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Review of BMR handling springs (SP083) paired with the Ford Performance track shocks

J.P.B.

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Review of BMR handling springs (SP083) paired with the Ford Performance track shocks and struts (M-18000-F)

Now that I have these installed for a few weeks, I am able to review them for both the street and road-course. But, some background information is required.

First, both springs and dampers were installed at the same time as a set of other suspension upgrades that were carefully selected to complement each other. While it’s not possible to strictly isolate the individual affects, I believe that I can comment on “major effects” of the springs and with the FP track dampers in the context of the overall suspension upgrade. I got valuable advice from many folks when researching these upgrades, but forum-member BmacIL deserves particular thanks for his comprehensive and thoughtful advice. Also, thanks to BlueMustang for his very helpful impressions of this pairing.

So, for the record, here are the modifications that I made to my base model 2017 GT.

• BMR: handling springs (SP083: front: 250lb; rear: 980lb)
• Ford Performance: track struts & shocks (M-18000-F)
• Steeda: rear billet shock mounts (555-8151)

Other upgrades:
• Ford Performance: rear toe links (M-5972-M) and toe link to knuckle connector bushing (M-5A460-M)
• Steeda: IRS subframe bushing support system (555 4447)
• Steeda: IRS subframe alignment kit (555 4437)
• Steeda: K-member 4-pt chassis support brace
• Steeda: Strut tower brace
• Performance alignment

Second, there are inevitable tradeoffs between street and road-course performance, and in the interest of full disclosure, I favor road-course performance. Prior to my GT, I tracked a 2015 Ecoboost Mustang; and prior to that I raced motorcycles at the same track. FYI, my local is the Atlantic Motorsports Park, and it is widely considered the most technical road course in Canada. I daily drive my GT, so I am sensitive to the tension between the tradeoffs of suspension performance.

OK, on to the review. I will break it down into separate points, and I will start with the street. I will also make direct comparison to the Ecoboost Mustang, and in a few cases to the 2012/2013 BOSS 302 Mustang.

Street performance:

1. Both the stock GT and the Ecoboost Mustang suspension have a lot of soft rubber bushings, and the IRS can sustain a lot of deflection in some circumstances. These cars are softly sprung “grand tourers” by design. With the factory springs and dampers, both cars felt disconnected from the road; specifically they had delayed and un-intuitive reactions to changes in the road surface. The upgrades (in large part due to the springs and dampers, but also due to IRS bushing support system) have almost completely CORRECTED this problem in the GT. The car is now “hunkered down” and predictable.

2. These springs and dampers result in a much more FRIM ride compared to stock. But, it is NOT TOO HARSH; it’s still a largely confortable ride. The road surface is now transmitted to the driver, but in an informative way. You will feel all the road imperfection, but this is “knowledge” you do not have as a driver in the stock setup.

3. Some road conditions are transmitted more than others to the cabin and to the driver. However, it was not what I predicted… Rough and broken pavement is not as harsh as I expected, and, oddly, minor “undulations” seem to be the biggest challenge to the suspension. However, the car is never unsettled. It is never skittish (which I had been worried about). Indeed it’s extremely effective at dealing with a broken surface: ONE-DOWN then ONE-UP and it’s all done.

4. Unexpectedly, the suspension gets BETTER WITH SPEED. There is a bridge joint I have to cross on a regular basis, and it was very harsh on both the stock GT and the Ecoboost. I gritted my teeth on my first approach to this bridge joint with the new suspension, and low-and-behold it was actually better! And, the faster I go the less harsh this joint feels!!!

5. STEERING RESPONSE is very noticeably improved. I chalk this up to the combined effect of the 250lb front springs, the strut tower brace, and the 4-point chassis brace to (i) reduce the amount of flex in the front end, and (ii) maintain a stable wheel alignment during cornering. The effect is that steering response is immediate, and the car changes direction much more quickly. This makes the car really fun to drive on twisty roads (but with unexpected consequence on the track; more on this later). The Ecoboost Mustang, with 200lbs less weight over the front wheels, had a real advantage over the GT Mustang in terms of steering feel and response. For street driving, these upgrades corrected that discrepancy.

6. There is now noticeably less tramlining on the highway (it’s not entirely gone; I do run 275s up front after all). But, this might not be attributable to the suspension changes. The reduction in tramlining could be a consequence of the extra weight of the GT over the front wheels and the alignment changes I chose after the suspension upgrades. I can’t be sure about the source of the improvement.

7. A final note about the effect of tires on the firmness of the ride. I run 18x10 wheels and a 275 square tire stance. Tire pressure and temperature have a noticeable effect on ride quality. I found that running just a little less pressure, 29-30psi rather than 32psi, made a noticeable improvement on ride quality for my setup.


