C3 front scrub radius?

Mike, The kingpin angle of a C3 spindle is 7 degrees, the angle on a C4 spindle is 19 degrees. The distance from the hub mounting face to where the hub centerline intersects the kingpin axis is 5 7/16 for a C3 and 5 3/8 for a C4.
 
BBShark said:
Mike, The kingpin angle of a C3 spindle is 7 degrees, the angle on a C4 spindle is 19 degrees. The distance from the hub mounting face to where the hub centerline intersects the kingpin axis is 5 7/16 for a C3 and 5 3/8 for a C4.
Click to expand...

Which C4 suspension (early or late) is that info from? Are there some drawings somewhere I can get a look at?

thanks a bunch,
Mike
 
With that info and the total tire diameter you can simply calculate the scrub radius.
 
Twin_Turbo said:
With that info and the total tire diameter you can simply calculate the scrub radius.
Click to expand...

Yes and no. The early and later C4 suspensions sure look different regarding the position of the upper ball joint, hence my question.
And, just eyeballing the same wheels/tires on the stock '69 and the C4 suspension sitting in the corner, it just looks much different than 1/16 inch. I'm just trying to figure out the datum point, as it were. I can do the geometry calculations after that.
 
The assemblies I measured for the C4 are w/ speed sensor hubs. I think that means 91-96. I have drawings for the C3 spindles and hubs but not the C4.


69427 said:
BBShark said:
Mike, The kingpin angle of a C3 spindle is 7 degrees, the angle on a C4 spindle is 19 degrees. The distance from the hub mounting face to where the hub centerline intersects the kingpin axis is 5 7/16 for a C3 and 5 3/8 for a C4.
Click to expand...

Which C4 suspension (early or late) is that info from? Are there some drawings somewhere I can get a look at?

thanks a bunch,
Mike
Click to expand...
 
cad drawing of the C3 spindle? That's the only susp. part I don't have, never got around to doing them.
 
I keep digging up "old" threads that interest me and my project, "Elvira."
I've been all over the interWeb - and VetteMod is the place for much of the best information, assistance and importantly images. Thanks Heaps to TwinTurbo and all the originators and "keepers" of the 'Flame" that fuels our passion for C3s!:beer:

Now, on to the issue: I've found this diagram:
12695c532eb501243.jpg that "kinda" answers 69427's question from a while back. But now, he no doubt knows the answer!

But for me is the early C4 front upright really 19 degrees?! Wow. What is the Caster on the front end? 24 degrees? I'm looking at using these early C4 uprights for my front end, and would like to do some modelling before -- Buying.

Any help?

Thanks and Cheers - Jim
 
You can sort of see the steeper C4 king pin angle in this pic.


45c5380f6df5b9.jpg
 
Yes! And Thank you! The difference is quite obvious. I'll take 19 degrees as a given for my study.
Looks like a Van Steel front assembly in the foreground - or at least similar to the one I currently have on the project (that I'll be replacing).
Very good picture for comparison. Thanks again. :beer:

Cheers - Jim
 
Is the 19° possibly an apples to oranges comparison because the lower ball joint is below the spindle instead of on top like a C3?
 
Chris

I'd look for point of rotation to point of rotation - Ball center to Ball center ought to be the measure in reality. I bet the line between the the center lines of the upper/lower tapers in the spindle are "pretty close." Maybe not exactly "spot-on" but close enuf.

If I go for the C4s I'll shoot some picks C3, C4, C5 and we'll have a fair compare between several generations. Although the C4 seems to have at least 2 (if not3) variants!

BTW - your project is progressing nicely. You'll note my "chilly weather" has had me on the 'net and not in the garage.

Cheers - Jim
 
I measured the angle of a C4 upright at 19 degrees. I had a comparison picture but cant find it now. This was a (I think) a 91 part. The lower joint is really a bitch to grease because it is so deep inside the wheel.
 
phantomjock said:
Chris

I'd look for point of rotation to point of rotation - Ball center to Ball center ought to be the measure in reality. I bet the line between the the center lines of the upper/lower tapers in the spindle are "pretty close." Maybe not exactly "spot-on" but close enuf.

If I go for the C4s I'll shoot some picks C3, C4, C5 and we'll have a fair compare between several generations. Although the C4 seems to have at least 2 (if not3) variants!

BTW - your project is progressing nicely. You'll note my "chilly weather" has had me on the 'net and not in the garage.

Cheers - Jim
Click to expand...


:beer: Thanks Jim, just another thought, if you’re going through the trouble of a front steer spindle swap, why not have a look at the C5 stuff? Much better bearing and brake options for road race applications. The aftermarket is all over the C5/6 spindles with different steering arms for different Ackerman. There’s also a thread on pro-touring.com where a guy has re-engineered the c4 spindle for a different Ackerman. I’ll try to find it and post the link later
 
Looking forward to your Ackerman Link - so to speak!

Because I'd like to run 15 inch wheels - the early C4 fit and C5 require much larger rims - think you know that and $$$ tires to burn up track side. Yes bearings and brakes are also a consideration -- and in the mix.

For now I'm just happy to be somewhat started on the old girl again. Even though the little one demands attention too - that's why I call her "Lolita!"

Soon the weather will be good and the track will be calling!

Cheers - Jim
 
Chris - Great link! Thanks. That gave me this:
12695c55b1752abf1.jpg
It uses a steel spindle - not unlike many of the circle track roundy-round cars - and those are available with a wide range of wheel mounting options.
It could even use a C5 (race rated) hub mounted - rather than a stock car setup. I recall he use 3/16 cold rolled steel plate.
Here is one DIY that shows an interesting approach to getting the right wheel bearing, and working to a scrub radius (keeping on thread a bit)
12695c55b495b4a67.jpg

This is a modular approach used by the stock car crowd. Keeping with the topic of Scrub Radius - these are available with several KPIA, 7, 8, and 10 degrees I recall. I suspect you "could" put some shims in to get more. Because its modular - I imagine you can buy just the bits, i.e., the black steel piece. The spindle shown is for a wide-5 hub setup - and huge bearings.
12695c55b495c938d.jpg

and another CAD too for thought:
12695c55b495e5b00.jpg

So, I chased the rabbit down the hole..

Here is a post from the page I got to from the original link. It shows the ball joint centers as a good comparison too. You can follow that link - but it is not a hypertext.

And here is a nice shot that saves me some time and $, while sorting this out!
12695c55b119e1659.jpg

So now I'm also chasing Wide-5 hub mounts, IMCA Sportsman Hubs, and, of course, the Mad-Hatter!

Not sure where I'll wind up - just call me "Alice!"

Cheers - Jim
 
Well, back to the ACKERMAN link, this is what really I got to (initially):
12695c55bd4e19ba3.jpg

A nice setup the guy designed for the Tri-5s.

It works the steering issue, but I got concerned about bearings and that is when I jumped down the rabbit hole!

Cheers - Jim
 
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