InfernalVortex

iTrader: (4)

This is my 5th place out of 16 "trophy" (Novice class). Our autocross group is super cool.



I cant wait to get more seat time now. Should only get better from here because this course was way too tight in some parts that didnt suit the car at all.

SlickTrackGod

Ooohhhh (Homer Simpson Voice). Some has been saving their pennies in a jar- Thats a high quality rearend you have on order. Would like to see pics of that once you get it. Yes I would agree with having them leave off the spring pockerts if you can... and YES ask them for the bare brackets to to keep for whoever knows why- just good cheap insurance and good resale like you stated.

Sway bars are always a fine tuning thing. HOWEVER, I look at the rear end of the car entirely different then the front. The average sway bar sizes where designed with factory roll centers and factory ride height in mind. With that said, the average sway bar combo for track use generally comes in around 36mm front and 19mm rear with those aprox spring rates you have listed Brian.

Now to Hellzwings also (including still with Brian) when you lower the rear rc of the car and try to retaint he lateral leverage of the body roll with a higher spring rate- what happens is you increase the rear of the cars straight line ride stiffness. It will start to buck the car's weight fron the rear onto the front wheels over every bump...kind what I have always refered to as "porpoiseing"' Like a dolphin. now the best way to thing of this is think of it's exact reciprical+ low front spring rate and brake dive. The front spring rate is increase just enough to relieve brake dive and the front RC from diving faster with it dynamically. If you raise the front spring rates too much, the car will drive very very stiff and a lght sway bar will cause the car to still roll- even though brake dive is eliminated. You have to balance forward suspension travel with lateral suspension travel. Low rnt spring rates and a big bar wll cause brake dive, yet no body roll. The RC will dive with the chasiss squat, however, if the rear is not doing the same the roll axis canters and the outside front is overloaded and the inside rear becomes light and jacks high into the air making the car loose. The steering wheel also has alot of wandering as the suspension is traveling quite a bit and changing things like toe, camber , and caster readings from static to dynamic travels. Lessening these travels and balancing the fore/aft AND side to side rates make for a flatter smoother and easy to drive vehicle..

Now with all that said, lets go back to the rear springs vs bar. The rear spring rate always needs to be softer then front rates because of the direction the car travels as well as the lesser weight bias of the chassis. When you increase the rear rate (even on a rear engine car) the car can jack unless anti lift(or also called brake squat) is introduced into the rear upon unloading. This is done on a third gen by shorting the Tq arm length. The shorter the length, the stiffer you need rear springs not to yank the chassis downward and invert the LCA angle causing wheel hop. THis is how we basically tune a length of TQ arm to a car's weight bias as per which wheel set (front, rear, or of course a pecentage of both) will take the load of the chassis being pushed up or pulled down upon braking and acceleration forces. I am speaking of Tqarm just so everyoine understands how this also comes into play on spring rates and chassis weight variations between cars of identical make.

Lets now take the TQarm out of our heads to re-simplify things. Lets look at the main thing we need rear spring rate for- it is to hold the most load of the chassis upon acceleration. THis is when the chassis will load backwards onto the rear springs (of course the tqarm and instantaneous center comes into play-including LCA angle- but lets just say this is not an adjustable factor and we tune the chassis based on the existing arm length any one of you perticularly have). If you are getting too much chassis squat on the rear upon throttle bursts coming off a corner, then a rear spring rate increase is in order as to lessen the rear suspension travel and eliminate wheel hop (shock dampering/ mainly compression valving of the rear shocks comes into play here also. As well as throttle/brake imput traits of the driver. Smoother throttle apllications can yield less need for spring and shock damper increases.)

Submitting for now so I do not loose this novel...more in next post-

SlickTrackGod

Omce we get the rear spring rate where we need it ride quality wise to control bump travel and acceleration thrust qualities, we then match the fore aft spring qualities of the rear suspension with side to side roll qualities needed for sway bar. Just like the nose of the car, if the spring rate for a 15" high rear RC is balcne enough to control fore/aft chassis movement, the that same spring rate is "mostly" going to do the same control of fore and aft chassis movement to a RC 2" lower. HOWEVER, the side to side roll qualities of the lower RC will in fact leverage the sway bar much more...hence the need for a larger sway bar.

To take this the next step. A swaybar connects both sides of the chassis. Above I included the word "mostly". The lower leverage of the rc will in fact leverage the fore and aft just a tad bitmore, but will leverage the side to side much much greater in proportion.
The added connection of the sway bar side to side will also add in a slight increase in fore and after rate also because the one side will "help" the other side if a blunt force is applied only to the "other side" wheel on bump impact.

