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#1056317 - 03/10/18 03:29 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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SSLance Offline
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All I can add is this... Speaking from experience, up-down and fore-aft adjustment of the center link gets very tight on these cars very quickly because of the lack of space. All Dirt track chassis builders shave the triangulation bar hump off the cross member first thing, us street car guys need that to stay in place. Tie rod to frame and sway bar arm clearance gets tight pretty quick as well.

I'm not familiar with how much higher the B Body steering arms are than on the G Body spindles, but the various bump steer correction kits available offer a huge amount of adjustment and are very simple to install and set up. I have the Baer kit on my car but almost all of the aftermarket guys have one now, UMI, Ridetech, Speedtech, etc. Wheel clearance would have to be taken into consideration but you won't have to worry about centerlink clearance issues like with all other options.


Lance
1985 Monte Carlo SS Street Car
#1056320 - 03/10/18 04:10 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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MC96 Offline
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The "bump steer correcting" centerlink is a reboxed 3rd gen camaro centerlink, we ran one on the car in my profile pic for years, yes the idler and pitman spread apart from one another. You have to cut about a half inch out of each tie rod.
All I know is it seemed to work better.
Its going to limit your steering a bit both ways? noticeably? idk.
Just "square the box" make your idler pivot to pitman grease zerk the same distance as your idler zerk to pitman shaft.

I have 2 brand new in the box if youre interested...

The Howe is nice it must be fairly new. I have a similar Allstar one in the garage, it use slugs so its a bit more adjustable. You cant fit it (and Im assuming the howe) on an F41 car though, the mount for the jounce bars gets in the way. Funny story, I was at a large racing swap meet last fall and scored this sucker for 20 bucks.
http://4raceparts.com/center-link-chevelle/
I got it home and set it on top of my allstar centerlink, its the same thing and matches perfectly , just no bends that set the center back, so I can use stand offs to play with ackerman.
I still had to cut off and drop my f41 bar mount down (also had to drop it to clear my sway bar tube, another Howe piece, with my UMI brace)
I can measure it idler stud to pitman stud and get the spacing for the center holes too if you need.

Ill make someone a deal on that Allstar centerlink too...
https://www.summitracing.com/parts/aaf-all56330


The low profile adjuster Bob
https://content.speedwaymotors.com/ProductImages/10620187_L_650f1996-915c-4cc1-bb77-67db35537a24.jpg


Im hoping we havent scared the OP off, obviously we get excited seeing this stuff.
I wont speak for everyone but the forum seems dead lately, this has been such a breath of fresh air. Everyone is on FB now, which is fine, but I sure get tired of "what bolt pattern is my car" "what can I swap in for a motor" "can I put a camaro rear in" every day. Its nice to be able to come here and have a more educated discussion.

Last edited by MC96; 03/10/18 04:11 PM.

86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
#1056321 - 03/10/18 04:27 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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I forgot to mention some things about bump steer, UB machine makes an awesome, cheap bump stud, and you can build up a kit for about half of what the other places charge. Because of how poorly they operate their business they have been unavailable for months. Oh well, Speedway and Keyser make some but they are threaded all the way and I dont like the way you adjust it, they seemed to bend easier too. A set came on a car we raced last summer.


Im thinking you can probably make enough gains on the outer end to justify not buying a centerlink. Lance seems to be pretty content with his package, for how long who knows his car is a soap opera! lol

Im not sure on B spindle geometry either but I know with a metric spindle the bump kit clears just enough with a 15" steel Basset. An aluminum wheel would be iffy as they are thicker, but those kits can be trimmed too. Asphalt guys use those spindles quite a bit and they worry about bump more, leads me to assume the studs are build around that application.

Johnson builds some awesome stuff. I thought about buying an uncompleted car from them and locating the body mount holes on it. But even after moving the suspension mounts around I couldnt really justify it. Ive got something else in mind there.

Last edited by MC96; 03/10/18 04:28 PM.

