important to measure and note your Or it could also be possible that the signal is smoothed in the programming. That makes every little detail that much more important. close to where I wanted it. Jacking weight will not alter the left side or the rear percentages. Guess I have to try it. 1 of the section on "Adjusting The Corner Weights," and that is 685. 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. Picture the following: Your car is really fast in right-hand turns, but understeers in left turns. Avoids a mess on scale pads and tires,prevents dirt fromcontaminating lube. Find the difference from the desired average ride heights. So, we are not reinventing the wheel here, just refining the process. It is best to get 50 percent left-side weight when possible. Are they adjustable? You need: 1. It puts power down better, and any decent FWD car will be carrying a wheel in the air around a turn anyway, so by default the outside rear gets 100% weight transfer when it's being asked to turn anyway. 2. Be sure to have the weight of the driver in the seat. Basically, I don't see much of a relationship between 'static' corner weighing via adjusting spring length and the addressing of fundamental L/R weight imbalance as those difference are what drive suspension and mass motions when moving. adjustments were 1 turn to the right front and 3/4 turn to the left rear. Free Download Chapter listings from. pounds of preload to the scale weights. 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. 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. important for oval racers, especially on dirt ovals. Delta which is simply the difference between the two diagonal tire weights. Wedge Delta should be positive for oval racing. I weigh 220. Make sure the vehicle is loaded with driver, passenger, and cargo just like you will drive it or . 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. Did you mean it was off several hundred pounds per corner? turn to the RF simply to raise the ride height of the front of the car. . should have their spring perches in the same spot and your left rear and right When a NASCAR crewchief says he's "adding wedge", Useful fabrication tips for just about any project, A crash course in 3D printing | Making Stuff: Part 2, How to make the move to an aftermarket ECU, 10 Must-Have Tools for a Scratch-Built Car, Fitting tires and wheels when an off-the-shelf option isnt listed. The roll center is an imaginary point around which the rear of the race car rolls. At the front, we will move the LF and RF adjusters up by 0.0625-inch. Finding these values and maintaining them is at the top of the list for being consistent in your racing effort. Improper weight distribution in your race car - strip burner, autocrosser, circle tracker, etc. First some baselines. If you go to a tuning shop that provides this service, estimate that it will cost you $90 $150 to have them corner weight the car for you. will help with those turns. So as long as you are draining the fluid from your shocks, also remove or cut away the seals. the same time. Determine your ride heights. When working with static weight distribution, we use two percentages to analyze the car's corner weights: Left weight percentage and rear weight percentage. Bite tells us how much we One of the keys to obtaining a good setup is using the correct procedure to weigh your race car. the scales and zero them with no weight on them. Remember that this is a sample car, so don't use these numbers, but do use this method. turns to the Right Rear: I still needed more weight on the LF and RR so I added +4 to the LF: I still needed more so I added +2 to the RR and drove the 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. Yep, old struts that are drained of fluid and have little to no resistance. There are legal issues too at the front. I see disconnecting the sway bar, and how to do it, but disconnect the shocks? You can make this adjustment in several ways: If you don't want to change the ride height of the car then 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. Do this by making equal changes to the adjusters on each side. Corner weighting your car is My track width with CE28 17" x 9" wheels Jun 7, 2018 #8 . Once you get the car up on the scales you'll Cross Weight Calculator | Eldridge Racing | Micro, MiniSprint Parts and . 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. The third, and probably the best, option seems to be to invest in a set of hub stands, as this not only takes care of the bind issues via their built-in rollers, but it just makes the task of doing the alignment a lot simpler as well. 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. track are left turns then having more weight on the Right Front and Left Rear 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. right swapped). suspension). Air up the tires as they will roll through tech. If you shocks are working normally they are not worth worrying about. Scale Type: . That is what you need to read on the spring rate fixture at installed shock length. It is possible that their circuitry uses a high capacitance value to smooth out the signal or slow it down. Get the rear percentage as close to the manufacturer's specs as possible. . on each wheel to speed shock adjustment. Right Rear weight: < Enter your corner weights in pounds or kilos and click 'Calculate'. Reduced stopping power with normal brake pedal: Pad fade - due either to unbedded new pads or to temperature beyond. Oval racers favor left turns so they typically desire more weight Caster creates stability as the geometry . You will need to weight your vehicle on each tire to use this tool. - can make your car dive like a dump truck or a block of wood on ice. stiff springs on your coil overs. For this exercise, we will just be changing the pre-load on the springs to redistribute the loads, or weights on the four corners. 11. coil over 5 turns. Keeping track of Bite and then leave them connected. I made a 4-scale system for my off-road cars. Take care that the car does not accidently slide off the scale pads. Or am I missing something? 2. 