2015 GT PP Steering Wandering Issue

[KA06GT]

Hey guys,

Just a question. I bought my 15 Performance Pack used with 13K on the clock. I've had it at the dealer a few times getting some other issues sorted out from another thread I started awhile back.

I noticed the car feels like it wanders in my lane, almost like I'm having to fight it sometimes. It's not the normal on rails feeling you'd expecting from a performance oriented suspension setup from the factory at Ford, so I thought, okay after 13K it might need an alignment. I paid the dealer to do an alignment and they said it was a little off, but it's all spot on now and they gave me the printouts so I could verify. Yet the car feels exactly the same.

It's almost like the wheel adjusts itself to the left just a little and then I have to give more steering input to keep it straight. I've been reading of some of the steering rack issues, but mine isn't exactly like that. It's what I would describe as "floaty" feeling. The car is unbelievable in the curves, but straight highway driving on my 30 mile commute to work drives me crazy because it pulls back and forth.

So I've been looking at Steeda's "Stop the Hop" kit https://www.steeda.com/Steeda-S550-Mustang-Stop-The-Hop-Starter-Kit-555-4455

I've read a few places that the rear IRS subframe movement could cause issues such as what I'm describing because the soft bushing allow for a lot of lateral and vertical movement within the entire subframe..

Anyone have any input before I order that kit or have any experience with this problem?

Sponsored

 

[vernonator]

Does it happen in the same spot every day? You could be tramlining - wide tires are a bit more prone on a heavily crowned road. I notice it sometimes on my '16 GT/PP as I drive into town on roads used by BIG tractors hauling grain.

 

[KA06GT]

Does it happen in the same spot every day? You could be tramlining - wide tires are a bit more prone on a heavily crowned road. I notice it sometimes on my '16 GT/PP as I drive into town on roads used by BIG tractors hauling grain.

I find it happening in all different places most of the time. It's like it will pull in one direction, I straighten it up, and then it will pull in the other direction.

I had considered tramlining, but wasn't sure. Would my stock Pirelli's being at the end of their life and needing replaced only make tramlining worse if that was the case? I've been planning on buying some 275/40/19 Nitto NT555 G2's here soon to replace them.

I hate to link another forum, but this is the thread that pointed me towards the Steeda products. https://mustangforums.com/forum/suspension/731505-2016-mustang-gt-pp-w-irs-steering-wander.html

When I give it some throttle, just like in the video in that thread, mine will pull to the left and require some driver input to get it back straight, then it's like it wants to fight me and pulls the opposite way.

I have crawled under the car with the rear end of the ground to check out the rear subframe and with the naked eye it does look like the subframe shifts a bit and all the bushings aren't exactly in line. I have pictures of all four subframe mounts if it helps explain what I mean. I believe the alignment kit in the "Stop the Hop" starter kit might cure that aliment though. I just wonder if the subframe moving in the bushings is causing the toe to change a little to one side or another with each bump in the road?

 

[TheLion]

I find it happening in all different places most of the time. It's like it will pull in one direction, I straighten it up, and then it will pull in the other direction.

I had considered tramlining, but wasn't sure. Would my stock Pirelli's being at the end of their life and needing replaced only make tramlining worse if that was the case? I've been planning on buying some 275/40/19 Nitto NT555 G2's here soon to replace them.

I hate to link another forum, but this is the thread that pointed me towards the Steeda products. https://mustangforums.com/forum/suspension/731505-2016-mustang-gt-pp-w-irs-steering-wander.html

When I give it some throttle, just like in the video in that thread, mine will pull to the left and require some driver input to get it back straight, then it's like it wants to fight me and pulls the opposite way.

I have crawled under the car with the rear end of the ground to check out the rear subframe and with the naked eye it does look like the subframe shifts a bit and all the bushings aren't exactly in line. I have pictures of all four subframe mounts if it helps explain what I mean. I believe the alignment kit in the "Stop the Hop" starter kit might cure that aliment though. I just wonder if the subframe moving in the bushings is causing the toe to change a little to one side or another with each bump in the road?