86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
#1056328 - 03/11/18 04:26 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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I'm hoping the same thing, that Justin wasn't scared off by me, us, jumping on his thread. I believe that he has to cross these bridges as he progresses through his build once he gets the frame back on the ground and tries to fix the ills of the metric chassis. Most of my info on what effect change in the metric chassis comes from the roundy- round guys. You just have to take the info and reengineer it for what we need from our cars. And like any race car that is a winner, giving out that free info to the also ran guys doesn't happen often.

When making changes to the DS909 centerlink years ago what I found was the same problems with centerlinks available from the venders for stock car parts. Limited space to make something that improves steering geometry. Their redesign worked for their application but couldn't be directly brought over to our cars without compromising something else. Their methods to improve left turns worked great for them, but turning right was not in the play book.

I tack welded inner tie rods mounts in numerous different places on a centerlink looking for something better when building the new link for the tall B spindle. In the end the inners are on the stock 12 7/8" spacing and dropped 11/16" lower on the link. At that time what I found was that reduced toe in from ride height to 2"' droop close to zero and roughly a 60% reduction from 2" to 4" droop. But because the bump on my car is bump in at droop and bump in on compression what the result was reduced at droop, increased toe in at compression. My plotted points of the bump "curve" are actually an arc, not a straight line. The arc can be manipulated via the inner tie rod position but it rotates around the fixed point of zero bump at the fixed ride height point. Also the plot is about a 1 to 2 ratio, meaning total droop from ride height is 4", from ride height to full compression is 1 3/4". So if you are rotating the curve around the ride height point reducing droop by 50% increase bump in compression by 50%. But when you are only looking for checking bump from 1" compression to 2" droop the comprise ended up being almost zero bump from ride height to 2" droop and about 1/8" at 1" compression. The numbers before making a centerlink change were almost 1/4" toe in at 2" droop and near zero at 1" compression. And that 1/4" is per side not total, so toe in at 2" droop was 1/2",toe in at full droop was absurd. For me this was a compromise I could live with. Running the back roads at speed over the quick rises and drops in the road, getting the suspension into the 2 and 3" droop range made for some moments. With the modded centerlink this was made MUCH more liveable, the finger dents in the steering wheel were gone.
Before the new link when jacking the car at the front crossmember the tires would squeal as they toed in against the smooth concrete floor, it was that extreme. Afterward that didn't happen anymore. Yes still toe in at full droop, but MUCH better.

As far as the Baer bumpsteer correction outers I remember Marcus telling me years ago that the Baer rep showed up at his shop with a bunch of Baer and other parts installed on a G for him to play with. It was noted that the Baer bump correction kit was pretty but could do nothing to correct the problem with bump on a G spindle.
Each steering arm on each spindle is different, whether a G,B,F or even the AFX. So correction for one can't be compared to the others. In my case the outer would have need to be down 11/16", don't think that could happen with the Baer kit. And yes, I have a UMI outer correction end laying in a drawer somewhere from a decade ago, it wouldn't do what i need either.

Enough about that. Spent several hours today playing with the alignment rack tweaking the rack setup, checking what the results from the LCA pivot mods did, checking wheelbase length, wheel centers in the wells, tire clearance, playing with toe, and working on a final spring cut number. Totally happy with the results of moving the lower ball joints forward 11/16", a win win all the way around. Did some preliminary Ackerman checks and it seems no real world gains from moving the spindles forward. The spindles forward would be the same as moving the centerlink rearward which should increase Ackermann. Need to get the car at ride height before saying how much change, but it looks minimal at this point, maybe 1/2 degree more. Played with my laser bump checking setup also just for S&G, it shows promise that it's not far off. But need to do the actual bump check setup for accurate numbers, no springs, shocks and full travel.
Installed the shocks and cranked up both rebound and compression to see if the shocks contributed to holding the front end down and effecting the ride height. Even with a big someone at each front corner rocking the car up and down the ride height came back to the same numbers, TOO high. Hoping to find time to pull and cut springs tomorrow.
Have i mentioned i'm getting a little weary of all this thinking.
Bob

#1056329 - 03/11/18 05:00 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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SSLance Offline
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Ugh... Can't really wrap my head around the large increase in ride height, but it is what it is. If alignment is right and it's still high, time to cut the springs I guess.

