IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: Steve Wood on July 09 2019, 12:12:31 PM
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In the old days of four links, there was an opinion floating around that suggested that the lower control arms should be close to parallel to the ground and the upper bars should handle most of the adjustment.
In those days, there was not much available for G bodies. Chuck made some drops for the rear of the lower control arms but they did not seem to take off. I have a pair of them and on my GN, the rear end would rise up like a Mopar Super Stocker from the 'sixties and it would hook really well for a few feet and then it would come back down and unload. My GN is lowered an inch with Eibach springs on both ends and it may be that this caused the instant center to be too far back and too high above the anti squat line. I never tried them on my son's T top although I have been thinking about it for a few years :rofl: :rofl: :rofl:
Later Kevin Slaby came along with some drops for the front of the uppers. I have no experience with them.
I see there are quite a few options out there today for drops with coil overs, and such.
Now, back to my question. Is there any current opinion on the advisability of keeping the lowers close to parallel to the ground and using the uppers to establish the desired instant center, or does it really matter as long as it works and does not create instability when you stand on the brakes?
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Actually I just started with the Mazda rear suspension(Stock Mustang set up). Bottom adjustable bars are parallel to the ground. Really haven't tested it yet because we are working on the launching of the car. Like make the damm brakes hold the car on the starting line. Oh the car does launch straight now with an anti roll bar.
As far as the Buick, Russ used adjustable uppers and lowers. NOW IF YOUR GOIN TO KINDA PUSH THE CAR YOU MUST BRACE THE REAR CROSS MEMBER. IT WILL BEND !!. She also has double adjustable front an rear shocks. Now the fun begins. Lots of trail and error. Sorry but I don't know what goes threw Russ's mind "tuning" the suspension. We had a lot of hooking really well for a few feet and then it would come back down and unload then take off again.. Or shake the tires. Ring an pinions LOVE that :icon_redface: $$$$$$. This is all I know.. It's Russ's job now. I will poke around the next time she races.
so all I have is a lot of bla bla bla bla in a nut shell. You can have all the power in the world BUT ya have to get it to stick! I can't imagine what a 1.30 60' feels like :chin:
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I figured Jeremy would come straighten me out :D He's pretty wise for a kid.
I guess I will get out my copy of Door Slammers and see if he talks about it. I don't remember if that was addressed or not.
I started thinking about it yesterday after seeing this on Summit [size=78%]https://www.summitracing.com/parts/bmr-cck007h (https://www.summitracing.com/parts/bmr-cck007h)[/size]
Lots of adjustment holes on the bottom.
The pit of my stomach gets a lot deeper on a good 1.6 short time. I no longer want to go any quicker...mayb e not even with a bit of seat time. I start wondering about what I am going to hit if it does not go straight. :rock:
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I started thinking about it yesterday after seeing this on Summit [size=78%]https://www.summitracing.com/parts/bmr-cck007h (https://www.summitracing.com/parts/bmr-cck007h)[/size]
Lots of adjustment holes on the bottom.
The pit of my stomach gets a lot deeper on a good 1.6 short time. I no longer want to go any quicker...mayb e not even with a bit of seat time. I start wondering about what I am going to hit if it does not go straight. :rock:
we are still in the stock location for the shocks.
Funny the Mazda on the street feels like a 1.3 60'. Then go to the track an do MAYBE a high 1.5 pushin threw the lights :icon_redface: Butt dyno doesn't work good any more. :tongue
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:rofl: My butt dyno has let me down untold times in the past 60 years and more. One thing is for sure, if you cannot hold it on the line, you are wasting everyone's time. Sometimes, if you can hold it on the line, you may need a better converter. I had a 9/11 that would easily flash to 4000 rpm but it would still be slipping 30% at the line. Fortunately, it finally broke a sprag or something and I was freed from that.
I have always been interested in theory, but, I also noticed some of my smartest friends were the slowest of the bunch if they actually went to the track.
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Now, back to my question. Is there any current opinion on the advisability of keeping the lowers close to parallel to the ground and using the uppers to establish the desired instant center, or does it really matter as long as it works and does not create instability when you stand on the brakes?
