Anyone (non-GT2) run 305/30-19 rears w/o Rubbing? It seems like this setup has worked for some and not others... If you got it to work, can you please list:

Wheel size and offset
Spacer sizing, if any
Ride height change from OEM
Tire brand and model

I think this could be helpful for a few of us

Thanks!

 

ABSOLUTELY !!
315 25 19 is a HORRIBLE tire chocie for our cars. there is simply not enough sidewall.

my 996tt has 19x12 wheels with 305 30 19 bridgestones (they run VERY wide adn the sidewall is SUPER thick).

my car sits lower than a Stock Gt2.

absolutely 0 rubbing issues.

in fact, i ran OEM lobster forks (997c4s wheels) on my car at one time and there was no rubbing at all.

your offset question is hard to answer because there are a few variables at play... (is it a concave wheel, step lip, rolled lip, deep dish, etc etc.)... but thats something i would not worry about. the reason being, so long as tehyre made for our cars, you'll be fine.

 

allow me to give you my credentials.
since joining the forum and having my 996tt, i have probably gone through a dozen various sets of tires.

305 30 19 is the way to go. the car feels much more planted, predictable, and gives you the PROPER type of understeer that our cars need.

315 25 19 does not communicate (at the limits of adhesion) like a 305 30 19 does.

 

How much camber are you running? How much offset? Also, what are you running in front with same questions?

I have heard the opposite with people running into rubbing problems with that same size. Camber and offset would obviously affect the result greatly.

 

Nikolas
my offset is VERY aggresive.
as far as camber, i am running around 2 degrees of neg camber in the rear, and around 1.6 up front.
rear shocks have always been set to be a little softer than stock (it helps with my driving style).

 

I would *definitely* prefer 305/30 for the reasons you have mentioned. The reason that I asked the question is that others on the forum have definitely reported rubbing on the fender liner with 305/30-19. (Some even rubbed through the boost hose between turbo and IC inlet)

I have 19x11.5 rears with 7mm spacers to get the outside edge of the tire almost flush and 315/25-19 ContiSportContacts and a 1" drop. If I feel my finger around the rear edge of the tire, there is only room for 1 finger laid flat between the tire and fender liner at the narrowest point by the aforementioned boost hose. Based on listed tire specs, the 305/30-19's are 0.5-0.8" taller than the 315/25 (and only 0.4" narrower...)

 

If your running AWD on a 996 this thread might be a good read of why 305/30/19 is bad...

https://www.6speedonline.com/forums/...ire-se-up.html

 

235/305 is 2.8% within the same rolling diameter. (this is what the 997tt has stock)
245/305 is 1.7% within the rolling diameter.
the concensus is that as long as the rolling diameter is within 3% front to back, you are safe.

 

also,
i am willing to bet that a SURPRISING amount of 996tt owners are driving around with a faulty front diff anyway

 

Ok... Just trying to help....

You do know the 997 AWD differential is a different ratio than the 996. You should not use 997 tire ratios on a 996. The 997 has an electromagnetically controlled AWD system and the 996tt has a viscous fluid drive AWD. It seems the 996 AWD system wont tolerate tires that are out of spec for too long...

Anywho, good luck with whatever you choose... 305's sure do feel better.

 

I am assuming that 305/30-19s are paired with 225/40-19s...
(792 vs 798 revs per mile for Potenzas for instance)

 

if you guys are worried that much, then your only real option is to stick with TWO specific 315.25.19 brand, Michelin and Continental, they have the thickest sidewall out of any 315s out there.


search my old posts, i have probably made a dozen of these threads.

 

This all started b/c 315/25-19 tires are no longer being made... A few sites still list them, but they don't exist if you call... "backordered" etc

 

then you really have no choice but to go 305 30 19.
get a pirelli or something japanese, they run smaller compared to a michelin,bridgestone, continental


i personally do not think that you will have any problems.
did you guys know that once you reach a certain threshold, (i believe its around 550lb of torque, which alot of us have), the front diff is useless, as the clutches slip anyway..

 

Easiest solution for everyone is to go RWD
That's my plan once my 315s go.