Mustang suspension

Skankin · 08-15-2001, 10:38 AM

I put this together in response to a corral post... but then couldn't post it... so here's some info:

How much do ya wanna spend? The more $$$, the better the handling (provided you don't get swindled by some of the aftermarkets over-priced & under-engineered scams).

CHASSIS:

First ya gotta look at the chassis. It's a front heavy pig with the front & rear connected by a flexible, sheet-metal floor pan. If you want the suspension to work, ya gotta stabilize the chassis.

Subframe connectors are a must, and a lower chassis brace really helps the stock k-member. While you're under there, get the torque boxes welded up... the factory just tacks them together.

REAR SUSPENSION:

The rear suspension is a diverging/converging 4 link. It controls lateral motion by binding up. Unfortunatly, it also binds while the suspension rolls. Along with the high roll centre (much higher than the front) & poor weight distribution, this is why the rear springs (200# stock) are so much less than the fronts (400# stock). Other problems include the rear brake jacking (from the upper control arms) & the snap oversteer (when lateral forces compress the rubber bushings & abruptly unload on the axle/wheels/tires).

Why does ford use this rear arrangement? It's cheap & easy, and it does provide lots of anti-squat for the front heavy beast (so you can accelerate quite well).

As you've probably noticed, the UCA's cause some problems, and if you wanna handle, they gotta go.
BUt this removes the lateral location, windup control & some antisquat.

Most people go for a panhard bar for lateral location (cheap & easy).

To control the pinion angle/windup, you can go for a 3 or 4 link, or a torque arm. To gain some of the antisquat back, the torque arm is probably the best choice (although weight & ground clearance may be an issue).

IRS - Independent Rear Suspension like on the 99+ Cobra's... far less unsprung weight, better ride, but it'll take your money too! (the stock setup is pricie, and needs some work). You get some camber in the corners, but the wheels won't be flat under acceleration & braking.

FRONT SUSPENSION:

When the mustang went to the fox3 chassis in 1979, they cheaped out, and ditched the short-long-arm /
double-wishbone suspension and any hope of a dynamically beneficial suspension. Okay, maybe that's a little harsh. They did reduce weight & simplify the components.

The front is composed of a modified MacPherson strut. I believe it's "modified" cause it's not a
coil-over... it's got a heavier inboard spring between the LCA & chassis.

When you corner, the lateral forces try to roll the tire off the side of the rim. THis decreases the contact patch, and your ability to turn. This is why lower profile tires (bigger wheels) are better for the corners.

With the SLA suspension, it's compression actually adds negative camber, which negates the tire deflection & maintains the contact patch. (I'd really like an SLA!)

With the strut, the camber goes positive as the body rolls, making the contact patch even worse. This is why the racers will dial in large amounts of static -ve camber. They also run high spring rates, which decreases the amount of compression/geometry change.

If you add more caster, you can get a little bit of -ve camber from steering... but you can start to add some bump-steer too. This is why some people have found offset-rack bushings to be helpful.

Another problem is ackerman angle. When you're turning, the inside tire is making a tighter radius than the outside, but ford's geometry didn't take this into account (it was thought that the tire scrub provided better turn-in response). This can improved by moving the rack rearward (like with MM's unique rack bushings).

Back to roll centres. The rear is quite high, but the front is pretty low. To make things worse, the front's centre of gravity (COG) isn't nearly as low, so you get plenty front roll, which wrecks the geometry. This is why the front sway bar is so heavy.

A lower COG offers better handling/performance, but lowering the front cause the front roll centre to go MUCH lower than the COG (as the LCA's get more angled). This means you have to go to disproportionately heavier front springs, or change the LCA locations (get a new k-member).

K-members often improve geometry & reduce weight... partly with lighter LCA's & coil-overs. I'm not too keen on putting the spring loads on the strut towers, but many people do it.

The struts & shocks are crucial, and should not be skimped on.

