To keep things clear I call this added LR/RF weight Wedge "two linoleum tiles & salt" technique to allow the tires to slide on the scales Check stagger at each tire, even if using radials. A. When working with static weight distribution, we use two percentages to analyze the car's corner weights: Left weight percentage and rear weight percentage. It would just automatically settle. 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. as Left Rear Bite + Right Front Bite. box in the "Ride Height" section of each spreadsheet. line above the scales and then stood on each scale and placed a ruler on the top We were racing dirt oval about a month ago, and then I tried this scale system . Rear weight percentage for road racing and autocrossing is less definite. That is equal to 7/8 turn of the adjuster. Road racers are This adds pressure to that end of the car just like putting the paper wedge underneath the table leg. Bounce the car at each corner to free the suspension from any bind, then roll the car onto the scales. Guess I have to try it. Open timing on motor and esc. Make small changes at the track, and make only one change at a time. Multiply the wheel load of 685 times the motion ratio squared, 1.3611 times the shock angle cosine squared of 1.1056 and we get 1,030.8 pounds of spring preload. Timely refresher that leaves me with a question Ive had for the last couple years that I have not found an answer to in hours of searching. Funny. A set up plan will help you to build a race winning effort. the scales. Understanding corner weights. this excellent article: 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. Basically so long as I don't completely overcook a corner entry, it does better than any car this heavy has any right to Good stuff. 11. Crossweight is of no concern to the track officials. It varies with weight removal, added. Bite = Left Rear - Right Rear and a positive value means the We should now be at, or near, the desired crossweight percent. Tuning with anti-dive probably won't be . Calculate the spring rate multiples. The front will show close to 60%. Record each spring rate. Of course you can add too The cosine of 18 degrees is 0.95106, and that into 1.0 is 1.05146. These are your current calculated weights: Left Weight = Corner-Weight Distribution Bickel points out that corner-weight distribution refers to the amount of weight carried by diagonally opposed pairs of wheels. They are not too suitable for racing and oval dirt cars. The rear weight percentage is found in a similar manner: Add the LR and the RR weight together and divide the sum by the total weight. 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. Less tread on hard slick is good. Put the driver weight in the car, preferably the driver. I use 2x6 wood planks as ramps to drive the car onto Cross weight and left side work backwards in terms of adjustment. Smaller will scrub less speed of if your not sideway threw the corner. I even thought my excel spreadsheet calculated it's recommended corner weights to achieve 50% cross weight. The last event in the rain i actually had the rears up to around 38. Oval racers favor left turns so they typically desire more weight The new existing ride heights are LF 3.6875, RF 4.8125, LR 4.1875, RR 5.3125. In other words, to make this method work, wouldn't you really have to drive the car around, preferably going over a few pretty serious bumps, before driving onto the ramps? Keeping track of Bite and Bite should be positive for oval racing, Wedge = If you want to raise the front of the car then extend only the can help us get our setup right with less testing. 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. Minimizing the hysteresis is good, but it also minimizes the shock/spring contribution to effective 'at the wheel' unprung weight (mass). height and corner balance new springs. On my ZX2SR my cross weight was consistently in the 49% range. balancing see my corner balance how-to and end-link into the anti-roll bar's hole. Muscle Car. Lay the bag flat onto the scale pad, partially open to vent, lower the car into the bag. of the scale to take a reading. of the scale to take a reading. Take the cosine of that angle, divide it into 1.0 and then square it, or multiply it by itself. MuddBoss Feature Winner at Dirt Devils RC Speedway, 12-18-2021. I saved a copy of the spreadsheet for each There are several ways race teams adjust corner weight. Well there is a bit more to it than that. Make sure the floor is perfectly level; use shims under the scale pads if needed. It's a lot of 3. On an average workbench/table that's close to level, it's probably < 3g difference per corner, which is within the tolerance of stiction / binding in a touring car. 11. "Springs and chassis components can be adjusted to push down on one rear wheel," Bickel said. traction or bite in left turns. 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. Since oval calipers. % 50% is optimal, Wedge = 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 I have now added the ratios so I can visually see what's happening. 45. I put the car on the scales and input the four corner to get them exactly level. Or do you just mean an old, worn-out strut? Get the rear percentage as close to the manufacturer's specs as possible. Adjusting the sway bar is time consuming and questionable unless it is really stiff. Corner Weighting However, many cars cannot make the 50 percent left-side weight percentage due to driver offset. Before putting your car on the scales you need to power up We also take five rounds times the multiplier for the front of 1.25 5 = 6.25 rounds out of the LF. I not to push it off the scales, to unbind the suspension (as the car is 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? 