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2016 WRX STI pulling straight while accelerating during a turn/bend

6K views 16 replies 5 participants last post by  XJman 
#1 ·
I am hoping some experienced STI people (or maybe even a Subaru mechanic) can help me out with this. I recently went from a 2011 WRX to 2016 STI and notice something I didn't encounter with my 2011 WRX, nor any other AWD Subaru I have driven. (Actually in the past two months I have driven 5 different Subaru's and none of them does what my STI does). While either driving on a highway, country road or accelerating the car will pull "away" from the turn/bend (turning left car pulls right/straight) while accelerating, does not matter if turning left or right it happens both ways and if you keep the wheel turned to correct for the pull the second you let off the gas to shift or slow down the car will correct itself and turn towards the way the wheels are turned. This is under normal driving conditions, and normal acceleration. For example if I am driving on the highway to work, and there is a sweeping bend to the left and I am doing 65mph and I have about 10% throttle, when I let up on the gas, the steering frees up and the car turns more into the bend, when I accelerate the car will pull straight in the bend. It really is kind of unnerving. I have read multiple posts/articles etc. and I never hear of this. My WRX never did this. Is this a function of the differentials in the STI which the WRX didn't have? Or could there be something amiss. I may be wrong, but isn't the STI 59% biased towards the rear, so why would the front wheels seem to pull the car more. You can imagine in northern NJ there aren't to many straight roads, so this seems pretty pronounced. Every morning coming out of my complex there is a long bend, and going through gears 1-3, each shift I can feel the wheel loosen up. Only time it feels normal is on a perfectly straight road.
I am going to take this issue to the dealership, but I would like to be armed with some information if other people experienced this. Or be at ease if folks say this is normal for STI's.
I also had a pulling problem with the car that eventually was fixed with 2 new tires, but before they did, they twice told me it was normal with an STI.

Any help is greatly, greatly appreciated.
 
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#3 ·
Thanks for you feedback XJman. How come I didn't feel it in my WRX nor in my current daily driver, a Impreza OBS? Is it that is just more pronounced in the STI because of the LSD's. And if it is understeer, didn't they greatly reduce it in the 15/16's?.
 
#9 ·
if it is understeer, didn't they greatly reduce it in the 15/16's?.
Not particularly. Subaru added the ATV system to reduce understeer, but ultimately the car is just as unbalanced as any other AWD car at the limit.

That being said, I think there are a few factors at work. Firstly, Subaru's factory alignment is very VERY mild. I believe the OEM specs call for a very mild -0.5 deg up front and a (less controlled) -1.5 degrees rear. If you had a non-factory suspension alignment on the older car, that is very well the defining difference. A proper alignment will wake this car up.

The LSD up front does mean the STI will push a bit more than cars with an open front diff. However, the rear-ward bias and more effective DCCD combined with the ATV should greatly balance this effect. So, where do I think the difference is?

Your mind. Here's why -- The new STI has a considerably more aggressive caster alignment than the old car. This means the kingpin offset during off-axis steering input will yank much harder at the wheel than the older car. This has the effect of feeling like the car wants to push harder to the outside of the corner. Hold onto the wheel, and you'll find that the overall limits are considerably higher than your old WRX. It also makes the car massively more communicative than the old car.

Cheers!

Zax
 
#4 ·
Also I have been doing a lot of research on understeer and this isn't a case of flying into a corner or on a track, this is simply driving normal speed on a highway going around a slight bend, maintaining speed, and upon slight acceleration the car wants to pull out of the lane by going straight instead of following the bend. Not a case of wanting to go straight under braking. Is understeer found in both hard braking and slight acceleration? thank you for your patience.
 
#6 ·
thanks again. I am just a little gun shy so far. Car has about 1600 miles, and since mile 10 it had a pull to the left. Alignment done by dealer. Still pulled to the left. Second one done. Still pulled. They tried telling me this is normal for an STI. 3rd time, the road forced the tires and replaced two of them. Goes straight now so I just want to make sure everything else is correct.
 
#7 ·
You can tweak the suspension to help a little but in general you'll always have understeer. Part of owning an awd vehicle. Personally it bugs me, but I don't let it bother me as i love my wrx in general

Sent from my Nexus 6 using Tapatalk
 
#11 ·
someone responded to my thread in another forum with a good description of what I am encountering, "lift off/over steer. I think I am going to look into another alignment as maybe something is out of whack. Anyone have any recommendatons for a performance alignment shop in northern NJ? Zax, I do appreciate your input, and I am hoping for that proper alignment. Its interesting, when I push the car, I don't find the understeer ( I know I am nowhere near the limits) as much as I did in my 11 WRX. But I do notice it more just in everyday, normal driving.
 
#15 ·
For a given steering angle and speed:
steady speed ->perfect circle.
acceleration -> car turns bigger circle.
deceleration -> car turns in a smaller circle.

The symptom sounds like understeer or oversteer but the cause is not high speed and grip limit.
My car can do this consistently in 35-mph normal street driving. I like to know what caused it.
 
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