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. You can drop the front end slightly or raise the rear end for more aggressive turn-in. For information on corner Do these percentages apply for front wheel drive cars? Measuring from the center of the tires I got 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. We were racing dirt oval about a month ago, and then I tried this scale system . Once the corner In our example, the front average is 4.25 and the rear is 4.75. I needed 3 tiles on the left front and 1 on the left rear Corner-Weight Distribution Bickel points out that corner-weight distribution refers to the amount of weight carried by diagonally opposed pairs of wheels. You will have to repeat this every time you lower the car onto You should read the spring preload amount. . Go in hard, let off and let the drag brake pivot the car, and get right back on the throttle. the driver seat and reconnect them so there's no preload on them. Because it's targeting LF/LR = RF/RR to equalize the left vs right handling characteristics. Check stagger at each tire, even if using radials. calipers. The following are screen shots from the We also take five rounds times the multiplier for the front of 1.25 5 = 6.25 rounds out of the LF. It is a critical set-up tool. to get a balanced diagonal weight on the tires. Plan to win in a repeatable fashion. Tuning with anti-dive probably won't be . The outer rear tire drives "around" the outer front tire, allowing the chassis to efficiently turn into the corner because the rear tire used cheap linoleum tiles (49 cents each at Home Depot) to shim two of my scales 3) Reverse stagger: The opposite of stagger when your left side tires are . Bite and Wedge Delta are Don't just blindly cross weight it thinking it's the "right" way. On my ZX2SR my cross weight was consistently in the 49% range. Record these. There is a reason for this order. things being equal). Recheck the ride heights and adjust to fine tune, making changes to the front and rear at the same time. For our example we use: LF 200, RF 250 - 250 200 = 1.25 multiplier for the front. 4. 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. 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. In circle track racing, we often, and almost always, have different rate springs on each corner of the car. I needed 3 linoleum tiles (0.045" thick tires. Grassroots Motorsports Understanding Corner Weights. cross weight. And there is a methodology, or possibly several that will make this routine easier. 1 Establish the corner weights you think you need for your car. 8 Read the ride heights as they exist. Ah, OK, thanks for the clarification. your scales. rear. One of the problems with cross-weight is that it will change the handling balance from a left to a right turn. These are your current calculated weights: Left Weight = Grassroots Motorsports Understanding Corner Weights June 2017 -Center spring steering, corner judder w/ swing axle or beam axle . R. racing junky Member. Full of fuel, everything done, full of oil, lead bolted down. To find RF weight: Today's oval Then measure from the lower wheel rim edge up to a spot on the fender on a piece of masking tape. Wedge Delta is equal to (Right The first is to use traditional lift-off oversteer. This is for a race prepped 1984 Audi 4000 quattro(2375lbs. Right handers vs left handers feel quite a bit different-I run out of suspension on right handers much more often, and on left handers the car loves having me hanging out over the inside of the contact patches working the corner. preload (extending the shock) to the Left Front, and one positive turn to the Right Front. My car is a 1987 Honda CRX, set up according toITC class rules. Wedge is a term used in the bite, a negative value means the Right Rear is favored. Iretighten them after I've made all my adjustments. scales are connected properly--you can really screw up your suspension settings 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? Wheel offsets are very important. 35 psi hot tire pressure target . Choose the cold temperatures because when the tires get hot, they will expand and your ride heights will be providing more adequate heights to pass tech after the race. (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will be 50%. Same with go-karts with solid rear axles, they'll lift. The cosine of 18 degrees is 0.95106, and that into 1.0 is 1.05146. Some racers like to take matters into their own hands-and that's OK. Once static weight percentages are set, work on cross-weight percentages. 50% then Wedge Delta will be 0. Right Front tires. "There's a lot of freedom when it comes to setups using various styles of springs" in dirt late model racing, said a source. 6 Check your ride heights and make small adjustments for ride height and crossweight percentage if need be to finalize your setup. You need a nice, flat and level surface for the scales. Forum Actions: Forum Statistics: Threads: 167; Posts: 1,367; Last Post: . rear should be the same. It's the effective distribution that changes when you have suspension bind. Check static weight before working on cross-weight. I plugged in a bunch of numbers into my calculator and it all checks out. If you don't have adjustable end links on your Corner weighting is huge. If you want to raise the rear of the car then extend the RR end-link into the anti-roll bar's hole. you run on the track. To test this, put the car on scales, and just tip the setup board and see how much the numbers change. Right Front tires. The important thing to remember is that the laws of physics are the same whether you are racing on an oval or a Check your tire pressure and bump it up to the hot pressure Typical racing scales will calculate this for you automatically, but you can rig up something that will work using a single scale and 3 equal sized spacers to get a good estimate. Rebound adjustments will allow you to alter your car to a corner entry condition without affecting corner exit or vice versa. dry)! Intercomp 102030 5X5 Hub-Mounted Corner Weight Scale. We have 4.1875 front and 5.1875 rear. Maybe I'm over-thinking this, but I was amazed when I got my new scales, and let my car down on them for the first time. We run an extremely high banked 1/5 mile clay oval in Alabama that is always wet and low bite. will help with those turns. 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. To do this, we add five rounds of pre-load to the RF. the scales. Find a fairly level spot and mark on the ground with duct tape or marker where the tires sit on the ground. battery (-15lbs), ride height lowered approximately 1 inch, all 4 Bilstein PSS9 coil over Still, it is a worthwhile goal to strive for 50 percent left-side weight. Shock Angle-measure the angle of the shock installed and at ride height. . You need a nice, flat and level surface for the scales. shifted by more than 1 pound after rolling the car on the scales. Changing the ride height at any corner will change the cross-weight percentage. 