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Thread: Brunton Super Stalker Track Day Alignment Settings

  1. #11
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    Straight from Dennis Brunton.....ride height regarding the classic chassis (1 of 2)


    RIDE HEIGHT
    We will start with some general discussion here….
    You could well think, “OK this one is easy!!” You can adjust the spring perches to lift the car up or down, this lets you set the ride height, or height of the frame above the ground, or ground clearance to where you want it? Clear those speed bumps in the parking lot!! Neat!!!WRONG!!!!
    The ride height adjustment is one of the most important adjustments to the suspension! The designer of the car went to a lot of trouble to figure how much suspension travel the car requires and has selected the shock length, angle and motion ratio accordingly. He also designed the elements of the front suspension and all the linkages in the rear suspension. All the arms and levers in the suspension have purpose, an angle and they interact with each other to make the car behave in certain ways. All of these characteristics are optimized and only work at or near a specific ride height. The ride height dictates the starting position of ALL THE ELEMENTS OF THE SUSPENSION, WITHIN THE FULL AVAILABLE TRAVEL!
    IMPORTANTEGRANDE
    The front suspension has a sweet spot, or area of movement where bump steer is zero, static camber is what is required at zero load, and increases via the shorter upper arm, to be at the required camber at full cornering load. The suspension must be at the designed static load point when the car is at static ride condition.
    THIS IS THE FRONT RIDE HEIGHT
    The rear trailing arms, Panhard rod and shock brackets are positioned to have a small amount of acceleration jacking, and a small amount of axle steer under roll. The car must ride at a certain position in the suspension travel for this to work.
    THIS IS THE REAR RIDE HEIGHT!
    The height of the frame above the ground has been decided by the designer. If you want it higher, put bigger wheels on it!! WE ADJUST THE RIDE HEIGHT BY COMPRESSING THE SPRING IN THE SHOCK WITH THE ADJUSTABLE PERCH.
    THIS IS SOMETIMES CALLED PRELOAD.IT DOES NOT STIFFEN THE CAR OR CHANGE THE SPRING RATE.
    IT IS THE RIDE HEIGHT ADJUSTMENT, NOTHING ELSE
    It is the ride height that is important. If you set the ride height, and the spring is loose or has unacceptable preload, you need a different length or rate spring! The stock AVO shocks can be set to correct ride height without any preload issues (see preload chapter).
    If you are extra large and find that you cannot keep the car off the bump stops, adding suspension travel would be a very poor “solution”, because you will allow more body roll. YOU NEED TO STIFFEN THE SPRINGS!!!
    If you are light weight. Do not set the car lower because you can, without having bump stop issues.
    THE RIDE HEIGHT MUST STILL AT THE CORRECT POSITION TO PRESERVE THE SUSPENSION CHARACTERISTICS
    There is another factor to conside… the Bump/Droop ratio. On its journey down the track, a car will hit bumps, and go through dips which load up the springs, which rebound and shoot the car back up, until gravity brings it down and compresses the springs again like a “POGO STICK”. Fortunately, we have shock absorbers to soak this up. But they can’t be too harsh, because they stop the car not us, so we would leave our seats on the rebound! To prevent this we allow the suspension to actually go past the ride height, in rebound, for a short way to calm things down. This is known as “droop”, not to be confused with ED, for which Viagra is a better solution than springs.The Setting of the ride height also sets the amount of Bump and or Droop travel available..e.g. If you undo the perches until the car sags onto the Bump stops, you have 100% of your available suspension in Droop…zero in Bump. Tighten the perches till the body is up to the limit of your suspension, you have 100% bump zero Droop. pretty simple really!Body Roll and Roll Stiffness. The roll control on the Stalker is the stiffness of the springs, working in compression, on the outside wheels, which are the primary players in a turn. (You could use anti roll bars, or even tension springs in the inside wheel suspension for roll control but we did not)The STALKER shock length, travel and spring rates, the frame tubes,droop stops and roll center are positioned so that:- The car will not hit droop, or bump stops under rollif adjusted to the recommended ride height!


