vwdave

Ok, I have a mild L98 with 265/50/15 BFG Radial GT's. I boxed the entire rear suspension, polyurethane bushings all over the rear. I also have KYB GR2's in the back. I have no weight transfer. The front end comes up, but the rear doesnt go down and press the tires into the pavement.

What can I do to improve this? I cant run DR's yet because I dont want to kill the 10-bolt, I just dont want to burn the tires off up to 40mph.

87CIZ

iTrader: (8)

the car squatting is not pushing the tires into the ground, it's actually doing the opposite.... if you want it to work right you should be lifting in the rear on takeoff. Unless your spinning crazy off the line i wouldn't worry about weight transfer.

The gr-2's are like bottom line for handling performance shocks, if you want weight transfer you'll need to get shocks dedicated for it like the 90/10's or such.

About the spinning, it helps to feather the gas. Learning to drive at the strip takes quite a few runs to get it down right. You just can't punch it and go (unless your car is slow) but looking at your specs looks as if you need to take a few runs and learn how to drive it especially since you don't want to run DR's it's time to save up for that 12 bolt or 9inch

vwdave

I think thats where we differ. If the rear is squatting and the front is lifting, you are changing the center of gravity towards the rear of the car. That weight is not getting there because I am thinking the rear shocks/springs are too stiff.

And I know how to drive that car. I've owned it for 5 years and I have only been beaten off the line by a similar car one time. I know how to feather the gas, but I am still burning tires at part throttle and slowly pushing down. Its not until mid-top of second gear where till it grabs. Its not driver error, its a poor rear suspension setup.

ss86

iTrader: (1)

If you want to go the drag route, remove the front sway bar, light spring rates all around, and 90/10 shocks.

Figuring out the optimum placement of your rear control arms for the instant center should help stop spinning signifigantly. I would aim for a little over 100% antisquat so you get the jacking affect that pushes the tires into the ground. Don't go too far over 100% or you will make your problems worse, you'll most likely hook extremely hard only to have the excess jacking effect take force off the tires and make you spin out more. That's not my experience, but I've heard it said many times. And yes, for traction, a rear end that rises (over 100% AS) is better than one that squats (under 100% AS) in most cases.

vwdave

Most of my rearend isnt adjustable. Doesnt someone make a rearend coilover conversion kit?

Anyways, I do have Spohn LCA Relocation brackets. Car is not lowered. Currently it is set in the bottom set of bolts. Would it be better for it to be moved up 1 bolt hole? The way I see it, is it cannot hurt.

IHI

iTrader: (1)

QA1 makes a Stocker Star AL shock $140/ea for our cars that will help dramatically over what your running now, these are about the best your gonna get for a bolt on shock until you start fabbing and install regular coil over shocks back there, but they are'nt really needed as stock set-up is plenty good.

Keep the LCA in the bottom hole of the relocation bracket.

Weight transfer is good, but planting the tire is a result of anti squat, since the car will stay level or actually rise on the hit it's driving the tires into the ground, with just standard weight transfer like your talking about it's putting more of the energy into the chasis instead of the tire. I'm currently dealing with chasis/tire problems and going through this, too much anti squat for my tires/combination and am going back to a stock length torque arm so the chasis will take more energy and relieve the tires a bit....there is such thing as too much of a good thing

Pic below tell the tale of weight transfer and anti squat:

weight transfer:


anti squat-notice how the rear end is actually separating from the body instead of the body coming down on the rear end

BMmonteSS

Thats a really good before and after shot of how anti-squat works. I know it sounds backwards but it's true, if your body is slightly seperating you have your anti-squat about right. Also notice in the second pic above, the front wheels aren't touching. He's got 100% weight transfer without the squating.

If your still not believing, move your lower a-arms up to the stock position and try launching it again, I guarantee you won't improve your 60'.

Dewey316

Actualy, moving to the center, or top hole might help. He has indicated he was using the lowest hole in the relocation brackets, which means he probably has some very big AS, probably too much.

VW -- are you hooking for a fraction of a second, then abotu 20ft out of the hole, breaking traction?

vwdave

Actually.....It does something like that.