Road-course performance:

1. The ride is now VERY FLAT. Even with the stock sway bars (more about this later) the car has much less lean during hard cornering. There is also much less nose dive under hard breaking and the car no longer rocks back on its haunches during hard acceleration. The effect is that there is much less weight transfer during hard driving, and this leads to (i) a more “planted feel” at speed and (ii) smoother transitions that minimize disturbances that unsettle the suspension.

2. The car now communicates everything to me, as it should. In addition to feeling the road, I can instantly feel how the suspension is reacting to my inputs. This is why you want “TRACK FRIMNESS”. By the way, it’s not too firm; the car has yet to react unexpectedly and is easy to apply power smoothly.

3. There are some unexpected consequences of the sharp steering response. The effect is that even very small mistakes get quickly transmitted to the chassis. As I approached the limit in my car (which is now MUCH FASTER than before) it demanded much more technical skill. This suspension simply demands more precision. It's not that car gets dangerous, or jittery, when I make a mistake; it's just that it communicates my mistakes instantly. That delightfully crisp steering response on the street becomes “hypersensitive”; if you are just a little too abrupt on turn in, you will feel it in the chassis. The EcoBoost, and the stock GT, were much easier to drive at their limit (albeit slower). The BOSS 302 under the same conditions over the weekend, was also easier to drive at the limit. The good news is that the upgraded GT suspension will help teach you to be a better driver… if you are willing to listen to it (and your instructor). For this reason, I feel this is not a suspension setup for a beginner (more thoughts on this later).

With my general impressions out of the way, I thought I would break the review down into the basic stages of a road course turn.

Maximum braking on approach: The car is very stable. Since there is much less nose-dive it feels more settled, and this gives you confidence to go deeper. I suppose the back brakes could now be more efficient leading to shorter stopping times, but I can’t be sure that I actually was stopping any more effectively. But, stability leads to greater confidence and smoothness, and this encourages you to go deeper.

Turn-in / transition to cornering: This is where the increased sensitivity has pros and cons. The cons: the margin for error is smaller. If you are off a little on your input timing, or you are too abrupt, you will feel that mistake. The car will NOT soak it up for you. You need to pay attention. The pros: (i) You will feel your mistakes instantly. Yes, this was also a con because it can be distracting. But, this is how you learn to be precise and smooth. (ii) You will feel that you have made a mistake but it will not punish you; the car was never unpredictable or jittery. (iii) Precision and smoothness are rewarded with more speed throughout the rest of the turn!

Cornering on a balanced throttle: There is MUCH LESS body roll. As with the turn in, there will be less weight transfer (if you have done it right), and the car feels like it maintains more speed. There is also LESS UNDERSTEER. The car still understeers, but I was surprised how much less I was fighting it. All this said, for me, actual improvements in speed were gained by avoiding mistakes during the transition to cornering. That is where I have some work to do.

Transition to acceleration and exit: This is where it gets interesting. I had struggled with a particular decreasing radius turn going down hill with less than ideal camber. There is no consensus opinion on the best line for this turn, and it slows a lot of folks down, including me. Not only was I able to carry more speed, but I was able to build a surprising amount of acceleration on the transition to exit. At one point I swore that the throttle caused the front end to tuck in. On the next lap I realized that I was actually getting very progressive, and manageable, throttle steering. A turn that had once been a problem for me was now delightful to manage with partial throttle and a touch of oversteer. I am sure than any well tuned suspension can delver this. That is not the interesting point. The interesting point is that I am still on the stock sway bars; I am seriously thinking of staying with the stock bars.


Critiques: As expected, nothing is perfect and there are some issues. Three things stand out at this point:

(1) Some people say that, with an “upgraded” suspension, the GT mustang “shrinks around you” once you get it on the track. I disagree. The car still feels big. If still feels bigger that the Ecoboost Mustang (on the same track), and it feels bigger than the BOSS 302 (on the same track). It's still a 3700lb car with a lot of weight over the front wheels.

(2) The suspension is not perfect. Under cornering conditions much faster than what was possible with the stock suspension, the suspension can very occasionally shift in a way that is delayed relative to my inputs or changes in the road surface. Either way, it seems to be localized in the rear, and I think there may still be some deflection in the IRS. It’s distinct, very noticeable, and somewhat distracting; fortunately, it does not happen often, and the car can still be driven quite easily. This does not seem to be the fault of the spring and damper pairing; rather, I suspect there is still something in the IRS that needs correction.

(3) My upgraded GT rides flatter than the BOSS 302 and yet it feels less planted. I believe this is related to issue (2) above. Both cars communicate a lot of information about the road and the cornering dynamics to the driver; let’s call this “signal”. My current suspension still shifts in a way that is unrelated, or delayed from, my inputs; let’s call this “noise”. I think the BOSS 302 feels better because it has a little better “signal to noise ratio” than my car does right now.