And I hear ya about taking all that apart and putting back together again and again, been there done that with my soap opera time and time again, only I'm usually doing it with a race event deadline looming...


Lance
1985 Monte Carlo SS Street Car
#1056330 - 03/11/18 05:57 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Yeah a curved curve (that sounds intelligent) means a tie rod is the wrong length for the application.

If it was too long or too short by an inch or more I wonder if you couldnt relocate the pick up point on the spindle? I dont know if I have ever came across one for the B body spindle, but they make "spindle savers" for metric spindles, that could be copied with some thicker material, and a tapered boss added to it outboard or inboard of the arm. You could also move it forward for some ackerman gain, at the expense of your ratio. Heck with enough time playing with it you could locate it so the bump came out right.
https://www.google.com/search?q=met...434j1j9&sourceid=chrome&ie=UTF-8

The 11/16ths you mention, do you mean the thread for the outer tie rod? Other than thread size and length are all GM tie rods the same at the pin end?

A lot of those bubble style caster/camber gauges dont like to check in the double digits, I would like to build something that you can just slap your cell phone on and use. Iphones have a digital angle finder within the compass app.


86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
#1056338 - 03/12/18 05:14 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Had a disappointing day. Pulled the spring for cutting. After checking ride height many different ways and always coming up with the same number 27 3/8", scratching my head and wondering why the car is 7/8" higher than before starting this project, it was time to cut. Previously before installing the springs 1 3/4" was removed from the spring end to what I thought would compensate for the 1/4" thickness of the new GM insulator that replaced the crushed to nothing old GM cushion. That cut resulted in no change to ride height.
The math I've seen says a 1/2" off the spring will net a 1" drop. The spring free length with the new cushion was 13 5/16", 13 1/16" spring alone. To lower the car 7/8" to 26 1/2" should require 1/2 of 7/8", a 7/16" reduction in free length. As recommended I choose to eliminate the 1/4" cushion, the springs were cut 3/16" shorter, a total of 7/16" shorter installed. By the way that was a 1/2 coil cut.
Well that 1/2" to 1" ratio thing may work for others but bombed on me. That 7/16" shortening netted a 26" on one side and 25 3/4" on the other, a 1 3/8" and 1 5/8" drop to a height I can't live with. It looks cool but the tire will be into the top of the wheel wells and rub them often.

The car will come apart again, not a big deal as bump steer is next on the list to check, springs need to be out for that. The 1/4" cushions will go back in, that should get things close to where I need to be. The old cushions could be used as shims to fine tuning height if needed. When the car was four corner scaled several years ago with driver the left side was 75 lb heavier than the right side. If I have to error one side or the other on height my thinking is the left should be slightly higher if it comes to that.

When the car was set back on ground and measured, the heat was turned off, the lights turned off and the door locked, tomorrow is another day.

Mason the steering arm on a B spindle is about twice the thickness of the G arm, and is 1/2" shorter. I don't think a strengthener is need there.
The 11/16" I was referring to is how far the lower ball joint moved forward, Nothing to do with tie rods.

As far as tie rod length goes moving the ball joint forward required lengthening the tie rods a little. Can't see how it would be possible to shorten the tie rods. This because to get better Ackermann the steering arm needs to move outboard. This is limited to about 3/8" because the tie rod is getting close to the 16" wheel. The other option to improve Ackermann is move the centerlink rearward, no room for that either. Ran most of the number of what can be done to improve Ackermann on my setup via full scale modeling and there appears to be no easy way and the gains are minimal. A redesign of the centerlink isn't out of the question, bending the steering arms isn't ruled out yet. Those are down the road and will be looked at before I get the car roadworthy. If the bump is livable it and Ackermann is a down the road project.

