71roadster

I have been looking at correcting the problem of my front wheels going into a positve camber when it should be going negative. The front suspension was designed in the '50's when tire technology was so poor that they designed in positive camber to keep the tires from coming off the wheel in a corner (think leaning to the outside when turning). Well, tires have vastly improved and will keep getting better (carbon nano-fibers are coming to a tire near you soon!), so now is the time to correct this built in deficiency. Except for you dinosaurs still running 15 inch wheels - you guys are hopeless!

Anyways, there are two ways to do this. Lower the inner mounting point of the upper A-arm (drilling new holes in the frame-OUCH - but popular in the 1st gen camaro crowd) or extending the upper part of the spindle. Well, I found several ways to do the latter fairly easily and will probably be looking at one of the coleman adjustable ball joints modified to fit my A-arm. I must say the I am REALLY suprised that VBP hasen't jumped on this, but it may be outside their ability to properly evaluate.
http://www.colemanracing.com/section/index.htp?id=1191 http://www.colemanracing.com/section/index.htp?id=617</A> http://www.colemanracing.com/section/index.htp?id=629 http://www.colemanracing.com/section/index.htp?id=630


These are bolt on, but arent adjustable and are a little pricey. http://www.drgas.com/promotor/spindleex.html http://www.hotrod.com/howto/50358/index.html

And here are some excellent articles on determining roll center and other critical front suspension geometry.
http://www.circletrack.com/howto/1816/index.html http://www.circletrack.com/techarticles/4637/index.html <A HREF="http://www.circletrack.com/techarticles/0304_meas/index.html" TARGET="_blank">http://www.circletrack.com/techarticles/0304_meas/index.html

Any thoughts are welcome, except for personal attacks (tho I expect the dinosaur comment deserves a fair response)!!!

Chris

bb69

Chris,
I have been following similar topics for my Camaro. As you said, many people redrill the upper mounting holes using a template made by Guldstrand. This mod would work in the same manner as it does for the Camaro. I just received the Camaro suspension geometry, and will be working with it. The next step will be with the Vette suspension. (The Camaro needs it more.) I haven't looked into the spindle, but keep us posted.

Ken

norvalwilhelm

I'm glad to see you posted this. Alot of the information you posted I have read before in magazine articles but have been unable to find them. You sent them to me in one neat package.
Thank you Chris

terryrudy

After you do yours I will want a ride. then maybe it will be time to tear down my front suspension and go with the trick upper a-arms as well. :)
-terry

71roadster

you better wear diapers! With all new front suspension/steering on top of the 383 and TKO, we're both gonna need some depends.

Chris

soon, sort of soon...

PROSOUTH

Norval and I talked about this earlier. Since that time I have lost my archives of info due to the great Trojen Worm of '03. So thanks for sendiing me the information as I needed it too.

I think the ball joint I chose was from Speedway. It was a Moog joint that they carry. It does require a redrill of the control arm but that is no problem on my tubular upper A-arms. If there is a better one please let me know.

I do have one question though, What was it I read about using an offset upper control arm shaft to set the A-arm back without drilling and relocating it to help with adjustments of the camber? Would this help or even be necessary?

Jim

75 BBC Stingray

I remember Norval mentioning this a bit back, but I could never find the item on Hot Rod's site. Thanks for the link to the article and the manufacturer.

I remember reading somewhere that VBP control arms have a different geometry to correct for some short-coming of the stock system. Anyone remember what it was? Could it be that they lengthened the lower arm compared to the top to increase the tendency toward neg camber? I would be curious if the spindle extender would be useful for both the stock stamped arms and the VBP arms. I believe I read in your sig that you have them?

PROSOUTH

Good point I missed, I just looked it up in the catalog and they have relocated the ball joint mounts to allow up to 5 degreees positive caster and a greater camber adjustment range for better handling and road tracking. A-Arms are shipped pre-assembled withoffset cross-shafts, poly bushings, and installed ball joints.

Mine have no ball joints. They are new but I bought them off of the net second hand. I only have the upper tube A-arms at this time. I am purchasing either the transverse set-up or 550# springs to go with these.

OPINIONS? Jim

OK......................I'm Lost......HELP? Does this mean I do or do not still need the extended Ball joints? JIM

Turbo-Jet

this is the simplest way to determine RC

71roadster

The VBP A-arms simply relocate the upper ball joint a bit further back, increasing caster. The increased caster will only very marginally reduce the camber but I suspect it is still in the positive zone when compressed, and we want to be negative on the outside wheel (tilted in at the top) in a corner. And as for adding camber in static position, that is a bad way to solve the current problem.

The extenders wont affect the caster at all.

e3pres

That way is valid if the car is at rest. To determine roll center at various points in suspension travel (i.e. During cornering), draw the instant centers for each side. Connect the each instant center to the centerline of each tire (R to L, and L to R). Where the two lines intersect is the the roll center for that specific instance.

:cheers:

71roadster

Does anyone have any idea where an ideal static roll-center should be?

Chris

joe73vette

I think 2-3 inches above the road is a good target. There are a couple of good books on this subject, you should have at least one if you are going to monkey around with the car's geometry. Joe

Turbo-Jet

'Racecar Vehicle Dynamics' by Miliken is the bible. it is written for engineers and filled with lots of math and physics, but still a good purchase for anyone interested in vehicle dynamics and suspension design.

:yesnod:


[Modified by Turbo-Jet, 3:49 PM 2/25/2003]

Turbo-Jet

Yep and this is where computers come in handy. If you can model the suspension geometry, then you can plot the RC and many other parameters. Depending on the software, you can add input functions and simulate the dynamic response. Get the loading, stresses and vibration in the high-end packages. But good old AutoCAD can be effective for geometry problems.