Wilwood ProSpindle kpi/sai

[69_Sportsroof]

I've been doing a ton of reading and playing around in suspension designs, and was planning to use the prospindle.

In the drawing from wilwood's site it shows a 79 degree angle from the ground plane to the ball joint axis, which leaves 11 degrees... Correct?

http://www.wilwood.com/PDF/flyers/fl193.pdf

[Ron Sutton]

I've been doing a ton of reading and playing around in suspension designs, and I have something I can't figure out.

I've found many people(including reputable sources like Ron Sutton) saying that the wilwood prospindle has around 8 degrees KPI/SAI built in. But looking at the drawings, I swear it should be 11 degrees... It is simply the angle between true vertical and the line drawn between ball joints correct? In the drawing from wilwood's site it shows a 79 degree angle from the ground plane to the ball joint axis, which leaves 11 degrees... what am I missing?

http://www.wilwood.com/PDF/flyers/fl193.pdf


I was wrong. I "assumed" the Wilwood Pro Spindle was a true copy of the Pinto/Mustang II spindle, which has an 8° KPI. But Wilwood only copied some things. The KPI in both their standard height & dropped spindle is 11°. With 11° KPI ... the "dynamic Camber" split between the inside & outside front tires (when turning) will be quite large ... making it nearly impossible to get both tires to have full contact patch.

My apologies for the misinformation. If you can post a link to that post, I'll go there & correct it.

Best wishes.

[69_Sportsroof]

Ron, no problem at all. I just assumed I was wrong ha-ha. That is in your great (seriously)write up here:
https://www.pro-touring.com/threads/111963-Front-Suspension-amp-Steering-Geometry-for-Track-Performance

I was thinking that 11degrees with additional caster would be quite a lot which also confused me. How bad is bad? I am in the planning stages of a suspension design and was planning to use the pro spindles.

[Ron Sutton]

Ron, no problem at all. I just assumed I was wrong ha-ha. That is in your great (seriously)write up here:
https://www.pro-touring.com/threads/111963-Front-Suspension-amp-Steering-Geometry-for-Track-Performance

I was thinking that 11degrees with additional caster would be quite a lot which also confused me. How bad is bad? I am in the planning stages of a suspension design and was planning to use the pro spindles.

I don't know if I can quantify it. How bad is not having full contact patches of the tires?

Since you haven't bought them yet, Can you switch to a Pinto/Mustang II spindle with true 8° KPI? I have a source in the racing world that uses these.

I corrected my error in that post. Thanks for the link.

[RSX302]

I was trying to find information on the ATS AFX spindles. Although expensive, would these be a good alternate?

[Ron Sutton]

I was trying to find information on the ATS AFX spindles. Although expensive, would these be a good alternate?


I think so. The KPI is 8°. The ball joint pads are dropped, which is a more modern set-up. If you want to just bolt it on & go, you should talk to the Speedtech guys or shops that have worked out the geometry with the ATS AFX spindle ... so You have some confidence the roll center, camber gain, Ackerman & bump steer will work out. if not, you should work out the geometry ... either on your own with a software like Performance Trends Suspension Analyzer or hire someone like myself to work it out with you.

[RSX302]

Funny you bring that up. I tried the demo version.

My lower arm is currently flat and forward. I was just playing around to get an idea of how movement changes antidive.

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[Ron Sutton]

Funny you bring that up. I tried the demo version.

My lower arm is currently flat and forward. I was just playing around to get an idea of how movement changes antidive.

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I couldn't open the attachments. Can you change them to JPEGS & post them?

[RSX302]

Bummer..I entered from my iPhone. Let me try and fix

[RSX302]

Let's try this, I emailed to myself and switched over to Windows

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[Ron Sutton]

Hey Ron DeRaad,

I like a lot of anti-dive, but ... IMHO ... you've got way too much in this design. Around 40% is my typical target.

[RSX302]

Cool thx Ron
Yeah, 72% antidive was based on moving the rear lower frame point up 1" from flat. Flat was 25% antidive. Doesn't take much to move that value.

Is that all you see? I will be extremely happy if that's the case.

Sorry, Didn't mean to hijack the thread. At least this is with the pro-spindles...dOH

I think I'm off a little on the upper ball joint dimension as the ball joint is actually inside the rim a little more. I think this is reflected in the 11.75 deg spindle angle shown in the image. As you were staying, the Wilwood's spindle was 11degs. Was hard to get to with it on the ground. Now that I have everything blown apart for the engine replacement, I will be able to double check my measurements. I had everything drawn in CAD first. Made it much easier to transpose the numbers to the suspension software.

[Ron Sutton]

Cool thx Ron
Yeah, 72% antidive was based on moving the rear lower frame point up 1" from flat. Flat was 25% antidive. Doesn't take much to move that value.
In my world an inch is a ton. I'm constantly working in 1/16" increments.

Is that all you see? I will be extremely happy if that's the case.
Ah ... sorry ... I didn't think you were asking for more. I can't evaluate a front suspension design from what I can see over the internet. Too many things need to be checked dynamically. Frankly, I wouldn't if I could. Providing the entire suspension design parameters would be giving away my business trade secrets.

Sorry, Didn't mean to hijack the thread. At least this is with the pro-spindles...dOH

I think I'm off a little on the upper ball joint dimension as the ball joint is actually inside the rim a little more. I think this is reflected in the 11.75 deg spindle angle shown in the image. As you were staying, the Wilwood's spindle was 11degs. Was hard to get to with it on the ground. Now that I have everything blown apart for the engine replacement, I will be able to double check my measurements. I had everything drawn in CAD first. Made it much easier to transpose the numbers to the suspension software.

Cool. Keep playing & have fun with it.

:cheers:

[RSX302]

I completely understand.. thanks

[69_Sportsroof]

RSX302, regarding your a-arm movements, I found these which I plan to use to help with fine adjustments when I get around to building my suspension. They are slugs you put in to the plate(where the arm mounts) and allow for 1/16 inch adjustments that are repeatable.
http://www.joesracing.com/i-21091114-joes-slug-type-a-plate.html
http://www.joesracing.com/i-21091157-slotted-a-arm-slug-kit-0-1-2.html

I found the wilwood pro spindles while looking to see what seemed common in aftermarket setups and a lot of people mentioned them as being a nice strong unit. Another thing I've seen is people seem to have clearance issues between the upper ball joint and the wheels, so I thought I could use the 2" drop spindle. I downloaded the suspension analyzer demo and and plugging some numbers in, but I know it should affect ride height(obviously) and I think it will affect scrub radius. Does the drop spindle result in an unrealistic wheel offset needed to maintain a decent scrub radius?