Overall impressions: If you are interested in road course performance, you would be very hard pressed to find better value for money in the pairing of BMR handling springs (SP083) paired with the Ford Performance track shocks and struts (M-18000-F). With a small number of supporting mods the changes in the handing are PROFOUND.
The advantages of this suspension improve with speed. If you spend most of you time in traffic, and at lower speeds, then you are simply not going to appreciate the amazing engineering that went into these, and you are certainly not gaining anything in terms of comfort. This pairing is perfect for those driving hard in autocross or on a road course. I love this set up! But it’s not for everyone. Here is my very subjective sense of the spectrum of different damper and spring pairings.

(1) Very soft grand touring car:
  • Base GT suspension

(2) Moderately soft grand touring car:
  • Factory Performance Pack suspension

(3) Daily driver, performance driving mostly below the limit (a corner carver), with occasional track days:
  • Factory Performance Pack dampers with BMR min-drop springs (SP763)

(4) Daily driver and high performance driving at frequent track days or autocross, but with slightly more preference for a softer street ride:
  • Ford Performance track shocks and struts (M-18000-F) with BMR min-drop springs (SP763), in combination with supporting suspension and chassis mods. (Done right, I expect this might feel a lot like the BOSS 302.)

(5) Daily driver and high performance driving at frequent track days or autocross, with more preference for a track spring. Specifically, a flat ride with road surface and suspension dynamics clearly communicated to the driver, predictable weight transfers, and optimized reactions to weigh transfers.
  • Ford Performance track shocks and struts (M-18000-F) with handling springs (SP083) combined with supporting suspension and chassis mods.
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BmacIL

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Awesome!!! It makes me glad to hear this.

A couple things...
I've done some thinking and one thing that I think would make the car easier to drive on corner entry is the non-PP GT swaybar. The bar itself is identical (so identical roll stiffness), but it does not have the integrated 'sticky' bushings that were added to sharpen on-center response. If you don't desire an increase in front bar stiffness, this would be a good suggestion to make it a little easier. I think the next thing to address critique number 2 are the RLCA bearings (BK055 or BK081) and to a much lesser extent, TCA048 vertical links.
 

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Awesome!!! It makes me glad to hear this.

A couple things...
I've done some thinking and one thing that I think would make the car easier to drive on corner entry is the non-PP GT swaybar. The bar itself is identical (so identical roll stiffness), but it does not have the integrated 'sticky' bushings that were added to sharpen on-center response. If you don't desire an increase in front bar stiffness, this would be a good suggestion to make it a little easier. I think the next thing to address critique number 2 are the RLCA bearings (BK055 or BK081) and to a much lesser extent, TCA048 vertical links.
RLCA bearings only allow forward and aft rotation of the lower control arm around the rear pivot point which already uses a spherical bearing stock and a very small amount of vertical "rotation" or "twisting" of the arm until the bushing bottoms out and I do mean SMALL amount that only matters in high HP drag cars that can result in a very minor amount of wheel hop. The stock bearing configuration does not allow horizontal movement because the back inner and outer rear are Spherical Bearings stock. When you add in spherical bearings to both toe link ends, toe angle can no longer change either.

41127501770_cf3d223fc2_b.jpg


Unless your drag racing, there's nothing moving laterally with his setup in the control arms. There is only one bushing on the lower control arm and knuckle assembly that's rubber in his setup and that's he RLCA bushing you mentioned.

His described movement may actually be the IRS lockout kit's limitations for controlling lateral movement or possibly tram-lining of the rear end due to wider off-set wheels (yes the rear has a scrub radius just like the front). The tubular braces, while strong, are taking all of the IRS lateral movement the stock bushings cannot manage in their permitted movement range until they bottom out, which is quite a bit of energy. I have a hard time believing two single tubes by themselves can avoid flexing in extreme g cornering, especially under load.

The vertical movement of the IRS is already well controlled by the steeda lock out collars which work just fine and don't permit any vertical deflection (up into the chassis or down away from it), but they do nothing to control the fore, after, or lateral movement which is entirely handled by their tubular supports all of which is transmitted to the bend radius which acts kinda like a sway-bar that resists lateral movement of the IRS.

42888585582_e997ffdc76_b.jpg


There are other ways to lock out the IRS sub-frame which are more effective and lower in weight. Each has it's pros and cons. The Ford Performance sub-frame bushings fully lock out the IRS movement in a very similar way to BMR's CB005, but they are a permanent and involved modification as the replace the stock IRS sub-frame to chassis bushings entirely.

