This will result in equal understeer/ oversteer balance in right and left turns. Disconnect at least one side of both the front and rear sway bars. - Make sure the tires are centered on the scales. © 2021 Motorsport Marketing. - To increase rear weight, move weight as far back as possible. 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. This was a very interesting post to me. Understanding weight transfer is crucial to fast circuit driving as it enables you to become conscious of how the car’s balance is changing around each corner. 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? People who have never corner weighted a car are often confused by this as it seem counter-intuitive to raise a corner of a car to make the mass on the wheel increase. Set the tire pressures to normal race pressures. Rock or bounce the car helps. So if you have 60% on the front , you should have 30% on each front wheel. Using dead struts and lots of bearings will help. In the Mudboss setup post for high bite dirt ovals the author lists shock length. - Check stagger at each tire, even if using radials. Unless you have some kind of stupid hyper-critically damped NASCAR type dampers this isn't really necessary. 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. Like stories like this? At all ovals, the heaviest weight is being transferred towards the RF upon entry into a corner. Maybe there's some sort of bind in the scales. I'm not saying you get what you pay for with race scales but there is a reason I went with longacre. }); Static weight distribution is the weight resting on each tire contact patch with the car at rest, exactly the way it will be raced. All are welcome. Due to friction in bushings, linkage, and shocks incorrect readings will result. One of the most important aspects of car setup is the static weight distribution and the cross-weight percentage. Adjusting the spring perch to increase pressure on one corner will increase the weight pressure on the diagonally opposite corner. ICYMI: Ferrari Announces Return to Prototype Racing With 2023 Le Mans Hypercar Entry, Registration for Track Night in America Opens Monday—With Prizes Up for Grabs. Then move components like the battery or fuel cell. This approach is commonly used in oval track racing. It would just automatically settle. Does that mean measuring end to end or eye to eye? Comments, compliments, criticisms, questions. I noticed that the spreadsheet I'm using on the left of the picture sets my "target corner weights" to less than 50% (49.6%), why is that? Static weight can only be changed by physically moving weight around the car, not by spring adjustments. The anti-roll bars must be disconnected when taking these measurements. Alignment should be close to race settings. If we raised the front left corner up, this would have a direct effect on the diagonal rear right corner weight, as it would lower the ride height. Then just leave them attached. The other two corners will lose weight. The advantage to wedge is that the left rear tire carries more load, so the car drives off the turns better. Unequal cross weights can destroy a road racing car's handling and sap driver confidence. - Always record the cross-weights and ride heights for reference at the race track in case changes are needed. Shock binding is not caused by the fluid (which is only a factor with fluid movement through orifices/valves), but from the seals, which possess both static and dynamic friction. Cross Weight = Right Front + Left Rear. 327 Topics. Y4szeIqlItT1h6j8v6aN1xn4yLzitzGoVrjOIcw8dqvcSrC6fCcQZlE8Q06g2OaC. Be sure to have the weight of the driver in the seat. You could also raise the left front or right rear ride heights to do the same thing. Interested in hearing peoples' opinions and (preferably) experiences. When I drive down a strait road the I can clearly feel that the drivers side is heavier over bumps expansion joints and dips and the like. How would you make something like that? To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. 240 Forums. I commented on this to the youtube video 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. I would imagine that disconnecting the shocks is only applicable to setups where the shock and spring are separate, like a lot of solid axle cars, or Mk2 Supras in my experience. (Important). Oval-track cars sometimes prefer an offset weight that favors performance toward turning left, while drag racers focus on distributing load where it’s needed to launch in a straight line. 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. Here are some points to remember when weighing your race car: - Make sure the floor is perfectly level; use shims under the scale pads if needed. The shims will be shown as cross weight on the scales. Disconnect and adjust later. looking forward to getting it back! By David S. Wallens your racing effort more successful. All rights reserved. Cross-weight percentage compares the diagonal weight totals to the car's total weight. Or do you just mean an old, worn-out strut? For most karts, the following weight distribution is recommended:43% Front Weight 57% Rear Weight 50%/50% Left/Right Weight. googletag.pubads().enableSingleRequest(); STR Competition Racing Car Scales System 2000KG Rally Hot Stock Rod Berlina F2. Now picture a ½" shim on the glass under the Left Rear and Right Front corners or just under any one corner. For pure race cars this isn’t a consideration. 