    All of the above are designed to be correct
    AT THE DESIGN RIDE HEIGHT
    All these things lined up at the same time…an astrologers’ dream!!
    For anyone who is thinking that, “if you don’t have enough droop, then when you go over a rise, the droop stops will hit the axle and make the wheels leave the ground”, or“the spring will launch you into the air” YOUR TAKE ON THE SITUATION IS INCORRECT!!If you are going over a rise fast enough to take off. You, the car, the axle, the wheels, and the sandwich in your pocket are all going to take off at the same time, to the same height!!! You are all going the same speed, and will be subject to the same amount of negative g’s. The springs will not assist the launch , UNLESS THEY ARE IN A REBOUND STATE FROM A DIP PRIOR THE LAUNCH.The axle will not know if it is hanging under a car, or has a car sat on it! Now, if you leave the ground under a bridge, and the roll cage hits the bottom of the bridge, Watch out, there’s an axle with wheels on comin through!There is a dynamic where the spring moves the suspension to full droop in zero g condition, but that is another subject, and does not contribute significantly to roll or jump stability.
    Same applies if you have great tires, a high CG and turn too hard. She’s going over boys!You don’t need to bottom suspension to roll the car, the height of the CG is going to roll it. It does not matter IF THE BODY IS RIGIDLY MOUNTED, or ON THE BUMP OR DROOP STOP. If the body is attached via a skewer (roll axis) which allows body roll,(It is), the rollover will occur a little earlier, because the sprung CG moves outboard slightly in a turn

    A STALKER, WITH 53” TRACK AND CG 10.5 INCHES ABOVE THE GROUND, WILL REQUIRE A 2.8 G TURN TO LIFT THE INSIDE WHEELS.
    If you can find tires to provide enough grip to achieve this, I want some PLEASE. The ‘ole bottom line, is:
    THE STALKER IS TIRE LIMITED, NOT ROLL LIMITED IN TURNS! YOU CANNOT LIFT THE WHEELS, OR TURN IT OVER, WITHOUT HITTING SOMETHING!!
    Stalker V8, chassis #85

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  2. #12
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    Straight from Dennis Brunton.....ride height regarding the classic chassis (2 of 2)

    Setting the Ride Height
    OK, we’ve been through the why’s, here is the how!
    Rear…Basic.
    Jack the car up by the frame, not axle. The axle will droop to the frame at full shock travel. You can put a ¼” or so piece of rubber on each side as a stop. It is not desirable to allow the axle to hang on the shock.Now let the car rest on the ground, sit in it, and get someone to measure how much it sags. Adjust the shock perch so that the axle sits 1 5/16” above the frame tube with you aboard. You can set the other side y counting how many threads the perch is up, for now. We will deal with fine tuning the corner weights later.Front…Basic
    On the front, set the ride height so that the lower arm is parallel to the ground, WITH YOU IN THE CAR. That is the ride height!ADVANCED ADJUSTMENT
    You can increase static camber by lowering the front. Do not drop it more than ½”. A reasonable trick is to set the static camber at zero, with the lower wishbones level, then take track tire temps and add negative camber by lowering the front until the tire temp is ALMOST even across the tread. As long as you don’t lower by more than ½”, you will be in the “zero bump steer zone” so the camber change will not upset toe setting.As you lower the car the angle of the upper arm increases, so does the camber/bump ratio. This will make the “camber increase” progressively more dramatic as you lower the car. You will find that, because of the low CG and body roll, the Stalker needs very little camber.Note: The tire will usually be a tad warmer in the inside…this is because the negative camber increases under brakes, without the compensation of positive camber introduced by body roll.Here you have an executive decision. Even temps will mean that on average, (you corner AND BRAKE on the tires), your tire workload is distributed evenly across the tread and you will get max life out of the tires (the dynamics in a turn, are very different to those under braking). It does not mean they are working optimally in cornering or under braking! You need to remember inputs to your bum on the track to decide if you have a turning, or braking deficiencyIt is not possible to get the tires dead flat on the ground in both turning ANDbraking, unless you go to The Ultimate Setup: ZERO SUSPENSION!The suspension at the back is soft enough and the frame and body is close fitting enoughthat Roll Bottoming can occur if the Ride Height is incorrectly set ( This is when body roll causes the car to hit a bump, or droop stop)Bottoming the suspension in a turn will cause sudden, violent oversteer, and possible loss of control, especially if you are thinking about your girlfriend when it happens.If you have the RH set at 1 5/16 it is VERY unlikely that you will hit the droop or bump stop. You would need almost six degrees of roll.6 degrees of Body Roll looks like this; the rear RC is pretty much on the axle C/L
    If your car corners like this do NOT add suspension travel…more roll travel is the LAST thing you need. This baby needs to be stiffer! You need to add spring rate.You can also see how important ride height adjustment is…With the RH correct, you can induce enough cornering G’s to roll the body six degrees before the suspension stops put an end to you good handling.If you drop the Ride Height, you will hit the bump stop before 6 deg., or raise the ride Height, the droop stop will hit before six degrees. Both have the same result. Your sweet handling will end as soon as either one hits.