The BMR CB005 aluminum top rings lock the crowned center tube in the stock sub-frame to chassis bushings to the sub-frame itself, thus preventing their movement. The concept is the same as the Ford Performance Aluminum Sub-frame bushings, but it's not permanent if you want to return it to factory and is much easier to install because your just sliding a few locking rings over the existing bushings.

42938141861_f04521ca44_b.jpg


It controls by far the majority of the sub-frame movement and adds only 4 lbs. The entire kit weighs 6.5 lbs, but your replacing the stock front bushing to sub-frame supports with their own supports. The stock supports weigh about 1.25 lbs each so your net weight gain is only 4 lbs. It's easy to install, self centers the IRS (the BMR supports double as alignment bushings to the front two bolt holes). It's by far the most efficient IRS lock out kit on the market.

I use BMR for some things and Steeda for others, yet Ford Performance for other things still. It seems each company, while they all offer their takes on various solutions, have some designs for certain issues that are the best and most efficient solutions while other solutions they offer make too many trade offs or may only partially solve the problem. No one company has the best solution for everything despite what they may say and they are all adamant on why you should choose "their solution" regardless of how well it performs, that's just business.

Some things you may want to buy as a whole package and stick with the same company in a "set" for "package" because the particular issue requires hamonious operation of multiple parts, such as pairing springs, sway-bars and struts for example (although you can mix and match, your more likely to run into unintended performance characteristics). Other issues like the IRS movement is a "stand alone" issue and may be resolved independently, it does not "work better" when paired with steeda or ford performance or BMR springs / sway bars. It just addresses that one issue by itself regardless of all other modifications. In those cases I use whoever has the best solution.

For example the Steeda Differential bushing kits are better than BMR's for street cars because they offer an 80 durometer street bushing and a 90 durometer performance bushing AND aluminum bushings. Each a solution tuned for the particular application. BMR has one 95 durometer bushing and quite a few people report NVH issues with it on street cars...I've used the Steeda kit on my Ecoboost and went with the black bushing and experienced a substantial gain in NVH that I wasn't willing to tolerate, I had a lot of clunking that was very audible from the drive train. It may not have bothered some, but it bothered me.

On my GT I tried their red bushings this time around and while there is some minor NVH (still a little clunking), it's far more muted and not loud enough to really bother me. Tire and exhaust noise is quite a bit louder. It works as advertised. If want more connected feel and at some point am willing to tollerate move clunking I have their black 90 durometer bushings or could even go aluminum. It's scale able and it works.

Then obviously I chose Ford Performance for their super reliable, emissions legal and fully warrantied Power Pack which also offers 95% of the performance of after market calibrations but managed to make the GT350 throttle body WORK well.

These are just examples of why I chose what I chose and how each company offered the best of what I was looking to achieve for my particular application. Each company has some offerings that are the best I could find, while in other areas their solutions were not as good as others.
 

BmacIL

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Your assertion about the movement of the front bushings is incorrect and has been proven via video. The bushings allow for significant dynamic toe change during cornering and under acceleration and braking.
 

BmacIL

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And starting at 1:43:
[ame]
 
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J.P.B.

J.P.B.

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Thanks for the detailed feedback on item (2) in the critique!!!

I want to add a clarification about what is in my Steeda kit. I have the IRS subframe bushing support system (555-4447), and that kit does NOT include their subframe braces (555-5754). It was not a matter of choosing to include them or not (or choosing Steeda vs BMR); it was simply that at the time of purchase I happened to get lucky and get a screaming good deal on the 555-4447 kit.

I mention this in particular because one of the photos posted by TheLion shows a subframe brace to control lateral movement that I do not have. I am very interested in your thoughts about that (or the lack of such support) being the source of what I am feeling.

Thanks again.
 
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Great review [MENTION=32569]J.P.B.[/MENTION] You have a very similar setup to me, except I’m running CB005 BMR instead of the Steeda subframe braces and I am running BMR sway bars. In addition I have Steeda RLCA bearings. I would recommend adding the RLCA bearings to complete your suspension build. However you have a great setup already and I’m glad you’re enjoying it.
 

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[MENTION=32569]J.P.B.[/MENTION] You will need the subframe braces to complete the job that the CB005 does, that Bluemustang and I have. I'd recommend doing that or going to the CB005. Either way you'll definitely notice another improvement.
 

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And starting at 1:43:
The RLCA bearing does NOT allow toe angle change. The video you posted shows an S55 that has rubber bushings in the outer toe link end where it attaches to the hub knuckle. Of course the toe angle is going to change because the outer toe link end has a rubber bushing during that test. The RLCA bearing's movement has NO bearing on Toe angle. Toe angle is controlled by 4 points, being the inner and outer toe link bushings, the rear inner and outer lower control arm bushings. 3 of those points are spherical bearings stock on PP cars with the outer toe link bushing now being upgraded to a spherical bearing by the OP.