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. It made using scales real easy. I plugged in a bunch of numbers into my calculator and it all checks out. googletag.defineSlot('/3756454/GRM_Home_banner', [728, 90], 'div-gpt-ad-1493922548383-0').addService(googletag.pubads()); Yep, old struts that are drained of fluid and have little to no resistance. My left rear is something like 150lbs heavier than the right rear, with both fronts even at ~740lbs each on a 2425lb FWD car. It is better to make small adjustments at each wheel rather than a larger one at one wheel to minimize the change in ride height at each corner. 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. Corner weighting is huge. its all about the … This keeps the ride heights as close to ideal as possible. 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. Cross-weight is also called wedge: If the percentage is over 50 percent, the car has wedge; if below 50 percent, the car has reverse wedge. Weight transfer in corner occurs even with zero body roll, even with no suspension on the vehicle, like a go-kart. The only way to change the static weight distribution percentages is to physically move weight around in the car. - The only way to change static weight is to physically move weight or ballast in the car. Rebound controls the sprung weight of the chassis or weight transfer while Compression damping affects the unsprung weight of the chassis or the tire contact to the racing surface. For road racing and autocrossing, the ideal left weight percentage is 50 percent. 371 Posts. Rear wheel drive racers are fanatical about knowing recording and setting these variables. Reply Quote. The images used are taken from the iRacing Super Late Model setup screen. A good starting point would be ¼ – ½ tank … While this is commonly kept at or around 50% for road racing cars, oval racing cars can vary wildly from car to car within the same class of racing. - 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. Picture the following: Your car is really fast in right-hand turns, but understeers in left turns. 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. Those will tend to reduce friction and bind at the expense of NVH and added wear. Because it’s located at the front, the vast majority of door cars have a weight bias that favors the nose. Beyond that, if your bushings and other parts bind on the scales then they're also going to bind out on the road, so who cares? Cross weight is a calculation that is only useful for “wedge” adjustment for oval track racing. Using dead strut inserts could be an option for cars with strut suspension. Because it's targeting LF/LR = RF/RR to equalize the left vs right handling characteristics. Are they adjustable? We had a good Miata set up for ST. Cross weight is a calculation that is only useful for “wedge” adjustment for oval track racing. However, many cars cannot make the 50 percent left-side weight percentage due to driver offset. If you shocks are working normally they are not worth worrying about. Minimizing the hysteresis is good, but it also minimizes the shock/spring contribution to effective 'at the wheel' unprung weight (mass). 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. I retighten them after I've made all my adjustments. If you get the car neutral in left turns, it oversteers in right turns. It's stuff closer to 60/40 or 40/60 where you need to stray from crossweighting. 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. My big stumbling block on this subject is how to get accurate readings by removing all the friction/bind from the tires, sway bars, bushings, etc. If a wheel has too much weight the tyre will become overloaded. These tell us all we need to know about the setup relative to the weight distribution. 3/ Cross weight Percentage / Corner Weight Balancing: This is the real big one & part of the whole corner weighting exercise that will yield the greatest improvement in vehicle handling balance. - Use blocks the same height as your scale pads to move the car off the scales to make adjustments. Essentially what we are looking at is the balance between the right front … Final alignment will be done after weight balance. I'm anxious to see what Proform says about my experience. … A laser level works best to set levels. Caster/Camber adjusters at front spindles should be set at II top & II bottom. You've tried springs, shocks, different bars, neutralizing the anti-roll bar, and nothing seems to work. I weigh 220. Decrease rear weight percentage Increase front weight in .25% increments Move seat forward Check toe out Tight in center of corner Increase air pressure in the left front 1/2 lb. Corner Weight Racing Car Scales STR 'Wireless App' Bluetooth car Setup Race Road. Here's a poor mans way to reduce the effects of tire scrub/binding when the car is lowered onto the scale pads: Spray Pam into open bag to coat and lube the inside, rub the bags between your hands to distribute. It was a good car. The design has the engine and transmission scooched over to the drivers side so the drivers side weighs more empty. Total TW = LF+RF+LR+RR (LeftFront + RightRear etc) % Front … First the weight on each wheel is measured. Because corner weights are fundamental to the handling of the car, every professional racing team measures and adjusts corner weights before and after every track session. The engine is typically the heaviest piece in any door car. A jumbo ziploc bag prevents lube from escaping when not in use. Do these percentages apply for front wheel drive cars? Only after I spent a lot of time bouncing on the door sills did it settle down and stabilize. The front will show close to 60%. They all seem a bit generic and don't offer specific advice for production based cars where you can't really get purpose built race car perfection. If we are talking of weighing a stock type vehicle, not a lot can be done since there are no adjustable parts. Subscribe now. $1,690.06 + $121.72 shipping. … 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 distance from the ground to an inner suspension arm pivot point will also accomplish the above goal. 