Attn Pozzi, Here's my Alston SF Camber Gain Measurements

[Craigon69]

Back on the old board, waaaay back last Apr, I told David Pozzi I would take my Alston Subframes Camber gain measurements There were severa resons why I did not get to it, bit one big one was that the sheet metal was all on and it was a pain to remove the coil overs/sway bar, etc. I recent removed all the front sheet metal for 2K/blocking, so I figure I better make good on my promise. I don’t know what these mean or if I did it correectly, so while I got it all apart let me know! I can do other measurements too, but will need instructions!

Thsee are in 1/2 inch increments measured from the bottom of my rotor to the floor with a starting position where the lower control arm was level (Suppose I should dial in a tad neg camber at that initnal position huh?). The digital level was placed on the hub and rotors (measured twice, each time they matched).

My original post was missing all the up swing number. Doh! Here are all the number again, this time including the up swing..

Reference point is from ground to bottom of rotor.
- 18 3/8" = 84.7-
- 17 7/8" = 85.6-
- 17 3/8" = 86.5-
- 16 7/8" = 87.3-
- 16 3/8" = 88.1-
- 15 7/8" = 88.6-
- 15 3/8" = 89.3-
- 14 7/8" = 89.7-
- 14 3/8" = 90.0 Lower control arm Level.
- 13 7/8" = 89.4 +
* 13 5/8"s = 89.3+ This i where the lower a-arm pivot is level with b-joint pivot.
- 13 3/8" = 89.1 +
- 12 7/8 = 88.8 +
- 12 3/8 = 88.5 +
- 11 7/8 = 88.3 +
- 11 3/8 = 88.2 +
- 10 7/8 = 88.1 +
- 10 3/8 = 88.1 +
- 9 7/8 = 88.2 +
- Bottomed out after this...perhaps it dropped another 1/4" and read 88.1+.
==

I have these #'s and pics of me doing this at http://chemagic.com/craigon/Chassis.htm . Again, not sure if I did it 100% correct, so le me know (send David email on this topic too)

[baz67]

What was the stactic camber and caster you had to do these?

Brian

[baz67]

At what level is your static ride height? It looks like static is when you have 0 camber. I like that is goes a little positive in droop. It may be a bit much. One thing that does stand out is how quick you gain negative camber after two inches of bump.

Brian

[David Pozzi]

Here is the same data but converted to a more normal form:


ALSTON SUBFRAME
MEASUREMENTS BY Craigon69
CAMBER READINGS CORRECTED TO ZERO INCHES AT BALLJOINT LEVEL POINT:

HEIGHT CAMBER IN DEGREES - BUMP (wheel up) + DROOP (wheel down)
5" = -6
4.5" = -5.1
4" = -4.2
3.5" = -3.4
3" = -2.6
2.5" = -1.1
2" = -1.4
1.5" = -1.
1" = - .7 (neg camber) LCA level, but is not straight to balljoint
.5 = - .1
0" = - 0 lower a-arm pivot is level with b-joint pivot.
.5" = +.2 (positive camber)
1" = +.5
1.5" = +.8
2" = +1
2.5" = +1.1
3" = +1.2
3.5" = +1.2
4" = +1.1

This curve is very very close to a First Gen Camaro sub with Guldstrand Mod.
I would guess that this sub should handle very well if it has enough torsional rigidity, A arm stiffness, proper bump steer, and proper spring and bar rates. So far, I like what I see.

Craig, thanks a bunch for posting this info! :icon996:

[Craigon69]

I'm not well versed in suspension theory/mechanic's, and I followed step by step instructions initially setting it up (Alston manual), and also from David to get the above numbers. So, I'd be interested in having someone replicate it to see how our numbers match up (double check my measurements!). If anyone is interested, the easiest time to do it is when you are setting up the alignment during install. I can forward the instructions I used (from David) if interested.

Baz67, regarding the static camber/caster, I take it you mean what the manual had me set it to? I posted the alignment pages from the manual at the bottom of this page:
http://chemagic.com/craigon/Referance.htm . I think the numbers you are asking about are on Pg28 and are 0 (90 deg on level) Camb and 1 to 5 neg Cas. For your second question, I'll be able to tell for sure once I have the car back down, but as you said, I think it is close to zero.

I'll probably put it back together today, so I can roll it out and apply/sand some filler (doing that is nasty in the home garage).

Thanks for being patient with all my "how do I do this" questions David.

[jeffandre]

This curve is very very close to a First Gen Camaro sub with Guldstrand Mod.
I would guess that this sub should handle very well if it has enough torsional rigidity, A arm stiffness, proper bump steer, and proper spring and bar rates. So far, I like what I see.

Craig, thanks a bunch for posting this info! :icon996:

David or anyone,
How does this compare to a stock 2nd Gen? Assuming I keep the stock-configured (Vette Brakes tubular) UCA's and LCA's, what are the best things I can do to maximize my potential mechanically (for running on tracks like Sears Point and Thunder Hill, not so much high speed stuff)?

I would consider modifying the control arm mounts geometrically (will be beefing them up a bit, especially the lowers), changing spindles, etc.

Thanks in advance for any information you can provide,

[MoeBawlz]

can someone do the same or has someone already done the same to the Wayne Due C4 frame?