Bubble gauges get me close to what I need for now. The car will go to that fancy computer rack soon after I'm done. Will be moving the rear tires a little rearward using the adj rear LCAs so the thrust angle will be dialed in again, and the pinion angle reset. The caster camber and toe I set can be verified. The Ackermann can be checked and the bump from ride height to full droop can be measured. Been down that route on the rack when i did the modified centerlink. I actually did the centerlink swap on an alignment rack so I could see the before and after on their fancy computer screen. That shop now has the latest and greatest Hunter rack, I haven't used it yet.

Happy motoring.
Bob

#1056345 - 03/12/18 04:39 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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I'm also not so sure about the 2:1 motion ratio our cars supposedly have. I've had the same issue where small adjustments on spring\shock height have a much bigger affect on the wheel than anticipated. I now make VERY small adjustments on my coilovers when trying to fine tune front ride height. I also drive the car around a bit and let it sit before measuring again each time.

I should add...welcome to race car suspension tuning Bob! Things rarely go as planned especially with cars with personality disorders like our street \ race car hybrids.

The thing is, you are now at a point where smaller adjustments are needed for fine tuning vs large swings trying correct horrible geometry. The smaller adjustments are more time consuming and more detailed, but are necessary to really dial things in. You won't really notice most of these smaller changes until you push the car hard on the track. Driving on the street won't really show the increase in grip levels that you have achieved.

It's okay to walk away for a while as well...been there done that, many times over.


Lance
1985 Monte Carlo SS Street Car
#1056346 - 03/12/18 05:10 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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May be a dumb question, but are you clocking the springs in the LCA's? Torqueing the LCA bolts at ride height?

Spring height is 2:1, spring rates are 4:1 (motion ratio squared). Based on my simulation, I calculated a 0.55:1 motion ratio. It depends a little on your wheel offset too though.

Bob, if you want to send me some dimensions, I have a matlab optimization routine that can place the inner tie rods for you and plot bump steer. Whether they physically can go there is another story, but at least it will tell you where they want to be. I'd need pivot locations for the UCAs, LCAs, BJs, inner/outer tie rods, and pitman/idler in XYZ coordinates.

Also, a little roll steer isn't a bad thing. Especially if you can't control what the rear does so well and you need to compensate.

Last edited by SickSpeedMonte; 03/12/18 05:15 PM.
#1056350 - 03/12/18 06:36 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Bernie
Can you share that info with the rest of us following this?
Thanks.


83 SC, 355 w/TPI
#1056352 - 03/12/18 10:10 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Frustration, I'm well versed. Have two kids that are old, now have two grandkids that are like cars. The old kids did what they were told, the new kids do what they want, despite what I say or do.

Thanks for some future help Bernie. I can make an educated guess where the IC is, guess at where the RC is. But don't have the software to plug numbers in and know exactly what they are. Last week got an invite to my 50th class reunion, trigonometry class was awhile ago.

Being the LCAs are stock the springs are set exactly the same place in the arm each time, centered between the locating holes. Last night while think about the differences side to side moving the spring relative to the locating holes was thought of to balance left to right.
In my case the spring cut ratio is more on the order of 3:1. A 7/16" shortening netted 1 3/8" drop. Tonight intend to reinstall the 1/4" cushions and see what that does. If 1:3 that will raise the front end a little less than 3/4". When I can get back into that 26 1/2" range the car will be driven for a while to see if that changes.
The pivot points in the UCA and LCAs are Delrin and move very freely, no "sticktion" as they say. If anything the new upper and lower are tight yet but contribute nothing.

Tonight will also be doing a bump check before the springs go back in. Previously have done a bump check using a laser off the tire and plotting the bump at the front edge of the tire. On the alignment rack those bump numbers from ride to full droop were very close to what i got. My numbers included ride height to 1 3/4" compression which is difficult on a rack. Having a dial indicator, digital level and knowing how the Longacre and other bump checkers work I will put something together to mimic what they do also. Bump is the last piece of the puzzle for now. Was hoping to run a Hershey autox at the end of this month, but need to get some miles on the car so i can remember how to drive it.
Bob

#1056360 - 03/13/18 06:55 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Got some time tonight, wow, three day in a row got to play with the car.

