Wider back wheels AWD???

Slug71 · 11-02-2007, 03:28 PM

Can the rear wheels on a AWD car be wider than the fronts? I heard its bad for a AWD car but i thought it was just bad to have different size tires as in diameter??

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Crawdads · 11-02-2007, 03:53 PM

Its bad for the diffs to have tires different size diameter....good luck trying to find tires that are different widths and the exact same diameter.

It doesnt make any sense to put wider tires in the back anyway...some Auto-x guys in Evos and STis put wider wheels up front (with the same TIRE front and rear)...some people also experiment with staggered setups for competition use only...not for long term street use.

Slug71 · 11-02-2007, 04:27 PM

So as long as its only the width that differs it should be ok? I was thinking going 225 Rear and 205/215 Front. Not a big difference.

moss · 11-02-2007, 04:32 PM

So, can someone explain to me how Porsches can run staggard?

flukewrx · 11-02-2007, 04:53 PM

Most Modern Porshe's run a Mid Engine RWD or Rear Engine RWD layout.

LionZoo13 · 11-02-2007, 05:01 PM

Quote:

Originally Posted by flukewrx

Most Modern Porshe's run a Mid Engine RWD or Rear Engine RWD layout.

But the Carrera 4s are staggered too and to boot they aren't the same outer diameter. The fronts are 235/35-19 and the rears 305/30-19.

SueBaroo · 11-02-2007, 05:03 PM

^ True that

moss · 11-02-2007, 05:03 PM

Quote:

Originally Posted by flukewrx

Most Modern Porshe's run a Mid Engine RWD or Rear Engine RWD layout.

Mhh hmm... so the 993/996/997 911s are RWD? and the Carerra 4s as stated above.

I think I could like a handful of modern AWD porsches running staggered.

grippy monkey · 11-02-2007, 05:15 PM

all 4wd porsches are staggered

LastResort · 11-02-2007, 05:24 PM

Just because porsche does it on a toally different platform doesn't mean you can do it on a subaru. And you need to calculate the outside diamater of the wheel/tire combinations before just looking at the wheels and saying, hey that's good!

LastResort · 11-02-2007, 05:34 PM

That's almost 3% difference. and I can't remember of the allowable tolerance is 2% or 5%.

rougeben83 · 11-02-2007, 07:23 PM

Yes the AWD turbo porsches run staggered because they have that engine hanging over the rear axle. They need as much grip in the rear as possible to keep you from spinning into a tree.

Why would you want to run wider tires in the back? You're not doing your handing or performance any favors by doing so anyway. If one thing, having wider tires in the front to help keep the front end gripping would at least have some sort of logic behind it.

flukewrx · 11-02-2007, 08:09 PM

Quote:

Originally Posted by moss

Mhh hmm... so the 993/996/997 911s are RWD? and the Carerra 4s as stated above.

I think I could like a handful of modern AWD porsches running staggered.

If you read what I said it says MOST Modern Porshes. I did not say ALL.

If you really want to know how they are able to do it, you probably will have to ask the Porsche Engineers. However, having the engine in the rear of the vehicle instead of in the front probably has something to do with why they are able to run a staggered fitment.

Just because it works on a Porsche does not mean it will be able to work on a Subaru, however, feel free to try for yourself.

austinpike · 11-02-2007, 08:39 PM

Quote:

Originally Posted by Slug71

So as long as its only the width that differs it should be ok? I was thinking going 225 Rear and 205/215 Front. Not a big difference.

A 225/40 is not the same height as a 205/40 or 215/40. They need to be the same within .25" in circumference. The only combos I can think of off the top of my head are 255/40/17 with 225/45/17 or 275/40/17 with 245/45/17.

Go here and play around for yourself:
http://www.miata.net/garage/tirecalc.html

Slug71 · 11-02-2007, 09:13 PM

Quote:

Originally Posted by rougeben83

Yes the AWD turbo porsches run staggered because they have that engine hanging over the rear axle. They need as much grip in the rear as possible to keep you from spinning into a tree.

Why would you want to run wider tires in the back? You're not doing your handing or performance any favors by doing so anyway. If one thing, having wider tires in the front to help keep the front end gripping would at least have some sort of logic behind it.

Yes there is no logic behind why i want to do it, But it looks good

Thats the only reason.

Slug71 · 11-02-2007, 09:17 PM

Looks like 225/40/17 and 205/45/17 might work though!!

Uncle Scotty · 11-02-2007, 11:25 PM

....d00000000000000000d.....

the GD chassis is a pig and understeers as it is...why do ya wanna make it WORSE???

this is a really dumb idea...been discussed here before....more than once

....and the answers will not change, this time

ya better off putting the bigger tires on the FRONT

Crawdads · 11-03-2007, 12:29 AM

Different width tires are almost NEVER going to be the same diameter/circumference...there are very few exceptions (like the 225/45-17 and 255/40-17 mentioned above)

Porsches can run staggered sizes because they are DESIGNED that way and the gearing is set up to accept it...if the Porsche owner put 4 of the same diameter tires on he would be in trouble.

