anyone know the taper on C6 Vette ball joints?

[Vince@Meanstreets]

If you are using the factory steering mount,yes.

Where is your inner rear toe bar mounted? You'll have to play with different heights.

[Vince@Meanstreets]

Originally Posted by byndbad914

Vince - thanks for posting that. I was unaware of those custom made parts for the Vettes and am down a different path on my Nova, but had I known about those, I likely would have bought them and just used the pins or tried to find those tapered adjustable pins separately, then made my own custom length tube to fit the Nova dimensions...

BTW Vince, have you noticed horrible bumpsteer in your experiences with using these spindles?

To me it apprears bumpsteer is HORRIBLE and it can't be fixed, just minimized. I pretty much gave up on setting up a dial indicator to measure it and have just used a tape measure while I roughed in the tie rod angle on the Nova. The first 1" of bump is okay, worse than any suspension system I have designed or set up on circle track cars, but can be tolerated. Beyond 1.5" of bump it goes to heck very quickly. Looking at my own Vette it appears they set the ride height such that the lower arms aren't parallel to ground, but angle down a bit so the car goes from toe in to zero at parallel then start toeing in again on bump - something I do NOT want at all on a track car. I want one direction of motion during bump. Anyway, setting the car up as they did gets some more motion without huge toe change, but still, not great.

The rears are oriented with the toe arm back which actually means the rear toes OUT on bump. I can't imagine how that bad idea got incorporated. Nonetheless, I am now working out swapping the rears on the Nova and figuring out how to put the toe link to the front.

I have been super tempted to take a torch to the toe arm on the struts but have no idea how that would hold up with the aluminum material on the track. If it was a forged steel spindle I would be bending that puppy to fix this. For now I intend to see how it works out. I will be limiting suspension motion anyway with stiff springs and bump rubbers.

Also anyone considering building their own control arms my machinist has the specs to make upper and lower ball joint pucks.

[byndbad914]

Originally Posted by Vince@MSperfab

Where is your inner rear toe bar mounted? You'll have to play with different heights.

I don't have the rears mounted since I decided to reverse the spindle orientation with the steering arm to the front now for toe in on bump. I will be spending a fair amount of time when I do tho' moving the inner around and trying to find the best location for it...

[mfain]

Originally Posted by byndbad914

I don't have the rears mounted since I decided to reverse the spindle orientation with the steering arm to the front now for toe in on bump. I will be spending a fair amount of time when I do tho' moving the inner around and trying to find the best location for it...

Tim,

I'll offer an observation based on my own recent redesign of my front and rear suspensions. The bumpsteer characteristics are not so much influenced by whether the spindle is front or rear steer, but more by two other factors: the tie rod (or toe rod in the rear) length and the height of the inboard and outboard tie rod ends. The IRS performs exactly the same as a front independant suspension with respect to bumpsteer. The C4/C5/C6 Corvettes IRS achieve toe-in with bump (a safety factor to tighten the car during cornering) by making the toe rod longer than that required for zero bumpsteer. The longer toe rod causes the outer pivot to swing in a bigger arc than the uprights which causes the tires to point in -- with either bump or droop. With a forward facing steering arm as you are comtemplating, a shorter toe rod would cause toe-in. With a "zero bump-length" toe rod, but with the inboard end too high (or the outboard end too low), you will get toe-in with bump and toe-out with droop. The opposite is true with the inboard end too low. As Vince indicated, the most common cause of bumpsteer in the front suspension is the "wrong" rack length that makes the tie rod either too short or too long. There is a very short, clear explanation (with a diagram) of this issue in the Woodward Catalog Tech Section (page 64 at the following link: http://woodwardsteering.eu/images/ba...ion%20tech.pdf) A much more thorough explanation is provided by Ron Sutton in his Front Suspension sticky in the Chassis and Suspension section of this forum. I just completely rebuilt the front suspension of my car to accomodate high travel/low roll geometry. I moved every suspension pick-up point and the rack mount, and I made every point adjustable with slugs. I had to buy a new custom rack to get the length of the front tie rods correct for zero bumpsteer. As a note,the longer I made the control arms (which shortened the distance between the left and right control arm pivot points), the shorter the rack had to be. Also, the lower I moved the rack, the shorter the rack had to be. I see you have a very nice fixture for mocking up the suspensions. I build half or full scale mock-ups using wooden dowels with screw eyelets for pivots to get close to the correct geometry before I start bending an cutting metal (picture below). I also use a wheel profile mock-up to check clearances before I finalize things like my control arm configurations. Clearance for deep backspace wheels (for low scrub radius) and high travel is a b.......h. Hope this helps.

Pappy