IW STi Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
373 Posts
Discussion Starter #1
I have noticed that after reading nearly every review I could find regarding the sti, that there is often a negative comment regarding understeer :( (i guess they need to pick on something).

Likely, the understeer is planned for safety reasons (it is much easier to avoid loss of control) so inexperienced drivers don't keep putting it in the ditch when pushing the limit. :cry:

I was woundering if any of you are considering suspension additions or mods to address this supposed understeer issue. And if so, what would you do? 8)
 

·
Registered
Joined
·
886 Posts
when will we know which front end?

Right now I am pondering ways to get/afford the car; until then any mods are not part of the equation for me.
 

·
Registered
Joined
·
373 Posts
Discussion Starter #4
thanks for the info. link, thats exactly type of stuff I am looking for

apparently, even with all of the factory upgraded suspension sti has over its sibling, understeer is still an issue (unless this has been addressed in the US-Can. version, we will see....)

I was also thinking about lowering with good quality coil overs that can easily be adjusted to raise for winter months but I must admit due to my limited knowlege wrt suspension I am afraid of wasting a pile of money for nothing or worse yet creating other handling issues.

I don't know who these guys are, but I found this link which brings up some issues regarding the sti which might be of some use.
http://www.speed.org.nz/garage/sti_light_dawns.phtml
 

·
Registered
Joined
·
281 Posts
Paris AUto Show - Press Release

It is the nature of AWD cars to understeer. The front tire only has x amount of traction. On a RWD car, 100% of x goes to steering. However, on an AWD car some percentage of x goes to moving the car as well. The remaining percentage is available for steering. This said, there are a number of ways to overcome the tendancy to understeer. The quickest, cheapest way is to play with your tire pressure. I have found that by running a little less pressure in the front tires and a little more in the rear, the car is more neutral. If this doesn't gain you enough, then then rear swaybar links and/or a thicker rear swaybar will get you in the ballpark. See the link above for more info.

J.B.
www.wrxtra.com
 

·
Registered
Joined
·
373 Posts
Discussion Starter #6
how much tire pressure are you talking. 1 or 2 psi or more. The more you go below manufactued ratings, the more uneven wear/reduced life you get.
 

·
Registered
Joined
·
281 Posts
For the most part, the manufacturer's recommended ratings are to provide the best fuel ecconomy and wear. Additionally, they help keep the car "safer" by providing understeer. However, most of us buy these cars for the performance aspect. With 17" wheels, I would not recommend going below 30 PSI at any time. During hard cornering, you will not have enough air in the tire to keep it from rolling under and creating SEVERE wear to the sidewalls and side treads. Subaru recommends 33 PSI front/32 PSI rear for 17" wheels. I have found that 31 front/32 rear gives a more neutral ride, and 30 front/33 rear starts to give it a hint of oversteer. This is where I run my car.

Pressure will vary from tire manufacturer to tire manufacturer as far as what works. I have not noticed any uneven wear on my Potenza SO2's and I have about 25k miles on them.

J.B.
WRXtra
 

·
Registered
Joined
·
9 Posts
jbhebert said:
It is the nature of AWD cars to understeer. The front tire only has x amount of traction. On a RWD car, 100% of x goes to steering. However, on an AWD car some percentage of x goes to moving the car as well. The remaining percentage is available for steering.

J.B.
www.wrxtra.com
It's about a understeer not a power understeer. And even on power in turns AWD cars are rather prone to oversteer cause because of lift front looses trackion and diff is sending power to rears.
Why EVO does not have this problem?
 

·
Registered
Joined
·
281 Posts
I'm not quite sure I understand the question. As you mentioned, the front end of an AWD car will start to loose traction when accelerating into a corner. However, this results in understeer, not oversteer. It comes from a combination of having the weight shift towards the back of the vehicle (due to acceleration), the weight shifting to the outside of the corner, and the fact that the front wheels are driven. Most any AWD car will understeer if driven like a RWD car when accelerating through a corner. I personally have not driven an EVO, but every test I've read indicates that it does, as well. There are ways to counter this, as mentioned in posts above. Additionally, an AWD car can be "tricked" into oversteer by turning the car opposite the direction of the turn quickly prior to entering the corner. This causes the weight to shift to the outside of the corner.

J.B.
WRXtra
 

·
Registered
Joined
·
9 Posts
The question was simple, why in reviews usually STi is showing too much understeer compared to EVO?
EVO is AWD.
As to weight transfer you're right. Lift at the front causes understeer. But doesn't RWD under power do the same?
And the last note, I heard all cars sold must show understeer. The car which would oversteer would not get a homologation.
 

·
Registered
Joined
·
886 Posts
I think the reason the Evo doesn't have as much understeer as the STi is because the evo has an active yaw control on it and the sti doesn't.
 

·
Registered
Joined
·
281 Posts
The reviews I've read state that the EVO drives much harsher than the STi. And difference is likely to be in the way the suspention is tuned. The EVO probably has a much stiffer rear swaybar that will significantly reduce understeer. The STi has been set up a little softer to be more comfortable during normal driving. Again, this is something that can be remedied.

On a RWD car, you are still getting weight transfer. However, since the front tires are only steering and not being driven, the do maintain more lateral traction. Additionally, the rear wheels are pushing the car, and if the car is in a turn, they will try o push past the car if given a chance. In an AWD or FWD car the front wheels are pulling, which makes it harder for the back end to come around.

As for cars being required to understeer, I have not heard anything about that. If you watch the WRC or SCCA rally coverage, you'll see that the drivers can get pretty much any car to oversteer if they really want to.

J.B.
 

·
Registered
Joined
·
33 Posts
Cheapest answer: bigger rear swaybar.
does anyone know what size rear swaybar is stock on the current STi? My guess would be 22mm
 

·
Registered
Joined
·
281 Posts
While I'm not sure what size the STi uses, I will also note that if the STi uses the same plastic sway bar links that the WRX uses, you'll want to replace those first or at the same time you upgrade your swaybar. The plastic links will still flex with a thicker swaybar, limitting the effectiveness of the upgrade.

J.B.
WRXtra
 
1 - 15 of 15 Posts
Top