Mustang II Suspension Question Moved from Suspension section

[TBART70]

I have an after market Martz chassis for my 70 Camaro (should have bought a different one) with mustang suspension, the lower control arm is 15" from bolt center to middle of the ball joint. My question is if I replaced the control arm with one that is 15 3/4" long and move the inner bolt hole in 3/4" how much of a difference will there be in geometry. I found a real nice control arm from TCP (chris alston) that I would like to utilize because some of the features of my chassis is not that great. Any help would be greatly appreciated. Also does anybody know how I can figure out the total geometry on this thing? Also would like to put ATS spindles on it. Mostly purchased it for the WOW factor it is only a street car no racing intended. Most people at the cruise nights won't even know that it isn't the best suspension but it looks cool. As long as it handles as good as stock or at least a little better I will be happy, but I figured if I could improve a little I will.

[sinned]

Mustang II front clips are street rod parts, not designed for hard core handling. You would need to redesign the entire front end to get any real handling out of it. Figuring out the end numbers is the easy part, taking all the nesessary measurements is the hard part.

[RobM]

every one says that but i never hear what is actualy wrong with them... I have yet to blue print one out. what are the major down falls of the mustang II? they are prety easy to fabricate and it would be cool if i could work the bugs out and give it a try in my car.

[TBART70]

I am a newby on suspension dynamics still learning, I know that there are some people on here that know their stuff. Have spent many hours reading their posts. The problem with my chassis is that it was flimsy, it added some supports to it, seems to have helped alot. The mustang suspension on the other hand many have said it is less than desirable. That's why I would like to make some minor improvements. Also learn the pro's and con's of it.

[sinned]

every one says that but i never hear what is actualy wrong with them... I have yet to blue print one out. what are the major down falls of the mustang II? they are prety easy to fabricate and it would be cool if i could work the bugs out and give it a try in my car.

Control arms are way too short resulting in drastic lateral RC migration as well as excessive scrub radius.

[parsonsj]

Dennis has it. Here's some more thoughts on the MII suspension as sold by AME.

jp

[red65FB]

Hi - Newbie here. While I understand the negatives of the MII suspension, I believe that there are enough people running MII's that would like to improve them. Until now, the only advice I have seen is "start over". There must be something that can be done in the world of bolt-on's that would improve the existing geometry.

To add to TBART70's suggestion, I myself would appreciate some ideas to improve what I have.

AT

[alcino]

Works for me. But my car was designed for it

[sinned]

Hi - Newbie here. While I understand the negatives of the MII suspension, I believe that there are enough people running MII's that would like to improve them. Until now, the only advice I have seen is "start over". There must be something that can be done in the world of bolt-on's that would improve the existing geometry.

To add to TBART70's suggestion, I myself would appreciate some ideas to improve what I have.

AT

No, there is nothing that can be done to improve the geometry other than to start over. It doesn't matter if throw a million dollars at it, without throwing the control arms in the garbage and starting from scratch it a junk street rod design (or in Al’s case as kick ass OE design that works well ONLY on factory Mustang II chassis').

[TBART70]

I looked at pictures of II Much unbeleivable car.
He said his lower control arms were in the 13 in. range and went to 15.6 in. Mine are 15 in. now and I want to go to 15 3/4 in. I do not know what the uppers are I have to measure. As long as my suspension is durable and reliable I will be happy. If it handles good that would be a plus. I will have a 17x9.5 wheel with a 5 in. backspace with a 275/40/17 tire on the front. I don't know what these demensions will do for scrub radius, camber gain or RC migration ( had to look up definitions on them) but hope before the car hits the road in a few years I will understand them better.

[red65FB]

Alcino - love your car. Great write-up in PHR. What's different in your set-up vs. a bone stock MII? TBART70 mentioned longer LCA's. Are these fabricated? My car is a 65 Mustang FB with an old school factory MII cross-member transplant - not a kit. Apart from the obvious differences in wheelbase, and frame construction, I don't see why changes that worked for you wouldn't offer improvement in my application.

Any word on wether or not AFX's planned MII spindles will improve geometry?

AT

[RobM]

is that scrub radius caused but the factory setup or droped spindles?

