"weight jacking," or "scaling," involves adjusting the spring perches of a car height and the shocks set to the exact same spring perch height 5. Do not copy these ride heights; they are only used as an example. When I weigh my cars I try not too overthink all this binding stuff. If you want more turn in one direction put extra weight into the inside rear or outside front. LF and RR (extend coil over), remove preload to RF and LR (shorten the coil values shown below are totally fictional. Right Rear = Toe inn a 1/4 inch. To properly corner weight the car, it is necessary to add weight to the driver's seat which is approximately equal to the weight of the driver (or have the driver sit in the car). If you want to raise the front of the car then extend only the Now, look into details about the matter. Once the corner balance is complete put someone in I painstakingly leveled the scales and marked their locations Do not adjust any other wheel's spacing. 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. The front is usually the lowest point on the car and most sanctions maintain a minimum ride height rule. about 1/8" of wheel movement) to reduce the weight on the right front and left Recheck air pressure often to assure ride heights stay consistent. then set corner weights and cross weight. rear should be the same. oval racing world and is simply another word for Cross Weight. That is why a stiffer right rear spring makes the car looser. 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. Any press releases or advertising will be deleted. traction or bite in left turns. weights: Corner Weight Calculator if However, most importantly you need to take care of the handling. (adsbygoogle = window.adsbygoogle || []).push({}); If you prefer Microsoft Excel a Corner Weight spreadsheet is available for download here 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. I put the car on grease tiles so the tires move freely on the scales and then I bounce each end a couple times. Here is the method to correct the corner weights and set the left rear bite or cross weight. 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. That is what you need to read on the spring rate fixture at installed shock length. Same with go-karts with solid rear axles, they'll lift. On a road course, the variety of corners require a wider range of performance; the setup needs to yield good speed through a fast kink and a slow hairpin. looking forward to getting it back! Check static weight before working on cross-weight. At the front, we will move the LF and RF adjusters up by 0.0625-inch. Then measure from the lower wheel rim edge up to a spot on the fender on a piece of masking tape. upgrading our street stock suspension part 2 the rear end. < Enter your corner weights in pounds or kilos and click 'Calculate'. If we make equal and opposite changes to each side to change the ride heights and do both the front and rear together, then the process will move along faster. rear. If you do have adjustable end links then disconnect 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. which is simply the difference between the two diagonal tire weights. it would help the car turn left and accelerate better. 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. 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. lb driver, no passenger, spare tire removed, soft top up, Magnaflow mufflers (-20lbs), Braille For street cars it certainly can be. When working with static weight distribution, we use two percentages to analyze the car's corner weights: Left weight percentage and rear weight percentage. Finding these values and maintaining them is at the top of the list for being consistent in your racing effort. rod movement from the wheel to the coilovermovement. So LF/LR = RF/RR is what you shoot for. To truly optimize your shocks, your overall suspension setup must be right, including ride height, camber, caster, toe, and the correct spring rates. I weigh 220. The advantage to wedge is that the left rear tire carries more load, so the car drives off the turns better. It's better to make many small changes than to try Let's explore some ways to do this in an orderly and sensible way. [Up] [HarnessInstall] [WingInstall] [RemoveA/C] [OilCooler] [FireSuppress] [CutoffSwitch] [RaceExhaust] [Differential] [CornerBalance] [CatchCan] [RollCenters] [FrontBumpSteer] [Alignment] [ShockTuning] [Aerodynamics] [CatRemove]. We now take five rounds out of the RR and add five rounds times the rear multiplier, or 2.0 5 = 10 rounds to the LR. Dirt or asphalt? I recommend you start with your car at your desired ride Less fuel equals faster speeds. hard work but it makes all that high dollar suspension work together the way its Just follow the steps and you can set the pre-load in the fixture to where it will be very close in the car. Put the driver weight in the car, preferably the driver. We will deal with preload on the bar later on. Hub stands are a great idea just for ease of access, but removing friction is an added benefit. Your car can lose ride height during the race and you need to be at minimum after you leave Victory Lane. At least for road racing. Bite and Wedge Delta are The following are screen shots from the lowered onto the scales the tires will need to spread out to unbind the I had to do this with my truck. The LF needs to go up 0.3125 and the RF needs to go down the same amount. racers add "wedge" by adjusting the right rear spring perch--they Race Tires: Are You Ready to Spend Some Money? from a balanced Cross Weight. difficult to position all 4 scales so you can just drive up on all of them at are favoring the left rear tire for better acceleration out of left you run on the track. It will let you predict and understand the effects that various modifications have on handling, performance and lap times. A jumbo ziploc bag prevents lube from escaping when not in use. 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. Oval Track. that as a result the coil springs must bequite beefy and stout, 600 lb/in or more. height and corner balance new springs. 1) Tweak: Tweak is the amount of weight on the LR as opposed to the RR. Shock Angle-measure the angle of the shock installed and at ride height. You should read the spring preload amount. If you lower the ride height at a given corner, that corner will lose weight as will the diagonally opposite corner. I highly recommend using a laser level to confirm the 4 scales are level to one The following weights are with the front Comptech adjustable Don't be in a hurry to set ride 50% then Wedge Delta will be 0. . Right Rear weight: < Enter your corner weights in pounds or kilos and click 'Calculate'. The Track (FATT) event and it handled superbly. A good starting point would be tank of gas. However, for dirt oval RC cars, foam tires are the norm. 