I put 275/40's on my stock 18's to compensate for the increased horsepowers from my build (235/40 fronts). Now, when I'm going around a wide turn on the interstate at a decent pace, I can feel the front outside tire being jabbed at by the brakes. This morning I thought I was going to understeer into the concrete barrier at the exit to my office.
It seems to be most pronounced around slight downhill, neutral camber turns. I'm not noticing the PSM light coming on, but that could be because I'm focused elsewhere. Why would stability management touch that corner of the car, anyway?
Do I need to reset PSM?
I don't have any answers for you but I think that is the brake activated to counter oversteer. Might be worth getting a fault code download to see if the car is complaining about anything.
I wonder if it would grab that corner when understeering? If that's the case, maybe it's an alignment issue. I think I'm only feeling it on right handers
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Don't know. What I remember for stability control basics is outside front for over steer and inside rear for under steer. At least IIRC. Though I suspect that it's an over simplification. General idea is the car rotates about the braked wheel.
Checking alignment would be good. Wouldn't hurt to make sure all the harnesses got hooked back up correctly when the engine went back in. A fault code download might help with this.
Did they get the tires on the right wheels? Had a shop once put a rear tire on a front wheel. Caught it before driving so don't know what weirdness might have ensued.
These nannies are amazing when they work and a bit spooky when they get it wrong and take over. I can't help but see irony in what's supposed to prevent under steer causing it. Then again it may have saved you from something worse. Won't know until you get it sorted.
Les
It could be that you are running non-stock sized tyres and the change in rolling radius is confusing the PSM.
Just make sure it's not a typo. Did you put 275/40 or 275/35 on the front? What is the rear size? I know a few guy with 986 able to run square setup on the autocross but they had the PSM off as it does interfered occasionally. The stock setting is 235/265 F/R. It's OK to increase or decrease the overall diameter of the tires and you don't have to keep the exact diameter ratio between F and R as long as the front is smaller than the rear. The most you can do is the same but that's pushing it.
If you're running square try to put the new tires in the rear as they will be slightly taller. You supposed to put new tires in the rear anyway for safety reason.
I was hoping the OP would clarify this as it's an interesting puzzle. The way I read it is he went to 275/40 on his stock rears and kept the OEM 235/40 fronts. I would have expected as he said for 275 rears to get the increased power down better and given an overall more under steering setup. Just seems odd for PSM to be going on the outside front for what would seem to be an already overloaded tire. I would have been inclined to step the front width up by the same amount to 245 to keep the balance.
How can you tell it's the outside front tire? Your new setup could simply be inducing plain old ordinary understeer. In which case, PSM is helping you and not hurting. If this is the case, PSM would be braking the inside rear tire to keep you from plowing into the barrier.
+1 on the above. For my track tires I , like many here, run 245/40-18(some run 235/40-18 F) front and 275/40-18 rear with no issues on my CS. I am not familiar with your car build or driving skills.
However you may simply be carrying too much speed into the turn in towards the Apex, and the PSM is taking a corrective action. Are your tires new? And of course check your tires and alignment, and let us know what you find.
U might also need to adjust your tire pressures, front vs rear, to get the car neutral handling again. Those front tires may be a bit wide for an 8.5" rim. Front tires need a few extra psig to eliminate understeer, or similarly on the back tires if it is oversteering.
Turn off the PSM and go slide it carefully somewhere where nobody gets killed, to see if the handling is still neutral, or if it is now understeering or oversteering with those oversized tires.
This should be in the Track 101 course...
