IRS and king pin angle

voodoovette

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Dec 5, 2008
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92
Location
Crystal Lake Illinois
I am installing a new IRS suspension in my 73 corvette that has both upper and lower control arms with a CV slip axle. I am fabricating my own upright and my question is if king pin angle is important with an IRS set up. Can I set it up vertical or do you need it at an angle like the front suspension. Every article I have read is for a front suspension and I just want some clarification before commenting to a specific design, thanks.:sos:
 
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Welcome to the motley crew of the Flying Dutchmen....

someone FAR more knowledgeable about suspension will be along, I"m sure....

:cool::stirpot:
 
The kingoin angle in the front is important because of it's effect on scrub radius. Not a big concern in the back.
 
Exactly, and the kingpin angle also affects the caster change/effect when turning the wheels (since the steering axis will start to right itself, this is evident by most cars lifting one side of the chassis when steering sharply)

Easiest way to set it up would be to design it so that with the selected wheel diameter & width you keep the kingpin angle/steering axis inclination such that it intersects ground level about the center of the tire contact patch. That way you can set a tiny bit of toe and have no scrub effect.
 
Exactly, and the kingpin angle also affects the caster change/effect when turning the wheels (since the steering axis will start to right itself, this is evident by most cars lifting one side of the chassis when steering sharply)

Easiest way to set it up would be to design it so that with the selected wheel diameter & width you keep the kingpin angle/steering axis inclination such that it intersects ground level about the center of the tire contact patch. That way you can set a tiny bit of toe and have no scrub effect.
Thanks TT and BBSHARK,
This is what I needed to know for I can get started fabricating the uprights. The upper control arm clearance is going to be real tight but I believe I will have enough with having the upper control arm attach point as low as possible on the upright, reducing the bump stop and if I must, notch the frame. I appreciate all the advice I can get, thanks.
 
Whose CV are you using? I have been contemplating using them because they are almost indestructable. Can you put some photos or other info up too?

Thanks
 
PCF_mark,
I am going with 934 CV joints. The kicker is I am using a "ford" 8.8 aluminum IRS differential, I know I used the "F" word, but It was easy to find and cheap. Also the "drive shaft store" will sell individual 31 spline output shafts for the 8.8. They are made for the 930 CV but I will MFG an adapter plate, not very difficult, for the larger 934 CV. On the outboard end, I will run a C5 corvette hub that has been re-splined for the larger 33 spline outer stub axle. I am in the process of fabricating the uprights and will post some pics when I get them done. Also I sent the 8.8 housing to Strange Engineering and had the cheap and weak caps replaced with billet ones. I went this way after adding up the cost using the original differential, U-joints and slip axles and decided I needed something stronger and a true double wishbone rear suspension.
 
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