    TO CHECK RIDE HEIGHT ON THE TRACK
    If you set the RH to 1 5/16, and you are around 200 lbs you will have about ¾” of preload and should not get near the bump limit. If you are heavier, you may find that you are adding excessive amounts of preload (¾” to 1” is optimum for our cars.) If this is the higher, add Spring Rate. I had no problems (solo) with stock springs, but if I took someone for a ride at the AX, I had to be very ready for the occasional sudden breakaway.The proof of the puddin’, is in the eatin’ so here is a great way to confirm the exact situation.
    1. Set the RH to 1 5/16
    2. With the car stationary (obviously) put a small cable tie tightly around the shaft of the shock, right against the shock body. Cut the tail off with a skinny Exacto #11, do a reasonably hard AX run, or practice lap.
    3. Stop and check how far the zip tie has been pushed up the shaft. This will show you how close you are to bumping out.
    If you are fairly light, and not getting near the stop, you could well say, “Cool, I can lower the car, lower is better!” Not so fast Fella! You are part right but, if you change the angle of the trailing arm, you could well introduce some axle hop, and even some rear steering OUT OF THE TURN!
    My advice: set the rideheight where it is designed-1 5/16”axle to frame clearance.At this point the trailing arm will be aiming slightly down from the frame mount to the axle.
    If you have the car set so that it gets fairly near to the bump stops…BE VERY CAREFUL IF YOU GO TO A BANKED TRACK!!!!! The banking will load the car up, and if you are close to the bump stop on the level, the extra load of the banking will put you over the edge. Stiffer springs all round, (More wrap or wedgies..) are the best solution for this. You will maintain the correct Ride Height on the flats as well as the banking.
    An acceptable alternative is to increase theStatic Ride Height a tad. Less than perfect camber control or axle behavior beats the hell out of bumping out and spinning into the wall.
    Here is a guide…Gateway @ 14 deg will load the car an extra 3%; Rockingham @ 23 deg gives 9%; this means you will pull 1.09g before the body starts to roll at all. Your “static ride height” will need to be increased by this amount to have the frame axle position the same on the banking. This unfortunately will mean that your RH will be too high on the flat sections…This guys, is where the art comes in…The Compromise required to set the car up to get the best lap time (and the stuff that cost McClaren $100M!!!).
    TIP
    Do not mess with the setup because your buddy is beating you. The only sensible reason for change, is if you can positively identify a problem and have a pretty darn goodidea of the cause !
    Stalker V8, chassis #85

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  3. #13
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    It's all so simple....
    Kitcat:AKA, Sir Spinsalot
    '97 Caterham Super Sprint, 1700 Crossflow-sold
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  4. #14
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    Thanks Shane. I will keep cranking on the perch adding preload to see if I can get to 1 5/16 inches of clearance.

    Do the Gaz shocks need a lot more preload to make the clearance right? I as as I started with 1 inch and am going up from there and it from Dennis's post above I saw this line
    "If you set the RH to 1 5/16, and you are around 200 lbs you will have about ¾” of preload and should not get near the bump limit. If you are heavier, you may find that you are adding excessive amounts of preload (¾” to 1” is optimum for our cars.) "

    Here are pictures of my rear shocks. The weird thing is I have more preload on the drivers side now but still less clearance (.25 inches). The passenger side has about .75 inches of clearance between the axle and frame with about half the preload now.