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. shouldn't match the front to the rear but your left front and right front shocks However, many cars cannot make the 50 percent left-side weight percentage due to driver offset. suspension). that as a result the coil springs must bequite beefy and stout, 600 lb/in or more. traction or bite in left turns. Strive for repeatable and take the measurement as a data point, instead of an absolute. , = change needed to get to target weight, Cross Weight = You cannot change the left or rear percentages by jacking weight around in the car, although this will change cross-weight. All of these measurements are widened by the 13. turning the front wheels to measure caster. I'm off by 0.1% (see numbers on left side of the spreadsheet). Once you have returned the wheel corresponding to the spring change back to its measurement, the other wheel measurements will be OK. 3. Bite and Wedge Delta are the scales and zero them with no weight on them. To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. 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. You can estimate your car's center of gravity This obviously means that decreasing cross weight or left side weight racers add "wedge" by adjusting the right rear spring perch--they Kart racing chassis are designed in a manner to allow it to turn the only way it can, without having a read differential - with the inside rear tire lifting off the track on corner entry. springs settled over the first 3 months. I looked back and I don't think I've ever done an article on this subject and I can't understand why. lot of force to the suspension. 3.If you plan on having to set ride height without the driver, measure the difference with and without the driver in the car at all four corners and record those differences. "This is called chassis pre-load. Took it to be corner weighted and it transformed the car in to a front runner that the drivers raved about. Drag Racing. If you do have adjustable end 2 1/2 turns. 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. So LF/LR = RF/RR is what you shoot for. This was a very interesting post to me. Your car can lose ride height during the race and you need to be at minimum after you leave Victory Lane. The rear is 2.125" wider. One of the most important aspects of racing is having a good handling balance. I use 2x6 wood planks as ramps to drive the car onto So, deviating from those numbers will mean you have a design other than what was intended for the car. However, if you have to apply opposite lock steering (turning the steering wheel to the right) and you drive the car throughout the corner balancing it with the throttle . If you don't want to change your ride height then a more balanced approach would It was a good car. In my situation, I have a lift, and I'd like to simply drop my car onto the scales, but it seems like that's the worst option as far as removing friction and bind. Classic Truck. of the scale to take a reading. If your car's diagonal corner weights are not equal then its handling will be unbalanced--it will turn better in one direction than in the other (all other things being equal). scales are connected properly--you can really screw up your suspension settings Typically, this adjustment will make the car tighter on corner entry or in the center, and a little looser on exit. It would just automatically settle. shocks set to same length left to right (front to rear will be different). Brake pads badly taper worn - replace. 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. 10. turns. If you don't have adjustable end links on your anti-roll bars intentionally favor a turn direction. the scales. track are left turns then having more weight on the Right Front and Left Rear If you increase the amount of cross weight or left side, you will decrease the amount of bite in the kart. For ovals we want a So we turn the RF adjuster up (to lower that corner) 2.5 turns and the LF down (to raise that corner) 2.5 turns. Adjust the front up by 0.0625-inch and the rear down by 0.4375-inch. 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. Bite = Left Rear - Right Rear and a positive value means the important for cars with upgraded (stiffer) sway bars because they can exert a the sway bars because they fail so often and the bars only added a couple of All of these factors play a huge part in what each corner of the car will weigh. If your car's diagonal corner weights are not equal then its handling will be Your ride heights determine your arm angles up front, as well as the cambers, and, to a lesser degree-excuse the pun-the caster angles. You will have to repeat this every time you lower the car onto We had a good Miataset up for ST. need to roll the car back and forth a few inches several times, being careful You will never find a perfectly level spot at the track, so don't waste time looking, unless you can set up your scale pads and set up ramps level. When that time arrives, you walk across the racing surface, into the dirt oval's imperfectly defined center, and meet your instructor. That's all total speculation though. The new existing ride heights are LF 3.6875, RF 4.8125, LR 4.1875, RR 5.3125. Set them to hot pressures is the norm as I understand it. The suspension of the racecar uses the same general theory and needs to be adjusted so that the car is stable. You can change ride heights later on, but remember that your front moment center geometry will change and your rear geometry will also change, including link angles and pinion and third link angles, as well as rear alignment in some cases. 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. Granted, moment centers will stay fairly consistent with small movements of the chassis in dive and roll from the ride heights being off a little. The effect of shock rod seal frictionat the wheel will be reduced by the crank leverage ratio. On a road course, the cross-weight percentage should be very close to 50 percent, within a half-degree either way, to keep the handling balance similar in a right-hand turn compared to a left-hand turn. 57.5" front and 59.625" rear. 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 Taking the time and making the effort always pay dividends. "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. 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).

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