[David Pozzi]

Jeff,
I posted 2nd gen camber curve specs somewhere, can't find it right now, I think it's on the old board somewhere.

A second gen has less camber gain than a first gen with guldstrand mod, but more than a C4 Vette. Makes the vette look pretty tame, doesn't it?

I thought of doing a Guldstrand type mod on my wife's 73, but I didn't figure out what I wanted in time to do it. The suspension geometry of a second gen is kinda wierd.

If you can get 5 to 5.5 deg positive caster, you will do pretty good but for track use, dial in -2 to -2.5 deg neg camber setting.

If your upper arms are not made for extra caster, you might think of getting some or modifying yours.

[jeffandre]

I will be purchasing some type of digital alignment tool to setup my front end the best way I can, using your advice of course. I will consider modifying my UCA mounts as needed, and I will check into doing the same for the UCA's themselves.

I will check the old forum posts to see if I can find the info, I do recall mention of this stuff somewhere... Info is great to have before I get started, so thanks, I appreciate it! I will be starting sometime in March at the earliest.

[David Pozzi]

Now that I have the car aligned and rebuilt, I plan on re-measuring all the suspension points and getting a better model for my suspension software. We will be pulling the engine probably next month, and that would be a good time to do a redrill of the A arm mounts, but I need to figure out where they might go or if they should be done at all. I don't see anyone doing a second-gen upper A arm relocation like the Guldstrand mod. I wonder if Guldstrand has a template for the second gen's???
David

[David Pozzi]

I forgot to mention, I also bought some 1/2" taller upper balljoints for the second gen. I got them from Marcus.
Once I get a feel for the car's handling, I'll try them.
David

[apex69]

I forgot to mention, I also bought some 1/2" taller upper balljoints for the second gen. I got them from Marcus.
Once I get a feel for the car's handling, I'll try them.
David


DP, do you have a part number for those 1/2 inch taller ball joints?

[jeffandre]

DP, do you have a part number for those 1/2 inch taller ball joints?

Me too!

Also, I am considering getting one of these tools for alignment setup at home (will have a shop do it once the car is road ready again). It is from Summit, Rebco part # REB-320-8920 or 8941, let me know what you think (it's listed on the second page of the link, part #REB-320-8920; the catalog has the other part #) .

http://store.summitracing.com/default.asp?target=esearch.asp&N=110&Ntk=KeywordSearch&Ntt=rebco

[David Pozzi]

Here is the web page for Marcus: http://www.SCandC.com
I got a pair from him, don't recall the price, but not cheap by stock standards, but they are rebuildable and VERY well made!

I'm confident they will improve the camber curve, but they haven't been tested yet.
David

[Marcus SC&C]

If anyone`s intereted in the tall UBJs,just e-mail or give us a call at www.SCandC.com We assemble them from individual components,lube and set their preload and include poly boots configured for the taller studs. This for a little less than you`d pay for just the base components. Also AFAIK we`re the only place with tall studs for the 1st gen and Chevelle. We worked with the manufacturer and purchased all of the production run in order to encourage their production. Marcus SC&C

[jeffandre]

Here is the web page for Marcus: http://www.SCandC.com
I got a pair from him, don't recall the price, but not cheap by stock standards, but they are rebuildable and VERY well made!

I'm confident they will improve the camber curve, but they haven't been tested yet.
David

David,
Please explain to me in layman's terms if possible what I would be gaining by getting the upper and/or lower ball joints as shown on SCandC's page. What is it that I am trying to correct geometrically and should I consider where my current a-arm planes are before going with longer balljoints? I remember something about the lower arm being parallel from center of bolt plane to center of balljoint sphere, or something like that. Thanks in advance for your patience, I am very new to this stuff but love geometry and do not mind going the extra nth to gain a little bit when it comes to cornering (I love transitional lateral g's more than any other driving feeling).

[David Pozzi]

More or less, using a taller upper balljoint is the same as lowering the inner upper A arm pivot, aka - Guldstrand mod. You are adding more angle to the upper arm and that causes it to swing the spindle / tire more negative when the car leans in a corner. As you know, keeping the front tire flat in a turn is a major part of good suspension geometry. If your car leans 3 degrees and your camber was set at 0 deg, the cornering camber would be 3 deg positive (tire leaning out at top) minus the usually small amount of neg camber gain designed into the suspension.

CASTER
High amounts of positive caster lean the loaded wheel inward (neg camber) when cornering but only when the wheel is turned, the camber goes back to the static setting (your basic alignment setting) when you straighten the wheel. The advantage of this is, the tire sits more vertical when driving straight down the road and has less side thrust generated than a highly cambered tire.

[jeffandre]

I am starting to get it! I think it would be a good idea to go to the local bookstore and hunt out suspension and handling books to more fully understand the basics. No sense in tearing up my stock front frame and moving stuff around until I actually know what I am doing. Thanks again for putting up with my simple questions!

I think the longer ball joint idea is fantastic, I will get my ride stance set (my front ride height is adjustable), then work my alignment to the targets considered optimal for road racing and autocross, then check my UCA and LCA angles and camber curve before cutting anything or buying the ball joints. I predict that I will have a lot more fun getting the front suspension setup to my liking than the rear has been (and I have enjoyed the heck out of that, I live for tweaking, even the small stuff that most people wouldn't even consider).