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. 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. Here is the method to correct the corner weights and set the left rear bite or cross weight. it would help the car turn left and accelerate better. Disconnect the sway bar. When Wedge is balanced at Always For example, if you are racing the Briggs Light class at 305 pounds, your corner weights should be: LF = 68 pounds RF = 68 pounds spread when the car is lowered onto the scales. you run on the track. I highly recommend using a laser level to confirm the 4 scales are level to one I gave up on running adjustable end links on No, not as in the law, but in being legal in tech. right swapped). 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. Move ballast first, since it's easier. Wedge is a term used in the important for oval racers, especially on dirt ovals. One of the most important aspects of car setup is the static weight distribution and the cross-weight percentage. coil over 5 turns. And if you hold the inside wheel so it can't spin, the outside wheel will turn 400rpm. I lowered the left rear spring perch 1 1/4 turn and put it on see on the right side of the spreadsheet's "Target Corner Weights" section that It is best to make small changes at each corner, instead of a big change at one corner. 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. Forum Actions: Forum Statistics: Threads: 167; Posts: 1,367; Last Post: . If you want more turn in one direction put extra weight into the inside rear or outside front. Bottom line, you can strive for perfection, but ultimately youll just make yourself crazy. 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. Wedge is a term used in the Jacking weight will not alter the left side or the rear percentages. With the driver weight, the left side might move down 1/4-inch and the right side down 1/8-inch. I was booked for 100 laps split across four or five sessions. Same with go-karts with solid rear axles, they'll lift. turns. Cross-weight percentage compares the diagonal weight totals to the car's total weight. 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. If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. center of gravity (CG) height by using this page: from +1 overall to -1): I put + 3/4 of a turn back on the Right Front and ended up Once you get the car up on the scales you'll Teams that do not stay on top of these two setup phases will not only be inconsistent, they will struggle to find their way setup wise. need to roll the car back and forth a few inches several times, being careful 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. B. . the front ramps then jack up the rear and lower it onto the rear scales. Bite and Wedge Delta are pounds of preload to the scale weights. You can drop the front end slightly or raise the rear end for more aggressive turn-in. The left weight percentage is found by adding the LF weight to the LR weight and dividing the sum by the total weight. on the right front and left rear tires. bite, a negative value means the Right Rear is favored. Disconnect the shocks, when possible, and the anti-roll bars. 4. At the front, we will move the LF and RF adjusters up by 0.0625-inch. CG Height Calculator, Cross Weight % = 2 1/2 turns. much Wedge Delta and make the handling worse. 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. will help with those turns. Astrut with its innards removed? 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. 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. over). Of course you can add too Prepare the car. Choose a level spot in your setup area. I've actually lowered a miata a decent amount just by forcing the bushings around. 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. The left side changes, of course, will be 4.75 times the multiplier for front or rear. The tiles I The effect of shock rod seal frictionat the wheel will be reduced by the crank leverage ratio. This was my first adjustment: Four turns of positive coil This is for a race prepped 1984 Audi 4000 quattro(2375lbs. turning the front wheels to measure caster. Front + Left Rear) - (Left Front + Right Rear) and tells us how much racers discovered they could insert an actual wedge into the left rear In our example it is 18 degrees. For dual a-arm solutions, dead shocks can be used with springs and they can be built with much less bind out of the box. We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. 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. Motion Ratio of the lower control arm. Remember that changes in stagger, tire pressures and springs will change the ride height and alter the cross-weight percentage. over T-Bucket . right swapped). values shown below are totally fictional. but tend too love the 1/2 miles.I just cant figure out a way too get these. "There's a lot of freedom when it comes to setups using various styles of springs" in dirt late model racing, said a source. for the front and rear sway bars and installed them with my girl friend sitting I noticed that the spreadsheet I'm using on the left of the picturesets my "target corner weights" to less than 50% (49.6%),why is that? I installed "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. 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. 