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on May 13, 2010, 7:28 pm, Daze wrote:
did it get all your questions and concerns answered?
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Very interesting but of course it just stirs up up my hunger for more details. I found this image which partially satifies my analytical side.
The MustangII wheelbase is 96.2 and my 67 is 108 and so it is easy to see how the wheelbase affects the ackerman angle. I don't have a handle, yet, on the steering angles but that should be easy to attain.
I spent most of yesterday trying to find details about the MII suspension, steering arm length, angle, etc but found nothing. The only thing that came close was a statement by Heidt that their 2" dropped spindle maintains all of the stock mustang geometry. That's a big statement without much supporting detail but it does show they know there is a difference.
There other thing that was very interesting for me, I am still leaning towards MII, is that most of the aftermarket Mfg's have engineered out the bad elements and made improvements to their design. Heidt again appers to be the leader or least the one sharing details. They talk about the 2" dropped spindle dealing with a lower stance but more importantly addressing the bump steer issuse and improving the roll center. They build in a 3 degree angle on their cross member so that the upper control arm has the proper dive in angle. And again they say that their spindle maintains all of the stock mustang geometry so I hope they mean ackerman and turning radius. They offer different configurations but the one that appears to have the best performance is the tubular A arms upper and lower which eliminates the strut rod and the coil over shocks.
The only other issue I found was the power steering rack tends to be mismatched with factory ford power steering pumps but is easily fixed with a flow restrictor from SpeewayMotors that reduces the flow from 3gph to 2gph.
Did I answere your question
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couple things its not just wheel base, its also track width. Because its an angle if you increase the track width as you increase the wheel base along the same line from the ball joint to the center of the rear axle than you maintain the correct ackerman. Make sense??
Steering arm length should be a non issue in relation to a mustang II kit because it uses a Mustang II R & P which is designed to work with the specific steering arm ratios.
Also if the 2" drop spindles reduce bump-steer, bump-steer must be a normal issue on a Mustang II because bump-steer is a function of spindle arc, tie rod arc, and tie rod to spindle mounting location, which there again is determined by all the new parts being installed with the Mustang II kit.
I would be careful with any post that says "maintains the correct Mustang suspension geometry" because that could make that claim and maintain the correct Mustang II steering geometry because its still a mustang.
Either way I think you will be happy with the MII kit, its not like it is a bad set up, in contrast it is a very good set up.
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excellent points It's really nice having someone to bounce things around with.
The stock MII track width is 5" narrower than my mustang and the equation demonstrates the affect that trackwidth has ... I agree. The MII kit comes with a new crossmember that moves the trackwidth back out to 67 stock. My assumption is that trackwidth then becomes a non-issue at that point ??
Good catch on the stock geometry phrase ... I will try to validate which mustang they are referring to.
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I did the math Assuming the ball joints are in the same relative location to over all track width
for both the Mustang II and the 67 Mustang and assuming the track width for an MII car is 55" and a 67 Mustang is 60":
for the MII spindle to have the perfect ackerman on a 67 Mustang you would either need to change the arm to 76.83 degrees in relation to a line between the ball joints on both sides of the car, or you would need to increase the wheel base on the 67 Mustang to 128.21" (these #s are not completely accurate because I based them on over all track width rather than ball joint to ball joint width, but should be close enough to paint a picture of whats going on)
Based on that info you will have more Ackerman:
1. Steering response will be smoother.
2. Your vehicle will react smoothly to any steering input.
3. steering will be less aggressive and more input at the steering wheel will be required to make a turn than would have been required on a Mustang II in stock configuration.
It's amazing the arm angle is only different by 2.33 degrees but thats enough to really change things
Here is the measurements I came up with when I did the math.
I too love the brain storming and thats exactly why I set up this forum. I have a really good knack for problem solving, but some times another point of view is all it takes to make a good idea a fantastic or brilliant idea.
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Hey Joe, I am surprised you didn't have any thoughts on the post I made with... the weal base and track width calculations.
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Still formulating I liked the comparison a lot but of course it was not precise enough for my over analyzed approach. I took some measurements from my 67 and I am putting together some lines and dimensions. More to come
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my "over analyzed approach" can't weight to see what your "over analyzed approach" comes up with
as I was doing those calculations I kept thinking to my self, "I wish I new the actual distance from the ball joints in both the donor car and the car getting the MII front end". Hope you can get both those measurements so we can see exactly what the ackerman difference is. In fact once you have those numbers please let me know as I would also like to do a comparison to the first generation Mustang. I have no intention of using an MII kit but would like to know exactly how far off the ackerman is for a 65-66 car.
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Definitely cut from the same cloth ...
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