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Old 08-20-2019, 02:29 AM   #1
Ej20ForesterGuy
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Subaru Stars Rear wheel spacer effect on handling

I wanted to post this here because it's a question more related to suspension and handling than the wheels themselves.

I have a JDM 2002 Forester XT, and I'm wondering what effect installing 10mm spacers in the rear wheels will have on handling. I'm only wanting to do the rears because the front wheels are flush with the fender, while the rears sit inside the wheel well by about 10-15mm and makes it look like a housewife car.

Track width would become 1,735mm front and 1,755mm rear.
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Old 08-20-2019, 12:11 PM   #2
jamal
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A wider track means less weight transfer to the outside tire in a corner, giving it more grip. So the result of rear spacers would be slightly more understeer.
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Old 08-20-2019, 10:39 PM   #3
Ej20ForesterGuy
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I already get a bit of understeer on hard exits. Would it be advisable to do 15mm in the front and 10mm in the rear?
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Old 09-13-2019, 12:23 AM   #4
Ej20ForesterGuy
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Anyone? I read a rear strut tower bar will help reduce roll, but I would like a bit wider stance in the rear so it's flush with the fenders. Rallyarmor mud flaps will follow, so it will offset the extra width in the front, but I'm just trying to fix the understeer. VDC does induce overseer when I hit the throttle, but it's limited by the physical setting of the car and cuts throttle when I know the car could handle more with the right setting
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Old 09-13-2019, 03:36 PM   #5
jamal
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No, a strut tower bar will not reduce roll. Or have much effect on anything at all.

A swaybar, yes. Larger swaybar means less roll. A larger rear swaybar means the rear end does more to resist roll, which on these cars means the front and rear outside tires get more evenly loaded in a corner, which means more grip and better balance. I don't know off the top of my head but your front bar is likely 20mm, rear bar is probably 13 or 17. Going to a 20-22mm rear would be a good improvement.

Spacers, or lower offset wheels to be more "flush" are not ideal from a suspension geometry standpoint especially up front. Stock, when you steer the wheels, they pivot essentially at the center of the tread. A wheel spacer changes this (scrub radius), moving the pivot point of the tire farther inside. The result is that things like bumps, patches of snow and slush, etc, have more of an influence on the steering and will cause a stronger pull to that side.

And an 02 forester has vdc?
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Old 09-19-2019, 12:18 PM   #6
Norm Peterson
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Quote:
Originally Posted by Ej20ForesterGuy View Post
I'm only wanting to do the rears because the front wheels are flush with the fender, while the rears sit inside the wheel well by about 10-15mm
Quote:
Originally Posted by Ej20ForesterGuy View Post
Would it be advisable to do 15mm in the front and 10mm in the rear?
If the rear bothers you by being 10-15 mm inside the sheetmetal now, I suspect that pushing the fronts 15 mm outside the sheetmetal isn't something you're going to appreciate later.

I doubt that the handling changes from playing around with 10 or 15 mm spacers would be enough for most people who aren't factory test drivers or race car drivers to notice. Truth be told, I can't make 10 or 15 mm away from flush even being an appearance problem worth doing anything about.


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