If you leave a sway bar size alone when lowering rear RC and just increase spring rate to control side roll, what you are doing is causing the inside spring to release and the outside spring to stay less compressed+ an overall higher dynamic RC with a car that still rolls the rear as well as jacks the rear under hard braking. You are in essense bringing back the very quality you were trying to rid the car of by lowering the rear rc static height.

Better to just try and increase rear sway bar size first. I will reiterrate that the somewhat known sorted combo for a V8 car with factory roll axis points in the varying range of ride heights is a 36 front and from 17-21mm rears- mostly averaging a 19mm. Now using that priciiple, by lowering the rear rc and keeping spring rates the same, this basic common sorted combo with a rear RC 2" lower will obviously require a higher range of rear sway bar. the *** end of the car will no longer lift the inside rear wheel as much-THUS- a larger bar will not yank the inside wheel off the ground as much as a higher rear RC will from roll axis canter.

Dean

SlickTrackGod

The last tip I will remind or educate everyone on it to always remeber that you can fine tune a particular bar even more by widening of narrowing the axle mounts of the sway bar. Use this tool...trust me Youc an get an 18 out of a 19mm, you can get a 23 out of a 24mm, etc. All by narrowing the sway bar axle mount positions along the bar length.

hellz_wings

iTrader: (2)

If you adjust this 22mm bar all the way out, it ends up being how stiff?

SlickTrackGod

Best advice I can give you is to stop worrying about hitting a certain number. You need to tune the car by feel. If the current bar you have too stiff then narrow the mounts. If that does not work and the bar is still too stiff (car unbalanced) then go to the next smaller bar availiable and move the mounts back out to OEM position and try again the tuning process.

Do the opposite if the bar is too soft. If you think you need just a tad more bar then move up in bar size and mount it more narrowed. Example+ you have a 19 with wide mount, move to a 21 with narrow mount will be more like a 20mm. If still not enough then move the mounts out to normal OEM spacing and it becomes the 21mm it is suppose to be.

I am ONLY listing numbers so as to be able to describe how to fine tune sway bar use. Forget about numbers, do it to feel.

InfernalVortex

iTrader: (4)

Dean one of these days Im going to congeal as much of what you say as I can into a car setup flowchart.

Are there any books you recommend, Dean? I get hte impression a lot of your knowledge is first hand instead of learned in a book, which means you probably have some unorthodox (and effective) solutions for things and i would imagine a lot of other guys who do what you do have their own occasionally unorthodox, yet effective tuning secrets...

But what you say makes sense, but it's really hard to pile all of it back into a cohesive "Symptom = X, Problem = Y, Solution = Z, Process = Za, Zb, Zc, repeat" type methodical approach when everything affects everything else. I know that hoping for a book demonstrating a general methodical approach is probably asking a bit much, though...

SlickTrackGod

Years ago I tried to read Fred Puns" How to make a car handle"...and could NOT make sense of a lot of it because frankly...I hate f&cking reading..lol.

Whan i used to Autox my Vette when I was 20 years old, I come out of a Karrman Ghia that I built to try and keep it low but yet not rub tires , and mainly the most important thing was to make it put up to my abusive driving. I have always been hard on cars (purposely) I just like driving hard and am lazy to slow down. I throw cars through cornersm Literally throw them. I have just learned over 3 almost 4 decades of just feeling a car with the seat of my pants and messing with things to see how they change. I am a complete backyard mechanic with absolutely no formal training or reading at all.

It all started with my father in his Corvette whuch the neighborhood idolized as a kid growing up. I'll share a little secret with everyone- the movie Little Giants with Ed Oneill (Al Bundy) plays the part of my father in a real life script , My buddy Greggory Bradford was/is an actor and wrote the movie about my oldest brother's life and his passing (the movie script was changed to a comedy and released as Little Giants, the actual title was "Some Boys Were Meant To Be Men"). Anyways, Ed Oneil drives a flashy Red Corvette and is idolized byt he town (That was my father in real life in the 60's, he was twice Calif State champ as head coach of a PeeWee division pop warner football team. Corvettes were a big impact in my life at an early age as well as racing. I then met Mark Donohue in 1973 at Riverside Raceway at the age of 7 and had model cars of him and all of the CAn Am cars. I studied Mark Donohue- one of the only persons I read about as a child, and understood he was a "driving Engineer". My father would take all us boys with him to watch Dick Guldstrand in the pits at Riverside. I was one of the only kids around let into the pit garages. That is how I was able to met Donohue. my father and Guldstrand have been friends for over 45 years (I am age 47). It has been a lifetime of tinkering with personal vehicles and just good ol plain common sense. Look at it, figure out what it does, how it moves, what load is applied. Then think when in the seat how that load transmit into motion or feeling to the driver.