I'll stick my nose in here.
If you cannot adjust the bottom bars on a 4 link, you do not have full adjustment. Typically, 4 links are installed w/one or two of the bottom's holes below the bottom or frame level and about 2 holes above. You then have adjustment for a wide range of power.
Almost everyone starts with the bottom bars in line w/the bottom/frame of the car. The driver side bottom sets the diff in the wheel well. The pass side bottom squares the diff. The pass side upper sets the pinion angle. The driver side upper corrects body 'twist'. I have never been around a 4 link car using a sway bar.
Instant center (oem) on an A body is usually around the frt bumper to the bottom of the radiator support. G body IC is usually around 1 1/2 ft in frt of the bumper at bumper level. Most start a 4 link w/IC at just below the drivers butt.
To answer your original question, lowering the IC below the body keeps the frt down on high powered cars. IMO, an IC as high as the drivers shoulders can bring a 12.0 car high enough off the track to cost time. Inability to carry the frt is hard on parts.
All that said, I do not like a full competition 4 link on the street. They are overkill on slower cars and not optimal on high end fast cars.
If this picture posts, it is a 1.40 60 ft. The white car went 8 competition rounds in Pro at Eddyville this last weekend. A balanced, dedicated race car w/ladder bars.
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My original question was if there was a reason that so many try to maintain the lower bar parallel to the ground while doing the bulk of the adjustment with the upper bar.
One note, you do have experience with a sway bar on a four link assuming you still have one on your Buick. :D
One of the problems with the triangulated four link used by the factory is the short upper arm which is primarily used for packaging purposes . Of course, the triangulated design allows the manufacturer to avoid a wishbone, or some other design that keeps the axle from shifting sideways. The lack of mounting holes which remove the possibility of "tuning" the IC without some modifications is a pain in the neck. I suspect many don't understand it is a four link for this reason.
]I had a file of IC locations compiled from various buicks that I had played with over the years that I plotted with the Performance Trends software. I apparently lost it on some hard drive I replaced as it has been missing in action since I was running Vista on some machine. Dumb is as dumb does
On cars with no adjustments, spring ride heights and tire size throw IC location around quite a bit. I have seen it ten ft in front of a car, but, I suspect your estimate of 1.5' in front of the bumper is pretty good on average.
I notice that you seem to think that certain short times are good for a G body, while others seem to think they are slow. I suspect the difference is what role power plays. One can take a 400 hp Buick and get a 1.6 short time, but give it 700 hp and it may pull a 1.49 or so. It takes power to accelerate the brick.
Grumpy's daughter is trying to push her stock block, basically stock bodied car into the EIGHTS spraying alcohol. She is running a 200 R4 and a stock 8.5 GM rear axle. Now we all know that a stock block cannot make 1200 hp and that a 200 R4 and a stock 8.5 rear axle cannot run 8's, don't we?
There are several others knocking on the door as well. She drives her car on the street when she feels like it.This hobby is not nearly as cut and dried as many would have us believe. :cheers:
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I think the lower bar parallel to the ground is done because it is easy to attain with the non adjustable lower and that I what these g body(and a body) cars came with. I never thought much more about it than to get it there then work with the tire pressures. With all the adjustable stuff out there now all kinds of insanity can commence. As pointed out in the 60' post different tires have different needs. One of the reasons I like the m&h bias ply is it can be brought back when it spins or that was my view on the street when we would gather for late night activities.
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My original question was if there was a reason that so many try to maintain the lower bar parallel to the ground while doing the bulk of the adjustment with the upper bar.
The vast majority of cars w/4 link, ladder bars, torque arm all stay parallel with the body. Most need a shorter IC and nothing more. 4 links came about for 4 spd cars w/rpm and no real torque curve. I had one in '72. I have seen a number of really short, really high instant center 4 spd cars. A 4 link will react quicker than almost anything else.
One note, you do have experience with a sway bar on a four link assuming you still have one on your Buick. :D
I do.