The front 2 wheels and the back 2 wheels need to be traveling the same speed (most of the time)...by running different size tires you would have one set rotating faster than the other and the center diff would die a horrible death.

Its dumb when people do it on VWs, and its even dumber on a Subaru...and like Uncle mentioned above, you would be better off with bigger tires in the FRONT.

Slug71 · 11-03-2007, 12:47 AM

Yes but if you go to this do-da http://www.miata.net/garage/tirecalc.html 225/40/17R and 205/45/17F is such a little difference that it should be within tolerance. And ill be doing it on the GC Wagon chassis not GD.
I dont know maybe it is a bad idea, thats why im asking.

austinpike · 11-03-2007, 12:50 AM

Quote:

Originally Posted by Slug71

Looks like 225/40/17 and 205/45/17 might work though!!

No. the circumference is 75.7" vs 76.2". That's 1/2" difference. Too much. But hey, it's your car...

Slug71 · 11-03-2007, 12:52 AM

Looks like ill be bagging that idea then.

Patrick Olsen · 11-03-2007, 10:29 AM

Quote:

Originally Posted by austinpike

No. the circumference is 75.7" vs 76.2". That's 1/2" difference. Too much. But hey, it's your car...

That's just a nominal difference. You'd have to go check the specs for individual brands/models of tires to figure out what the actual difference is.

And I thought the accepted difference was 1/4" diameter, not circumference. Unfortunately, I can't find my Owner's Manual (or any of the other stuff in my glove box - what did I do with all that at my last track event...

) to confirm that.

Pat Olsen

austinpike · 11-03-2007, 11:34 AM

Quote:

Originally Posted by Patrick Olsen

That's just a nominal difference. You'd have to go check the specs for individual brands/models of tires to figure out what the actual difference is...

Yes that assumes mathematically "perfect" tires. I would rather start with a calculated difference of nearly zero, assuming they would still be within 1/4" tolerance in the real world. That may not hold true comparing one brand/model to another, but within one model I would expect it to be a pretty good indicator. (assuming the OP is at least planning on running the same kind of tire on all 4 corners.)

Quote:

Originally Posted by some Subaru tech document

All of the tires on your AWD Subaru must be within 1/4 of an inch of rolling circumference.

http://www.subaru.com/common/faq/tech_info.jsp#4

IronMonkeyL255 · 11-03-2007, 11:34 AM

Tirerack says 1/4" circumference, or 2/32 tread depth.

BHawk · 11-03-2007, 11:44 AM

Our AWD system is different. the Porsche has a more rear biased system. Also their suspension geometry is different. Not to mention the engine is in the back. Long story short if you put wider wheels and / or tires on the back your car will suck to drive compared to what it does now. Like a few have said so far wider up front would likely be a better choice.

11-02-2007, 03:28 PM	#1
Slug71 Scooby Newbie Member#: 159963 Join Date: Sep 2007 Chapter/Region: NESIC Location: Albany, N.H - U.S.A Vehicle: 2003 Subaru Baja Black & Silver	Wider back wheels AWD??? Can the rear wheels on a AWD car be wider than the fronts? I heard its bad for a AWD car but i thought it was just bad to have different size tires as in diameter?? * Registered users of the site do not see these ads.

11-02-2007, 05:34 PM	#11
LastResort Scooby Guru Member#: 99289 Join Date: Oct 2005	That's almost 3% difference. and I can't remember of the allowable tolerance is 2% or 5%. Last edited by LastResort; 11-02-2007 at 07:23 PM.

11-03-2007, 12:47 AM	#19
Slug71 Scooby Newbie Member#: 159963 Join Date: Sep 2007 Chapter/Region: NESIC Location: Albany, N.H - U.S.A Vehicle: 2003 Subaru Baja Black & Silver	Yes but if you go to this do-da http://www.miata.net/garage/tirecalc.html 225/40/17R and 205/45/17F is such a little difference that it should be within tolerance. And ill be doing it on the GC Wagon chassis not GD. I dont know maybe it is a bad idea, thats why im asking. Last edited by Slug71; 11-03-2007 at 12:48 AM. Reason: Forgot something

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11-02-2007, 03:53 PM	#2
Crawdads Scooby Specialist Member#: 30907 Join Date: Dec 2002 Chapter/Region: SWIC Location: Cat Keyboard Cat Vehicle: SWP GDB-G	Its bad for the diffs to have tires different size diameter....good luck trying to find tires that are different widths and the exact same diameter. It doesnt make any sense to put wider tires in the back anyway...some Auto-x guys in Evos and STis put wider wheels up front (with the same TIRE front and rear)...some people also experiment with staggered setups for competition use only...not for long term street use.