Look at my first image, please explain how it's possible for the toe angle to change if the Toe link has spherical bearings in both ends like the OP said he upgraded to? There are 4 points of motion. The RLCA bearing plays no role in toe angle.

It's primary purpose is to transmit load energy carried by the vertical link into lower control arm and ulimately the sub-frame. It doesn't matter if it moves outward slightly because the toe link forces the hub to move in parallel relative to the sub-frame. The RLCA bushing may pull outward a bit because the lower control arm is moving backwards (toward the rear of the car) slightly until the RLCA bushing reaches it's limits of travel.

The RLCA bearing as a small impact on wheel hop as do the vertical links only in Drag racing applications. For track, Auto X or Street use, spherical bearings in the toe link at BOTH ends, differential bushings and cradle lock out eliminates toe deflection, any possible lateral movement (side to side) of the suspension and sub-frame and drastically reduces wheel hop in power down situations. If your a drag racer, by all means upgrade the RLCA bearing and vertical links as there is some measure able benefit in further reducing wheel hop.

For street, auto x and track it's not going to really benefit you and may make the car a bit edgy in corners (what others have reported). Some small compliance keeps a car from having so much edge it becomes hard to drive. Too much compliance makes it a mush box that's difficult to drive at it's limits. The trick is to balance the car. I think we get too caught up in replacing crap because vendor X says it will make it better or because we don't fully understand it's application....but I digress, both videos show exactly what I'm talking about.

You need to fully understand the rear integral link's theory of operation to understand it's motion paths and load paths. But hey, if you want to spend the money for an RLCA bearing and the absolute butt pain it is to upgrade it, by all means have at it!

Here is a great article that illustrates and explains the IRS Integral Link design at a good level of detail and further reinforces what I'm trying to explain: https://www.edmunds.com/ford/mustan...15-ford-mustang-gt-suspension-walkaround.html

The front RLCA bushing more or less is a load path to control Knuckle rotation and limits rear or forward movement of the hub / lower control arm. It does NOT control toe angle in any way.
 
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TheLion

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Here you go, so you can really understand how the integral link suspension architecture functions. It's really a great design (originally pioneered by BMW and now used by Ford and few others as well):

42234043604_e3fe11e8aa_b.jpg


It's a very compact design that also isolates the different functions of each component. So you can tune the different aspects of compliance independently without affecting the other aspects. It also allows for more room for other things like cargo, fuel or even passenger room / trunk space.

That's why the Mustang's trunk is substantially bigger than the Camaro SS's trunk because GM used a more traditional trailing arm design which takes up a lot more room.
 

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Review of BMR handling springs (SP083) paired with the Ford Performance track shocks and struts (M-18000-F)

Now that I have these installed for a few weeks, I am able to review them for both the street and road-course. But, some background information is required.

First, both springs and dampers were installed at the same time as a set of other suspension upgrades that were carefully selected to complement each other. While it’s not possible to strictly isolate the individual affects, I believe that I can comment on “major effects” of the springs and with the FP track dampers in the context of the overall suspension upgrade. I got valuable advice from many folks when researching these upgrades, but forum-member BmacIL deserves particular thanks for his comprehensive and thoughtful advice. Also, thanks to BlueMustang for his very helpful impressions of this pairing.

So, for the record, here are the modifications that I made to my base model 2017 GT.

• BMR: handling springs (SP083: front: 250lb; rear: 980lb)
• Ford Performance: track struts & shocks (M-18000-F)
• Steeda: rear billet shock mounts (555-8151)

Other upgrades:
• Ford Performance: rear toe links (M-5972-M) and toe link to knuckle connector bushing (M-5A460-M)
• Steeda: IRS subframe bushing support system (555 4447)
• Steeda: IRS subframe alignment kit (555 4437)
• Steeda: K-member 4-pt chassis support brace
• Steeda: Strut tower brace
• Performance alignment

Second, there are inevitable tradeoffs between street and road-course performance, and in the interest of full disclosure, I favor road-course performance. Prior to my GT, I tracked a 2015 Ecoboost Mustang; and prior to that I raced motorcycles at the same track. FYI, my local is the Atlantic Motorsports Park, and it is widely considered the most technical road course in Canada. I daily drive my GT, so I am sensitive to the tension between the tradeoffs of suspension performance.

OK, on to the review. I will break it down into separate points, and I will start with the street. I will also make direct comparison to the Ecoboost Mustang, and in a few cases to the 2012/2013 BOSS 302 Mustang.