Dialed in the toe and toyed with thrust angle, the sting method. Started the build stages for the new bumpsteer gauge I'll make. Decided to install the old laser bump checker I used previously. Because the car was sitting so low from the spring cut, 25 3/4", I knew I was already compressed 3/4" and using almost 1/2 of the 1 3/4" compressed travel I would have at 26 1/2 ride height. With the laser setup a rough idea of how bad the bump was from 3/4" compression to 4" droop.could be had. Well surprisingly bump from 26 1/2" ride height to 2" droop was virtually a straight line, zero bump. Starting at 2" droop it was a very gradual toe in increase to 3", maybe 100". From 3" to 4" droop was a sharper increase to about 3/16". Checking bump from ride height to about 1" compression, pushing down on the car for a little more compression, that is where the the bump in wasn't very good, about .125" at 1". This was only a preliminary check, the right way will be done a little later after the new gauge setup is built.

At 11 pm took a long look at the car, do i really want to install the 1/4" cushions to see what happens? Sure gets easier the 3rd time. Cushion back in, car is sitting back on the ground, left side went from 25 3/4 to 26 1/2, right side from 25 5/8 to 26 5/16. So that 1/4" cushion raised the left 3/4 and the right 11/16", a 3:1 ratio. HUH?

Going to make a 1/16" steel shim to install above the cushion on the right side. Hoping the ride height on the left will end up at 26 1/2. Maybe the new bump gauge will be done by weeks end and I'll pull the spring on the right to check bump and install the shim at that time. Getting pretty good at setting up the internal spring compressor at the right time when dropping the LCA.

Oh, before pulling the springs with no cushions on top a few time i could here the spring move against the seats, a distinct sound. But that had no effect on ride height, it was still way low.

And Bernie, I did rotate the right spring indexed with two holes showing, the left move to just showing the second hole to the right. This thinking it may add a little height to the right side. It made no difference.

Bob

#1056365 - 03/13/18 01:59 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Do you have driver weight in the front seat? I know my LF drops about 3/16-1/4" when my 175#s sits in the seat.


Lance
1985 Monte Carlo SS Street Car
#1056369 - 03/13/18 02:33 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Not concerned with that right now. Will have the car scaled again when I do the alignment on the big boy rack. I sit in the car for that.

I'm 170 also, hard to find that much weight laying around the shop that will fit comfortable in the seat. Sitting behind my shop there are two 125 lb blocks of lead, I'd have to dig them out of the dirt. Another block is bolted under the bottom shelf of the workbench with the vise to stabilize it. They were used as counterweights in key punch machines back in the day. Man, I'm showing my age again. You most likely have no idea what a key punch was used for.
Bob

#1056370 - 03/13/18 03:06 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Key punch? **confused** laugh

As Ron would say...is the car going to drive itself? wink Personally, I wouldn't be concerned with a 1/4" here or there in ride height variances until you are corner balancing the car and doing final setups. I think you are pretty dang close as is and I'd run it like that.

I used to use 3 pieces of leftover granite slab from our kitchen remodel 10 years ago and a couple of small exercise weights. I'll look for some leftover weights on craigslist once I get my shop set up once again. Little easier on the seats than rough granite slab edges... I once used 2 BBC and 2 SBC heads as well, desperate measures and all...


Lance
1985 Monte Carlo SS Street Car
#1056387 - 03/14/18 02:34 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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http://www.columbia.edu/cu/computinghistory/029.html Wwwwaaaaaaayyyy back in 70s, early 80s before PONG.
I'm thankful Al Gore invented the internet.

Instead of steel for a spring shim using .060 alum, will install between frame and cushion. Need to see what that does for ride height, will it really add 3/16'" to the height as expected now.