One of the problems with the triangulated four link used by the factory is the short upper arm which is primarily used for packaging purposes . Of course, the triangulated design allows the manufacturer to avoid a wishbone, or some other design that keeps the axle from shifting sideways. The lack of mounting holes which remove the possibility of "tuning" the IC without some modifications is a pain in the neck. I suspect many don't understand it is a four link for this reason.
They have a number of advantages for street cars.
]I had a file of IC locations compiled from various buicks that I had played with over the years that I plotted with the Performance Trends software. I apparently lost it on some hard drive I replaced as it has been missing in action since I was running Vista on some machine. Dumb is as dumb does
On cars with no adjustments, spring ride heights and tire size throw IC location around quite a bit. I have seen it ten ft in front of a car, but, I suspect your estimate of 1.5' in front of the bumper is pretty good on average.
I notice that you seem to think that certain short times are good for a G body, while others seem to think they are slow. I suspect the difference is what role power plays. One can take a 400 hp Buick and get a 1.6 short time, but give it 700 hp and it may pull a 1.49 or so. It takes power to accelerate the brick.
I think you understand that perfectly. With Tim's car, the numbers match. ET, mph and 60' all match. IMO, the proof of that, when it got slightly quicker et the mph dropped slightly. He is using nearly all the power he makes. Quicker 60's will take more power. I would guess he is about the easy limit of his rear suspension.
Grumpy's daughter is trying to push her stock block, basically stock bodied car into the EIGHTS spraying alcohol. She is running a 200 R4 and a stock 8.5 GM rear axle. Now we all know that a stock block cannot make 1200 hp and that a 200 R4 and a stock 8.5 rear axle cannot run 8's, don't we?
OMG. Hard for me to fathom. What kind of rear suspension?
There are several others knocking on the door as well. She drives her car on the street when she feels like it. This hobby is not nearly as cut and dried as many would have us believe.[size=78%] :cheers:
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Yeah, evidently if is not as cut and dried as I believed.
Look, you have a good grip on this. Anything normal or reasonable will push straight ahead. Abnormal, unreasonable will not run 4 link.
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You boiled it down pretty well, Texas.
A rear end tries to rotate itself two ways. It tries to flip over backwards and the passenger side tries to flip laterally. Once attached to the body, the rear end will push the body toward the instant center using rotational force. Even leaf spring cars. The most efficient direction for oem is straight forward.
A good example of lateral rotation is top fuel. You cannot get the rear tires close enough.
I need to so more seen and less heard from.
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As Dan (Grumpy) said some where, she has dual adjustable shocks...but there is nothing easy about it. Her husband is one of the smartest guys out there and builds a lot of her stuff. He is a test and tune kind of guy. He leaves no stone unturned. He keeps to himself and does not spend all day on social media bragging about how good he is. Unusual in these day, in my opinion. I don't know what adjustments he has built into the rear end, but I guarantee he has tested every permutation that he could come up with. He's old school with brains. Technology does not bother him.
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My thoughts are with good 26-28" tires a stock suspension turbo Buick should go 1.5x 60fts before you start having issues that need to be corrected by changing angles, and go to adjustable shocks.
To me I like the adjustment point on the uppers on the chassis side, makes more sense than doing on the housing side like some of those goof anti-hop, lift bars.
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Rich, I used the Performance Trends 4 link software to plot the potential IC locations. It really helps if you are dealing with adjustable mounting points. If you are not, you can draw it out yourself without much effort,.
As you can see from some of their charts, with adjustable four link set ups, you might have 96 potential points. Problem is that 80% of them might not make an improvement so testing is required if you are serious about it.
http://www.performancetrends.com/4link.htm (http://www.performancetrends.com/4link.htm)
Now Kevin Slaby sells some G body upper front mounts that drop the front a bit. I don't know if Jason installed these are not. Kevin has some good articles on suspensions which don't take a masters degree to read :D
http://www.baselinesuspensions.com/ (http://www.baselinesuspensions.com/)
I notice that some people think all they need to do is position the IC behind the center of gravity and on the anti-squat line and that is it.
