anyone know the taper on C6 Vette ball joints?
 

as the titles states, I am hoping someone knows the taper on the ball joints for C6s...

I have uppers in the used spindles I got but they don't measure to what I consider a "normal" GM taper. The lower reamed taper in the spindle measures out the same but I am hoping to confirm the angle since, again, it is not what I expected.

Normally a 1:6 taper

I guess I need to verify what you mean by "normally" - normally for GM or normally for a C6 Corvette?

From my days working with circle track stuff, GM is normally 10 deg, or as you note, a 1 in 6 ream. However, the upper I have is measuring out around a "normal" Chrysler at roughly 7 deg.

Normal for the OEM's (almost all of them). Nearly all ball joint tapers are 1:6 nowadays unless there is a taper washer. Looking online, I see people say both about the C6 tapers. I will see if I can dig something more definitive up.

This is interesting..... http://www.fastcar.co.uk/forum/showp...9&postcount=50

I just went to the shop and picked up a new C6 spindle and a low friction ball joint that Howe provided to me for the lower end. The factory ball joint is installed in the upper end. I measured them with a digital caliper (not a micrometer which would probably be more accurate). The upper comes out 2 inch. per foot taper consistently, a number I've heard several times on another forum. The Howe technician provided me with a lower ball joint stud that fits correctly -- part number 224240 which shows to have a 2 inch. per foot taper. I just called the Howe tech and he confirmed that (by the way, he said "Corvette" as the application without me mentioning it, so it kind-of sounded Corvette specific). Measuring the tapered hole in the spindle I get 1.92 inch. per foot taper, but my caliper may not be that accurate on inside diameters. As a side note, I was originally told by a manufacturer that the GM C6 taper was "proprietary". When I measure the Howe stud I actually get 1.84 Inch per foot. Hope this helps. By the way, Howe has an excellent stud taper/fitment chart.

Pappy

Thanks to both for the info. 2 inch per foot = 1:6 so that all lines up. Interesting I spoke to a guy at Speedway and he thought all the late-model metric stuff was 7 deg taper, which is closer to what I measured... but I will take Howe's word over it any day as they make 'em :)

I am already looking at Howe adjustable ball joints so I can vary the roll center and didn't even think to talk to them directly about Corvette stuff so I will contact them.

I think what I am going to do at this point is machine up an insert to replace the ball joint in the spindle with the taper, then use a ball joint in the upper arm which is more of a "normal" setup, simply flipping the joint over and have it point up into the spindle v. down like say an old Camaro/Chevelle setup. Having the joint in the spindle is odd so I was going to have to make a thread-in tapered item to screw into the IMCA uppers I am looking to use anyway. This way I get the exact ball joint I want in the IMCA uppers and the exact reamer dimensions for the top side of the spindle.

The joys of trying to do custom stuff but maintain as much "off the shelf" stuff as possible for ease of maintenance - I end up with two ball joint holes at the top and no tapered side to bolt into :D

edit - sorry, forgot this part from the link above
"One unique feature of theGMR uprights is they have matched the stock lower ball joint taper perfectly using a custom built reamer. They will not disclose the exact taper but we can assure it is not either of the standard 7 or 10 degree tapers.Their uprights matches the stock taper perfectly to ensure quality fitment with the stock GMR components"

I can say that the math on my upper didn't seem to match either exactly so maybe that is what they have found as well, but maybe Howe determined it to be "close enough" to 10deg that is works? This is why I am thinking I will just make a plug for the upper side of the spindle and ream it to an exact known 1:6 Howe ball joint for the IMCA upper.

Well 1:6 is actually like 9.xx degrees or something, so technically they are right, it isn't EXACTLY a 10 degree taper...

yeah, it is like the roof on our houses, they're called out in pitch, not angles, but in the case of ball joints everyone talks angles.

and the thot plickens... I found some Viper stuff on the Howe site that is 1.69"/ft taper which is almost exactly 8 deg - which is also exactly the angle I calculated my upper ball joint on the Vette spindle to be. Not 7, not 10, but 8 degrees.

