Talking with Maximum Motorsports today about a Torque Arm / Panhard Bar setup for the Bullitt. Basiclly he said that I'd have to buy the TQ Arm & PHB plus subframe connectors and new rear springs. This puts the total bill at about $1100. I can buy/swap a Cobra IRS for that price. So that begs the question. Which one is better for a street/autocross car and why? Not really looking for an opinions, but real facts as to why one is better than the other.
TQ Arm/PHB or IRS
Bullitt5566
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Aww, more like on full compression the front tires will change toe either toe in or out depending on the suspension geometry. And also the outer tierods have to be parellal with front arms otherwise you will get a drastic change in bumpsteer etc when you lower it. Not sure if this makes sense Im tired. LOL I would think body roll would just effect weight transfer and not camber angles, but I could be wrong.*adding to my post above*
It isn't actually suspension compression of the front "A" arms that leads to the gain of camber, it is the body roll that does it.
Solution..... don't take corners! oh, wait a minute
Do aftermarket k-member change the front arm angles besides moving them forward like MM's unit.
I wonder if a unit like MaxiMo raises the lower arm pivot points. This is getting interesting now.
Well it might be an issue with the front arms pivot points being to low, but I wonder if the flex of the stock k-member
effects camber change as the car goes into a corner. Hmmmmm...........................
Does an SLA setup maintain negative camber in a corner and not go positive like the Macpherson design.
And how does it effect toe angles and bumpsteer characterics on an SLA design.
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When you lower an SN95, or most cars for that matter, what happens? You increase negative camber. One loses that negative camber at a faster rate than gained on the outside wheel when on a hard corner. I am sure it can be explained better, but the words are not finding me, at the moment.... lol
You have seen the best example of this on your most recient AX camera view.
Jazzer
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No, you increase *positive* camber when you lower a fox-chassis front end.
The A-arm is already at it's horizontally-longest position when it's level. For a fox-chassis Mustang, that's about at resting stock ride height. As it articulates up (either statically from lowering or dynamically from suspension compression), it only becomes shorter in the horizontal, which pulls the bottom of the spindle closer to the car, which causes an effective outward tilt of the top of the tire (aka loss of negative camber aka positive camber gain), which is what you can see in my video. It shifts all the weight to the outside of the tire, which is why most guys who drive their Mustangs hard in the corners end up wearing out the outer shoulders off their tires.
NOW, if the A-arm resting ride height is sloped downward towards the tire, then, yes, you will get negative camber gain under compression, right until the point when the A-arm hits horizontal, then you'll fall back into positive camber gain.
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^ That is some ****ed up ****, right there!
EDIT: on the way to work, I realize now what I failed to see upon your initial statement
Where it is true that a negative camber gain is achieved via drop in ride height, it certainly is not "infinite"*. As the "A" arm travels upward under compression the center of the strut changes relative to the point at which it pivots. So, where the "A" arm "starts" to the outside of the strut mounting point, it ends up on the inside of this point at higher compression, adding camber along the way. This is exasterbated by the body roll that happens moving the strut mounting point even FURTHER toward the outside of the tire. Add all this up and you get the images found in those cool-angle AX vids.
Jazzer.... again schooled by TGR
* This is where an SLA comes into play :yes
EDIT: on the way to work, I realize now what I failed to see upon your initial statement
Where it is true that a negative camber gain is achieved via drop in ride height, it certainly is not "infinite"*. As the "A" arm travels upward under compression the center of the strut changes relative to the point at which it pivots. So, where the "A" arm "starts" to the outside of the strut mounting point, it ends up on the inside of this point at higher compression, adding camber along the way. This is exasterbated by the body roll that happens moving the strut mounting point even FURTHER toward the outside of the tire. Add all this up and you get the images found in those cool-angle AX vids.
Jazzer.... again schooled by TGR
* This is where an SLA comes into play :yes
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So, with that said, what would be the better way to go with the MM front setup for a street car that is also used to autox:
1. A-arms in lower mounting location, parallel to the ground and the mounting location is in line with the steeering rack.
2. A-arms in upper mounting location (1 inch higher), angled downward but mouted above the steering rack.
3. Go back to the off road look - A-arms in lower mounting location, angled downwards but the mounting location is in line with the steering rack
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Mustangs start with the A-arm at about that middle green line.
One thing I should correct, it's not the A-arm being parallel to the ground that's the key angle, it's the A-arm being 90 degrees to the strut.
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Correcting the steering isn't something I haven't hit yet, but what I would start with is:
4: A-arms in upper mounting position, with a properly installed* bump-steer kit
* - properly installed takes a lot of time because you have to adjust it and measure the actual bumpsteer, adjust it again, measure it, wash, rinse, and repeat until you've minimized toe change under compression.
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I think once you get the outer tierods for example parrellal to the lower arm then bumpsteer toe etc should be eliminated correct.
Is that vid you posted for a coilover front suspension since the strut is closer to the outer A-arm or is the stock stand alone spring strut assembly.
So when you lower it the front arm pivot points should be raised and the arm lengthened to gain more negative camber.
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Theoretically yes. And in theory, "in theory" and "in practice" should be the same, but in practice, they're often not. I can't give you a practical answer, though as it's not something I've tackled yet.