The serious racers might start there as a good theoretical starting point and then start testing points behind the CG and above or below the line and know that different track conditions can respond better with another setting...thos e guys might become pros someday :D
When the IC is out in front of the CG, it will aid in lifting the front end and set the rear end down...this could be desirable at times if the track is super sticky, but it is taking "plant" of the rear tires. I am always amazed at how well G bodies actually work with a factory suspension that is so poor with regard to weight transfer.
Dialing in shocks may be harder than setting the desired IC. you want to keep the weight on the tires to avoid unloading them and suffering tire spin somewhere off the line.
Guys like me do better from a 50 mph roll :rofl: [size=78%] [/size]
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I have thought that way for a long time but I was curious after seeing some of the lower drops sold with the coil over brackets. Glad to hear your input on the matter...mainl y because you didn't tell me I was wrong. the mirror takes care of that :rofl: :rofl: :rofl: :rofl:
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When you throw in a coil over and double adjustable shock, then the adjustable links, man can a guy who likes to change things can get into trouble. Especially if he isn't taking notes on what works and what doesn't. This isn't a sat afternoon activity. Could take weeks or months depending on your getting after it. Just one change can throw the whole thing off and if you cant go back to what worked you get to start over. Kinda like when you are bleeding brakes and you let the reservoir go dry.
It takes plenty of persistence.
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When you throw in a coil over and double adjustable shock, then the adjustable links, man can a guy who likes to change things can get into trouble. Especially if he isn't taking notes on what works and what doesn't. This isn't a sat afternoon activity. Could take weeks or months depending on your getting after it. Just one change can throw the whole thing off and if you cant go back to what worked you get to start over. Kinda like when you are bleeding brakes and you let the reservoir go dry.
It takes plenty of persistence.
WINNER WINNER CHICKEN DINNER :rock:
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I'm the guy with the broken parts, trying to be a racer. Hope the sis in law visit is going well.
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Yep, Rich! You got it perfectly :) It's not PnP
Two identical cars usually are not...
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Jeremy, that reminded me that I used to have a set of those Lakewood anti-hop bars that raised the rear of the upper bars. I never installed them because I figured they were an invitation to break the ears off the diff. I don't know what I did with them...might still be out in the shop some place.
I scanned a bunch of articles and many said, set the lowers parallel to the ground--but none said why LOL
If the center of gravity is somewhere in the range of 54-55% (front end bias) of the wheel base, and the IC is at the front bumper, or further forward, one is not going to get chassis separation. That's the reason I have always been interested in pulling the IC back. I guess if one does not make enuf power to blow the tires away easily, it is not that important but it is one of the things that has always nagged at the back of my mind.
with a 108" wheel base, that puts the cg about 60" behind the front hubs so the IC has to come way back to achieve chassis separation. I may have a different opinion in the morning LOL
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What do you plan for tires? Could make a difference. I think the lower arm parallel to the ground doesn't let that arm get leverage like it does when at an angle. This is why the bushings are a big deal and can be made better with the stiffer material in the bushings so the arm stays and doesn't move all over the place. I think this is why you see those cars with wheel hop that could be remedied with some new bushings.
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tire height does make a difference as does spring height. This is more a theoretical discussion arising from someone wanting to borrow my set of drops and I thought drops were probably not what he needed. Instead I voted for lowering the front of the rears.
Without looking at the car and taking measurements, it is flying blind and I don't like doing that.
On my cars:
I have run 275's/60's for years. But, last year, I went back to a 26" set of street tires on my GN as the front tires were 20 years old LOL
that car has lowering springs all the way around and sits two inches lower than the other car that has the 28" DRs on it.
The lower car has the Lower control arms almost parallel to the ground with the front end just a hair higher than the back.
The car that is about 2" taller, has the back of the lower arms quite a bit lower than the front end which means it has the IC pulled back quite a bit in comparison to the lower sitting car.
I need to get some fresh gas in the challenger and get it off the rack. Then I can take some measurements that are accurate because my lift is adjusted level and my floor is not so level.