I do not calculate things on paper, When I speak geometry, I literally speak it from a visual standpoint. Yoiu can NOT build a suspension with numbers, you build it through trial and error period. The best engineers in the world can not get it right on paper they need guys like me to sort thiings out in the real world.

In NASCAR, I teach my drivers what to tell me by throwing things at the car and asking them for ffeedback. If they go I like it, we keep going, if they say Holly Sh*t, we go the other way...lol A little sarcasm, but really a very serious comment. it is done by testing and trial and error. I have an uncanny ability above anyone that anyone has ever witness to be able to read a race car on a track while I am NOT in the drivers seat. I watch and I listen, I read pedal imputs, chassis attitude, and the drivers line. I know more about the car they are driving then they do. They come in and I tell them what they just felt...and they go, damn, I guess yiou are right. I follow it by " that is the kind oif stuff I need YOu to start telling me so I can fiune tune you better. I can not see their steering wheel most of the time so I can not tell effort or smoothness. I just watch the car. WEhen it comes in I adjust it from what I see.

When I drive? I never get beat- Arrogant? ....Confident. I know what I need. I am a perfectionist with my own vehicles.

hellz_wings

iTrader: (2)

Awesome story Dean. I think a balance between engineering 'on paper' mixed with real world (ie: you) tuning is what will yield the best result.

Going back to the sway bar discussion.. If a rear bar is already 24mm (as mine is), would the Strano adjustable bar be able to adjust itself to be stiffer than a stock rear 24mm bar? If so, this could work for me.

SlickTrackGod

The problem you have is the UE brackets. I have always said I do not like that UE setup. THe body side does not need to be lowered. It is why I have always suggested the Jegs unit. You have a roll center that is stuck too low with a relocation bracket setup that was more produced for the 4th gen cars with also a taller ride height then you have. If there is a way to cut that body side mount off there I would get rid of it.

THis would solve your sway bar issue needs. Otherwise. You will have to just go up in rear spring rates. From what I recall, Pablo was up about 300lb spring rates and had the rear RC as low as you. The problem you will have compared to Pablo is he was running that way on massive sticky tires that will produce the adequate lean. He was pushing hard into corners and plowing that car. He could practically go full throttle mid corner and you could here the outside front tire scrubbing where he was understeering. The only thing that helped him was the fact he had massively wide front tires and grip. He also was not subjected to long braking zoones where the rear end could jack-IE Calif Speedway coming off the high bank turn 2 @ over 130 and then diving down to 30mph into the infield chicane- that car would jack the rear end 2" I gaurantee by the end of that braking zone. from what I know Pablo has never had it up to speed like that and hard on the binders.(I mean hard like those tires should be able to handle and yank that car down from speed fast) Those 300 lb springs would jack that car-I speculate?- call it what you will, I have a strong educated assumption. Lets just say I know it would without even trying it. he would need a Tqarm probably about 8" shorter. His ride straight line would have to feel like a mac truck driving down a cobble road. Fine for lower speed stuff, but you will impact hard on high speed stuff Hellz if yous tart running spring rates that high. The car will buck you in the assz over every road imperfaction.

As for the Strano bar? I do not feel it is needed. A 24mm bar is fine for a car that has the weight bias and center of gravity range these cars have. To lower the panhard that much like you did and raise the swaybar so high would cause a loss of independent rear suspension use. The car is not heavy enough and a bar that large will start causing you wheel skipping under hard straight line braking. Why? there might be the leverage weight into corners, but there is not the rear weight on staight line driving to handle that large of a rear bar.

I had my 25mm rear bar on there from Spohn. I had progressive rear springs which made for a little softer straight line traction, I had 200lbs less up front not to roll over and lift the diagonal rear tire, and when I put extended ball joints up front I was back down to a 23mm rear bar. You should NOT be up over a 24mm rear bar on a V8 car. if you have to go that high then your rear RC is too low. If you can not get it higher, then you will have to up spring rates at a cost of rear jacking under long braking zones.