[sinned]

As I recall Al’s control arms are the stock pieces it came with, or at least the stock dimensions. The reason it works on his car is because it was designed to work as a package with the entire chassis. That is the biggest problem with today’s incoming group of PTers, looking for the easy way out. You cannot simply throw some parts at a frame and expect it to work. Engineers spend hundreds of hours designing suspension systems as they are quite intricate and are definitely one of the "do it right or die" systems; kind of like brakes. If you don't know what you are doing, it is best to seek the assistance of someone who does to aid in the design/construction of what you are doing. I have over 8 months of design, and redesign, and redesign and hundreds of dollars spent on "wall art" trying to make everything work properly. It's just not as easy as you all would like it to be.

No, you cannot make Mustang II parts work on another chassis and expect it to handle well enough to run with any of the more advanced groups on a road course. Sure it will drive and turn on the street but handle well, not likely. Even in Al’s case his car could handle better with some redesign work on the UCA/LCA length and pick-ups. I realize it ran .99g on the skid and does well on the road events. It also weighs half of most the cars out there and runs R compound tires.

The scrub radius concern comes in as the control arms are so short that you need a very short backspacing to get the fitment right.

[red65FB]

As much as I would love to start over again, I bought this car pre-modded, prior to my doing enough research to know what I should be really looking for. I come from tracking a modded C5 and a Miata previously - those were great handling cars, so I'm not expecting miracles, nor am I trying to shortcut the right way to do things. I will say that for what it is, the car handles high speed canyon runs quite well with more stability than I thought possible - on street tires.

Your right - R-compounds and stiff springs will make just about anything stick like glue, a band-aid if you will. In the meantime, until I win the lottery, I plan to squeeze as much as I can out of the car as it is. I'm holding out some hope for the rumoured AFX MII spindle...

[alcino]

sorry if i ryled things up here.

What's different in your set-up vs. a bone stock MII?

Only the rubber bushings replaced with the poly ones. Everything else is factory, but the alignment settings.(-1.75d camber, 3.5d caster, 0.5inch toe out)

I agree with dennis about the wandering RC from the short arms, or so I think. When I'm hauling ass on the road course it can be really scary during transitions when the weight is being shifted from one side to the other. I don't know how to explain it other than the car starts to feel unpredictable and I say "oh *****!" in my head. Is that the RC moving dennis?

I also agree that there is room to improve. In the future I would like to get wheels with the most backspacing possible in the front, with taller dropped spindles(AFX?) or taller balljoints and making long control arms to fit. I'm hoping to get close to 3 more inches on the control arms.

Dennis do you still have that suspension program? Could I give you some dimensions on my ideas and see how they would turn out?

[Norm Peterson]

0.5inch toe out

half an INCH . . .

(BTW, The same bits worked fairly well on the Pinto, with no evil traits that I ever found.)

Norm

[sinned]

Yeah, I have WinGeo. Send my the numbers and I'll run them.

[red65FB]

sorry if i ryled things up here.


Only the rubber bushings replaced with the poly ones. Everything else is factory, but the alignment settings.(-1.75d camber, 3.5d caster, 0.5inch toe out)

I agree with dennis about the wandering RC from the short arms, or so I think. When I'm hauling ass on the road course it can be really scary during transitions when the weight is being shifted from one side to the other. I don't know how to explain it other than the car starts to feel unpredictable and I say "oh *****!" in my head. Is that the RC moving dennis?

I'm running similar alignment numbers, except for that toe out thingy. I wonder if this could be causing some of your transitional instability at higher road coarse speeds? You could be exagerrating the RC problem. Also, I noticed the rear of your car is very tall, this might also be adding to that sensation. I'm no expert, but screwing around with my rear ride height has resulted in improvements at the wheel and SOTP.

I too have been thinking about some of the solutions your thinking of. I'm running 4.5 BS on 17x8 rims - there seems to be room for moving the LCA and balljoint outward. Coupled with maybe a larger rim diameter to clear everything?

[RobM]

that toe out give you better ackermen right?

[baz67]

I would think no. Ackermen is a determained by the steering geometry. It does not matter what the toe is set at to the geomtry.