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Old 07-21-2004, 11:05 AM   #1
CtGT
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Default 17x9 Front/17x8.5 Rear?

Has anyone seen the new Super Street with the Cusco WRX? It is running 17x9 Racing Hart CP035's in the front and 17x8.5 Racing Hart CP035's in the rear. I forgot the exact tire size but the fronts are a little wider than the rears.

Can you do this on a WRX with no problems down the road? How would this affect handling, etc.?
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Old 07-21-2004, 11:20 AM   #2
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Unless the tires are very close to the same height front-to-back (I think Subaru says within 0.25" ), I would guess this would be ill-advised for a street WRX. You don't want to have a significant difference in speed between the front wheels and rear wheels as you'll cook your center differential.

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Old 07-21-2004, 11:26 AM   #3
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True. I didn't even think of that. I will have to check the tire sizes again.
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Old 07-21-2004, 11:51 AM   #4
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Doesn't make very much sense.
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Old 07-21-2004, 12:00 PM   #5
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Quote:
Originally Posted by subieworx
Doesn't make very much sense.
It makes sense to me... if you notice, in the same article, the Civic has the same thing.

The reason that this is done is to cut down on any understeer or maybe to get even tire wear...

I ran a 555R in the front of my Celica with stock rears for a long time... the reason I did it was to completely eliminate understeer. It worked wonderfully.

People that race FWD cars do it too..
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Old 07-21-2004, 12:28 PM   #6
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Yeah but on an AWD car it doesn't make sense to me. I would think that upgrading your suspension would be a better route to cut down on understeer. On an AWD I would think you would want the same size tire wheel combo front/rear.
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Old 07-21-2004, 12:32 PM   #7
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AWD + stagger = no no.

That's weird that they would run a WRX with a slight stagger.
Perhaps they mounted a wider tire on the smaller width rim ? (to eliminate stagger and equalize the tread path on all wheels) ?

Anybody know the real reason?
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Old 07-21-2004, 12:37 PM   #8
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AWD is not true 50/50 split.. WRX is still FWD biased therefore having a larger contact patch on the front will allow better use of the available torque, and I'd imagine less understeer.
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Old 07-21-2004, 12:44 PM   #9
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Most AWD subbies aren't 50/50 but isn't the WRX 50/50 split? I know the STi the driver can adjust the center diff ratio.
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Old 07-21-2004, 01:07 PM   #10
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The WRX is suppose to be a 50/50 split, but it deffinetly displays more FWD characteristics than RWD.
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Old 07-21-2004, 01:09 PM   #11
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For sure....I totally agree
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Old 07-21-2004, 01:21 PM   #12
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Quote:
Originally Posted by SLKWrx
AWD is not true 50/50 split.. WRX is still FWD biased therefore having a larger contact patch on the front will allow better use of the available torque, and I'd imagine less understeer.
any adverse affect on the diff?
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Old 07-21-2004, 02:08 PM   #13
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Quote:
Originally Posted by sotti
The WRX is suppose to be a 50/50 split, but it deffinetly displays more FWD characteristics than RWD.
It displays these tendancies due to the extra weight of the AWD being located more over the front wheels than the back. If this car had an even weight distrobution we would have understeeer problems. Running a stagered tires setup though is not the way to get rid of understeer on this car. Buy a frickin sway bar and be done with it. If you get understeer at that point you don't know how to drive correctly. I have coilovers, rear sway and endlinks and rims and tires and I never have understeer except when in the rain.
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Old 07-21-2004, 02:09 PM   #14
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Quote:
Originally Posted by mrazntre
any adverse affect on the diff?
It all comes down diamter of the tires. If the fronts have a greater diamter by more than 1/4" the diff will not be happy as the gears will not mesh properly between the back wheels and front. With this setup the front axles will be moving fast than the rears which will cause problems.
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Old 07-21-2004, 02:27 PM   #15
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Eh it has nothing to do with any kind of gears it has to do with overheating the viscous lsd unit in the center differential. Anyways, there are guys that run wider wheels/tire in the front than on the rear because you have more weight up front and of course urning the wheels is decreasing the grip you have as well. There are some autocross EVOs that run 275/285 tires in the front and 245s in the rear. Larry Fine autocrosses an STI and runs 275 tires in the front and 245 in the rear as well. As long as the diameter of the tire is close, you are going to be fine.

A WRX has a 50/50 split, it's not biased to one side or the other unless there is wheelspin.

STI is rear-biased 65R/35F or somewhere around there, but the reason they run wider in the front is front end grip, which may cause more oversteer and may cause more understeer depending on how the car is setup.
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Old 07-21-2004, 02:45 PM   #16
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I ran 245/45-16 and 225/50-16 on my '99 2.5RS for G-stock autocross.

