C6 front suspension measurements needed

Here's my dilemma: I'm building a custom frame for a two seater sports car & want to use the front suspension (upper/lower control arms & steering knuckle) from a C6. I'm looking for specific measurements from the stock setup, namely the measurements of the mounting points on the cradle & frame relative to each other and if possible the relative position of the center of the wheel and the orientation of said mounting points relative to probably the ground to give me the proper geometry. Normally, I have a few different people I work with on things like this but Covid shot all of that down. I work with Covid positive patients (I'm a PT in skilled nursing) so I can't have my usual help around. If anyone has the numbers, or can assist me in getting them I'd greatly appreciate it. I saw in the downloads section here that there's numbers for C5 front suspension but not C6. Now I've read & have had people say that the front upper/lower control arms & mounting positions are the same in the C5 & C6 and can interchange plus the geometry between the two front suspensions are the same, although the steering racks are different and mount differently. If that's true, then I should be able to use that information then.

C5 and C6 LCA & UCA are the same front and rear. The track width and wheel base could be adjusted obviously for your design. The thing that you will have to guess at are Center of Gravity and Roll Center, F/R weight distribution etc.

Not sure if you would want them, but someone sells a prefab cradle for C6 suspension front and rear. If I remember correctly it was a bit bulky, so may not be of interest. I think I saw them on racingjunk.com. And, someone may have posted photos here.

Superbuickguy just did c5 front suspension, but you probably have seen that thread. If not, check it out.

And I have a pair of the C7 uprights that have been "molested"-- BUT IN A GOOD WAY. The upper ball joints have been pressed-out and a sleeve inserted. This lets you choose an extended ball joint to work camber change. The lowers have been reamed for 6141 ball joints - a more common BJ from circle track racing.
If you are planning on using the "stock" GM upper and lower control arms - forget about these.

But--if you are thinking of designing your own, they could be very useful. They still take the GM/SKF bearing. The C7 uprights are much lighter than the earlier C5/6 uprights, GM learned a lot about strength to weight and changed their castings. This image is not of mine - but representative. https://cdn11.bigcommerce.com/s-njw...7-stingray-84036209__18854.1605701917.jpg?c=2

I'm going to full race mode and my suspension is now all rod ends.

I would let these go for less than what they cost from GM Parts Direct (they had the best price) and no charge for the machining. In fact I'd make a deal for Black Friday too! (need to get them off my shelf!)

Sounds like a real cool project. Look forward to seeing the plan/layout and pictures of the build too!

Cheers - Jim

Let me think about it...I currently have all the C6 & even all of the C5 components that I need...it's just the geometry for the front UCA's & LCA's that is still eluding me. If you know ANYWHERE I can find that info, I'd appreciate it. I've scoured the internet & called a few automotive engineering friends of mine but nobody has it. The project is stuck until I figure out how to get those measurements unfortunately.

phantomjock said:

And I have a pair of the C7 uprights that have been "molested"-- BUT IN A GOOD WAY. The upper ball joints have been pressed-out and a sleeve inserted. This lets you choose an extended ball joint to work camber change. The lowers have been reamed for 6141 ball joints - a more common BJ from circle track racing.
If you are planning on using the "stock" GM upper and lower control arms - forget about these.

But--if you are thinking of designing your own, they could be very useful. They still take the GM/SKF bearing. The C7 uprights are much lighter than the earlier C5/6 uprights, GM learned a lot about strength to weight and changed their castings. This image is not of mine - but representative. https://cdn11.bigcommerce.com/s-njw...7-stingray-84036209__18854.1605701917.jpg?c=2

I'm going to full race mode and my suspension is now all rod ends.

I would let these go for less than what they cost from GM Parts Direct (they had the best price) and no charge for the machining. In fact I'd make a deal for Black Friday too! (need to get them off my shelf!)

Sounds like a real cool project. Look forward to seeing the plan/layout and pictures of the build too!

Cheers - Jim

Click to expand...

A couple of paths here and sound s like you have chosen (or are close to choosing one).


I've personally opted for path 1, but that comes with its own set of consequences.

On path 2, there are a couple of guys here that are moving more or less that way. It comes with its own set of fabrication challenges and skills required too. [Chris and Pappy come immediately to mind]

I've not seen anyone here take option 3 - but I'll admit there are some advantages if starting from scratch.

To your question:
For the C5/6 layout, I recall Performance Trends has the points in their sample software you can get as a free trial. I don't recall if just the rear, or both. You'll have to some digging around - Its been a few years since I've used up my trial version.

For the PT trial, you can try it here: http://performancetrends.com/SuspAnzr.htm

Not specifically what you were asking for, but maybe encouraging. A fellow did a version on his 1929 Ford Roadster here: http://1929fordhotrod.com/johnsblog/category/the-front-suspension-for-the-1929-ford-roadster/

A set of numbers that may require some checking are here: https://www.pro-touring.com/threads/13842-C5-suspension-measurements

And if you are into CAD, might try these too: https://grabcad.com/library/corvette-c5-control-arms-1?locale=es

Also as a member check the download sections here too. There might be some data there

Best of luck - Post Pictures too!

Cheers - Jim

C5 suspension points from download section:

http://www.vettemod.com/forum/downloads.php?do=file&id=93

BBShark has a good link there too. I just found an XLS spreadsheet I'll load up too. Always surprised what I've saved over a bit of time!
Sorry its too big to load here and work a file xtn change, so will post in Download section.

Cheers - Jim

Thanks, I actually downloaded that file when I joined the forum, saw its from the Performance Trends Suspension Analyzer, but I've never talked to anyone that's actually used their free canned tune in that program. Not saying I don't trust their measurements, but I was hoping to find someone that has used those measurements successfully before I take them as gospel and weld up the tube frame.

