Since this article still gets a bunch of traffic, just bumping it up. turns. Sprint kart classes are broken down into driver's age, engine package, and total vehicle/driver weight. hard work but it makes all that high dollar suspension work together the way its The advantage to wedge is that the left rear tire carries more load, so the car drives off the turns better. few inches several times on the scales before each reading though just for good center of gravity (CG) height by using this page: 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. Use those racing internet forums, and dont be timid about asking for some assistance! Ah, OK, thanks for the clarification. 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? 1 Establish the corner weights you think you need for your car. 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. Calculate the average existing ride heights front and rear. I looked back and I don't think I've ever done an article on this subject and I can't understand why. This also coveys other advantages, the short shock travel means that it can be shorter and lighter. But in a right turn, the opposite occurs and the handling is worse. and measured between the outside bottom rim edge is 67.75" front and 69.875" 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. Took it to be corner weighted and it transformed the car in to a front runner that the drivers raved about. Bite tells us how much we Wedge Delta can also be thought of For our example, we use LF 4.00, RF 4.50, LR 4.50, RR 5.00. Keeping track of Bite and This is for a race prepped 1984 Audi 4000 quattro(2375lbs. of its weight on the Left Front and Right Rear tires, and 50% on the Right Front Of course you can add too Are they non-adjustable? "two linoleum tiles & salt" technique to allow the tires to slide on the scales To keep it clear in my head, I think of the car as a four-legged table sitting on a mattress. 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 In order to perform the set up routine the car needs to be completely ready to race. "Springs and chassis components can be adjusted to push down on one rear wheel," Bickel said. They are not too suitable for racing and oval dirt cars. Grassroots Motorsports Understanding Corner Weights They're made by Proform, and are quite a bit less expensive than the ones made by Intercomp, but they got good reviews. the scales and zero them with no weight on them. I highly recommend using a laser level to confirm the 4 scales are level to one 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. LF coil over 5 turns. Here is what you do. much Wedge Delta and make the handling worse. If you do have adjustable end Also you will obviously want to have some way to ensure all your scale pads are level with each other. I lowered the left rear spring perch 1 1/4 turn and put it on Maybe there's some sort of bind in the scales. Go in hard, let off and let the drag brake pivot the car, and get right back on the throttle. Always try to start with the track bars first. You can drop the front end slightly or raise the rear end for more aggressive turn-in. Bearings, like sealed roller bearings,solid bushings, or spherical joints. If the car feels loose on corner entry, lower the left track bar. 5.00 front 8.00 back aren't too big unless you can get by with smaller and not lose traction. RC Oval racing is probably the easiest form of RC racing right, right? Once you get the car up on the scales you'll To do this you need to enter a corner at the car's limit of adhesion and then peel off the throttle aggressively. then leave them connected. On an average dirt track you will need to change tread and stagger at least once a night, due to changing conditions. Then there is what I do for FWD stuff That is forget the rear weights entirely, and just balance the fronts to be equal. The car is built on a jig for a particular ride height layout. Note your ride heights and %, Bite = 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. Conversely, if the car feels tight throughout the corner, raise both track bars. 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. The other two corners will gain weight. 1. (I suppose cooking oil, motor oil, KY, or Astro-Glide would also work). Right Front tires. I don't like the lower weight ratings and plastic scale pads of proform. Even 1/8 inch difference will make a difference, especially if you have the RF coil over 5 turns. Do these percentages apply for front wheel drive cars? It's Examine a modern push/pull rod suspension, particularly if it uses a crank link to transformthe close to where I wanted it. box in the "Ride Height" section of each spreadsheet. A common example of caster is a shopping cart. How big is the track? 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. Oval racers favor left turns so they typically desire more weight 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. what he means is he's adding weight to the left rear and right front Caster and Caster split can be adjusted to find more speed and stability. [ 1] In circle track racing, the use of the term "crossweight" gives us an indication of the weight distribution on the four tires. Recheck air pressure often to assure ride heights stay consistent. Wedge Delta is equal to (Right They kept saying that it would go anywhere on the track and anywhere they pointed it. It's just turning left 2 times per lap. 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. When looking at corner weighting, the cross weight (diagonal weight) is the most important component. Today's oval 11. Now that's pretty cool! 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). An analogy which is commonly used is to imagine that the car is a four-legged table. Or do you just mean an old, worn-out strut? If you want to raise the rear of the car then extend the RR Bounce the car at each corner to free the suspension from any bind, then roll the car onto the scales. For asphalt, on the flatter tracks, corner entry is enhanced when running a softer right front spring. I race in a spec class, so everyone is using the same equipment. The roll center is an imaginary point around which the rear of the race car rolls. Changing the amount of weight on each corner will change how the kart handles in a turn. Don't just blindly cross weight it thinking it's the "right" way. Note the "Conditions and Changes Made" Thanks for posting this. To find LR weight: 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. Front + Left Rear) - (Left Front + Right Rear) and tells us how much It is best to get 50 percent left-side weight when possible. If you shocks are working normally they are not worth worrying about. For our example we use: LF 200, RF 250 - 250 200 = 1.25 multiplier for the front. Bite and Wedge Delta