Got 1/2 of the new bump gauge made today, the part that attaches to the rotor. Only had a piece of 9x25 14 gauge stainless laying around. so that's what i used. A PITA making a 2 3/4" hole for the hub. Added a 1/2x1/2 steel angle to the top edge for rigidity, also a place to stick the magnetic digital angle gauge. Overkill as usual, but it's pretty. Need to fab the other half by the weekend so full bump can be checked.
Bob

#1056395 - 03/14/18 02:49 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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MC96 Offline
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Curious to see our OP's progress


86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
#1056445 - 03/18/18 12:04 AM Re: Front suspension mount blueprinting [Re: MC96]  
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Originally Posted by MC96
Curious to see our OP's progress

Haven't made much more progress on the frame, kind of stuck in "parts jail". Hopefully I'll be able to have an update before the end of next week.

#1056457 - 03/18/18 03:40 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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As with Justin not a lot of progress this past week. My wife in the hospital with diabetes related problems, grand kids sitting and cold weather all take priority over the car.

Did find time to make spring shims using .060" alum. Finished the bump steer gauge, got a coat of paint on it yesterday so the steel tubing doesn't rust when it goes to the storage shelf. The gauge will give me accurate number to see what area of the bump "curve" needs to be corrected. May get time this week to get some bump numbers.
Bob

#1056484 - 03/20/18 05:44 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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Found some time to get some bump numbers. Checking the right side first, no wheel/tire, spring, shock, sway bar, just a rotor, frame blocked at ride height at #2 body bushing, alignment very close to desired, spindle center set at 12.25" to duplicate loaded tire.
The first thing I noticed was a slight flex in the plate bolted to the rotor, it can skew the measurements if to much weight is pushed against it by the roller bearing traveler. Reducing that will be taken care of.

Before and after doing this front end rework a laser bump plot was looked at.This was only done from ride height to full droop, springs were installed both times. But it gave me an idea of what to expect when doing the full range bump with the new gauge. That laser setup is what was used 9 years ago to reduce the bump 60% on the droop side back then, measurements were done full range, no springs. I felt for a primitive setup it got good numbers, but they were + or - 1/16".

Even though the steering arms were raised about 1/2" due to the 9 1/2 degrees caster those quickie laser plots showed very little toe in until about 2 1/4", increased gradually until full droop of close to 4" where it was about 1/4" toe in. So actually not bad at all from ride height to 2 1/2" droop.

Didn't have much time today to play with the new gauge but made a couple good passes that closely duplicated each other. As I said a little more rigidity of the wheel plate and the numbers will become more repetitive.

So here goes, these are all toe in number, there is no toe out as I was hoping.
At ride height of course 0 toe.
At 1" droop. .012" and .010"
At 2" droop .025" and .024"
At 3" droop .038" and .032"
At 3 5/8" (full droop) .036 and .029"

Next was compression.
At 1" comp .032" and .038"
At 1 1/2" comp .062" and .070"
At 2" comp .100" and .120"

There are a couple things that jump out at ya. First is the droop bump isn't terrible. Considering some say you only need to worry about bump in the 2" droop to 1 1/2" compression range the numbers actually look pretty good. There are no bump stops on the LCA for this check, with the stops installed the full compression travel is on the order of less than 1 3/4" so the high toe in at 2" should never happen.

Next time I see the car several full range numbers will be run again to tweak the setup for reliable numbers. The digital angle gauge found another use. It's used to keep the wheel plate level so the camber gain doesn't influence the bump change. Kinda a PITA because you constantly need to level the plate. Pretty happy with the way the gauge turned out for a $25 tool.

Having some bump info now what needs to be done is work on getting the ride height set and drive the car for 10 miles. Once signing off on the ride height the rear axle will be moved rearward about 1/8" and pinion angle set, again. Then dial in the alignment on my rack at what they would call race weight, drive the car for awhile. Then it's off to the 4 wheel computer rack.

A bump correction will be thought about for now and will happen some time in the near future. It's no big deal to pull the springs later, getting good at it. Overall the bump isn't terrible and is certainly drive-able and race-able, for now.

