Biggest front tire size?

[Norm Peterson]

The LCA curves toward the rear mount and there may be more of a clearance issue with 20" wheels. Alot depends on the build of the car. '05-10 base V6's have no steering stops, '05-10 GT's have the thinner steering stop and '07-10 GT500's have the thicker steering stop.

I think it splits by OE wheel size rather than by GT/GT500.

The normal GT fitment was 17x8's that did need stops when up-fitting the car to any of Ford's 18" wheels. 18x8.5 wheels were optional on the GT in 2008 (at least), and they didn't need any stop replacement when fitting the GT500 wheels because the correct (thicker) stops had apparently already been fitted on the production line.

Maybe this note from the 2008 FRPP catalog will help.

NOTE:​

➀​

For vehicles with 16" wheels from the factory: -installing 17" x 8"
wheels, use steering stop 4R3Z-3932-BA -Installing 18" x 8.5" or
18" x 9.5" wheels, use steering stop 6R3Z-3932-CA

For vehicles with 17" wheels from the factory: -installing 18" x 8.5" or
18" x 9.5" wheels, use steering stop 6R3Z-3932-CA
​

Norm​

 

[06 T-RED S/C GT]

Norm and oldVor.. I finally got around to doing a test fit with one my Steeda Spyder wheels on the front passenger side.. Anyway just want to follow up and let you guys know that it cleared perfectly between the upper strut bolt stud along with the LCA front and back.. The Spyder also cleared the power steering rack and inner wheel well after turning from both left and right with room to spare..

I still have no clue as to whether the backspacing is 6.9 or 7.125 inches as the 18x9.5 SVT wheels are, but apparently they do fit and clear everything just fine even with a 20x9.5 inch wheel with 45mm offset and 275-35-20 Nitto NT555 G2 tires..



-Rocky

 

[Norm Peterson]

Good to hear

As a side note, I'm apt to overlook clearances to the endlink studs because it's been several years since my car was still running the OE endlinks.


Norm

 

[mavisky]

Do you happen to know what your backspace inches are by any chance.. Also what brand are your 20x10's ?

American Muscle AMR's. Car isn't in my possession right now so can't measure, but you're free to look it up on their website if they list it.

 

[06 T-RED S/C GT]

Good to hear

As a side note, I'm apt to overlook clearances to the endlink studs because it's been several years since my car was still running the OE endlinks.


Norm

Speaking of OE endlinks Norm.. I forgot to mention my car still has the OEM swaybars and also checked to make sure it cleared the endlink studs and it does clear with no problem.. So as I said before, I don't know if the backspace inches are 6.9 or 7.125 just as your SVT 18x9.5 wheels with 45mm offset are or not..
What I do know, is they do fit and clear everything just fine without having to use steering rack stops..


-Rocky

American Muscle AMR's. Car isn't in my possession right now so can't measure, but you're free to look it up on their website if they list it.

I just checked AM's website.. They list your offset just as you posted as +48mm and your backspace inches are listed as 7.4 inches (188mm)

Being as your backspace inches are 7.4.. I have no idea how in God's name they're able to clear, especially on a 20x10 wheel in the front with +48mm offset on 285-35-20" tires.. But in the end, all that matters is that they do..

 

[mavisky]

Minor correction but I'm on 285/30-20's. I think if they were +50mm they'd rub the strut, but there is plenty of room on the fender side. I'm planning on moving to a +40mm on a 20x10 with my next set or maybe even look at getting a 20x10.5" up front with a 285 stretched a bit up front. With the right offsets you can get away with some craziness on these cars.

May want to check this thread too as it's related.
http://www.s197forum.com/forum/showthread.php?t=95582

 

[mavisky]

BTW I don't understand how people are claiming that a wheel that is the same width and with the same offset would have different backspacing. The backspacing is literally the half the width of the wheel + the offset. They're all directly related.

 

[Norm Peterson]

The width of a wheel is measured inside the flanges at the tire bead seats. That's the more important number as far as properly fitting tire sizes to wheel widths, and has become the convention. As the inboard flange is given a different thickness and nothing else is changing, the backspacing will vary accordingly. I know I had a sketch somewhere, but I can't find it.

Found this and swiped the picture. Note that the width is inside the flanges and is not the overall width.

Norm

 

[Pentalab]

The overall width of my 10" rims is exactly 11". Overall width of my 9" rims is exactly 10". Initially, I had a defective 10" rim, so when rubber removed, we measured the max width..at 11". 275's removed from 9" rims...and installed on new 10" rims. So the 9" rims are sitting in boxes.... so dragged one out and measured its max width...at 10"

 

[mavisky]

I agree that the rim width listed vs rim width measured does differ, but the offset and is is based off of the overall centerline of the vehicle and the backspacing is essentially the measurement to centerline +/- the offset. At least this is how i always understood the measurements to be.