That Strano bar is fine if you are needing to set up a car from scratch and do not know what you need, but it is no different then having fully adjustable compression and rebound shocks. Once you finally get then where you want them you barely touch them anymore. I would just get a 23 or 24 mm bar onto there and play with them mount wise- and try to get that body phb off there and get that side up to stock position.

SlickTrackGod

The only paper they use is note from previous trial and error. People that now work for automotive engineering firms like Ferrari and Keoniggslegg (I always froget how to spell that- close enough) have years of cars and knowledge to sort through. They are not building anything from scratch- no one does anymore- they are taking known platforms of suspension link systems with known rc heights and doing slight alterations to them. they build a prototype and then take a year to shake it down before they finally decide on a production run.

You see these "one-off supercars" everyone seems to be bulilding now days like Lambo, Ferrari, Audi, Toyota, etc etc, you never see those car unvailed on a race curcuit. They are smoke and mirrors and are all about just impressing the general public with space ship looks and HP numbers. Most are on a quest these days just for the car with top speed- friking rediculous- who will ever us that? rich people with small penises that race eachother by bragging how much their car cost and how many hpo model # XXX 00745 LFA Shaniquenzella Marfartii ZZZ.

No paper does not work. Only for keep charts does it work.

If GM engineers were so smart back in the 80's, then why are out factory RC so terrible, why is the ackerrman so terrible, why does the roof line crack, why was the frmae cracking and the wonderbar added, getting my point? there s call paper design has tons of flaws. The paper design was just art rendering. The suspension componants are alot the same from other models of GM cars. What made these cars unique fr their day was the unibody chassis. The platform that GM ended up with they got lucky with wheelbase and track width- why do I know this?... because they then f'ed it up with the 4th gen which was heavier, taller, and handled worse. Automakers are finally 3 decades later getting things right because they can check notes of what all went wrong and was reported back to them.

SlickTrackGod

I know it's not 3rd gen, but when they can get this 5000 lb tall longbed pig to do this on paper I will be impressed. Look how this truck rotated. it also has no suspension adjusts diffferent from daily use where it can carry 4000lb payload in the bed. Here it is with about 2500lb in it of lumber. That same alignment and those ssame shock adjustments etc are this on the track- no changes.

This is one amazing vehicle I am very proud of and have engineered over the years. Ift is probably my proudest acheivement and the biggest learning tool I have ever worked with (for 25 years). It is why I am as good as I am today in feeling a car because everything n this truck is exagerated in feel. A car is easy after dealing with something like this and harnessing it. I built this truck out of necessity years ago- it just happened to preform well on a race track also. It was 100% built for work and daily street driving.
http://racetrans.com/gfx/Heavy_Chevy_Hauler.jpg


http://public.fotki.com/makofoto/201.../mvi-0195.html

It is truely amazing how fast this longbed truck rotates.

InfernalVortex

iTrader: (4)

So you're saying the 3rd gen's track width and wheelbase is what makes them salvagable?

TEDSgrad

iTrader: (4)

I believe they will come back down on wheel size and increase tire wall also!

Yeah Dean, I saved more than a penny jar! I am willing to pay a little more to ensure I don't have to use Moser anything on my car. Should ship tomorrow. Neat little pinion nut: Mark Williams Enterprises now manufactures, in house, the GM 8.875 Chevy 12-bolt car 7/8"-16 thread pinion nut and washer combination. This nut, made from 4340 material, is heat-treated and replaces the OEM style part that is hard on the pinion. Our new nut / washer combination is comprised of much stronger billet pieces that won't destroy the threads.

For rear ends, it's all in who and how it is set-up!

SlickTrackGod

Very nice Teds (brian). Moser is crap. I had to have them redo one of my axles where the rubber seal wore the so called heat treated axle.

Infernal- the 3rd gen platform is awesome when you figure its proportions of track width, wheelbase, and suspenion pick-up points (pertaining to the mount width and suspension arm lengths) when dealing with a car chassis articulating off a flat level plain. The proportion make for a very stabile platform on a skid pad.

Dont know if you ever read one of my posts where I talk about PAX indexing and angle of attack. On some autox coursed you will never be able to conpete equally against kets say a mazda miata because yiu are longer AND wider. On a slalom your car nedes to go left to right to left about 2 feet wider over all, AND has to travel half the comparison in length oast and then again that same exyra before the next cone in a staight line slalom. This make for a sharper thus slower angle of attack through the same cones as a smaller car going faster with a more staight line.