MANUFACTURERS:
www.griggsracing.com has engineered the entire suspension, and does quite well.
www.maximummotorsports.com has some great products, and their new k-member should complete their package.
www.kennybrown.com - new k-members look REALLY good. He's 'fixed' the IRS as well... so you could get a complete package.
www.steeda.com - has a lot of bolt-in band-aid products, including an interesting 5link (4link + panhard). They offer some decent stuff, but I feel it's over-priced, and under-engineered (rather than starting from a clean slate, it seems to be bandaged together to try and remain competitive in specific racing classes).

Global West - some good stuff (subframe connectors), but a lot of band-aid compromises too.

The mustang-specific stuff is often pricie... as it's engineered to a particular chassis, and it's a straight bolt-in. There's also many hotrod suppliers with coil-overs, SLA front suspensions & nice 4-links, which could also be adapted for a decent price (welding required).
www.chassisengineering.com www.cachassisworks.com www.artmorrison.com www.colemanracing.com

But I digress...

lito · 08-17-2001, 05:10 PM

Nice post!

Currently have stock front arms with H&R #950/1050, Griggs bump steer kit for relocated rack, FMS rack alum bushings and steedas camber plates, respective H&R rears with MM TA & Panhard. Also added an excellent Torsen. Stock bar front '98 convertible in the rear.

I'm ditching the bilsteins because I came to the conclusion that front rates are just too much for this schocks. And are waiting on shipment of a new set of koni yellow double adjustables.

My question is, how to set them up. I know there is a recommended setting for the rears regarding TA setup but can find it anymore. What to do with the fronts also?

lito

------------------
92GT, SOLO RACER, COBRA BRAKES, R1 TIRES, GT40, GT40X HEADS 58CC, 24LBS, 70MM/65MM, E303, MAC 1"5/8 LT HEADERS, 3" XPIPE AND EXHAUST W/CUT OFFS, 4.10, H&R 950-1050 SPRINGS, BILSTEIN SHOCKS, MM PANHARD AND TA, MANY ROAD RACE MODS, CORVETTE, CAMARO, RX7 AND SUPRA SOLO EVENT EATER

www.killersracing.com
www.clubcopa.com
<IMG SRC="http://www.killersracing.com/lito/mustan

