Gulstrand Mod and New UCAs/Tall BJs

[firebob]

The new UCAs will be here this week and they will be going in with the taller BJs.
So my question is should I run through the Gulstrand Mod holes or should I mount them back in the original mounting holes? Just don't want to go too far and end up with some crazy mega bump steer problem or something.

69 Firebird
Robert

[MrQuick]

running both will give you a very aggressive camber gain....some like it but tires don't.


vince

[firebob]

Well like one of the other posts showed I may not be able to install the cross shafts all the way up against the frame mounting flange anyway without shimming it away because the G-mod moves the bolt locations lower to the crossmember and I don't think there is enough clearance. But then I'm not sure how much shimming it's going to take. I won't know till it's all back together and on the ground. I didn't want to have to do this too many times.

Robert

[L & H Kustoms]

Robert, I would recommend bolting the uca in the factory holes and as Vince stated to use tall bj and g mod creates a pretty severe camber curve. and you wont have any issues with the cross shaft/ tube to mount interference with the Gen II arms.

[firebob]

I was leaning that way but wanted to get some feedback from someone with more experience than I have. Trying to avoid a one step forward and two steps back kind of job. Thanks for the advice.

Also once I get the alignment all dialed in for the street I should be able to add the same amount of shims front and back to increase negative camber on track days with out changing anything else correct? I'm figuring 0* for street/1*neg@ track.

Robert

[onechev]

i believe you have to reset your toe because it will change when you bring in the uca.

[ArtosDracon]

i believe you have to reset your toe because it will change when you bring in the uca.

ANY time you replace just about any portion of the front suspension you *should* get an alignment, but especially if you're changing the geometry in any appreciable fashion.

@Robert, I don't know that you'll want 0* camber for the street, no camber at all can cause some unusual habbits on the highway, depending a lot on caster as well though. I would tape together some shim packs for .5* and 1-1.25* so you can swap them out easily. If you get the shims that have the cross bar holding the front and rear together it makes it even easier.

[79T/Aman]

0 camber should have the least effect on steering feel but toe and caster will have much more effect and can make the steering feel funny

[firebob]

More toe after neg camber increase makes sense but I can't imagine if I go from o*(or .5*) to 1* that the toe would change a measureable amount. Car will still have 5+* caster so that won't change steering feel. The full, front and rear taped together, shims sound like a great idea. I'm sure I would've thought of that after a couple of years.

Robert

[firebob]

Robert R.,
Do you know who sells the crossbar alignment shims?

Robert(D)

[68KMARO]

I would do a search on this as this has been gone over before with alot of great info. Also I would talk to Frank at Prodigy and Marcus at SC&C.

rich

[L & H Kustoms]

Robert R.,
Do you know who sells the crossbar alignment shims?

Robert(D)

Robert here ya go
http://www.camarocentral.com/1967_19..._p/sus-239.htm

[ArtosDracon]

What is the bolt center distance on the Camaro, I know circle track places usually have 6" and 6-7/8" linked shims in both straight and angled.

[clancj]

when i g-moded my camaro, the original "A" are holes made a nice location to placed strategically colored shims on a wire "roll-o-dex" in each abandoned hole for a wide variety of track conditions (camber and caster -pre measured). my normal highway street shims are a different color form my "track shims".

[firebob]

The spread on a FGF is 6 3/8". What kind of business deals circle track stuff? Man, I didn't really want to spend $85 on some shims!! I suppose they aren't easy to make but jeez louez.

Robert

[MrQuick]

where did you look? try Coleman, Speedway or Capital. www.cmwraceparts.com

Vince

[exwestracer]

The spread on a FGF is 6 3/8". What kind of business deals circle track stuff? Man, I didn't really want to spend $85 on some shims!! I suppose they aren't easy to make but jeez louez.

Robert

Day Motorsports shims

As far as how much camber gain is too much? For a 4" or taller sidewall, your swing arm length should be about 1 1/2 times the track width, for shorter sidewalls about 2X track width is a good place to start. Assuming the LCA is effectively level, the angle of the UCA should put the intersection point about 90-100" out for a normal race tire. Ultra low profile tires would want the intersection out past 120" or possibly further.

[firebob]

Woah cowboy!! I think I'm going to need a glossary of terms with definitions. Like, swing arm and track width? I got the sidewall heighth part covered. The rest make sense(pretty much). Assuming the LCA is effectively level I can measure the angle of my UCA and have someone smarter than me(my son) figure out how far out the intersecting point is.

[ArtosDracon]

He's spot on, and while it does apply, it's way above most people. If you'd like to know though Your supposition is correct, but ideally you need to know the exact angles of the upper and lower control arms between the center of the ball joint and the center of the pivot point, which isn't always exactly the same as the angle of the arm itself.

Swingarm length is the distance from a point at the center of the tire on an imagined line between the upper and lower ball joints, to the point where the upper and lower control arms would intersect if they continued past their hard points. Track width is the width between the center most points of the contact patch of the tires.

Now to utilize this for figuring out proper camber gain, you also need to know the roll center height and the center of gravity of the vehicle. You can plot all this information to find the degree of camber gain that will keep your inner and outter tires as flat as possible through roll. You'll never get it perfect, especially not on a modified stock style suspension, but you can find a happy medium.

[exwestracer]

Now to utilize this for figuring out proper camber gain, you also need to know the roll center height and the center of gravity of the vehicle. You can plot all this information to find the degree of camber gain that will keep your inner and outter tires as flat as possible through roll. You'll never get it perfect, especially not on a modified stock style suspension, but you can find a happy medium.

Here's a picture that might save 1000 words... While it may look complicated as hell, you can find the relevant points by simply measuring up from the garage floor (provided the gravel is all the same size ). You will need a chassis centerline to reference the width measurements off of. The point where the purple lines meet is the instant center (it moves with suspension action). The distance from there to the center of the tire is the swing arm length mentioned earlier. This one is very short (I picked it just so it would be on the page so you could see it), you'd want yours much further out. The lowest purple line runs from there to the ground at the center of the tire and locates the roll center (yellow circle) as Artos mentioned. If your son has some chalk laying around, get the measurements and draw it all out full size on the floor. It'll look just like the one above (minus the million numbers...SHEESH!), and you'll know everything you never really wanted to know!