Dewey316

That is what happens when you have too much rear anti-squate. I would move the LCA's up to the middle hole. Stock may even be better, you will need to look at how the LCA's sit in each position.
(a pretty small angle on the LCA's, they should be fairly close to level, with the axel side, just slightly lower.)

DeanE

Dewey is correct in my opinion.

What happens when you use relocation brackets incorrectly is you will dramatically raise your instant center for weight transfer. The instant center is what determines if the weight transfers directly back or it will rotate up and over then down on the rear wheels.

On initial traction off the line you are getting enough grip to raise the front and thus pivot wheight up and over then down onto the rear tires for a second. HOWEVER, once the nose starts to drop and the car continues in a forward motion the nose weight is now equal or under the front to rear instant center and the rear tires are not loading as much under forward momentum. Weight is often passing under the instant center from front to rear at this point and the tires will spin.

Raise the rear of the LCA's mounting point as high as you can without getting wheelhop trying to keep them as level to the ground as possible under forward acceleration even if they slightly invert under launch (without wheelhop that is). You must remember that when the nose of the car does lift the CG (Center of Gravity) is lifting in sequence and even the IC (Instantanious Center) will lift slightly and then drop. Consequently, rear squat will conteract the IC lift and it will remain close to the same hieght off the ground whether the nose is in the air or not.

The better the grip of the tires and the higher the HP of the motor the longer you can carry the front wheels off the ground- THUS the higher the IC can be keeping the nose weight rotated up over and onto the rear tires.

BMmonteSS

A little background info to organize my thoughts:

It's my understanding that you calculate your IC by drawing a line from the lower control arm to where it intersects the torque arm or a line drawn out from the torque arm. Which wouldn't raise on a torque arm car, just move forward and aft as you changed the lower control arm angle. If IC is at the center of gravity, you have 100% anit-squat. If its further forward, your lifting on the front of the car, which would tend to make the rear suspension compress or squat (think how the car would react if you lifted on the car at the IC). The oposite happens when it's behind the CG.

By having more or less than 100% anti-squat your effectivly using the forward motion of the rear axle to either drive the axle into the pavement or into the body of the car. Thats why greater than 100% AS is desired, you use some of the forward motion that would normally go up in tire smoke to help plant the tires.

It would seem that decreasing anti-squat wouldn't help traction, but just transfer more of the axle force into moving the car forward instead of planting the tires. I have heard of guys fully extending the shocks and that would cause tire spin after hooking well off the line. I can't imagine having too much AS with a torque arm setup, I have a factory 4 link setup that has both the upper links raised and the lower links lowered. It has alot more AS than possible with a torque arm setup, my car only barely seperates the body on launch. It pulls 1.9* 60's on street tires.

I would appreciate CONSTRUCTIVE criticism of my theory. (Key word is constructive dean)

DeanE

Here's a few good graphs on UE's website showing how IC is configured. Not the front to rear distance of the IC is solely based on torque arm length.

IC is the imaginary point that the chassis weight will pivot on front to rear. Just as the IC laterally is the imaginary point as which the tires pivot on. The Roll Center (RC) is what a chassis will pivots on laterally though., the IC is what the tires pivot on laterally as if they were linked to the IC with a solid link- but we are not concerned with lateral IC's here, just front to rear IC and how it affects both squat and weight transfer.

Too much of one or the other can and generally will have ill affects. You need to balance the weight transfer and anti squat based on your particular vehicle weight, grip, and HP.

Here's those UE charts showing some IC examples based on the lower LCA position. Now if you were to lower the rear of the LCA's you can see how they would raise the IC higher at the TQarm length intersection.
http://www.unbalancedengineering.com/Camaro/TA/

ps- I don't start crap unless someone else does. You happen to be pushing it with your attitude towards me- keep it up and I will no longer help.

BMmonteSS

Ok that link clears things up. I forgot about drawing the line from the rear contact patch through the moment center (intersecting points) The authors of that link seem to agree with me that the more anti-squat the better, only down side being axle hop under braking. They don't go into specifics of why this is.

Dean, I'll admit I did make a comment about your attitude in a earlier post, but I don't think it warranted your post in the last thread I posted to. Keep the tech coming, and we'll both leave the attitude at the track.