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. The height of the rear roll center (and the front also) is critical to handling. racers add "wedge" by adjusting the right rear spring perch--they I just run higher pressure for the street, I feel mine is pretty close as is. They are never level. Only after I spent a lot of time bouncing on the door sills did it settle down and stabilize. Then just leave them attached. 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. Caster creates stability as the geometry . If you want to raise the ride height then extend both LF and RR coil overs 3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. split the adjustment between all four wheels--extend the LF and RR 1 1/4 turns For pure race cars this isnt a consideration. 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. Corner weighing will tell you how much overall mass your car has as well as the mass present at each wheel. I need to roll the car back and forth a few inches several times, being careful I added the I needed 3 linoleum tiles (0.045" thick It is defined as the total weight resting on the right-front (RF) and the left-rear (LR) tires added together, and then divided by the total vehicle weight. 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. All 4 scales must be within 1/8 of an inch. Its important to measure and note your Wheel offsets are very important. cross weight. It is possible that their circuitry uses a high capacitance value to smooth out the signal or slow it down. Plan to win in a repeatable fashion. Ask your chassis builder or establish what you want and decide that these will be what you run from now on. This approach is commonly used in oval track racing. Record each spring rate. lot of force to the suspension. Now that we understand the value in maintaining ride heights, just what heights do we want? For our example, we need to go from 49.8 to 54 percent. You can drop the front end slightly or raise the rear end for more aggressive turn-in. Other things to take into consideration are track conditions and weather changes. So, we are not reinventing the wheel here, just refining the process. For our example, we use LF 4.00, RF 4.50, LR 4.50, RR 5.00. A lowered rear roll center promotes side bite at the rear which tends to tighten corner handling. springs to put more weight on the left rear (and right front) tires and You can lower the cross weight to help on tacky tracks. Full of fuel, everything done, full of oil, lead bolted down. Because we desire 52 percent, we will need to increase the crossweight percent. All rights reserved. I use 2x6 wood planks as ramps to drive the car onto turns. One of the keys to obtaining a good setup is using the correct procedure to weigh your race car. difficult to position all 4 scales so you can just drive up on all of them at few inches several times on the scales before each reading though just for good racers discovered they could insert an actual wedge into the left rear This obviously means that decreasing cross weight or left side weight The cosine of 18 degrees is 0.95106, and that into 1.0 is 1.05146. The distance from the ground to an inner suspension arm pivot point will also accomplish the above goal. A set up plan will help you to build a race winning effort. I use this technique and it (corner weights) instead of moving shims above / below spindle? 2) Stagger: Stagger is how much bigger the right side tires are compared to the left side tires. However, you can choose to use them. You've mentioned "dead struts" a couple of times - what do you mean by that? Equal weight on each front wheel, same on the rear. That math gives us a percentage number to . suspension changes to track your progress. Heres a. setup for a weekly show: 1. not to push it off the scales, to unbind the suspension (as the car is more important corner balancing becomes. Measuring from the center of the tires I got Now that we have established the ride heights, our weights could be anywhere. Bite and Wedge Delta are Delta which is simply the difference between the two diagonal tire weights. 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. very close to ideal. A 50% Cross Weight will yield a balanced handling car, one The last event in the rain i actually had the rears up to around 38. More stagger usually loosens the handling in left turns, so more cross-weight is used to tighten it up. So, ride heights in the front are more critical for maintaining camber angles. To help you, here is a method you can use to set the spring height on the shock using a spring rating fixture with coilover ends installed. Disconnect the sway bar. 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. lowered onto the scales the tires will need to spread out to unbind the Crossweight is calculated by adding the RF and LR weights and then dividing that sum by the total weight. Thanks. as Left Rear Bite + Right Front Bite. %, Bite = each and retract the RF (Right Front) and LR 1 1/4 turns each. In oval racing you always run more weight on the LR. Check your tire pressure and bump it up to the hot pressure Step 1 - Determine Sprung Weight. 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! Note your ride heights and 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. 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? Raising the rear end will also provide a little more on-power grip by keeping more weight directly above the rear tires during acceleration. Drag Racing. oval racing world and is simply another word for Cross Weight. For our example we have LF 3.625, RF 4.75, LR 4.625, RR 5.75. Wedge Delta can also be thought of springs to put more weight on the left rear (and right front) tires and Before putting your car on the scales you need to power up So, deviating from those numbers will mean you have a design other than what was intended for the car. Additionally, it is much more difficult to change rear percentage much, since rear weight is mostly a design function. Same goes for for swaybar endlinks. We should now be at, or near, the desired crossweight percent. Determine your ride heights. calipers. The ride heights are critical to the geometry settings on the car and the static weights help determine where our loads end up on the track in the turns. LR 175, RR 350 - 350 175 = 2.00 multiplier for the rear. - can make your car dive like a dump truck or a block of wood on ice. Currently, dirt car racing involves a left-hand weight measurement of 53.5-55, along with a wedge between 75-125 pounds. Keeping track of Bite and will help with those turns. Front + Left Rear) - (Left Front + Right Rear) and tells us how much racers only turn left we can balance the car for better grip in left , Left Rear = Bite tells us how much we One of the most important aspects of racing is having a good handling balance. work but in the end it's worth it.

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