My shocks are double adjustable, as many will be when at this level of prep. 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. Conversely, if the car feels tight throughout the corner, raise both track bars. Finding these values and maintaining them is at the top of the list for being consistent in your racing effort. To do this you need to enter a corner at the car's limit of adhesion and then peel off the throttle aggressively. 14. rod movement from the wheel to the coilovermovement. rear. 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. For the teams that are running very soft front coilover springs, you will have a very difficult time moving the adjustment ring with your shocks in the car because of the high amount of pre-load on the spring. Motor: 550 or 540 motors only. Here's how we find the multipliers. There is work involved in going fast for the full race and racing other racers clean. I always thought it was the other way, shock travel was increased in order to have more movement for better control over the suspension? Shock Angle-measure the angle of the shock installed and at ride height. And I cannot really move any weight around. I
weights and percentages and generates target wheel weights to achieve a 50%
Disconnect and adjust later. Let's explore some ways to do this in an orderly and sensible way. Wedge Delta can also be thought of
The following are screen shots from the
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. few inches several times on the scales before each reading though just for good
You could also raise the left front or right rear ride heights to do the same thing. I was surprised to find, contrary to my experience, that the Vette came is very close to itsexpected weight as soon as it was let down on the scales, without having to take bind out of the suspension. You cannot change the left or rear percentages by jacking weight around in the car, although this will change cross-weight. 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. Most oval track speedways are similar to those in the US for car racing such as sprint cars, speedcars (midgets) and sedans, with most tracks generally around mile (402 m) to mile (536 m) in length. Oval
so the suspension can settle and unbind. 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? To calculate cross-weight percentage, add the RF weight to the LR weight and divide the sum by the total weight of the car. extra weight is on the left rear and right front tires which gives them
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. If the car understeers or oversteers in only one direction, check the cross-weight percentage. My car is a 1987 Honda CRX, set up according toITC class rules. (adsbygoogle = window.adsbygoogle || []).push({}); If you prefer Microsoft Excel a Corner Weight spreadsheet is available for download here
the driver seat and reconnect them so there's no preload on them. My left rear is something like 150lbs heavier than the right rear, with both fronts even at ~740lbs each on a 2425lb FWD car. More stagger usually loosens the handling in left turns, so more cross-weight is used to tighten it up. We run an extremely high banked 1/5 mile clay oval in Alabama that is always wet and low bite. This will not change the left-side or rear weight percentages. May run 4 pole motors. For example, if you are racing the Briggs Light class at 305 pounds, your corner weights should be: LF = 68 pounds RF = 68 pounds That is why a stiffer right rear spring makes the car looser. Typically, this adjustment will make the car tighter on corner entry or in the center, and a little looser on exit. They kept saying that it would go anywhere on the track and anywhere they pointed it. 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. 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. 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. One of the keys to obtaining a good setup is using the correct procedure to weigh your race car. turns. You should read the spring preload amount. the same time. The left weight percentage is found by adding the LF weight to the LR weight and dividing the sum by the total weight. 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. 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. A lowered rear roll center promotes side bite at the rear which tends to tighten corner handling. However, many cars cannot make the 50 percent left-side weight percentage due to driver offset. Yeah, I'm a little puzzled by my result when I let me car down on my new scales as well. very close to ideal. You will need to weight your vehicle on each tire to use this tool. Left Front and Right Rear but you'll have to test to find out what works best. 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. . 13. are favoring the left rear tire for better acceleration out of left
that as a result the coil springs must bequite beefy and stout, 600 lb/in or more. Corner-Weight Distribution Bickel points out that corner-weight distribution refers to the amount of weight carried by diagonally opposed pairs of wheels. The more rear weight bias, the tighter the chassis will be coming out of a turn. 2. Here is a screenshot with some random-ass corner weights. Hot Rod. I see disconnecting the sway bar, and how to do it, but disconnect the shocks? It is possible that their circuitry uses a high capacitance value to smooth out the signal or slow it down. If the person reduces the force with which he's pressing against the ceiling, the weight read by the scales will decrease. If your car's diagonal corner weights are not equal then its handling will be
As an autocrosser I've always thought that cross weight should be set at 50% and be done with it. In contrast, the corners on most ovals are super speedways are of a similar radius, and run within a very narrow range - closer to three-to-five miles an hour in difference. If we subtract the existing ride heights from the desired, we have front low by 0.0625-inch and the rear high by 0.4375-inch. Once static weight percentages are set, work on cross-weight percentages. 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. Right Rear weight: < Enter your corner weights in pounds or kilos and click 'Calculate'. lb driver, no passenger, spare tire removed, soft top up, Magnaflow mufflers (-20lbs), Braille