I experience the same thing on my 2016 PP GT. It feels like it will pull to the left or right suddenly with the road. I believe the majority of that is due to the rear IRS movement. Just like on my Ecoboost Mustang, I cannot detect ANY steering slop. This car has absolutely no detectable play in the steering / front end. It's very tight on a PP car (GT or Ecoboost).

In my 2016 Ecoboost Base model I had before I traded in for the 2016 GT PP, I had done the rear sub-frame bushings from Steeda (no other sub-frame mods) and that made a substantial difference all by themselves. Helped with wheel hop on street tires on an actual street, but you would need to do a lot more to eliminate wheel hop on a drag strip. Drag setups are not ideal for track however and visa versa. Pick your poison as they say. I like the twisties so I lean more towards track setups which also tend to work well for daily.

The back end didn't feel like it was on a rubber band any more on my Base Ecoboost after the steeda sub-frame bushings. Now the GT makes quite a bit more power than the Ecoboost, especially at part throttle, being a decent sized NA V8, so it seems to exacerbate the cradle deflection even more during daily driving. But it really tightens up when you start to push it, even more so than the Ecoboost did (before I installed the sub-frame bushings that is).

It's interesting that the car seems to tighten up a lot when you start to push it compared to the Camaro SS. I believe the cradle tends to deflect and reach it's limits of travel as it's captured and can only move so far and that's why it has this sensation of suddenly tightening up.

The cradle quickly moves and reaches it's maximum point of travel due to a more sudden and higher magnitude of forces exerted on it. So the movement of the IRS is generally not perceptible to the driver during spirited driving.

But yes the car feels like it "wallows" during normal driving where cars like the Camaro SS feel much tighter during normal driving but don't really "tighten up" when you push them. It's more or less always the same. The "wallowing" sensation can be quite unsettling at times as it feels like the whole rear end si going to slide out, other times it feels like the front end is suddenly pulling left or right (like when you drive through heavy water that is only on one side of the road or the tire tracks in a deep groove).

The stock PP GT takes some getting used to and can still be unsettling at times even after driving it for a while. The trade off is the GT is pretty darn quite as far as NHV is concerned comparatively and that's what Ford was after as the Mustang is tailed more as a street rod than a pure track car.

Although in my humble opinion I'd prefer the rear IRS to be locked in place and deal with a little more NHV and clunky-ness from the drive train / suspension but have that consistent tight handling.

I generally dislike the feeling of the rear end "breaking loose" or "sliding" when it's not actually doing either which is how I perceive it. It may bother some people, while it may not bother others.

Maybe a good compromise would have been for Ford to lock out the IRS on PP cars but leave it as is on standard GT's as the PP cars are more performance oriented and the target audience is willing to accept a little more NHV than most people buying non PP cars.

BMR makes a really good IRS lockout kit by the way, the whole kit weighs only 6.5 lbs, so there's no meaningful weight gain. I went that route over Steeda this time. For a little over $200 you get nearly the exact same performance. A very small amount of IRS movement is ok, we don't want bolts to work loose or shear, which would be very bad and just a little flex helps absorb the peak forces exerted on them.

There's far less cradle movement in a Mustang GT with the BMR IRS lockout kit than a stock 2016+ Camaro SS, which has about half the movement of the mustang in it's factory form. It completely changes the car's handling dynamics and it feels tight and precise all the time. On my car and in my experience it also nearly eliminated that "pulling" feeling. There no more or less "pulling" than any other tight handling sports car would experience.

The IRS angles affect your steering. If the cradle rotates due to road forces / groove tracking, it allows the rear of the car to ever so slightly change direction despite the fact that the rear tires are still in the same position on the road. So it has a similar effect of altering steering. This also explains why the stock GT's tend to "wander". The IRS is squirming around and constantly changing the rear toe angles, causing a disconnection between the front and rear. I would highly suggest an IRS lockout kit and see if that helps.

