Impreza Not Too impressive: Handling Upgrades

Reader asks how to improve handling of his car without voiding warranty/attracting cops.

Today I'm sharing a reader's question that I thought would resonate with a lot of you.

"Hello,
I have been reading some of these articles and I am very impressed by the information provided.

This is my first all-wheel drive and I have to say, the handling is NOT as good as I thought it would be, especially on wet roads.

I have noticed that if I turn hard into a corner in the wet, the front seems to have a mind of its own and it looses grip. If I back off a bit, if feels like I'm not going to make the corner. I would like to achieve better handling, but I am unsure of the best way to go about this. Looking at the wheels, it seems obvious that there is plenty of room for wider wheels, but after reading your articles, I am reluctant to change the wheels. So, the next thing to consider is better rubber? Suspension improvements? Anything I do to this car, I need to consider that I can not make any changes that disrupt the  warranty conditions and I certainly don't want to risk turning the car into a danger and/or a cop magnet. Any suggestions? -- Peter W.

Peter, thanks for your question. At least from what I can tell from your writing you're experiencing strong understeer (or "plowing"/"pushing") in the corners, especially in the rain. I assume by backing off you mean letting off the throttle which is always a dangerous thing to do mid-corner, especially if it's sudden. You can get snap oversteer/understeer or a mix of the two by upsetting the car at the limit like that.

If the car is still under factory warranty, you must be careful as nearly anything will void a warranty if the dealer doesn't want to pay for whatever. Wheel changes are typically just fine and there is no reason I can think of that a dealer might void your warranty for changing out sway bars. Changing the actual suspension would probably void anything related to the drivetrain or suspension.

So I mention wheels and sways for a reason. Typical production cars are intentionally setup to plow in the corners (understeer). Understeer is exactly what it sounds like, you're in the corner and you are feeding in more steering than the car is actually doing. Oversteer is when the car steers MORE than the steering input (such as in a drift/power slide).

One of the best ways to try to neutralize handling in the bends and get away from that nasty understeer is to fit a larger rear sway bar, or better still to fit two performance oriented bars with a significantly thicker rear bar. You might be able to swap with a factory unit (look to the Impreza's big brother STi perhaps) or there are certainly many aftermarket replacements available.

Too much stiffness in the rear can also be troublesome in the rain, so be careful not to go TOO crazy in the rear, I like adjustable bars because I can drive the car and see how it's feeling and make adjustments as needed. If you go too crazy in the rear, it can sometimes be like driving on ice in the rain and it's very dangerous. On project Lexus I found that if I set the front bar on "soft" and the rear bar on "hard" (of the 2 settings), that it was like driving with the rear wheels on blocks of ice in the wet. However, once I set them both to soft, it was safe and predictable again. In the dry, both settings were "okay".

Tire choice will be very crucial for you as well. Really sticky summer tires rarely work well in the rain, so an all season may be a better fit for you. Nothing available right now as I write this beats the Contintental Extreme Contact DWS Tires for all around street driving (including wet and somewhat winter-like conditions). There are definitely better dry weather tires and even some of the higher end summer tires deal well with water and thus might be a good choice.

You can upgrade wheels as well without causing too many issues. If you're already at a 55 section width (215/55/17 for example) then I'd focus on getting lighter weight wheels. If you're not there and you're running a 65 or greater sidewall, then I'd look for a factory wheel that is an inch larger in diameter than your current. So if you're running 16s right now, you'd want a 17" assuming the sidewall is greater than 55. This will take a LOT of that unpredictable feeling out of the front end - a problem I've seen heavily in my fiance's 2006 Civic Ex. It's caused almost exclusively by sidewall flex and a very soft suspension.

With the wheels, focus on getting around a 45-55 sidewall, factory or factory-like, with a lower weight being a bonus. If you're looking at a really small width (like 195) you MAY want to step out 205 or even 215 (two "sizes" up) at the most. Again, look at the "upper" models of the same car and if they have a different wheel sizing, that's a safe one to use.

I wrote a while back about one slick way to "disguise" wheels. I've never had anyone guess that my wheels were anything other than factory (which means cops won't see it either), and all I did was take the center cap and turn it into a "Lexus" one. See this article: Blending In: Making Aftermarket Wheels Look "Factory"

In the coming months, if you want to learn more about suspension tuning for the street (not the race track), make sure your on my e-mail list and keep your eyes peeled for a product that I'm putting together on the subject that will detail EVERYTHING you ever need to know about getting great handling out of your street car.

Thanks for your question and good luck!

-N

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