So maybe the Vette and Viper are both running this funky taper. WTF? Being a mech engineer I deal with stupid crap like this on a regular basis - someone reinventing the wheel - I would love to hear the excuse why the standard 7 or 10 degrees is not quite right but 8 is perfect :wacko: Apparently I missed the class at school that discussed the finer points found in children's books such as porridge temps and mattress firmness. :bitchslap: Must have to have a PhD to get exposure to that kind of knowledge.

Chevy Corvette - built in America... using metric fasteners and other nonstandard items. Wouldn't surprise me one bit if taper was based on millimeters; man enters store, walks up to counter, 14mm over 100mm reamer prease!

edit - took a break, stepped back from the tree to see the forest, and thought this thru a bit here. I think I have a simple plan to circumvent the funky taper stuff for my project. I can run a Coleman lower control arm with a monoball lower and standard Chrysler K727 1.5"/ft taper, ream the spindle lower to this taper (as this will not open up the bottom diameter which is good), then press out the C6 upper and make an adapter to fit in it for the same 1.5/ft taper, run a Speedway upper A arm assy which takes a standard K772 ball joint which I can get variations from Howe and others. The only "custom" part is the adapter for the spindle upper and reaming which is all pretty cake to redo if I mess up a corner. Whacka$$ taper should then be circumvented. Now to let this simmer a bit and make sure I didn't miss something :)

It is a little different, I actually had a custom reamer made for the fabricated uprights we make.

http://thegmr.com/wp-content/uploads...NC-machine.jpg

lower BJ on C6 upright.
http://thegmr.com/wp-content/uploads...right-one3.jpg

edit - took a break, stepped back from the tree to see the forest, and thought this thru a bit here. I think I have a simple plan to circumvent the funky taper stuff for my project. I can run a Coleman lower control arm with a monoball lower and standard Chrysler K727 1.5"/ft taper, ream the spindle lower to this taper (as this will not open up the bottom diameter which is good), then press out the C6 upper and make an adapter to fit in it for the same 1.5/ft taper, run a Speedway upper A arm assy which takes a standard K772 ball joint which I can get variations from Howe and others. The only "custom" part is the adapter for the spindle upper and reaming which is all pretty cake to redo if I mess up a corner. Whacka$$ taper should then be circumvented. Now to let this simmer a bit and make sure I didn't miss something."


Tim,

I am heading in kind-of the same direction. I tried the Howe stud they sent me for the C6 lower (part number 224240) in a Coleman spindle eye (part number 808-700, Chevrolet lower taper K-6141 (10 degrees)) and it fit perfectly. That means the stud IS 2 in./ft. taper. When I try the same stud in the spindle, it is slightly loose at the small end (which was indicated by my 1.84 in./ft. hole taper measurement earlier). I tried the Howe-recommended "magic marker" test and that also showed the stud to be tight at the big end and loose at the small end. The fix I am going to use is to run a 10 degree taper tool through the aluminum spindle taper to make it the same as the stud. It will take very little material removal, and the stud is long enough to pull that off without running out of stud and pushing the threads out the top of the hole. For the top end, I will use a Coleman CM-12-2 heavy duty rod end which is 3/4 in. thick and has a 1/2 in. hole. I will run the 2 in./ft. taper reamer through it to create a taper. I will then check that taper against the taper of the C6 upper ball joint. I have measured that stud a dozen times and I still get right at 2 in./ft. taper, but who knows? Anyway, if that taper works, all is good for what I have planned. If that doesn't work out, I will go the same approach as you -- ditch the C6 top ball joint and build a sleeve to accept a more conventional ball joint. What a PITA.

Pappy

Nice piece! Do you ream the uppers too, or just the lowers? Edit: Jason, after looking at your website, I see you have provision for a press-in upper ball joint -- do you stay with the C6 piece, or are you set up for a different upper ball joint? Thanks

Pappy

thanks GMR and Pappy - further confirmation the angle is off from "normal" racer stuff. If I were doing a bunch I can certainly see the value in a custom reamer. Since I am doing one car, 4 spindles, I will go down the path of picking a "standard" and just getting that reamer.