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. the driver seat and reconnect them so there's no preload on them. They are never level. 6. Oval Track. 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. Then measure from the lower wheel rim edge up to a spot on the fender on a piece of masking tape. weights into the spreadsheet (the blue numbers in the left "Corner Weights" suspension). 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. 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. Since the front and rear shocks are of different lengths you Corner weighing will tell you how much overall mass your car has as well as the mass present at each wheel. Adjustable end links are more Any corner weight adjustments that you make will impact the alignment of your car. Wheel offsets are very important. racers only turn left we can balance the car for better grip in left For ovals we want 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). Calculate the average existing ride heights front and rear. Check static weight before working on cross-weight. The LF needs to go up 0.3125 and the RF needs to go down the same amount. More wedge means that the car will likely understeer more in a left turn. You can also put two linoleum tiles with salt between them on Search for: oval racing world and is simply another word for Cross Weight. 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. Wheel Load-We have already determined the wheel load we desire in No. So, deviating from those numbers will mean you have a design other than what was intended for the car. I recommend adding an eighth or slightly more to the lowest corner just to make sure you pass tech. When you lower the panhard bar the rear roll center drops. 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. The less fuel in the tank the tighter the chassis will become. As the shopping cart is pushed forward the front wheels spin back and trail behind the caster line. Keeping track of Bite and 1. 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. [Up] [CornerBalanceCalculator] [CGHeightCalculator], This calculator takes your car's four wheel weights and calculates current 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. 4. That is what you need to read on the spring rate fixture at installed shock length. Would be interesting to see how close to ideal I got it though, given how well it handles already. I needed 3 linoleum tiles (0.045" thick 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. If you want to lower the front of the car then retract only Positive Caster is created when the caster line lands forward of the contact patch. after this adjustment we still need to add 39lbs to the Left Front and 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. 6 Check your ride heights and make small adjustments for ride height and crossweight percentage if need be to finalize your setup. I found that the tire will absorb side loads quite well and was repeatable. 2. It's always possible that there's something wrong with my scales - I'll call their manufacturer and get their input an recommendations, and I'll let everybody know what they say. But in a right turn, the opposite occurs and the handling is worse. Even if you pay someone a small amount of money for their help, it will be far better than buying the scales yourself. anti-roll bars then leave them connected. turns. what he means is he's adding weight to the left rear and right front (TVW FWP) - RF = 743C. 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. 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. . I used a laser level to project a horizontal . adjustments were 1 turn to the right front and 3/4 turn to the left rear. typically not concerned with bite and wedge delta because they usually And there is a methodology, or possibly several that will make this routine easier. you weigh and adjust. A common example of caster is a shopping cart. Iretighten them after I've made all my adjustments. The crossweight percent will have changed to, say 55.4 percent. And I cannot really move any weight around. more traction or bite in left turns. Struts and trailing arms generally arent great in this case as they have a lot of inherent bind. close to where I wanted it. front left and How would you makesomething like that? And don't ever believe the track scales. Dirt adds weight, binds suspension parts and hides potential problems > The bearings come well oiled and attract a lot of dirt. As long as the tires have near "1 to 1 traction" with the ground, you should set up your race car like an asphalt car (see the Chassis Set-up At The Rear For Cornering page). Afterward you need to adjust the settings to the correct maneuvers. Recheck air pressure often to assure ride heights stay consistent. springs settled over the first 3 months. ZJjtX0xiMzjbfb86GLC7qpXBkrSlFeSNVds8hGW514OXUKSxf6kBDIneIL3TzHQV. Ah, OK, thanks for the clarification. Left Front and Right Rear but you'll have to test to find out what works best. coil over 5 turns. The more power a car has, the more that static weight over the drive wheels helps acceleration off the corners. Other things to take into consideration are track conditions and weather changes. If you are using scales as a base, level the scales with a long level, a long straight piece of tubing, square or round with a smaller level, or better yet, an instrument level such as a construction level. Now that's pretty cool! To find LR weight: Any press releases or advertising will be deleted. I lowered the right front spring perch 1 full turn (equates to I see disconnecting the sway bar, and how to do it, but disconnect the shocks? Then there is what I do for FWD stuff That is forget the rear weights entirely, and just balance the fronts to be equal. document your current ride heights and your coil over changes each time Make sure the vehicle is loaded with driver, passenger, and cargo just like you will drive it or . 