Dewey316

But remeber, unbalanced is a road racing builder, he is dialing in that much antisquit, for corner exit. Not drag race launches, on street tires.

There is no arguement to make. If you have too much AS, and not quite enough power (as Dean mentioned) to keep the weight pulled back. You will unload the tires after the initial launch. Theory doesn't override experiance. Rember, the rate of acceleration can also drop after the initaly launch, which will cause the oposite. Even if the car is accelerating, if the rate of accell slows, the suspension will act diffrently.

DeanE

Thats because the DeCoupled TQarm they are selling is designed for road course use where you want the car to remain a level as possible under changing conditions on corner entrances, through and exit as the power and braking changes are made.

Chassis movement can and will cause loss of "lateral" traction.

I actually have my car setup to promote squat on the rear outside tire and maintain about level on the rear inside to promote roll understeer (this is where the rear axle will steer inward into the direction of the corner as a result of geometry changes) Since the TQarm is centered on the rear suspension laterally the TQ arm does not result in hardly any squat in compared to the inner and outer LCA movements. Cars will generally lift in the rear under hard braking so the squat counter acts this and keeps things more parallel.

Its all about how you set it up. This is why anything you buy should have the most adjustment provisions you can get and then learn how to use them to your advantage in "your perticular application".

John, you beat me to the answer- BY THE WAY_ is that a picture of my car in your avatar thingy? It sure in heck looks like it.

BMmonteSS

I see how your using the lower control arms to balance rear roll steer to your liking, but this is a compromise with any given amount of AS that you would try to use. Of course under braking you want as little AS as possible, but this is traying away from topic of how less AS would increase traction in a pure excelleration condition.

I'm digging through corner carvers trying to find a good discription as to why AS does what it does. Here's another good example of how to calculate AS on a torque arm setup.

http://corner-carvers.com/forums/sho...ight=antisquat


Edit:
Here's another good thread, that sums it pretty good.

http://www.corner-carvers.com/forums...ght=anti+squat

The key phrase I cought is that AS increases traction as long as there is a change in acceleration, which is probably why your loose traction 20 feet out. You quit increasing the rate of acceleration and sustain a steady amount of acceleration, hence the wheel spin. I don't think decreasing the AS will prevent this. I'll comment later when I get some time.

Dewey316

I don't know that either c-c or frrax will have that info, as most of them are not concerned with a drag style launch. Dean's explanation erlier, is spot on, as to why it unloads.

DeanE

Forget calculating anything. Put the adjustment provisions on your car and tinker with them in your perticular application based on what parts your car has (that other peoples car's may and generally do differ from)

In VWDaves case above we have given a very reasonable senerio as to why he gets traction off the line and then goes into wheelsopin with his particular application. He needs to try and reduce his antisquat from what he has now to a slightly lower setting and then test the results of that change- if it works in his favor, then keep going until it hurts, then back it up.

DeanE

The thing to remember most when constantly adding to a chassis in the way of modifications is that with every adition of a new part, it can alter some of the settings of the pre-added parts so you will generally have to bo back and reset a parts setup to fit the liking of a new part added to make the car faster. Often by not doing this can result in one step forward and two stepos back.

A simple change in going from a BFG drag radial to a Mickey Thompsen drag tire can alone cause you to change geometry settings based on different grip and how the car raises more or less than before on the other brand.

Think how many times in life you have heard someone say that they bought some new part and were not happy with the results of it so they went back to what they were running. At least half those times it is because that person did not make to proper changes to everything else so that part will actually render gains- it generally is lake of knowledge on what to adjust and why those adjustments are there.

BMmonteSS

I guess the part of the equation I don't quite get is that if anti-squat will take your traction from say a 9 off line then drop to 7 20 feet out, how can reducing anti-squat and reducing initial traction to a 7 going to help overall traction?

Anti-squat helps traction under excelleration, thats proven. The guys on CC wouldn't be finding a way around all the negative benefits (roll steer, brake hop) if it wasn't worth having as much as possible.

Of course experimenting is the only way to prove any of this theory. I know from my experience that it's pretty dang hard to get too much anti-squat. I'm in the 200% range, and it works for my car, it might not on your car. I just like to know the WHY behind the HOW.

vwdave

What I am getting out of it is that it moves the CoG or Weight transfer forward and off the tires. Mix that with 311lb-ft of torque, 3.42 Posi and 3.06 first gear and tire smoke occurs.