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With the stock stuff, I think the "cowboy rake" works well. If you look back at Lawrence Conley and his "black" in the early days he had a real tall front tire and the thing leaned back with some real wide tires on he back hanging out if the wheel wells.
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Interesting discussion. Does anyone know what kind of a 60ft one can achieve with just a GNX suspension?
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Depends on the tire. That gatorback was a slippery unit in the eighties. One of the locals here had a gnx when new and had it into the twelves in short order but he had some sticky tires.
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seems like street cars go for the bars parallel to the ground to minimize roll steer and to minimize binding...
It's been a while since I saw a GNX launch but I seem to recall they lifted the rear end a bit on launch.
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It's been a while since I saw a GNX launch
1:54
Gn.....0:28
https://www.youtube.com/watch?v=x0p1805OgmE&feature=related
Pure stock, 60' was only about 0.1 sec difference. GNX was over 1 full sec quicker to 60 mph.
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I'm the guy with the broken parts, trying to be a racer.
ya wanna play an just go a little quicker.. Oh wait. I can do this. A little quicker again.. then ya have a little sensation on your bottom lip. It's a fish hook .. Your doomed :rofl: Parts break. Or maybe a weak link. One other thing.. From the 1.3s and faster poly bushings don't cut it. Russ was changing them every other race. Make sure you check the car over good before ya go racing. Great thread. :rock:
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yep...that's the road to hell! :rock:
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Dan, did Russ go Del-a-lum bushings? Or is there something newer/better?
I see that keeping the lower arm near parallel to the pavement helps reduce wheel hop along with good bushings as mentioned by Rich and Dan'
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I’d imagine it’s rod ended....
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yep, but on both ends or just the front? thinking about the diff ears. I think I have seen solid type ends for the ears, but, I may be dreaming
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here are some old articles but they are pretty simple and explain some of the concepts
https://www.hotrod.com/articles/traction-tips-street-strip-suspensions/
https://www.onallcylinders.com/2019/01/02/ask-away-with-jeff-smith-eliminating-wheel-hop-in-a-60s-era-chevelle/
https://www.onedirt.com/tech/chassis-suspension/finding-your-center-finding-your-front-and-rear-roll-center/
https://www.racingjunk.com/forums/showthread.php?t=17130
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Yup - TRZ has them. https://www.trzmotorsports.com/product/spherical-housing-bearings-2/
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Thanks, Jeremy :icon_lol: Yep, that is what I saw some place but I recall wondering if it was what I thought it was LOL
I have always been interested in suspension theory but I find it confusing because physics is basically physics. Yet it seems to me that it is not always clear cut as we have some very smart and experienced people that don't agree on how to "do it".
It seems to me that when you are getting into the Nines, it's time for solid "bushings" (rod ends) because the forces applied are so great that conventional set ups will not provide the consistency required. On the other hand, solids probably bind a lot in normal driving and the life expectancy is probably terrible if one is driving on the street. Perhaps the ones like Jeremy linked above allow more linear movement and prevent binding but they probably wear quickly in normal use. Maybe...
I'm running adjustable uppers that Chuck Leeper made with rod ends on the front but conventional bushings on the diff ears on my GN. I have not checked them in awhile but they seemed to be doing okay. Of course, they probably only have 15k on them as I don't drive it all that often in recent years. Pretty sure the diff bushings are over due to be replaced, tho. I am pretty sure I have some replacements but I am not sure which is which at the moment (or any moment :D ) They were the harder durometer ones that GM used on the 1LE handling package as I recall.
After reading a few hundred articles and my copy of Door Slammers again, I have come to the conclusion I should have asked you and saved myself a lot of time!
It seems to me, that a G Body that is going to be driven would probably be well served by parallel to the pavement lowers, or near to it, and uppers with the front end being adjustable downward to pull the I.C. back behind the CG a bit. The I.C. should probably be slightly above the neutral or anti-squat line to provide a little chassis separation.
I freely admit that in a month, I might have a different opinion!