Pappy - furthermore, imagine if you didn't really know what you are doing and just bought that ball joint on their recommendation and bolted it in! You wouldn't make it far before wallowing out the spindle and bending the castle nut threads and then just having it tear apart. Maybe they should read their own tech guide about misfit at the taper :whistling: BTW, you are right, I went out and yanked the boot off of one of the joints so I could really get a good measurement and it looks to be about 9.9 degrees (I got .155" of total taper over a length of about .900"). 2"/ft = 9.6 deg. Doesn't seem like a lot but there is a difference, enough that you can see the slop of course once you tried to fit it in the spindle.

So far I am still thinking I will go down the ~7deg 1.5"/ft taper route but seeing now how close to 2"/ft it is I am going to go back and look at some stuff. After my post above I realized that Coleman offers a lower control arm with the smaller, upper ball joint thread and that Howe has a hybrid lower joint with the smaller, upper body but large diam lower stud so that will buy me a little more clearance to rotors. Another option v. the monoball item that has a Coleman pin in it, but that only comes in 1.5 taper from what I can tell, not 2. I can easily go to 1.5" without opening the bottom up (that is always the case as long as I am less angle than what is in the spindle now) and clearly going to the 2" reamer will be of little consequence if I choose to go that route as the angle change is slight. Howe offers a quite a few "hybrid" joints so I suspect they have the Chrysler housing with the 10 deg stud in some form that I could use.

For whatever reason, this has happened before within our little community. BJ taper documented as different than spec and ripped the BJ's out. Could have been disasterous! Matter of fact a whole batch.

Make sure you check this every time...:rules:

Tim,

Howe offers a quite a few "hybrid" joints so I suspect they have the Chrysler housing with the 10 deg stud in some form that I could use.

I don't think the Chrysler housing is available with the 224240 stud (2 in./ft. taper), but Howe fixed me up with a heavy duty, screw in housing -P/N 22329X - that screws into a 22340 weld-in ring. I talked to a Howe technician this morning and he said he would investigate the C6 lower taper issue.

Pappy

thanks for the info. I spoke to Coleman today about their lower control arms with the monoballs and I believe this is my best bet. I can get either 10deg or 7deg pins - I think I am just going to go Chrysler and 7 deg. I can ream the bottom to fit the 7 deg pin, it is fully adjustable for roll center height, and if I need more I can swap the pins in the uppers as well for roll center variance. Then the angle matches the upper so I only have one ream to keep track of and a standard K772 upper will work.

On a good note, I got my Forgelines today built to fit my 2011 Z06 with the 395mm rotors and these are what I am using on the Nova (295 fronts/335 rears). I had already built the suspension up from my custom stuff I had in the Porsche then ended up finding a buyer for the roller so took it all back out of the Nova - turns out I could literally have reused everything from the Porsche with the Vette spindles and stock Vette wheel offsets. I had designed that suspension for the Porsche without much info on a Vette and decent info on a modern Porsche... but just having an idea of how suspension works... turns out the A arm ratios match the Vette, caster within a degree, kingpin inclination the same as a C6 Vette. Guess that explains why the car picked up nearly 10 seconds on the track when I put the new suspension in! Good news is this means the Nova should be impressive for cornering :hapdance: This time I am hoping to make inboard shock mounting work out as well, already designed the rockers.

also good to hear the Howe is going to reconsider the taper on the BJs they are selling for Vettes - they will have a problem some day if they keep up with what they have now. They just need to carefully measure the taper and make their pin match - just not that big of a deal for a mfr IMO.

For those still following this issue, I completed my "fixes" and here is what worked for me. I used a quality 2 in./ft. taper reamer on the lower tapered hole in the C6 spindle. I had to remove only a slight amount of material, after which the Howe 224240 stud fit perfectly. I then used the 22329X screw-in ball joint housing to capture the stud. For the upper ball joint, I used the 2 in./ft. reamer to enlarge the 1/2 in. hole in a heavy duty (3/4 in. threaded shank) solid rod end. The factory upper ball joint in the C6 spindle fit the now-tapered rod end hole perfectly. The rod end then screws into a threaded insert welded into 1 1/4 in., .095 wall chrome-moly tude that is part of my upper suspension link. Taper problem solved -- moving on.

Pappy

Interesting that the taper reamed in the bottom of the Vette spindle didn't work with a 10 deg tapered Howe ball joint but the upper BJ works with a 10 deg ream... you sure about that? The stock upper and lower BJ seem to have the same taper to me.