BMmonteSS

I believe the best way to think of AS as a lever arm, that moves the CG around. More AS moves the CG back further and quicker, but is harder to keep the CG there without lots of power. Less AS will result in less weight transfer, but will be much smoother about the weight that does transfer, possibly keeping you from spinning the tires once your underway.

This sound right guys?

IHI

iTrader: (1)

Think what you meant is less anit squat results in more weight transfer....weight transfer being defines as the back of the car squatting down and front end raising up.

More anti squat = less weight transfer
More weight transfer = less anti squat

Trick is finding that happy medium with the combination.

7plagues

iTrader: (1)

my car doesnt want to really smokem, if i punch it from 10mph and on. i get a good chirp out of 2nd and a little chirp out of third. Im wondering if its because i have v6 springs?

DeanE

I don't know what else to say to explain this any better than I have already other than to say I think you are still missing the explaination.

You have to look at the IC as a teeter-totter point. The high and further back it is the more its going to take to hold the back section of the teeter-totter on the ground because the weight on the front has much more leverage to fall back down to the ground and unload the rear after the initial launch bite. Dewey touched on this already as to how the car looses torque to hold the nose up and weight the rear as the car accelerates. Your car is rocking back and then rocking forward without the power or grip to hold it up over the IC you have- regardless of your antisquat. Anti squat can be adjusted with spring rates and the rock back forward can be slowed (not always eliminated, but at the very least slowed) with the proper shock valving.

I hope you get this now because I have nothing else to explain it without looking at a book for maybe a better explaination. You'll have to get out some popcicle sticks and play with them so you get a better understanding on how the tetter-totter works based on forward momentum push and the drain with acceletration push.

Sorry, but I can't add to this subject any more clearer than I have.
No offence, but you are just not getting it.

Dewey316

Yes and no, under exceleration...no. Under a rising rate of excelleration yes.

You also have to put the subsequent effects into play. For every action, there is an equal and opposite reaction. It is the reaction in this case (and a bit of gravity), that causes it to unload. Same reason you can have a car that understeers into a corner, oversteer mid corner, and understeer on exit, without changing power, it has to do with how the suspension reacts to all the other forces, that are not being taken into account when you are only looking at one piece of the puzzle.

vwdave

I am getting it. Actually, I understood it before your condesending(sp) post jyst now.

Dewey316

I don't think he was talking about you.

vwdave

He didnt quote anyone, so I donno.

vwdave

I moved the LCA angle. Seems to make traction problems worse. I could start cooking the tires in first and hold it that way till 3rd gear and 50mph. So, I am going to place them back down and mount two batterys in the trunk. Not to mention I am going to make a new piece of wood to go over the trunk to cover everything up again.

RWB____s

Its seems all this depends on the the static weight distribtution of the vehicle. Each car suspension geometry will have to be adjusted according to the static weight % in front, over or behind the rear tires.
So each car will have to be adjusted according to that particuler vehicles merits . what size/length/type torque arm or LCA adjustment will be different on each car according to each type of setup. Suspensions setup, trans type, launch method, driving skill
all comes into play. What works on one car may not work on another. Its called track and seat time guys. get those wrenches and E.T. clocks ready for some dialing in!

vwdave

I am putting 2 batterys in the back and going to make a cover to coverup the batterys.

Project

cover up or secure? I had a buddy that had his arm broken by a subwoofer after getting into a wreck at 55mph...it was loose (3rd gen to btw)

rx7speed

I've seen quite a few cars that when launch push the rear end up. when the car squats in the rear it isn't pushing the tires into the ground instead it's just pushing the body into the tires

kinda like pushing on a piece of foam vs pushing a piece of hard rubber into your hand
the foam is just going to give and not really put any pressure into your hand. the rubber on the other hand when you push on it from the top your hand is going to feel that pressure.

squat doesn't help it doens't push the tires into the ground harder.


EDIT: ok so I read further and you guys already covered that but oh well I tried

BMmonteSS

huh, interesting and yes that is a smirk on my face.