Street performance:

1. Both the stock GT and the Ecoboost Mustang suspension have a lot of soft rubber bushings, and the IRS can sustain a lot of deflection in some circumstances. These cars are softly sprung “grand tourers” by design. With the factory springs and dampers, both cars felt disconnected from the road; specifically they had delayed and un-intuitive reactions to changes in the road surface. The upgrades (in large part due to the springs and dampers, but also due to IRS bushing support system) have almost completely CORRECTED this problem in the GT. The car is now “hunkered down” and predictable.

2. These springs and dampers result in a much more FRIM ride compared to stock. But, it is NOT TOO HARSH; it’s still a largely confortable ride. The road surface is now transmitted to the driver, but in an informative way. You will feel all the road imperfection, but this is “knowledge” you do not have as a driver in the stock setup.

3. Some road conditions are transmitted more than others to the cabin and to the driver. However, it was not what I predicted… Rough and broken pavement is not as harsh as I expected, and, oddly, minor “undulations” seem to be the biggest challenge to the suspension. However, the car is never unsettled. It is never skittish (which I had been worried about). Indeed it’s extremely effective at dealing with a broken surface: ONE-DOWN then ONE-UP and it’s all done.

4. Unexpectedly, the suspension gets BETTER WITH SPEED. There is a bridge joint I have to cross on a regular basis, and it was very harsh on both the stock GT and the Ecoboost. I gritted my teeth on my first approach to this bridge joint with the new suspension, and low-and-behold it was actually better! And, the faster I go the less harsh this joint feels!!!

5. STEERING RESPONSE is very noticeably improved. I chalk this up to the combined effect of the 250lb front springs, the strut tower brace, and the 4-point chassis brace to (i) reduce the amount of flex in the front end, and (ii) maintain a stable wheel alignment during cornering. The effect is that steering response is immediate, and the car changes direction much more quickly. This makes the car really fun to drive on twisty roads (but with unexpected consequence on the track; more on this later). The Ecoboost Mustang, with 200lbs less weight over the front wheels, had a real advantage over the GT Mustang in terms of steering feel and response. For street driving, these upgrades corrected that discrepancy.

6. There is now noticeably less tramlining on the highway (it’s not entirely gone; I do run 275s up front after all). But, this might not be attributable to the suspension changes. The reduction in tramlining could be a consequence of the extra weight of the GT over the front wheels and the alignment changes I chose after the suspension upgrades. I can’t be sure about the source of the improvement.

7. A final note about the effect of tires on the firmness of the ride. I run 18x10 wheels and a 275 square tire stance. Tire pressure and temperature have a noticeable effect on ride quality. I found that running just a little less pressure, 29-30psi rather than 32psi, made a noticeable improvement on ride quality for my setup.


Road-course performance:

1. The ride is now VERY FLAT. Even with the stock sway bars (more about this later) the car has much less lean during hard cornering. There is also much less nose dive under hard breaking and the car no longer rocks back on its haunches during hard acceleration. The effect is that there is much less weight transfer during hard driving, and this leads to (i) a more “planted feel” at speed and (ii) smoother transitions that minimize disturbances that unsettle the suspension.

2. The car now communicates everything to me, as it should. In addition to feeling the road, I can instantly feel how the suspension is reacting to my inputs. This is why you want “TRACK FRIMNESS”. By the way, it’s not too firm; the car has yet to react unexpectedly and is easy to apply power smoothly.

3. There are some unexpected consequences of the sharp steering response. The effect is that even very small mistakes get quickly transmitted to the chassis. As I approached the limit in my car (which is now MUCH FASTER than before) it demanded much more technical skill. This suspension simply demands more precision. It's not that car gets dangerous, or jittery, when I make a mistake; it's just that it communicates my mistakes instantly. That delightfully crisp steering response on the street becomes “hypersensitive”; if you are just a little too abrupt on turn in, you will feel it in the chassis. The EcoBoost, and the stock GT, were much easier to drive at their limit (albeit slower). The BOSS 302 under the same conditions over the weekend, was also easier to drive at the limit. The good news is that the upgraded GT suspension will help teach you to be a better driver… if you are willing to listen to it (and your instructor). For this reason, I feel this is not a suspension setup for a beginner (more thoughts on this later).

With my general impressions out of the way, I thought I would break the review down into the basic stages of a road course turn.

Maximum braking on approach: The car is very stable. Since there is much less nose-dive it feels more settled, and this gives you confidence to go deeper. I suppose the back brakes could now be more efficient leading to shorter stopping times, but I can’t be sure that I actually was stopping any more effectively. But, stability leads to greater confidence and smoothness, and this encourages you to go deeper.