One of these would appear to me to be a good way to approach the upper adjustment. [size=78%]http://www.baselinesuspensions.com/kits/chevy.htm (http://www.baselinesuspensions.com/kits/chevy.htm)[/size] I don't know if anyone else offers similar but I would think there should be someone doing so.
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The guys I see struggle the most are the ones with suspension parts from 10 different places and they just bolt it on thinking everything will just work together.
I thought ahead enough to all of my suspension parts from one chassis shop. I can call them and get baseline settings for angles and shock settings. The only thing I bought else where was the sway bar, and that was because I didn’t want to wait 6 weeks for it.
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Well almost what Steve said :icon_lol: 9.7s with 1.40 short times was our awakening with poly bushings. Russ did them quite a few times. Her car could launch in rain. Suddenly car was all over the place. At that time she had poly bushing and UPR's adjustable upper control arms and stock shocks. Very simple set up. BUT if your racing all the time go with the "cool guy " parts. All her suspension now is TRZ's with Viking dual adjustable shocks.
... As you guys know I am not crazy about all the "cool guy" stuff. BIG learning curves. I am old an don't do "learning" anymore. Russ is the thinker. ummm WILD thinker! I did get a stock location intercooler back in. Front mount is GONE !
One cool guy part that helped a lot was a Fast type system. Everyone makes em now.
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The guys I see struggle the most are the ones with suspension parts from 10 different places and they just bolt it on thinking everything will just work together.
I thought ahead enough to all of my suspension parts from one chassis shop. I can call them and get baseline settings for angles and shock settings. The only thing I bought else where was the sway bar, and that was because I didn’t want to wait 6 weeks for it.
I agree on getting stuff from one place. The shocks are a new game you will have to conquer. Track conditions change to.
So are ya getting closer to the running/driving car ? :rock:
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It's kinda funny. Everything that I read agrees with Dan and Jeremy. They all say getting the instant center location is important, but, air pressure and shock settings are what separate the men from boys.... and that takes lotsa testing.
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Dan - I haven’t seen the car in two weeks. It’s close to running but lots of sorting out before it goes down the track.
Steve - it’s be funny to plot out and see what one of those donk lift kits does to the cg/ic
Obliviously as power goes up the window of what works and what doesn’t shrinks.
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I started reading several articles on the subject and discovered they were talking about off road stuff. I had never thought about what happened when you put tall donks under a lift kit. I'm not sure some of those things ever intersect.
I noticed that 90-10 shocks are basically obsolete on the faster cars these days. I learned quite a few things that might not be germane, but then, my thought process is seldom germane anyway.
The quicker we go, the more binary the set up becomes. :rock:
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I air pressure and shock settings are what separate the men from boys.... and that takes lotsa testing.
It racked my brain trying to understand it. 90/10 shocks are from the old school. We spent last summer living at the track and racing trying different set ups. All sorts of weather conditions.. Mid 90's hot an humid wasn't my idea of fun. But as Russ would say ya can't have it ideal all the time.. Most guys show up in April/May then they disappear till Sep/Oct. Russ thrives on this stuff. Like Melissa they keep on coming up with more ideas. :chin: Me.... way beyond my comprehension. :O
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Dan - I haven’t seen the car in two weeks. It’s close to running but lots of sorting out before it goes down the track.
THERE IS LIFE OUT THERE BESIDES CARS :rofl: ya just pick away. :cheers:
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Dan, yesterday at 2:45, it was 105.5. At 3:15, I think it was 106.7. Suddenly, it dropped to 102, then started to come up again. Then it dropped again. I went outside and there was a big cloud over the sun. I started to read and dozed off for about 30 minutes. I looked at the thermometer and it was 86! Went out and there were big thunderheads all over the sky. Texas, it is what it wants to be
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90/10 shocks.
I have not seen an actual 90/10 shock since the early '70's. They were replaced with 3 way adjustable frt shocks by about '75. I still own a pair. From memory 60/40, 80/20 and 90/10.
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those donk lift kits does to the cg/ic
Are you referring to 'no hop' bars? If so, I will have your answers. Do they raise the upper rear mounting?
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believe he is referring to cars or trucks with 24" wheels and/or lift kits