Nice thing about the BMR kit is it's also much easier to install than the Steeda lock out rings. Both kits require lowering the cradle a bit, but the BMR solution slides over the ends instead of around them and more or less drop in place where the Steeda lock out rings require much more force to get on. As far as the front braces, it's a wash, I don't see the Steeda braces having any really meaningfully different impact than the BMR ones but the Steeda solution is quite a bit more expensive as it's separate. Having done both I can't say enough about the efficiency of design of the BMR kit. It does the trick with the very minimal amount of parts / weight / difficulty.

BTW, I am running 275/40R19 Pilot Sport AS3+ tires in front and rear, so I don't think your tires are the cause. It's the IRS movement causing tandem toe angle changes of the rear tires, it more or less acts like rear wheel steering. Look up Honda Prelude, that car had rear wheel steering, very interesting sensation while driving it.

 

[KA06GT]

I experience the same thing on my 2016 PP GT. It feels like it will pull to the left or right suddenly with the road. I believe the majority of that is due to the rear IRS movement. Just like on my Ecoboost Mustang, I cannot detect ANY steering slop. This car has absolutely no detectable play in the steering / front end. It's very tight on a PP car (GT or Ecoboost).

In my 2016 Ecoboost Base model I had before I traded in for the 2016 GT PP, I had done the rear sub-frame bushings from Steeda (no other sub-frame mods) and that made a substantial difference all by themselves. Helped with wheel hop on street tires on an actual street, but you would need to do a lot more to eliminate wheel hop on a drag strip. Drag setups are not ideal for track however and visa versa. Pick your poison as they say. I like the twisties so I lean more towards track setups which also tend to work well for daily.

The back end didn't feel like it was on a rubber band any more on my Base Ecoboost after the steeda sub-frame bushings. Now the GT makes quite a bit more power than the Ecoboost, especially at part throttle, being a decent sized NA V8, so it seems to exacerbate the cradle deflection even more during daily driving. But it really tightens up when you start to push it, even more so than the Ecoboost did (before I installed the sub-frame bushings that is).

It's interesting that the car seems to tighten up a lot when you start to push it compared to the Camaro SS. I believe the cradle tends to deflect and reach it's limits of travel as it's captured and can only move so far and that's why it has this sensation of suddenly tightening up.

The cradle quickly moves and reaches it's maximum point of travel due to a more sudden and higher magnitude of forces exerted on it. So the movement of the IRS is generally not perceptible to the driver during spirited driving.

But yes the car feels like it "wallows" during normal driving where cars like the Camaro SS feel much tighter during normal driving but don't really "tighten up" when you push them. It's more or less always the same. The "wallowing" sensation can be quite unsettling at times as it feels like the whole rear end si going to slide out, other times it feels like the front end is suddenly pulling left or right (like when you drive through heavy water that is only on one side of the road or the tire tracks in a deep groove).

The stock PP GT takes some getting used to and can still be unsettling at times even after driving it for a while. The trade off is the GT is pretty darn quite as far as NHV is concerned comparatively and that's what Ford was after as the Mustang is tailed more as a street rod than a pure track car.

Although in my humble opinion I'd prefer the rear IRS to be locked in place and deal with a little more NHV and clunky-ness from the drive train / suspension but have that consistent tight handling.

I generally dislike the feeling of the rear end "breaking loose" or "sliding" when it's not actually doing either which is how I perceive it. It may bother some people, while it may not bother others.

Maybe a good compromise would have been for Ford to lock out the IRS on PP cars but leave it as is on standard GT's as the PP cars are more performance oriented and the target audience is willing to accept a little more NHV than most people buying non PP cars.

BMR makes a really good IRS lockout kit by the way, the whole kit weighs only 6.5 lbs, so there's no meaningful weight gain. I went that route over Steeda this time. For a little over $200 you get nearly the exact same performance. A very small amount of IRS movement is ok, we don't want bolts to work loose or shear, which would be very bad and just a little flex helps absorb the peak forces exerted on them.