Turn-in / transition to cornering: This is where the increased sensitivity has pros and cons. The cons: the margin for error is smaller. If you are off a little on your input timing, or you are too abrupt, you will feel that mistake. The car will NOT soak it up for you. You need to pay attention. The pros: (i) You will feel your mistakes instantly. Yes, this was also a con because it can be distracting. But, this is how you learn to be precise and smooth. (ii) You will feel that you have made a mistake but it will not punish you; the car was never unpredictable or jittery. (iii) Precision and smoothness are rewarded with more speed throughout the rest of the turn!

Cornering on a balanced throttle: There is MUCH LESS body roll. As with the turn in, there will be less weight transfer (if you have done it right), and the car feels like it maintains more speed. There is also LESS UNDERSTEER. The car still understeers, but I was surprised how much less I was fighting it. All this said, for me, actual improvements in speed were gained by avoiding mistakes during the transition to cornering. That is where I have some work to do.

Transition to acceleration and exit: This is where it gets interesting. I had struggled with a particular decreasing radius turn going down hill with less than ideal camber. There is no consensus opinion on the best line for this turn, and it slows a lot of folks down, including me. Not only was I able to carry more speed, but I was able to build a surprising amount of acceleration on the transition to exit. At one point I swore that the throttle caused the front end to tuck in. On the next lap I realized that I was actually getting very progressive, and manageable, throttle steering. A turn that had once been a problem for me was now delightful to manage with partial throttle and a touch of oversteer. I am sure than any well tuned suspension can delver this. That is not the interesting point. The interesting point is that I am still on the stock sway bars; I am seriously thinking of staying with the stock bars.


Critiques: As expected, nothing is perfect and there are some issues. Three things stand out at this point:

(1) Some people say that, with an “upgraded” suspension, the GT mustang “shrinks around you” once you get it on the track. I disagree. The car still feels big. If still feels bigger that the Ecoboost Mustang (on the same track), and it feels bigger than the BOSS 302 (on the same track). It's still a 3700lb car with a lot of weight over the front wheels.

(2) The suspension is not perfect. Under cornering conditions much faster than what was possible with the stock suspension, the suspension can very occasionally shift in a way that is delayed relative to my inputs or changes in the road surface. Either way, it seems to be localized in the rear, and I think there may still be some deflection in the IRS. It’s distinct, very noticeable, and somewhat distracting; fortunately, it does not happen often, and the car can still be driven quite easily. This does not seem to be the fault of the spring and damper pairing; rather, I suspect there is still something in the IRS that needs correction.

(3) My upgraded GT rides flatter than the BOSS 302 and yet it feels less planted. I believe this is related to issue (2) above. Both cars communicate a lot of information about the road and the cornering dynamics to the driver; let’s call this “signal”. My current suspension still shifts in a way that is unrelated, or delayed from, my inputs; let’s call this “noise”. I think the BOSS 302 feels better because it has a little better “signal to noise ratio” than my car does right now.


Overall impressions: If you are interested in road course performance, you would be very hard pressed to find better value for money in the pairing of BMR handling springs (SP083) paired with the Ford Performance track shocks and struts (M-18000-F). With a small number of supporting mods the changes in the handing are PROFOUND.
The advantages of this suspension improve with speed. If you spend most of you time in traffic, and at lower speeds, then you are simply not going to appreciate the amazing engineering that went into these, and you are certainly not gaining anything in terms of comfort. This pairing is perfect for those driving hard in autocross or on a road course. I love this set up! But it’s not for everyone. Here is my very subjective sense of the spectrum of different damper and spring pairings.

(1) Very soft grand touring car:
  • Base GT suspension

(2) Moderately soft grand touring car:
  • Factory Performance Pack suspension

(3) Daily driver, performance driving mostly below the limit (a corner carver), with occasional track days:
  • Factory Performance Pack dampers with BMR min-drop springs (SP763)

(4) Daily driver and high performance driving at frequent track days or autocross, but with slightly more preference for a softer street ride:
  • Ford Performance track shocks and struts (M-18000-F) with BMR min-drop springs (SP763), in combination with supporting suspension and chassis mods. (Done right, I expect this might feel a lot like the BOSS 302.)

(5) Daily driver and high performance driving at frequent track days or autocross, with more preference for a track spring. Specifically, a flat ride with road surface and suspension dynamics clearly communicated to the driver, predictable weight transfers, and optimized reactions to weigh transfers.
  • Ford Performance track shocks and struts (M-18000-F) with handling springs (SP083) combined with supporting suspension and chassis mods.
Great review. [MENTION=10281]BmacIL[/MENTION] got me sorted out with these as well. I've been meaning to write something up, but you pretty much nailed it.

I'll only add is that I've pretty much had set ups 1-4. Anyone looking to upgrade would be better served going right to 4 at least. Ride quality is vastly improved over option 3 as is handling.