Thinking of a 275/245 setup for my STi for concrete events. Just trying to find some wheels that don't break the bank.

Chris H.
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Old 07-21-2004, 05:13 PM   #17
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Quote:
Originally Posted by dwx
As long as the diameter of the tire is close, you are going to be fine.
How close is close enough?
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Old 07-21-2004, 06:14 PM   #18
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As long as the profile of the tire is the same the different widths of the tire wont have any effect on anything. when you look at a tire say its 225/40/r16 the 225 means its 225mm wide while the profile of the tire is 40 mm high. The widths will not effect anything its all a matter of contact with the concrete. When i had my old camaro i had 285/40/r16 on the rear, and only had 235 on the front.
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Old 07-21-2004, 07:39 PM   #19
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I've been running that wheel size setup for over a year now. 17x9/8.5. Selling it soon though. Tires are 255/40-17.

Kevin
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Old 07-21-2004, 09:26 PM   #20
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How will a 8 inch wide wheel and a 7.5 inch wheel have any if any change in stagger?It will change section width but very little there also.I have seen many JDM cars with wider fronts and somr road race cars that are AWD and FWD.The thought is for less under steer and more turn in.Its like the reverse of RWD with wider rears to make up for over steer. Brad
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Old 07-22-2004, 10:42 AM   #21
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Quote:
Originally Posted by manimal15611
As long as the profile of the tire is the same the different widths of the tire wont have any effect on anything. when you look at a tire say its 225/40/r16 the 225 means its 225mm wide while the profile of the tire is 40 mm high. The widths will not effect anything its all a matter of contact with the concrete. When i had my old camaro i had 285/40/r16 on the rear, and only had 235 on the front.
I think you don't quite understand how tire sizing works. When looking at a tire size, the middle number is called the "Aspect Ratio." It defines the height of the sidewall as a percentage of the width. It is not a constant when varying the width when trying to maintain the same overall tire height. It works like this:

A 225/40 tire has 225*0.4=90 mm of sidewall (multiply by 2 to get the total sidewall)
A 285/40 tire has 285*0.4=114 mm of sidewall (x2 to get total sidewall height)

For a 285/40/16 to have the same side sidewall height as a 235 width tire, the 235 needs an aspect ratio of 50 (making it a 235/50/16). That gives a sidewall height of 4.5" for the 285 and a 4.6" sidewall height for the 235. I used this calculator to figure that. Read more here.

Neil.
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Old 07-22-2004, 10:59 AM   #22
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what he said^
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Old 07-22-2004, 11:09 AM   #23
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So I am looking at getting Volk CE28N's in a 17x8 with a 225/45. A guy I know had these and they rubbed a little in the rear. What if I got the 17x8 +44 in the front with 225/45 and 17x7.5 +50 in the rear with 225/45. Same tire size? Can anyone see a problem with doing this?

Back to my original post about the Cusco wrx. I checked the tire sizes. They are 17x9 with a 245/40 in the front and 17x8.5 with a 245/40 in the rear. Whay would they do this. Different wheel width, same tire size?
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Old 07-22-2004, 11:17 AM   #24
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Quote:
Originally Posted by WickedSTI
How will a 8 inch wide wheel and a 7.5 inch wheel have any if any change in stagger?It will change section width but very little there also.I have seen many JDM cars with wider fronts and somr road race cars that are AWD and FWD.The thought is for less under steer and more turn in.Its like the reverse of RWD with wider rears to make up for over steer. Brad
The change in stagger is a result of running different width (and thus different aspect ratio) tires front and rear, not the absolute wheel width. You're correct when you say the section width changes, but only when comparing the same tire on 2 different wheel widths.

If you run different tire sizes front to back, the total tire height will be different. Unless you're really careful with how you size the tires this can be very bad for your center differential. How careful you need to be depends on Subaru's built-in tolerance for the diff. Like I said above, I think a ~0.25" difference is the maximum allowable height difference, but I don't know for certain.

As an example, Subrew2 said he was running a 245/45-16 front and 225/50-16 rear. These 2 tires are within 6 revs/mile of each other, with a total sidewall height difference of ~0.2 inch (4.3*2=8.6" in front vs. 4.4*2=8.8 rear - from here) This should be within the diff's tolerance levels and therefore it shouldn't be damaging to it. However, if he had used a 235/50-16 in back (giving us 4.3*2=8.6" in front vs. 4.6*2=9.2") it probably would damage the diff. Note that these measurements are multiplied by 2 to get the difference in total height.

Neil.
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Old 07-22-2004, 11:23 AM   #25
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I understand that. What if I was to run same tire sizes front to rear on different width rims (8" & 7.5") for offset purposes. I want the +44 up front because there is plenty of clearance but I don't want the rear fender to rub the outside of the tire so I want to go with a +50 in the rear?
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