Yes.Is that vid you posted for a coilover front suspension since the strut is closer to the outer A-arm or is the stock stand alone spring strut assembly.
The geometry of motion is the same irrelevant to where the spring is."Should" is a dangerous word to use there. Those are both things that you could do to mitigate the camber loss, but they're going to have other effects that you need to take into consideration. For instance, if you change the length of your A-arms, you're going to also need to change the length of your tie-rods (which should be within the range of adjustbility for alignment, but may not be). You'd also be changing your track-width, which could require changing backspacing on your wheels or fender modifications to prevent rubbing.
All things that can be dealt with, but just stuff to keep in mind.
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Wouldnt lengthening the outer tierods screw up toe angles as well. Interesting and then you got castor somehow to throw in there.
But its weird since you still have to add -2 to -3 degrees of neg camber and the outer tire still goes to pos camber when hard cornering. I guess the SLA setup just keeps the camber consistent all through out the suspension stroke.
But its weird since you still have to add -2 to -3 degrees of neg camber and the outer tire still goes to pos camber when hard cornering. I guess the SLA setup just keeps the camber consistent all through out the suspension stroke.
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Well, no... you'd be going to longer tie rods to correct the resulting wonky toe angles from moving the ball-joint outward.
For a McP strut setup, you can think of caster as just the angle the strut leans at when viewing the car from the side. Moving the balljoint outward doesn't change that angle (though moving it vertically certainly does).Interesting and then you got castor somehow to throw in there.
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This **** just got confusing
Just when I thought I had it figured out hahaI have MM's bolt through setup, which is a very nice kit btw. Install required a drill press, but it was VERY easy to setup properly in addition to their adjustable steering rack bushings as well. With the A-arms in the lower mounting location and the steering rack moved 1/4" up, the inner tie rods are in line with the A-arm mounting location, maybe off by 1/16" of an inch. Really good steering geometry.
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If Im correct doesnt castor angle effect high and low speed steering etc.
Ya the toe angles would get all screwed up running a longer A-arm. LOL
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Not sure you would want to raise the steering rack on a stock k-member. This will screw up toe/bumpsteer angles. If anything change the angle of the outer tierod and maybe raise the ball-joint/ spindle height.. Something like that not quite awake yet. LOLThis **** just got confusing
I have MM's bolt through setup, which is a very nice kit btw. Install required a drill press, but it was VERY easy to setup properly in addition to their adjustable steering rack bushings as well. With the A-arms in the lower mounting location and the steering rack moved 1/4" up, the inner tie rods are in line with the A-arm mounting location, maybe off by 1/16" of an inch. Really good steering geometry.
For example off-set rack bushings should be used with a tubular k-member since you change the A-arm pivot points etc.
Im getting lost now. LOL
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I have an MM K-member. Moving the rack up a 1/4" was the most I could safely move it up without oil pan contact, which was also recommended by MM. I wouldn't use solid bushings/move the rack with a stock k-member. Although, I think MM came out with solid bushings with a crush bushing to be used with the stock k-member to take into account the imperfections of the mounting flange so that might be the way to go. The rubber bushing are garbage though. Urethane's would be a minimum for the stock K. You really can feel the road much better.
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Now that I've thought about this a little more, I'm pretty sure the angle is less than 90* with MM's full front setup with the LCA's in the lower mount level to the ground. This would mean my camber does increase negatively during compression up to a certain length of travel.
So in my mind, moving the the A-arms to the upper mounting location while keeping ride height constant will improve camber changes during suspension compression, but could adversly affect steering geometry, even if you adjust for bumpsteer...?
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CB - I'm honestly not sure. :dunno
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I'll call MM and see what they say.
When I talked to them about my intial setup, they gave me the simple recommendation of lower mount for a street car and upper mount for a track only car.
When I talked to them about my intial setup, they gave me the simple recommendation of lower mount for a street car and upper mount for a track only car.
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Okay I called MM and for simplicity, the best possible location for the A-arm is parallel to the ground regardless of what mounting point you use on their k-member. If you want to get more technical, it's the ball joint pivot point that needs to be parallel with the center of the a-arm inner mount.
Inducing more negative camber in a turn is good, but doing it through vertical suspension travel is bad. When you brake, the front suspension compresses and if that vertical travel increases negative camber, the contact patch of the tire decreases, affecting braking performance. Likewise with IRS, inducing more negative camber with compression will affect acceleration due to decreased contact patch.
By setting the front A-arms parallel with the ground, the track width is maximized and the change in camber and toe is minimized during vertical suspension travel. Maintaining suspension configuration during vertical travel improves drivability and predictability of the suspension.
The proper way to increase negative camber is to increase positive caster. Doing so increases camber only when you turn the wheels.
Inducing more negative camber in a turn is good, but doing it through vertical suspension travel is bad. When you brake, the front suspension compresses and if that vertical travel increases negative camber, the contact patch of the tire decreases, affecting braking performance. Likewise with IRS, inducing more negative camber with compression will affect acceleration due to decreased contact patch.
By setting the front A-arms parallel with the ground, the track width is maximized and the change in camber and toe is minimized during vertical suspension travel. Maintaining suspension configuration during vertical travel improves drivability and predictability of the suspension.
The proper way to increase negative camber is to increase positive caster. Doing so increases camber only when you turn the wheels.
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