Okay, Grumpy! Suspension question

[Steve Wood]

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 

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?

[Grumpy]

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  $$$$$$. 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 

[Steve Wood]

I figured Jeremy would come straighten me out   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[/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. 

[Grumpy]

I started thinking about it yesterday after seeing this on Summit  [size=78%]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. 

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 Butt dyno doesn't work good any more. 

[Steve Wood]

  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.

[wmsonta]

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.

[Steve Wood]

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. 
 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.

[TexasT]

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.

[wmsonta]

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. 

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%]
[/size]

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.

[wmsonta]

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.

[Steve Wood]

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.

[nocooler]

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.






 

[Steve Wood]

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


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


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


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  [size=78%] [/size]

[Steve Wood]

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 

[TexasT]

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.