Anyone here use those successfully??

BBShark said:

C5 suspension points from download section:

http://www.vettemod.com/forum/downloads.php?do=file&id=93

Click to expand...

Awesome, I'll look for it in the downloads section when you get it loaded up! Thanks for the helpful info in the previous response too, I appreciate it!

As soon as I get this project closer to completion, I'll post pics. It's something new, a complete new design of an older design of a two-seat sports car. Everything was cruising along fine until Covid. My structural engineer that was assisting me is an older gentleman and decided to resign to his own house until everything gets better, and since I'm around Covid patients all the time, I can't fault him at all. It just leaves me in a complete lurch, I can fabricate...but that much engineering is where my skill set lacks lol.

phantomjock said:

BBShark has a good link there too. I just found an XLS spreadsheet I'll load up too. Always surprised what I've saved over a bit of time!
Sorry its too big to load here and work a file xtn change, so will post in Download section.

Cheers - Jim

Click to expand...

There was a guy on here a while back that was building a one off car that was using C5 geometry. His challenge (an I suspect yours) was that the geometry for a C5 is based on wheelbase, weight distribution, roll center, CG among lots of other things. What he did was slotted the UCA attachment front and rear to tweak things like camber gain.

Like to see pictures of what your doing. Sounds interesting.

BBShark -

I loaded that excel file a few days ago. Any chance you can clear it? If I need to reload - can do. Cheers - Jim

There ya go!

I figured it out - ZIP not XLS!!
But too big to load here.

I'm heading over to Downloads shortly.

Meanwhile - a work-around. Find the file attached as a "uni" file. Download (Save link as), then change the fname (file extension) to 7Zip. Open with 7Zip -- works, but klunky operation. I'll delete this when all loaded.
Thanks.
Cheers - Jim

I converted it to a pdf and downloaded.

http://www.vettemod.com/forum/downloads.php?do=file&id=128

Nice, thanks! Have any of you (or know of anyone that has) used these measurements to build a frame & mount the UCA's & LCA's to? The numbers look right, but man...without someone verifying that the numbers worked fine for their ride on the street and/or track...I just don't want to use them & find out that they're off a smidge (or a mile) lol. It seems like those numbers off that PDF from Suspension Analyzer are what I need though....

phantomjock said:

I figured it out - ZIP not XLS!!
But too big to load here.

I'm heading over to Downloads shortly.

Meanwhile - a work-around. Find the file attached as a "uni" file. Download (Save link as), then change the fname (file extension) to 7Zip. Open with 7Zip -- works, but klunky operation. I'll delete this when all loaded.
Thanks.
Cheers - Jim

Click to expand...

Just a quick thought (sometimes get too old before smart). There is an outfit that builds interface "frames" if you are planning on using the C5/6/7 control arms and hubs. Might save a bit/lot of engineering to use those on your "custom-built" frame. Had these been available, I might be done now with my suspension design/build. But now I'm so far down track, it will be what it will.

Here is a link to one in particular:
https://rick486.wixsite.com/dobbertinperformance/why-isnt-everyone-uses-the-c5-or-c6

He also makes a mid engine adapter if you want to go really wild. In hind sight I could have saved a heap of coin! But now I'm a smarter engineer for it!

Cheers - Jim

Not affiliated - just think its a really cool product.

For just numbers, check this too: https://www.clevelandpap.com/corvette-rolling-chassis-measurements/

The Cleveland P&P site has OA track width of a C6 (outside of tire) at 70" front and 71" rear. I measured the width (at the widest point of C3 body) at 69 5/8" front and 68 5/8" rear. I always thought that a C6 was much wider than a C3.

Interesting thought that you could use a stock C6 suspension under a C3 with maybe 1" flared fenders.

I actually called them a few weeks back & asked them about this! Their only about an hour away from where I live so I figured this would be easy. I talked to the one gentlemen up there & he told me to not come up & measure that because it was damaged in a wreck & he didn't trust it for those specific measurements that I need....at least he was honest.

I did find this though:

http://www.quarkdog.com/El_Camino/Pages/Sub_Pages/Front-Suspension.html

It looks like he used the numbers out of the Suspension Analyzer for his build, but manipulated them a bit to fit the narrowed front frame, but he built a complete custom frame for his El Camino so maybe the numbers are good to use for building the setup I need.

BBShark said:

The Cleveland P&P site has OA track width of a C6 (outside of tire) at 70" front and 71" rear. I measured the width (at the widest point of C3 body) at 69 5/8" front and 68 5/8" rear. I always thought that a C6 was much wider than a C3.

Interesting thought that you could use a stock C6 suspension under a C3 with maybe 1" flared fenders.

Click to expand...

I did find this though:

http://www.quarkdog.com/El_Camino/Pa...uspension.html

It looks like he used the numbers out of the Suspension Analyzer for his build, but manipulated them a bit to fit the narrowed front frame, but he built a complete custom frame for his El Camino so maybe the numbers are good to use for building the setup I need.

Click to expand...

First, that is a real comprehensive site you found. Thanks for bringing that in!
Second, one of the (potential) pluses to making your own control arms is you have the ability to make some important adjustment. Mind you, you can still get some with the C5/6/7 arms, but perhaps less. A big advantage to using the GM Arms - you don't have to struggle through the ball joint selection process. (Again, another trade off.)

In the words of a buddy; "Ain't Hot-Rodding Fun?!"

Cheers - Jim

Wow. I looked at the guys site. Very impressive. Merging an El Camino with a modern GTO with modern suspension components. Looks like the project fizzled out after a couple of years. Too bad.