started with the Left Front because I wanted to raise the ride height of the car
4 Establish the exact weight change in percent that a given spring height change will make and record that number. 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. Here's a box stock 2006 Honda S2000 with 5/8 of a
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. I lowered the left rear spring perch 1 1/4 turn and put it on
The only way to change the static weight distribution percentages is to physically move weight around in the car. The spreadsheet's second page has a good article that goes into more detail of
You can use rubber tires on very specific tracks and seasons. Crossweight is of no concern to the track officials. Just follow the steps and you can set the pre-load in the fixture to where it will be very close in the car. 57.5" front and 59.625" rear. Before putting your car on the scales you need to power up
My starting cross weight was 50.6%, I was off 7lbs
left to right (measured with a digital caliper) and my ride height was pretty
Once you have returned the wheel corresponding to the spring change back to its measurement, the other wheel measurements will be OK. 3. 5. Put the car on ride height blocks without the shocks in the car and then measure the shock length from center of bolt to center of bolt. scales. over
rear. then leave them connected. turns. 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. Here's the ending corner weights with no driver and 9/10 fuel: Grassroots Motorsports Understanding Corner Weights. Its important to measure and note your
Thanks. Adjust the rear down by using the same method as in No. 4m.net - The Most Opinionated Racing Message Board In The Universe. To add weight to a given corner, raise the ride height at that corner or lower the ride height at an adjacent corner. Right Rear. Make small changes at the track, and make only one change at a time. Note your ride heights and
Most people find this out pretty quickly. R. racing junky Member. upgrading our street stock suspension part 2 the rear end. Do not adjust any other wheel's spacing. 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. If you don't have adjustable end links on your
front left and
If you want to raise the rear of the car then extend the RR
3 To make changes to establish the crossweight percent, we scale the car and record the crossweight percent. Any press releases or advertising will be deleted. bite, a negative value means the Right Rear is favored. Disconnect the shocks, when possible, and the anti-roll bars. This makes the cornering force balanced from left to right and offers the best performance overall. Here are some setup tips that will help you really get the most of of your Slash: > Keep it clean. McMaster-Carr adjustable end links
section). 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. Corner_Balance.zip, Excel Corner Balance Spreadsheet Screen Capture. The nose weight is simple to remember the tricky ones are - cross and left side adjustments. For now, we don't want the bar to influence the ride height or the weights we set later on. It was a good car. To keep things clear I call this added weight Wedge Delta
Calculate the spring rate multiples. Check stagger at each tire, even if using radials. I saved a copy of the spreadsheet for each
When Wedge is balanced at
The rear is 2.125" wider. Please post on the appropriate 4m forum. When you adjust your coil overs
You can lower the cross weight to help on tacky tracks. If you do have adjustable end links then disconnect
It varies with weight removal, added. 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. (i.e., if we move the RF adjuster two rounds, then we will move the LF adjuster 2.5 rounds.) We delve deeper into race suspension tuning basics here. I've read all the info before, in various places, but it's good to have a refresher. Then there is what I do for FWD stuff That is forget the rear weights entirely, and just balance the fronts to be equal. To do this, we add five rounds of pre-load to the RF. 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. 5. [ 1] In circle track racing, the use of the term "crossweight" gives us an indication of the weight distribution on the four tires. When a NASCAR crewchief says he's "adding wedge",
cross weight. the front ramps then jack up the rear and lower it onto the rear scales. to balance your car in one big step. Adjusting the sway bar is time consuming and questionable unless it is really stiff. The springs OTOH exhibit little or no friction loss when compressed or extended. Wheel Load-We have already determined the wheel load we desire in No. It's just turning left 2 times per lap. Battery: 2 cell lipo max If you want to lower the rear of the car then retract the LR
Full of fuel, everything done, full of oil, lead bolted down. 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. While several different setup parameters could have caused this situation, a likely cause is excessivecross-weight. The less fuel in the tank the tighter the chassis will become. Caster and Caster split can be adjusted to find more speed and stability. Can do to just left sidesor right sides, or to all 4. At least for road racing. Only after I spent a lot of time bouncing on the door sills did it settle down and stabilize. Since the front and rear shocks are of different lengths you
Because it's targeting LF/LR = RF/RR to equalize the left vs right handling characteristics. your scales. the sway bars because they fail so often and the bars only added a couple of
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. I was booked for 100 laps split across four or five sessions. what he means is he's adding weight to the left rear and right front
Equal weight on each front wheel, same on the rear. 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. This adds pressure to that end of the car just like putting the paper wedge underneath the table leg. important for cars with upgraded (stiffer) sway bars because they can exert a
calipers. racers only turn left we can balance the car for better grip in left