There's far less cradle movement in a Mustang GT with the BMR IRS lockout kit than a stock 2016+ Camaro SS, which has about half the movement of the mustang in it's factory form. It completely changes the car's handling dynamics and it feels tight and precise all the time. On my car and in my experience it also nearly eliminated that "pulling" feeling. There no more or less "pulling" than any other tight handling sports car would experience.

The IRS angles affect your steering. If the cradle rotates due to road forces / groove tracking, it allows the rear of the car to ever so slightly change direction despite the fact that the rear tires are still in the same position on the road. So it has a similar effect of altering steering. This also explains why the stock GT's tend to "wander". The IRS is squirming around and constantly changing the rear toe angles, causing a disconnection between the front and rear. I would highly suggest an IRS lockout kit and see if that helps.

Nice thing about the BMR kit is it's also much easier to install than the Steeda lock out rings. Both kits require lowering the cradle a bit, but the BMR solution slides over the ends instead of around them and more or less drop in place where the Steeda lock out rings require much more force to get on. As far as the front braces, it's a wash, I don't see the Steeda braces having any really meaningfully different impact than the BMR ones but the Steeda solution is quite a bit more expensive as it's separate. Having done both I can't say enough about the efficiency of design of the BMR kit. It does the trick with the very minimal amount of parts / weight / difficulty.

BTW, I am running 275/40R19 Pilot Sport AS3+ tires in front and rear, so I don't think your tires are the cause. It's the IRS movement causing tandem toe angle changes of the rear tires, it more or less acts like rear wheel steering. Look up Honda Prelude, that car had rear wheel steering, very interesting sensation while driving it.

Now that is the kind of answer I was looking for!

Driving through standing water and it pulling the front end in that direction almost exactly describes the feeling I was trying to convey. I have a few times taken my hands off the wheel (in a controlled enviorment) and you can actually see the steering wheel move like something is turning it.

I couldn't figure out for the life of me why it felt so unbelievable planted and controllable in the twisties, but felt like driving a log truck with no power steering on a flat straight stretch of highway.

The handling abilities in the curves made me feel like the alignment wasn't the issue, but I figured I'd go ahead and pay the dealer to do that while it was there. I was really disappointed when I headed home with a perfect 4-wheel alignment and it was still all over the road.

This is my third Mustang in a row with offset tire sizes running 275's in the rear and I never experienced any tramlining to an extent such as what I'm getting with my factory 275 car. So I hadn't ruled that out completely, but I did see it as unlikely.

So Lion, in you opinion, you believe I'm headed in the right direction and taking out the deflection and movement of the IRS will improve my daily driving and improve that unsettling "wandering" feeling?

I'm okay with some increased NVH to make it move comfortable on trips and not feel like I'm going to hit the other lane at any moment. For the price of the "Stop The Hop" kit and the discount code from Steeda graciously provided by TJ here on the forums, that's probably the route I'll go, but I'll definitely look into the BMR kit you mentioned.

 

[NightmareMoon]

Did they give you a printout of the final alignment? If so, link us an image so we can review it.

First off, if you take your hands off the wheel in a sports car, expect the wheel to move a bit and the car to turn. These things are not setup to drive straight down the road like a caddy without a driver.

Overly twitchy steering is often a front toe issue. You may be used to cars with a little toe in, which has a heavier, stable centered feel. Fords specs I think call for 0 front toe, which some people aren't used to and it gives a lighter steering feel and allows the car to more easily turn itself if you do something weird like take your hands off the wheel. Tramlining is also often more a factor of tire tread pattern design than actually tread width. What tires are you running?

If the car is just a little unpredictable and likes to step out in the rear when you take off hard, check your rear toe settings. How the rear of the car behaves (or not) under power is often affected by rear toe.

The other thing to consider is that if the car is behaving erratically, you may have a loose wheel bearing or some other loose bolt in the suspension. If the car requires different amounts of steering wheel angle to go straight at different times, and it can't be explained by the crown of the road, then that sounds like something is shifting or loose. I've had a suspension bolt get loose and a rear hub go out on my car and it was downright spooky handling.

If properly aligned with all bolts tight, the car should absolutely not need subframe braces to perform reliably and consistently. My car has stock bushings and no extra braces and drives very consistently at all times.