I bought a 1.5"/ft (7 deg) reamer and got the lower spindle eyes reamed to that and put the Coleman lowers pins in and those fit pretty well. I now need to get the upper BJs out which is a PITA at this point - I have a press but the KPI of the spindle and so forth make it so I can't get lined up on the BJ to press it out (the lower end of the spindle hits the fricken press) so I may look into borrowing a puller tool at the FLAPS and see if I can get something setup to work. Nonetheless, I need to get them out and make a plug pressed back in with the taper reamed into it for my uppers.

I will have to get some pics in the future - been really busy lately and have a vacation planned next weekend so hope to be back on it in a couple weeks.

I measured the upper taper with a micrometer -- got 2.02 in./ft.. After I ran the taper reamer through the rod end, and inserted the upper ball joint, it appeared to fit perfectly. I painted the ball joint tapered shaft with a Sharpie, inserted it tightly, and rotated it. It scraped the Sharpie mark from top to bottom. By the way, I talked to the guys at Pfadt a while back, and they told me they had never had failure issues with the upper C6 ball joint -- not as much strain on it as the lower.

Pappy

Just from reading, I definitely prefer MFain's solution to the UBJ problem. I'd be very nervous about the overall affect on the upright after pressing that UBJ out -
From what I understand they are not designed to be replaceable - if the UBJ wears out you are supposed to get a new upright. You may put a lot of stress on it trying to push it out and then monkeying up a further solution.

No one else mentioned how the GMR had that caliper mounted - that looks very interesting and very stiff.

(Actually on 2nd glance, you are not really improving the mounting stiffness so much as just providing another solution to custom mounting and I guess it might be stiffer than cast in lug ears) .

Pappy - there is indeed less load on the uppers normally so you are probably fine as you note.

Preston - I will need to see what the upper looks like with the BJ out - I want to use a serviceable item and that is the point actually of why I want to get the stockers out of there and use a Howe piece with the upper As. It went in so it should be able to come out :unibrow: just need to make sure I get adequate support so I don't bend the upper "arm" of the spindle.

How about upper ball joint to wheel clearance?

good call on that - I am going to have to be careful how much stud sticks out of the upper to make sure it doesn't scrape the wheel. The 18s are so freakin' big I feel pretty confident but thanks for bringing it to the foreground of my mind again.

So the UBJ will go down into the top of the C6 upright like a normal arrangement or are you talking about mounting the UCA under the upright and pointing the UBJ upside down up into the upright ?

Either way of course your pivot point will change from C6 geometry but I'm sure you were totally aware of that.

http://www.victorypp.com/inventory/37

Not necessarily a recommendation - just an observation. Victory Performance (and I'm sure others) offer "ball joint ring taps". Any thoughts on tapping the upper end of the spindle for a screw-in ball joint? A good idea for aluminum? That might help control the height above the spindle that the ball joint sticks up. At one time I had also considered machining the upper spindle for a press in sleeve (with shoulder) that accepts a screw-in ball joint. A secondary machining operation could cut a recess into which you could "sink" the flange, also allowing you to lower the ball joint into the top of the spindle. Pressing in such an adapter ring would probably be a more precise operation than trying to press in a ball joint.

Pappy

Preston - short answer = yes, I am going to have the UBJ upside down. It does indeed change stock geom by lowering the pivot point, but since I am building a custom frame and pickup points for the Nova I will put the upper A pickup points at the correct height to have the roll center and camber gain that I want.

Pappy - I considered what you are talking about - getting the factory UBJ out of the spindle first to see what the material looks like after that procedure but being unsure if I could get good threads in afterward I decided to go the route I am. I also am not sure of what alloy that spindle is, tho' I admit to not doing any sort of search to figure that out :D but that would be important to know if you wanted to tap it as well. Another thing I considered was making a threaded collar (or buying if the OD fit in the existing hole), knurling it, pressing it into the upper, and having a good, steel thread interface to put a BJ into.

There are certainly multiple ways to skin this cat I believe so it is just a matter of picking one and just doing it. I do like the idea you have about using the stock upper if the taper does fit as well as you state after reaming.