I've already missed opening day autox at Hershey, it's this weekend. Do they run that in the snow?
Bob

#1056486 - 03/20/18 12:07 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
Joined: Mar 2012
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MC96 Offline
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MC96  Offline
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St. Johns MI
Less than an 1/8th through travel? Ship it.

Using some offset bushings for the additional wheelbase?

Afco or speedway makes those ones for the circle track guys. But Ive been told a rear camber bushing from a 90s Taurus works and has a hex to get a wrench on. Thats something I need to get my hands on.


86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
#1056489 - 03/20/18 01:31 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
Joined: Jan 2000
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mmc427ss Offline
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mmc427ss  Offline
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Pottstown, Pa
In the rear have adjustable upper and lower control arms. The reason to move the rear slightly rearward is the driveshaft yoke is to deep into the T56 rear seal at full droop. Noticed this when the rear was hanging at droop while on stands for the past month or so. When the new engine went in a Lakewood scattershield was installed. The shield moved the trans back because of the additional block saver plate thickness and a little additional bellhousing depth, this reduced the driveshaft endplay that was good previously. Of course you need to look at pinion angle again and then check the thrust angle when on the computer rack.
Bob

#1056496 - 03/20/18 03:02 PM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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SSLance Offline
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SSLance  Offline
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Peoria, AZ
That is not bad at all, it'll drive fantastic down the highway as is.

I'd sure like to see what you have there at 1" droop happen at 1 1/2" compression though. Basically you can mimic ackerman by making it bump toe out around full compression. I wonder if a bump steer kit such as the Baer Ridetech or UMI one that drops the outer tie rod end down from the steering arm could move the curve down the right amount?

With your tenacity for measuring details, you'd get giggly swapping spacers on that kit out and measuring the changes that makes. laugh


Lance
1985 Monte Carlo SS Street Car
#1056510 - 03/21/18 04:31 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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mmc427ss Offline
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mmc427ss  Offline
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Joined: Jan 2000
Posts: 4,064
Pottstown, Pa
Yep, one of the goals all along was to improve Ackermann. Getting some toe out at droop is a cheating way to do it. That is something to be figured out when I go into that phase of the project.
Improving the Ackermann involves the steering arms. Already know there isn't a lot to be gained by moving them outboard 3/8", more than that and tie rod to wheel clearance is tight. I was hoping that moving the spindle forward would be a larger gain, but so far it's marginal, maybe 1/2 degree. Won't know the real number until the front setup is where i want it. Still stuck playing with ride height.

Pickup some 1/2x 1/2 angle today to backup the stainless wheel plates. That should take car of the plate flexing.

When the modified centerlink was done years ago it was trial and error. The inner location was tried at a lot of location, up down, left right, forward rearward, looking for somewhere that corrected bump to livable. What I found then was everything was a compromise. Dropping the inner 11/16" at the stock location was done. That reduced droop bump by 60% at the expense of compression. It was a good choice because the car saw much more time in extreme droop than extreme compression, and the fat tires liked that a lot more.

Back then i had a little bit of knowledge and some crude tools. Now with the ability to look at most all aspects with accurate tools the bump and ackermann improvements can move to the next level. As I've been saying all along it's very difficult to get the metric chassis to be as good as the new cars, but it won't be from the lack of trying.

Gotta thank Lance and Ron for pushing my buttons again. Tearing the front suspension out of my car wasn't high on the winter projects list, but it certainly did eat up the cold month's to do list.
Bob

#1056514 - 03/21/18 11:11 AM Re: Front suspension mount blueprinting [Re: Warriorridge]  
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MC96 Offline
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MC96  Offline
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St. Johns MI
Based on my chart, for zero bump your tie rod outer pick up is too low and too long. But I think you're close enough.


86 SS
400SBC, 4l80e, MSD Atomic injection/trans controller, Tilt glass clip, all tubular arms, corvette brakes, 9" rear
In progress
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