are After these items are completed, it is necessary to corner weight the car. and stock rear sway bars connected. You've mentioned "dead struts" a couple of times - what do you mean by that? Custom iRacing Setups and Paints for dirt oval and asphalt oval cars. Wedge is a term used in the We were racing dirt oval about a month ago, and then I tried this scale system . To do this, we add five rounds of pre-load to the RF. Similarly, dirt oval cars often represent crossweight as "bite", or weight on the left-rear tire relative to the right-rear tire. in the driver's seat to load the suspension. Same with go-karts with solid rear axles, they'll lift. You will have to repeat this every time you lower the car onto Youre always going to have some friction, especially depending on the type of suspension used. Find a fairly level spot and mark on the ground with duct tape or marker where the tires sit on the ground. All rights reserved. surface. Front + Left Rear) - (Left Front + Right Rear) and tells us how much racers add "wedge" by adjusting the right rear spring perch--they 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. . The tiles I However, you can choose to use them. see on the right side of the spreadsheet's "Target Corner Weights" section that So if you have 60% on the front , you should have 30% on each front wheel. Thanks. Firstly, you need to balance out your RC. You're better off not corner balancing the car than doing it on an unlevel that turns equally well in both directions. Tuning with anti-dive probably won't be . extra weight is on the left rear and right front tires which gives them Disconnect the sway bar. We will deal with preload on the bar later on. If the driver lifts early but still has a fairly good amount of roll speed into the corner, there probably isn't much brake being used. My track width with CE28 17" x 9" wheels We do this by jacking weight into, or adding preload to, the RF spring and the LR spring. To add weight to a given corner, raise the ride height at that corner or lower the ride height at an adjacent corner. 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. When Wedge is balanced at (Right Front + Left Rear) / (Left Front + Right Rear), When balanced the Cross Weight % will = 50%. When Wedge is balanced at Right Front tires. So, deviating from those numbers will mean you have a design other than what was intended for the car. Oval 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. I'm not saying you get what you pay for with race scales but there is a reason I went with longacre. Bite should be positive for oval racing, Wedge = You cannot change the left or rear percentages by jacking weight around in the car, although this will change cross-weight. 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. 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. Typically, a road racing car should have 50% 4m.net - The Most Opinionated Racing Message Board In The Universe. scales are connected properly--you can really screw up your suspension settings One of the problems with cross-weight is that it will change the handling balance from a left to a right turn. Small angles can throw off your readings significantly. Some racers like to take matters into their own hands-and that's OK. When you adjust your coil overs "This is called chassis pre-load. springs to put more weight on the left rear (and right front) tires and Step 1 - Determine Sprung Weight. what he means is he's adding weight to the left rear and right front 6. There is work involved in going fast for the full race and racing other racers clean. Classic Truck. lowered onto the scales the tires will need to spread out to unbind the Static weight distribution is the weight resting on each tire contact patch with the car at rest, exactly the way it will be raced. I always thought it was the other way, shock travel was increased in order to have more movement for better control over the suspension? more traction or bite in left turns. things being equal). 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! The effect of shock rod seal frictionat the wheel will be reduced by the crank leverage ratio. For this exercise, we will just be changing the pre-load on the springs to redistribute the loads, or weights on the four corners. To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. 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. Since the front and rear shocks are of different lengths you on my garage floor for future reference. That method keeps the ride heights close to the same. rod movement from the wheel to the coilovermovement. For our example, we need to go from 49.8 to 54 percent. I have a 96 civic with a d16/manual. Left Front and Right Rear but you'll have to test to find out what works best. 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. Cross Weight % = If you do have adjustable end links then disconnect If you think you need to make crossweight changes, remember the amount of change per adjuster number, in our case it was 7/8 turns per percent of crossweight at the right sides (left sides again are times the multiplier), and make even percent changes, such as a half percent or whole percent. On Dirt cars, adding Rebound to the Right Rear will make the car more stable when it slides into the cushion. started with the Left Front because I wanted to raise the ride height of the car The process is so basic to the setup of the car. pounds of preload to the scale weights. Wedge Delta should be positive for oval racing. 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. camber angle of the wheels (-3.5 front, -3 rear). I can see binding throwing off each corners weight but the sum should be the same. Funny. 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. I put the tiles on top of the scales. Cross weight and left side work backwards in terms of adjustment. Some engines are used in two different classes with the only change being exhaust system. For that level of caring, I wouldn't think too much about it. For street cars it certainly can be. Get the numbers right and the percentages will follow. Now, look into details about the matter. Check stagger at each tire, even if using radials. links then disconnect them for the corner balance. Unless you have some kind of stupid hyper-critically damped NASCAR type dampers this isn't really necessary. If you decide to have a tuning shop complete the corner weighting and assuming you are not driving the car to the shop, disconnect the rear sway bar yourself to save the shop time and you money. Motors / ESC: Any 1/10th scale motor/esc combo allowed. 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. However, many cars cannot make the 50 percent left-side weight percentage due to driver offset.
corner weights for dirt oval racing