08-15-2001, 10:38 AM	#1
Skankin Registered Member Join Date: Dec 1998 Location: London, Ontario, Canada Posts: 1,349	Mustang suspension I put this together in response to a corral post... but then couldn't post it... so here's some info: How much do ya wanna spend? The more $$$, the better the handling (provided you don't get swindled by some of the aftermarkets over-priced & under-engineered scams). CHASSIS: First ya gotta look at the chassis. It's a front heavy pig with the front & rear connected by a flexible, sheet-metal floor pan. If you want the suspension to work, ya gotta stabilize the chassis. Subframe connectors are a must, and a lower chassis brace really helps the stock k-member. While you're under there, get the torque boxes welded up... the factory just tacks them together. REAR SUSPENSION: The rear suspension is a diverging/converging 4 link. It controls lateral motion by binding up. Unfortunatly, it also binds while the suspension rolls. Along with the high roll centre (much higher than the front) & poor weight distribution, this is why the rear springs (200# stock) are so much less than the fronts (400# stock). Other problems include the rear brake jacking (from the upper control arms) & the snap oversteer (when lateral forces compress the rubber bushings & abruptly unload on the axle/wheels/tires). Why does ford use this rear arrangement? It's cheap & easy, and it does provide lots of anti-squat for the front heavy beast (so you can accelerate quite well). As you've probably noticed, the UCA's cause some problems, and if you wanna handle, they gotta go. BUt this removes the lateral location, windup control & some antisquat. Most people go for a panhard bar for lateral location (cheap & easy). To control the pinion angle/windup, you can go for a 3 or 4 link, or a torque arm. To gain some of the antisquat back, the torque arm is probably the best choice (although weight & ground clearance may be an issue). IRS - Independent Rear Suspension like on the 99+ Cobra's... far less unsprung weight, better ride, but it'll take your money too! (the stock setup is pricie, and needs some work). You get some camber in the corners, but the wheels won't be flat under acceleration & braking. FRONT SUSPENSION: When the mustang went to the fox3 chassis in 1979, they cheaped out, and ditched the short-long-arm / double-wishbone suspension and any hope of a dynamically beneficial suspension. Okay, maybe that's a little harsh. They did reduce weight & simplify the components. The front is composed of a modified MacPherson strut. I believe it's "modified" cause it's not a coil-over... it's got a heavier inboard spring between the LCA & chassis. When you corner, the lateral forces try to roll the tire off the side of the rim. THis decreases the contact patch, and your ability to turn. This is why lower profile tires (bigger wheels) are better for the corners. With the SLA suspension, it's compression actually adds negative camber, which negates the tire deflection & maintains the contact patch. (I'd really like an SLA!) With the strut, the camber goes positive as the body rolls, making the contact patch even worse. This is why the racers will dial in large amounts of static -ve camber. They also run high spring rates, which decreases the amount of compression/geometry change. If you add more caster, you can get a little bit of -ve camber from steering... but you can start to add some bump-steer too. This is why some people have found offset-rack bushings to be helpful. Another problem is ackerman angle. When you're turning, the inside tire is making a tighter radius than the outside, but ford's geometry didn't take this into account (it was thought that the tire scrub provided better turn-in response). This can improved by moving the rack rearward (like with MM's unique rack bushings). Back to roll centres. The rear is quite high, but the front is pretty low. To make things worse, the front's centre of gravity (COG) isn't nearly as low, so you get plenty front roll, which wrecks the geometry. This is why the front sway bar is so heavy. A lower COG offers better handling/performance, but lowering the front cause the front roll centre to go MUCH lower than the COG (as the LCA's get more angled). This means you have to go to disproportionately heavier front springs, or change the LCA locations (get a new k-member). K-members often improve geometry & reduce weight... partly with lighter LCA's & coil-overs. I'm not too keen on putting the spring loads on the strut towers, but many people do it. The struts & shocks are crucial, and should not be skimped on. MANUFACTURERS: www.griggsracing.com has engineered the entire suspension, and does quite well. www.maximummotorsports.com has some great products, and their new k-member should complete their package. www.kennybrown.com - new k-members look REALLY good. He's 'fixed' the IRS as well... so you could get a complete package. www.steeda.com - has a lot of bolt-in band-aid products, including an interesting 5link (4link + panhard). They offer some decent stuff, but I feel it's over-priced, and under-engineered (rather than starting from a clean slate, it seems to be bandaged together to try and remain competitive in specific racing classes). Global West - some good stuff (subframe connectors), but a lot of band-aid compromises too. The mustang-specific stuff is often pricie... as it's engineered to a particular chassis, and it's a straight bolt-in. There's also many hotrod suppliers with coil-overs, SLA front suspensions & nice 4-links, which could also be adapted for a decent price (welding required). www.chassisengineering.com www.cachassisworks.com www.artmorrison.com www.colemanracing.com But I digress...

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08-17-2001, 05:10 PM	#2
lito Registered Member Join Date: Feb 1999 Location: Caracas, Venezuela Posts: 81	Nice post! Currently have stock front arms with H&R #950/1050, Griggs bump steer kit for relocated rack, FMS rack alum bushings and steedas camber plates, respective H&R rears with MM TA & Panhard. Also added an excellent Torsen. Stock bar front '98 convertible in the rear. I'm ditching the bilsteins because I came to the conclusion that front rates are just too much for this schocks. And are waiting on shipment of a new set of koni yellow double adjustables. My question is, how to set them up. I know there is a recommended setting for the rears regarding TA setup but can find it anymore. What to do with the fronts also? lito ------------------ 92GT, SOLO RACER, COBRA BRAKES, R1 TIRES, GT40, GT40X HEADS 58CC, 24LBS, 70MM/65MM, E303, MAC 1"5/8 LT HEADERS, 3" XPIPE AND EXHAUST W/CUT OFFS, 4.10, H&R 950-1050 SPRINGS, BILSTEIN SHOCKS, MM PANHARD AND TA, MANY ROAD RACE MODS, CORVETTE, CAMARO, RX7 AND SUPRA SOLO EVENT EATER www.killersracing.com www.clubcopa.com <IMG SRC="http://www.killersracing.com/lito/mustan