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. Ensure that the car has been bounced and settled. One of the keys to obtaining a good setup is using the correct procedure to weigh your race car. In this article, I'll try to explain several different points of set-up and demonstrate a little about how they affect your chassis. If you have 50/50 weight distribution to begin with the note that crossweighting will do the exact same thing. 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. Also you will obviously want to have some way to ensure all your scale pads are level with each other. This can make maneuvering in traffic difficult, even dangerous. 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. A strut with its innards removed? So 2.5" springs and experimenting is the way to go-  I think I know that much..  . Adjust or shim the drop links to make sure that there is no static twist or torque on the bars (with the driver in the car!). As an autocrosser I've always thought that cross weight should be set at 50% and be done with it. 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. When a car leaves the starting line, acceleration forces c… I can see binding throwing off each corner’s weight but the sum should be the same. Proforms are cheap scales. This article is from a past issue of the magazine. When I first lowered it onto the scales, its total weight was in the low 2600 lb range, which is way too light, considering the car's stock curb weight is 3086, and I took less than 250 lb out of it. Choose to adjust the corner that will result in the pressure on each front wheel being the closest to equal side to side. That seem like a lot. If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. When water settles in all four cylinders adjust the hight of the highest one and recheck. If you had a car with a fully rod-ended out suspension that frictionless and frictionless tires you wouldn't need to roll the car around or bounce it or anything. When working with static weight distribution, we use two percentages to analyze the car's corner weights: Left weight percentage and rear weight percentage. This will not change the left-side or rear weight percentages. | Posted in Let's look at what incorrect weight distribution can do to a car. To weigh the car it should be in “race trim” meaning race fuel and driver. It varies with weight removal, added. Then drop the car down, roll and bounce, then roll back up onto the scales to recheck results. Front toe should be set out to 1/16” to 1/8” (1-3mm). Right now I have (IIRC) 350 lb front and 200 lb rear springs (koni sport, eibach pro line, ST anti sway bars)  . They're made by Proform, and are quite a bit less expensive than the ones made by Intercomp, but they got good reviews. Repeat adjustment if needed. 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. This can be time consuming and take several tries. My set came from the estate of a general contractor and masson. - Move ballast first, since it's easier. You will need to weight your vehicle on each tire to use this tool. 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. Change another etc. 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. - To add weight to a given corner, raise the ride height at that corner or lower the ride height at an adjacent corner. I don’t get this. I had the same question. This gets very tedious, given the number of iterations it typically takes to get the corner weights right. 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). Take care that the car does not accidently slide off the scale pads. Thanks. Now that's pretty cool! Funny. More stagger usually loosens the handling in left turns, so more cross-weight is used to tighten it up. 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. Where roll couple is the total amount of resistance to body roll provided by the springs and antiroll bars at both front and rear, roll-couple distribution is the amount of roll resistance at the front relative to the amount at … Once you can understand how the car’s platform is sitting, you can figure out what the limiting factor is – what’s stopping you from going faster – and alter you driving … More caster may be needed over the weekend to fight tire wear … Bite and Wedge Delta are important for oval racers, especially on dirt ovals. Even purpose-built cars, like a contemporary Pro Stocker, have more weight on the front-end than the back. On my ZX2SR my cross weight was consistently in the 49% range. Suspension Mythbusting: Solid Axle vs. IRS. Blocks or ramps must be used so that the car can be rolled on and off the ramps. I use a water level to make sure my scales are at same height. For street cars it certainly can be. At the time Honda was still favoring their home market I reckon. Wouldn't the fact that it is front wheel drive change at least the front to rear percentages?
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