Those extra braces certainly won't hurt, but don't expect throwing random parts at the problem to solve anything if you haven't figured out why it was doing it in the first place. That's just literally just taking stabs in the dark. I highly doubt it will solve any wandering you're experiencing.

 

[KA06GT]

Did they give you a printout of the final alignment? If so, link us an image so we can review it.

First off, if you take your hands off the wheel in a sports car, expect the wheel to move a bit and the car to turn. These things are not setup to drive straight down the road like a caddy without a driver.

Overly twitchy steering is often a front toe issue. You may be used to cars with a little toe in, which has a heavier, stable centered feel. Fords specs I think call for 0 front toe, which some people aren't used to and it gives a lighter steering feel and allows the car to more easily turn itself if you do something weird like take your hands off the wheel. Tramlining is also often more a factor of tire tread pattern design than actually tread width. What tires are you running?

If the car is just a little unpredictable and likes to step out in the rear when you take off hard, check your rear toe settings. How the rear of the car behaves (or not) under power is often affected by rear toe.

The other thing to consider is that if the car is behaving erratically, you may have a loose wheel bearing or some other loose bolt in the suspension. If the car requires different amounts of steering wheel angle to go straight at different times, and it can't be explained by the crown of the road, then that sounds like something is shifting or loose. I've had a suspension bolt get loose and a rear hub go out on my car and it was downright spooky handling.

If properly aligned with all bolts tight, the car should absolutely not need subframe braces to perform reliably and consistently. My car has stock bushings and no extra braces and drives very consistently at all times.

Those extra braces certainly won't hurt, but don't expect throwing random parts at the problem to solve anything if you haven't figured out why it was doing it in the first place. That's just literally just taking stabs in the dark. I highly doubt it will solve any wandering you're experiencing.

Hey Nightmare,

I appreciate the input!

This is my 5th Mustang in recent years, and not the first with EPS, so I'm fully confident in how the car should be driving and what trade offs I get for this level of performance, but this is not a case of "twitchy" steering.

This is definitely something with the IRS or suspension movement in the wrong way.

It's unsettling, and Lion nailed it to a "T" with what I'm trying to describe. Considering he has had two S550 and used both kits I'm looking at with great success in resolving (or at least improving) the issue described, I don't feel this is taking stabs in the dark and just throwing random parts at it, especially since I have researched and had already came to that conclusion before Lion laid it out perfectly for me.

I'm little jealous that your PP S550 doesn't have the wandering issue experienced by Lion, myself, that other thread I had linked above, as well as some comments on the YouTube videos for the IRS bushing lockout kits. I can't ever seem to be that lucky.

Either way, if I order these parts and it doesn't fix it, I'll be sure and post up so someone else doesn't make the mistake I did!

Also I'm running the stock Pirelli's as stated above, but they are getting towards the entire of their life and will be switched out with Nitto NT555 G2's when the time comes.

Attached is the alignment you asked for. The previous owner gave me a print out when I bought the car, and he had gotten it aligned somewhere other than Ford, so that might be why the old values are out quite a bit, but like I said, the wandering issue had no change between the two alignments you see in the image, so at factory Ford alignment specs the issue is still there.

 

[KA06GT]

The parts have been ordered! Thanks to Lion, I changed what I was originally going to order.

https://www.americanmuscle.com/bmr-irs-lockoutk-kit-black-1516.html

https://www.americanmuscle.com/steeda-alignment-kit-for-bmr-irs-cradle-bushing-lockout-kit-15117.html

All in all, with a discount code for American Muscle it wasn't to bad if this ends up not being the problem I'm having. At least I'll have reduced the wheel hop if I ever decide to take it down the strip!

 

[NightmareMoon]

Alignment sheet looks ok, good luck with the subframe braces.

 

[TheLion]

I also noticed the PP steering is also weighted differently than base model. This in my opinion makes it feel more sensitive to the road. The roads where I live while not horrid are far from.smooth in many spots. There is plenty of grooving and varying ridges (some highways are cement with ridged or grated tops for traction).