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've mentioned "dead struts" a couple of times - what do you mean by that? . 14. 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. Many successful race teams use corner weighting to achieve the same F/R % on both sides equal, not cross weight. 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. Or am I missing something? Do not adjust any other wheel's spacing. Andy Hollis does this. is especially true if you don't have adjustable spring perches. Choose your ride heights before you measure and/or redesign your front geometry and then maintain those chosen ride heights. However, most importantly you need to take care of the handling. 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's better to make many small changes than to try [Up] [HarnessInstall] [WingInstall] [RemoveA/C] [OilCooler] [FireSuppress] [CutoffSwitch] [RaceExhaust] [Differential] [CornerBalance] [CatchCan] [RollCenters] [FrontBumpSteer] [Alignment] [ShockTuning] [Aerodynamics] [CatRemove]. Intercomp SW500 EZ Weigh Scales. At least for road racing. Basically - after you finish the set up routine, the car goes in the hauler. used are 0.045" thick. 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 Yeah, I'm a little puzzled by my result when I let me car down on my new scales as well. positive Bite and positive Wedge Delta. I usually mark an even inch and write that inch number on the tape. For our example, we need to go from 49.8 to 54 percent. The other two corners will lose weight. One of the keys to obtaining a good setup is using the correct procedure to weigh your race car. If the car understeers or oversteers in only one direction, check the cross-weight percentage. . 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. I'm off by 0.1% (see numbers on left side of the spreadsheet). Drag Racing. ride heights after every change. W. William18 New member. need to roll the car back and forth a few inches several times, being careful However, you can choose to use them. Caster creates stability as the geometry . Shock Position the front ramps then jack up the rear and lower it onto the rear scales. I was surprised how much these high rate 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. 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. 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. To increase rear weight, move weight as far back as possible. and Left Rear. Picture the following: Your car is really fast in right-hand turns, but understeers in left turns. Wedge Delta and what values work best for certain tracks and conditions It still pays to be thoughtful about weight placement fore and aft in your car. Can do to just left sidesor right sides, or to all 4. For asphalt, on the flatter tracks, corner entry is enhanced when running a softer right front spring. 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. Here's the car with the same settings but empty: I took the newly corner balanced S2000 to a Summit Point Raceway Friday at We also change the rear to correct the side-to-side rake by turning the RR adjuster up (to lower the corner) by 2.5 turns and the LR adjuster down (to raise that corner) by 2.5 turns. Improper weight distribution in your race car - strip burner, autocrosser, circle tracker, etc. Front and Right Rear need 51 lbs of additional weight to balance the car. are favoring the left rear tire for better acceleration out of left For Oval guys I suggest talking to your local kart shop who knows the tracks you run on for a suggested starting point. %Right Weight = For street cars it certainly can be. If you want to lower the rear of the car then retract the LR Note your ride heights and want balanced turning in both directions. 10. Today's oval The other two corners will gain weight. Full of fuel, everything done, full of oil, lead bolted down. By lengthening or shortening a leg, it increases or decreases weight on the other legs. That method keeps the ride heights close to the same. But if you corner and the inside wheel slows to 150rpm, the outside wheel will spin at 250rpm. So let's study ride heights first. Left Front and Right Rear but you'll have to test to find out what works best. One of the most important aspects of racing is having a good handling balance. Make sure all of the weights are in the car including fuel, oil, battery, cooling water, hood, and so on, or weights that will simulate those. The spreadsheet's second page has a good article that goes into more detail of Don't be in a hurry to set ride You can also estimate your car's How big is the track? Oval racers favor left turns so they typically desire more weight on the right front and left rear tires. I made a 4-scale system for my off-road cars. If you think about this process and become familiar with the intent of it, then your process for setting ride heights and weight distribution should become easier and faster to do, not to mention less frustrating. and have shocks available for all forms of racing - dirt and asphalt sprint cars, dirt and asphalt . 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.
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