These dampers are so good that non car people who have ridden in my car when I had option 3 actually noticed how much smoother it rode with option 4. Literally the only change was the dampers!
 

BmacIL

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You're correct in that the main toe control points are the link and the rear of the control arm points to the subframe and knuckle. The outer point of the arm that connects to the knuckle moves with the arm, so any time that you get deflection at the forward control point, your rearward outer point is coming with and rotating about the rear inner point. The only way this wouldn't induce toe change is if the toe link and the rearward control arm point distance were identical length and completely parallel.

Having said that, you also do get dynamic caster with the motion of the control arm via the forward bushing, since it will effectively shorten/lengthen the height of the vertical link. This means some camber change outside of the geometric change.
 

TheLion

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You're correct in that the main toe control points are the link and the rear of the control arm points to the subframe and knuckle. The outer point of the arm that connects to the knuckle moves with the arm, so any time that you get deflection at the forward control point, your rearward outer point is coming with and rotating about the rear inner point. Having said that, you also do get dynamic caster with the motion of the control arm via the forward bushing, since it will effectively shorten/lengthen the height of the vertical link. This means some camber change outside of the geometric change.
Right, but the toe angle change is linear and pre-defined. It's not erratic or unintended and it's VERY small and it's not really because of the RLCA bushing itself. The stock RLCA bushing doesn't move a lot. A few mm which isn't really going to result in a lot of meaningful toe angle change (due to the slightly shorter toe link / to rear arm ratio) and that change when it happens is linear and pre-defined as to how much can occur.

My general point was, the RLCA bushing isn't going to make a difference for track type applications. Money and time for it (considering it's a major butt pain to even do) is far better spent on sway bars, springs, dampers, toe link spherical bearing upgrades, sub-frame lock outs and differential bushings and eventually some power adders.

It's really a drag racer specific item for those with high HP FI setups. For NA it doesn't really matter (ask Braski, even with stock IRS and a Power Pack 2, with a good set of DR's the car doesn't really hop much as there's enough traction even when launching fairly high up around 5k).

Sure, throw enough power at any car and your going to have to replace just about...everything. But that's not 99% of our applications and that's why I'm sticking with my point of argument on this and the vertical links. The benefits just really aren't there for track / street / auto x applications and that little bit of compliance gives the car just a little less edge to keep it a little more forgiving. Great cars are easy to drive and drive themselves, not a razors edge basket case.

I never suggested they don't have an impact, they do, but it's not meaningful for the OP's application and issues. Anyway, I think we can move on as we are all in agreement on this enough so that nobody is going off the deep end and we have all helped the OP to find a solution specifically to address that occasional "rear end squirm".
 

BmacIL

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Right, but the toe angle change is linear and pre-defined. It's not erratic or unintended and it's VERY small. The stock RLCA bushing doesn't move a lot. A few mm which isn't really going to result in a lot of meaningful toe angle change (due to the slightly shorter toe link / to rear arm ratio).

My general point was, the RLCA bushing isn't going to make a difference for track type applications. Money is far better spent on sway bars, springs, dampers, toe link spherical bearing upgrades, sub-frame lock outs and differential bushings.

It's really a drag racer specific item for those with high HP FI setups. For NA it doesn't really matter (ask Braski, even with stock IRS, with a good set of DR's the car doesn't really hop for common pump gas NA setups).

Sure, throw enough power at any car and your going to have to replace just about...everything. But that's not 99% of our applications and that's why I'm sticking with my point of argument on this and the vertical links.

I never suggested they don't have an impact, they do, but it's not meaningful for most of us and it may even have some negative side effects like making the car a bit overly edgy on the track. We want a balance and balance means some controlled and purposeful compliance. No compliance on everything = extremely edgy hard to drive car.
Believe it or not, we agree on pretty much everything lol

Yes the change is small. The more serious/racecar you get, the more that small things like that are noticeable. There are definitely some benefits that are noticeable with removing that movement and the small amount of binding that bushing can cause during suspension travel (because of how Ford uses those indexing 'teeth'). There are some potential disadvantages too, as you pointed out. I would say whether or not it produces edginess on track is going to be dependent on the rest of your setup and your alignment settings.
 

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[MENTION=19599]Bluemustang[/MENTION] and [MENTION=32569]J.P.B.[/MENTION]

When you installed the sp083 front springs on your FR Track Handling front struts at full droop, how much longer was the spring's free height compared to the full droop length of the strut shaft? In other words, how much did you have to compress the spring to mount it on the strut?

I'm asking because I have a gt350 non-R front strut (droop is longer than GT struts), and I'm worried that the SP083 spring's free height is shorter than the full droop length of the gt350 non-R strut...
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