Dave - double checked and in the 18" wheel I have over 1.75" of clearance above the spindle "ear" so I will have plenty of room to fit the lock nut in over the stud. Actually I had checked this on my Corvette but it has 19" fronts factory so after your post I realized I forgot to remove 1/2" for that so my stomach churned a bit but I remembered there was a fair amount of space :)

I got the uppers out of the spindles yesterday after borrowing a tool from AutoZone. It will be easy to make a piece to press back in with the reamed taper for the Howe UBJs I have. I got rather lucky, in my scrap alum I had a machined cylindrical piece that I jacked up making and have almost thrown out numerous times - it was exactly the right size to fit around the UBJ and shorter than the piece in the tool kit or the tool would not have fit :D

That said, in regards to questioning if you could tap the upper, I can say it might be possible but a total PITA to figure out how to do. The Howe upper I have will not slip into the existing hole so it would have to be opened up a bit. Then tapped. That strikes me as a pretty tough item to get square; probably have to build a jig to bolt down to a table on a vertical mill just to get it set up for machining. Furthermore, the material is rather thin around the existing BJ and the overall thickness there is pretty short so getting threads in there and more than just a few strikes me as a bad idea.

...and to pretty much wrap this up
 

Here are the uprights with the plugs I made to replace the factory UBJ with a tapered, press-fit bushing.

I will say
 

That is pretty impressive!

That's a pretty cool idea.:thumbsup: Impressive!!!!!!!

I like it! The slugs press fit -- how much interference in the fit?

thanks all :) Press fit is around .001" to .0015" - the holes were a bit out of round once I got the UBJs out so I measured with a bore mic until I found the min and max diams, took the average with the assumption the hole will become round again after I press in the parts, and shot for .001" minimum.

Better late than never as I see you have chosen your path, but for others...

The C5/6 Upper and Lower are the exact same taper, AND when I was researching the same..... I was told by a Speedway tech that their "10 degree" reamer (as probably Coleman and others too) are not truly 10 degrees but slightly under, and ARE an exact fit ironically enough to the C5/6's slightly under 10 degree taper.... I was told by Speedway that they simply round up for advertisement simplicity, and call them "10 degree" but their techs will confirm differently if/when quized.

Cool Nova by the way!

thanks - I suspect it is all "close enough" as if I measure the reamer and the Howe joint they aren't quite the same. Frankly I hate the tapered crap altogether and have been only running heims for some time now but I thought I would try to go with more off the shelf stuff on this car.

One thing I wanted to do was move the UBJ as well so I was pretty much always on a path to dump the stock upper - here is a shot of my dual A assy as of today - all the numbers are exactly what I want in terms of roll center, camber gain, and overall adjustability. I now have to fully adjustable pivot points (top and bottom) that I can mess with ride height and roll center pretty much at will.

For the Nova I am starting with a 13.5" lower arm length, 10.5" nominal upper length, and what both calculated in my computer and was verified with my angle finder in the attached image is a parallel lower arm nets me an 11 deg upper angle for a static RC of ~2.5" which is what I was shooting for. The lower pivot is not a ball joint but monoball from Coleman and they make a set of spacers that come with it. I can swap those around to vary the upper A angle and therefore static RC but comes with a 1:1 change in ride height (move the pin up 1/4" and the car drops 1/4") so if I need to make a big change I can then just buy a longer or shorter upper ball joint insert.

Long-time lurker here - Jim (aka phantomjock).
AWESOME SOLUTION to the C5/6 UCA! That is exactly where I was "stumped" - just today, in fact. My Howe gm K6141s were about to get sent back - but not now.

I've pressed (not Pounded) the Uppers out and cleaned up the uprights. My plan for lowers is straight forward - but that damn upper ball joint was the bugger! You've done the deed!

Coleman Racing makes a steel/weldable Spindle Eye/Taper, but mixed metals might not be as sweet as using aluminum. Have you considered making a small run of those in aluminum? I'd be in for a pair. There would be a nice niche market I'd think.

Again - Nice solution. Thanks for sharing that.:king:

Cheers - Jim

BTW that is a BAAD 914!

thanks for the kudos Jim :) Unfortunately I am not going to do a run of those inserts - at work I am pretty limited as to how much personal use I get on the machines, and if I were to make parts for anyone else it can all go bad. I probably should have made some spares for myself and I didn't do that. Unfortunately it is the one bad apple sort of deal - a guy was doing some "personal" work and selling parts and that lead to him being let go and a serious clamping down on the shop usage. I am already about at my limit so I have, for example, stayed out of the shop for the past few weeks and let it die down a bit.