11-02-2007, 04:27 PM	#3
Slug71 Scooby Newbie Member#: 159963 Join Date: Sep 2007 Chapter/Region: NESIC Location: Albany, N.H - U.S.A Vehicle: 2003 Subaru Baja Black & Silver	So as long as its only the width that differs it should be ok? I was thinking going 225 Rear and 205/215 Front. Not a big difference.

11-02-2007, 04:32 PM	#4
moss Scooby Guru Member#: 10197 Join Date: Sep 2001 Chapter/Region: MAIC Location: Gtown, MD	So, can someone explain to me how Porsches can run staggard?

11-02-2007, 04:53 PM	#5
flukewrx Scooby Specialist Member#: 75081 Join Date: Nov 2004 Chapter/Region: BAIC Vehicle: 2003 WRX WRB	Most Modern Porshe's run a Mid Engine RWD or Rear Engine RWD layout.

11-02-2007, 05:03 PM	#7
SueBaroo Scooby Specialist Member#: 140838 Join Date: Feb 2007 Chapter/Region: SCIC Location: Banning, CA Vehicle: 2007 Forester 2.5X Had: 03 WRX/06 STi/08 Leg	^ True that

11-02-2007, 05:15 PM	#9
grippy monkey Scooby Guru Member#: 131067 Join Date: Nov 2006 Chapter/Region: SCIC Location: Inglewood! Vehicle: your "stance" sucks	all 4wd porsches are staggered

11-02-2007, 05:24 PM	#10
LastResort Scooby Guru Member#: 99289 Join Date: Oct 2005	Just because porsche does it on a toally different platform doesn't mean you can do it on a subaru. And you need to calculate the outside diamater of the wheel/tire combinations before just looking at the wheels and saying, hey that's good!

11-02-2007, 07:23 PM	#12
rougeben83 Scooby Guru Member#: 115154 Join Date: May 2006 Chapter/Region: MWSOC Location: NYC Vehicle: 2003 Legacy L Turbo silver	Yes the AWD turbo porsches run staggered because they have that engine hanging over the rear axle. They need as much grip in the rear as possible to keep you from spinning into a tree. Why would you want to run wider tires in the back? You're not doing your handing or performance any favors by doing so anyway. If one thing, having wider tires in the front to help keep the front end gripping would at least have some sort of logic behind it.

11-02-2007, 09:17 PM	#16
Slug71 Scooby Newbie Member#: 159963 Join Date: Sep 2007 Chapter/Region: NESIC Location: Albany, N.H - U.S.A Vehicle: 2003 Subaru Baja Black & Silver	Looks like 225/40/17 and 205/45/17 might work though!!

11-02-2007, 11:25 PM	#17
Uncle Scotty Scooby Guru Member#: 16200 Join Date: Mar 2002 Vehicle: OK Houston we have an Uncle	....d00000000000000000d..... the GD chassis is a pig and understeers as it is...why do ya wanna make it WORSE??? this is a really dumb idea...been discussed here before....more than once ....and the answers will not change, this time ya better off putting the bigger tires on the FRONT

11-03-2007, 12:29 AM	#18
Crawdads Scooby Specialist Member#: 30907 Join Date: Dec 2002 Chapter/Region: SWIC Location: Cat Keyboard Cat Vehicle: SWP GDB-G	Different width tires are almost NEVER going to be the same diameter/circumference...there are very few exceptions (like the 225/45-17 and 255/40-17 mentioned above) Porsches can run staggered sizes because they are DESIGNED that way and the gearing is set up to accept it...if the Porsche owner put 4 of the same diameter tires on he would be in trouble. The front 2 wheels and the back 2 wheels need to be traveling the same speed (most of the time)...by running different size tires you would have one set rotating faster than the other and the center diff would die a horrible death. Its dumb when people do it on VWs, and its even dumber on a Subaru...and like Uncle mentioned above, you would be better off with bigger tires in the FRONT.

11-03-2007, 12:52 AM	#21
Slug71 Scooby Newbie Member#: 159963 Join Date: Sep 2007 Chapter/Region: NESIC Location: Albany, N.H - U.S.A Vehicle: 2003 Subaru Baja Black & Silver	Looks like ill be bagging that idea then.

11-03-2007, 11:34 AM	#24
IronMonkeyL255 Scooby Specialist Member#: 38120 Join Date: Jun 2003 Chapter/Region: South East Location: Greenville, SC Vehicle: 1991 Rio Red Legacy Turbo	Tirerack says 1/4" circumference, or 2/32 tread depth.

11-03-2007, 11:44 AM	#25
BHawk Scooby Specialist Member#: 61860 Join Date: May 2004 Chapter/Region: MWSOC Location: Mid-Mo Vehicle: 2004 WRX STi Aspen White	Our AWD system is different. the Porsche has a more rear biased system. Also their suspension geometry is different. Not to mention the engine is in the back. Long story short if you put wider wheels and / or tires on the back your car will suck to drive compared to what it does now. Like a few have said so far wider up front would likely be a better choice.