    Drivers side: preload about 2 inches and just .25 inch clearance
    Name:  Drivers side .25 inch clearance.jpg
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    Passenger side the original 1 inch preload and about .75 inch clearance
    Name:  Passenger side .75 inch clearance.jpg
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    Last edited by searya; 09-12-2020 at 11:14 AM.

  5. #15
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    Okay just got back from the garage. I added another 1.5 inches of preload to the drivers side. Afterwards I had zero clearance between the axle and the frame.

    Then went the opposite direction and suddenly I got more clearance. Still not up to the 1.3125 Dennis says we should have but up to .75 or so.

    Anyway, was I doing it the wrong way earlier and now got it right? Pictures below are post adjustment and show the current shock and the new clearance I now have.

    Drivers side coil loosened all the way down. FYI still has preload even when adjusted fully out like the picture below.
    Name:  Shock when I have .75 inch clearance.jpg
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    Clearance that I now have is wayyyy better
    Name:  Drivers Side now with .75 inch clearance.jpg
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Size:  27.6 KB

  6. #16
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    Default Stalker suspension

    Disclaimer, I have never even seen a stalker! But that sounds like way to much difference in preload between RH and LH. When corner weighting my Seven, I was only changing 3 out of the 4 preloads by about 1/4 to 3/8" range with one corner around 1/2". Do you know your corners wts. DaveW

  7. #17
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    Quote Originally Posted by Dave W View Post
    Disclaimer, I have never even seen a stalker! But that sounds like way to much difference in preload between RH and LH. When corner weighting my Seven, I was only changing 3 out of the 4 preloads by about 1/4 to 3/8" range with one corner around 1/2". Do you know your corners wts. DaveW
    Great timing for that question!

    I spent yesterday afternoon at my friends house corner balancing the car and here is where I ended up up. I also included the distance each of the springs are threaded up (tightening the spring):
    25mm = 1 inch

    LF: 434 (8mm)
    RF: 414 (6mm)
    LR: 431 (0mm the shock is as loose as it can get but still has some preload)
    RR: 410 (6mm)

    Cross Weight: 844 vs 845 so 50%!
    Front to Back: 848 vs 841 so 50.2% vs 49.8%
    Side to Side: 865 vs 824 so 51.2% on drivers side vs 48.8% passenger side

    After the adjustments I do have close to an inch clearance between the rear axle and frame on both driver and passenger side which is much nicer than when I started.

  8. #18
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    Glad to here your getting it worked out.
    Stalker V8, chassis #85

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    Stalker Chassis #85 Owner Thread

    Get up in the morning and give the day your very best. You don’t get it back.

  9. #19
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    Thanks and I think I am set. Shot a message to Scott M. and he confirmed loosening the spring should increase the space between the axle and the frame.

    So now just looking for good weather and fun day at the track this weekend in Putnam, IN.

  10. #20
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    Wanted to follow up with an update.

    Went to Putnam last weekend and ran the advanced group event put on by 10/10ths. Lots of ex stock cars, time trial corvettes and gt3, gt4 Porsche’s. In the advanced group you can pass anywhere with no point by. This was my first time running advanced with 10/10ths and I had a blast!

    I am used to running in the top of the group but this was totally the opposite where there were only a few cars that I could beat. But even so the level of speed we got up to and fun associated with passing or being passed anywhere was exhilarating.

    In the end I set a new personal best at Putnam by over 3 seconds and could do it consistently! The car made me feel like I could do no wrong. Need a little extra steering....just blip the throttle and the rear would come around smoothly. Heading off line...just apply throttle evenly and the car would go where I pointed it. The balance was also amazing. Zero fear of spinning out whereas I previously have spun 3 times at Putnam while going 3-6 seconds slower.

    Thank you guys for all the help. And I guess the moral of the story is to ensure your car is corner balanced and aligned and your axle has more than a quarter inch of clearance from your frame

    Next up is my new post about tires and hitting up folks like Shane and other track day junkies to find out what tweaks and major changes (wings, engines, transmission) have been the best bang for the buck.
    Last edited by searya; Yesterday at 09:30 PM.

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