Fitting 9.5" wheels in back.. is my math correct?

[eikond]

I've been mulling over the idea of fitting some wide wheels on the back of the BRZ.

I have 2 18 x 8.5 +30 offset fronts and 2 18 x 9.5 +22 rear wheels. I think they would be a great combination. I'd probably keep the stock wheels and put some r-comps on them for autocross and other track use to keep the stock handling and suspension setup. But for daily driving or car show events, a nice set of "RWD" wheels would really make the car look amazing.


So, I've used a wheel offset calculator to see what I could figure out.
Converting from the stock 17x7 +48mm wheel to a 18x9.5 +22 wheel changes the the inner clearance by 6mm less and the outer clearance by 58mm more.
Converting the front wheels from the same 7" +48 to a 8.5" +30 gives 1mm less inner clearance and 37mm more outer clearance.

Now.. that would be assuming I could fit the wheels direct to the hub.. . But, I cannot. I will need 5x100 to 5x114.3 adapters. That will add another 19mm (thinnest I could find).

So when you add the 19mm to the equation you get +13mm inner in the rear and + 18mm inner in the front.. clearly this is not a problem!

However, the outer clearance does move out quite a bit.
The 37mm front changes to 56mm and the 58mm in the rear changes to 77mm.

Now.. those sound like really big numbers to me, but I don't use mm often, so when converted inches it doesn't sound so bad.
56mm is 2.2 inches.
77mm is 3.0 inches.


So.. if I were to move the wheels out 2.2" in front and 3.0" in the back would they rub on the fenders when the suspension compresses? This is assuming I fit tires that have similar "squareness" to them. I wonder if I were to slightly stretch the tires if that would help a bunch.
I hate the super-flush rubber band tire craze that is going around.. so I'm not about to adjust for massive negative camber and super stretch tires, etc.. just some slight stretch maybe..

[pithy_logorrhea]

If my limited understanding of rwd is correct, you will get understeer with a staggered set up. I'm not sure if you need to worry so much about fender rubbing as I hear the fenders are pre-rolled. I'm waiting for Bill (Scooby South) to put some 17x9 - 245s on to see how they work out. :P

[eikond]

Yes, you are right.. it would understeer with wider rear wheels and bigger tire contact patches. Plus it would be a little heavier than stock and that's not great either. However, I wouldn't be using these wheels for track purposes. I would keep the stockers and put some better tires on them for that use.


I just don't like the narrow little fwd offset stock wheels.. They don't do much for the appearance of the car. To save money, I'd like to use the wheels that I already own that are sitting in my basement. I think they would look really good on the car and they are free to me since I already own them.

I suppose if it was close, I could roll the fenders a little more (pull them really). Or instead of using the 19mm adapters I could look into re-drilling the hubs.




Look at how sunken these wheels are: I have to believe that having wider rear wheels (extending by 3" total) would fit just fine. I think the human thumb is roughly 3" long on average?? So for a frame of reference, imaging someone's thumb length adding to the position of the rear wheels. Then remember than suspension doens't move directly vertical when it compresses.. it swings up and in. I have to think it would clear.

[old greg]

Your math is right, but your eyeballing skills are questionable. The wheels are a bit sunken, but I'd say there's more like 1.5" of space, max. Your wheels just don't have enough offset and the spacer/adapters are only making things worse. Sell your wheels and use the money to buy a set that fits.

[dori.]

I disagree, you should make em fit. I can't speak for anyone else but I want to know what the limits are when it comes to fitting wheels with no suspension modifications.

[civicdrivr]

Id love to see how aggressive we can go without poking or stretched tires.

[RearDrive]

I'm going for 18x8.5+30 work emotions all around. The greddy guys fit 9.5" in the back (don't know the offset though) so it would probably be a tight fit or you may need the red fenders rolled a bit more but who knows until you try!

[Scooby South]

Originally Posted by pithy_logorrhea

If my limited understanding of rwd is correct, you will get understeer with a staggered set up. I'm not sure if you need to worry so much about fender rubbing as I hear the fenders are pre-rolled. I'm waiting for Bill (Scooby South) to put some 17x9 - 245s on to see how they work out. :P

thanks....Man.....looking forward to it myself..

Stock Rims are 17x7 with a 48.....Everything I have read and studied...says that 8's need to be 48..9's need to be 38-45 or so..so with a 30 offset you might run into some Poke..I will be test fitting my 17x9 42 with a 245/40/17 tire next week when my car gets here.....I would suggest waiting til I get some decent pics of clearance ..I only have 1 tire mounted for now..to ensure they are going to work...

Bill

[ZDan]

Fricking absurd. Under/oversteer from modest stagger is the *least* of your worries.
+30 offset 8.5 fronts, +22 offset 9.5 rears won't fit. Unless you do body modification. And then you still will have changed suspension leverage ratios adversely, and added a TON of scrub radius.
This is an 8 1/2" +45 fitment with 235/40-17 tires:


That fits. Another 1.5" pokey-outie? Not so much...

[civicdrivr]

Originally Posted by ZDan

Fricking absurd. Under/oversteer from modest stagger is the *least* of your worries.
+30 offset 8.5 fronts, +22 offset 9.5 rears won't fit. Unless you do body modification. And then you still will have changed suspension leverage ratios adversely, and added a TON of scrub radius.
This is an 8 1/2" +45 fitment with 235/40-17 tires:

http://i625.photobucket.com/albums/t...y/8b102fdd.jpg

That fits. Another 1.5" pokey-outie? Not so much...

Do you have a pic of the rear of the car? Im trying to run 17x8 +35s, hoping theyll fit without poking or a tire stretch

[Fly Guy]

I have some examples. The plain red car has 8" wide wheels with +45 offset.
http://www.ft86club.com/forums/showthread.php?t=5749
The Yokohama/Enkei/TRD car looks to have the 8" +35. The wheels look like they poke out farther, at least in the back. I hope we can get official confirmation on that.
http://www.ft86club.com/forums/showthread.php?t=3593
And the white one looks to have 8" wide +45 offset in front with 9" wide +45 offset in back.

[LSxJunkie]

Originally Posted by Fly Guy

I have some examples. The plain red car has 8" wide wheels with +45 offset.
http://www.ft86club.com/forums/showthread.php?t=5749
The Yokohama/Enkei/TRD car looks to have the 8" +35. The wheels look like they poke out farther, at least in the back. I hope we can get official confirmation on that.
http://www.ft86club.com/forums/showthread.php?t=3593
And the white one looks to have 8" wide +45 offset in front with 9" wide +45 offset in back.

Level that car and I'm sold. That'd be a perfect daily driver.

[Dadhawk]

Originally Posted by LSxJunkie

Level that car and I'm sold. That'd be a perfect daily driver.

I just don't get the black wheels thing, sorry. I think its because of my age. To me, when I see black wheels from any distance other than up close I think "Hey, dude you lost your hubcaps". Too many years of driving $300 cars with factory steel black rims on them I guess.

[LSxJunkie]

Originally Posted by Dadhawk

I just don't get the black wheels thing, sorry. I think its because of my age. To me, when I see black wheels from any distance other than up close I think "Hey, dude you lost your hubcaps". Too many years of driving $300 cars with factory steel black rims on them I guess.

I hear this argument a lot, mostly from folks about 20 years older than I am. (Not an ageist, just what I've noticed.) I grew up when few cars had hubcaps and the cars that did tended to keep them. I'm also used to being able to look at a black wheel and see spoke shape and layout. But hey, diff'rent strokes. You're allowed to like or dislike whatever you want. Silver wheels, grey wheels, and gold wheels look good to me too.