The wandering was really bad on the grated cement highways and deeply grooved highways. The front of the car is just disconnected from the rear of the car. Ford went too far in isolating them I'm my opinion. Not sure if I would say its a flaw as it was intentional design, just a disagreement in how much handling is compromised for the possible NHV issues they were trying to mitigate.

But even with this funkiness, mustang are still outselling the Camaro so I guess I'm in a minority view on that one. But hey, there are a few low cost but over effective and easily reversible mods to correct it so I can't complain too much.

The sub frame bracing won't eliminate it pulling but will reduce it noticeably so its not much different than any other performance car. I think its how the car should have come from the factory and its far more predictable and connected in the rear. The back follows the front nicely instead of sometimes and unexpectedly doing its own thing. One of the car mags noted that very thing but I forget which one.

 

[TheLion]

The parts have been ordered! Thanks to Lion, I changed what I was originally going to order.

https://www.americanmuscle.com/bmr-irs-lockoutk-kit-black-1516.html

https://www.americanmuscle.com/steeda-alignment-kit-for-bmr-irs-cradle-bushing-lockout-kit-15117.html

All in all, with a discount code for American Muscle it wasn't to bad if this ends up not being the problem I'm having. At least I'll have reduced the wheel hop if I ever decide to take it down the strip!

Yes the BMR kit is a much more efficient (only 6.5lbs weighed myself) and cost effective design. It removes all meaningful IRS movement (very small amount isn't going to make a difference in anything but an actual race car where 1/1000th of a second counts).

Its also easy to take back off if for any reason you wanted to return it to stock. It had a heck of a time getting those steeda collars around my subframe bushings in my ecoboost and that was when the whole darn irs was sitting on my garage floor! It would be even more miserable with the I re still connected...forget diff bushings in a street car. Even the poly ones added a ton of noise and diff whine. I took them back out of the ecoboost about 4 months after it put them in because I was about ready to pull out what little hair was left on my head lol.

I think irs lockout and vertical links are just right for a street / track / auto x car that's daily or frequently driven. Pair those with a 4 square tire setup (pilot sport as3 offer better grip than many summer only tires but have better tread life and are temp stable at lower temps if you drop below 40f) and its a great balance of performance, lifespan and nug.

 

[jasonstang]

The S550 rear end is very loose. I can feel it wiggle sometimes making tight turns.

 

[TheLion]

The S550 rear end is very loose. I can feel it wiggle sometimes making tight turns.

Those wonderfully squishy IRS bushings . But it makes for a smooth ride and no NHV at least...

 

[KA06GT]

First drive to work this morning after the install.

Lion you are 100% correct, those Steeda alignment bushings are a pain in the back side! My cradle was definitely not aligned perfectly from the factory.

This is my initial impression after my 30 mile commute to work this morning. The car feels much more solid and holds a line 10 times better than it did previously. Now on super grooved portions of the road it will still pull, so it did not elimination the issue completely, but it made such a noticeable difference that this should have been included from the factory.

After a week I'm going to throw the car back up in the air and recheck all my torque specs, and I'll update after I've done some more driving.

Another thing to mention, and I think I had read it somewhere before, but my shifts feel much better than they did before the install. I find that hard to believe the IRS could shift enough to effect then entire driveline all the way back to the shifter, but it definitely feels much crisper and less "bad notchy" feeling (not good notchy like an aftermarket shifter such as Barton or MGW)

 

[TheLion]

I'm not sure about the shifting aspect but it could be possible that due to the irs play the driveline is more prone to oscillating off throttle. That would certainly feed back into the transmission and could have some impact on shift feel but that's only speculation about it changing the angles of the drive shaft and it actually having an impact on the transmission. Maybe it feels firmer when you step on the gas? That would be because the irs is allowing the power to be transmitted more directly instead of absorbing some of it.

At any rate good to hear it made a big difference in your tracking issues and also greatly improved the way the car handles. I agree it should have come like that from the factory. Its a night and day difference.

Sponsored