That said, if you can find a shop with a lathe (which is pretty much any shop) and buy a taper reamer (Speedway has about the cheapest one I found and that is what I used), it is really easy to make these parts. It is all a matter of how much press fit you feel comfortable with. Dissimilar metals of course have a different thermal expansion so on parts that can get hot, like heat transferred from the brakes and so forth into the spindle, you could get a loosening of the parts, specifically steel into aluminum. The other way around, aluminum into steel, would get tighter as it got hotter and that would be fine, but I would be careful if you fall back on the steel insert idea. Make sure to get a good press fit, maybe go .002" press, freeze the steel part overnight, in the AM plop the spindles in the oven at 350 deg, make sure your press is set up and ready to roll, then with some good welding gloves and moving pretty fast, do one at a time to get the parts together and that should be pretty solid I would think.

I did not do any math on the spindle stress since the stock ball joint was already .005" (I literally measured this multiple times, then asked the lead machinist to measure it as I couldn't believe it, that is an insanely high press fit but I believe it is because the walls of the UBJ are rather thin compared to a plug like I pressed in), so I figure being around the press I used should be fine without generating too much "hoop stress". I would think .002 would be okay with steel...

edit - did some math. I will start off by saying this is for your reference, I can't guarantee anything... trust me, I will be watching these press in slugs like a hawk once I am using this car on the track... but I found a hoop stress calculator and messed around with it. At .005" press fit using an alum piece like mine, the stress is around 26.5 ksi, which is within yield on pretty much any decent aluminum. Using a steel slug would be just over .004" press for the same stress. Reality is the engineers didn't design to 26.5 ksi as the UBJ has a "thin wall" and the slugs I pressed in are more like a solid plug, so the stress would be much lower pressing in the UBJ. I guessed a .125" wall thickness for the UBJ and worked with that and got about 10.5 ksi, which would equate to a .002" press on my part. Gut feel was to shoot for .0015" so I wasn't too far off :) If you go with .002" on steel the stress will be more due to the steel material but I think that would work. Just get the temps very different and the press in won't be too bad.

And even MORE Thank-yous!
 

Tim -
thanks for doing those "maths."
I've got a line on a machinist locally that "does" ball joint re-tapering as a part of his business. I'll be heading over there tomorrow - numbers in hand with my steel slugs, uprights, reamer (mine from Coleman Racing), and 2 of my Coleman Universal Ball Joints. I can do a weld up fixture like the unit you got from Southwest Speed.

Wish me luck!
Pappy - looks like I've nearly got it sorted!

Cheers - Jim

Well, I'm back from South East Asia and working this suspension mod.
Getting close - but have a question maybe Tim or someone else can help with.
Does anyone know the taper on the Rear Toe Control on the upright? I'm looking to use tapered bolts with heims rather than ball joints. Unfortunately I don't have the toe control rods to measure.

These tapered bolts are widely used on circle track front suspensions. Speedway Motors has them in 2 version, GM and Pinto.


GM:
Stud is 5-1/8" long
Steering arm end has 7/16" thread
Tie rod end has 5/8" thread and is 3" long with 2-5/8" of thread
10 degree taper = 2" per foot
Pinto:
Stud is 4-13/16" long
Steering arm end has 1/2" thread
Tie rod end has 5/8" thread and is 3" long with 2-5/8" of thread
7 degree taper = 1.5" per foot

I'm hoping the C5 Rear Toe Control is either 7 or 10 degrees taper...
TIA - and Cheers - Jim

Well, thought I'd do a bit of measuring and see what shakes out.
The top (small end) of the location point measures 53/64" on my analog caliper. The large (lower) is 66/64" and over 116/64s and using the calculator I found here: http://www.magafor.com/841/uk.htm
I get pretty close to a 7 degree taper. [6.93 degrees]

Guess I'll be buying the Pinto shafts!

Cheers - Jim

I have this tracker kit and im getting a different measure than you are.

http://www.summitracing.com/parts/bae-3302001/overview/

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.