 

[Norm Peterson]

Keep in mind that the 'centerline' is at the center of the wheel's inside-to-inside "WIDTH" as shown in the picture I posted above. If the inboard and outboard flanges aren't the same thickness, the center of the overall outside to outside width will not be in the same place. This can and does happen.

It's best when referring to a wheel's overall width to be very clear that you're talking about overall width. Don't use "measured width" because that gets confused with the width of whatever wheels your tire sizes were measured on, which is a bead seat to bead seat (IOW, inside) measurement.

The only way to avoid confusion here is to be kind of picky about the way you describe what you're trying to say.


Norm

 

[06 T-RED S/C GT]

The overall width of my 10" rims is exactly 11". Overall width of my 9" rims is exactly 10". Initially, I had a defective 10" rim, so when rubber removed, we measured the max width..at 11". 275's removed from 9" rims...and installed on new 10" rims. So the 9" rims are sitting in boxes.... so dragged one out and measured its max width...at 10"

I was unaware and don't understand why the wheel manufactures list wheels at 8, 9,10 inches or whatever they are when they're actually 1" wider when measured.. Guess it makes sense to allow for differences in tire size ranges.. At any rate, I stand corrected..

Minor correction but I'm on 285/30-20's. I think if they were +50mm they'd rub the strut, but there is plenty of room on the fender side. I'm planning on moving to a +40mm on a 20x10 with my next set or maybe even look at getting a 20x10.5" up front with a 285 stretched a bit up front. With the right offsets you can get away with some craziness on these cars.

May want to check this thread too as it's related.
http://www.s197forum.com/forum/showthread.php?t=95582

So being that your on 285-30-20's, you have a slightly shorter sidewall from a 285-35-20.. With a +50mm offset, I think you'd be cutting too close to the strut despite having plenty of room on the fender side..

I would more than likely go with the +40mm on a 20x10 Niche Milan wheel like Gabe has on his 13 GT or just stay with your current setup as is..

 

[Norm Peterson]

I was unaware and don't understand why the wheel manufactures list wheels at 8, 9,10 inches or whatever they are when they're actually 1" wider when measured.. Guess it makes sense to allow for differences in tire size ranges.. At any rate, I stand corrected

Best guess I have is that the bead seat width is the more important measurement technically (from the tire sizing point of view at least, and likely for suspension design/engineering).

Overall width rarely matters, because normally there is at least a little tire peeking out a little further than the extreme width points of the wheel flanges anyway. Plus the fact that mfrs and most of the aftermarket tend to be conservative about their wheel widths (read: narrower than is physically possible).


Norm

 

[cbass]

Minor correction but I'm on 285/30-20's. I think if they were +50mm they'd rub the strut, but there is plenty of room on the fender side. I'm planning on moving to a +40mm on a 20x10 with my next set or maybe even look at getting a 20x10.5" up front with a 285 stretched a bit up front. With the right offsets you can get away with some craziness on these cars.

May want to check this thread too as it's related.
http://www.s197forum.com/forum/showthread.php?t=95582

I have 275/35's on a 19x10.5 +45 and have JUST enough sidewall to strut clearance to feel comfortable. If the wheels were a +40, I would have had to buy spacers.

 

[Norm Peterson]

+40 would give you more more strut side clearance. +50 is the one that'd have you chasing spacers and ARP studs if +45 is already really close.


Norm

 

[oldVOR]

My son's '05 V6 with '07 GT500 18x9.5 et45 wheels had heavy lock to lock LCA/wheel barrel lip interference. Installation of the thicker Ford steering stops removed the chance of interference and there is presently 20mm of clearance on both sides between the wheel barrel lip and LCA.

Base model 05-10 V6's didn't come with any steering stops factory installed.
Base model 05-10 GT's w/17" wheels had the thinner stops factory installed.
GT's and GT500's w/18" wheels had the thicker stops factory installed.

 

[Norm Peterson]

My son's '05 V6 with '07 GT500 18x9.5 et45 wheels had heavy lock to lock LCA/wheel barrel lip interference. Installation of the thicker Ford steering stops removed the chance of interference and there is presently 20mm of clearance on both sides between the wheel barrel lip and LCA.

Thanks, good to know it's that much. Wouldn't have guessed it'd make that much difference.


Norm

 

[cbass]

+40 would give you more more strut side clearance. +50 is the one that'd have you chasing spacers and ARP studs if +45 is already really close.


Norm

Holy shit I was tired. Yeah, sorry. I fucking do fitment shit at work all the time, I should have caught that.

 

[06 T-RED S/C GT]

Thanks, good to know it's that much. Wouldn't have guessed it'd make that much difference.


Norm

I test fitted one of my 20x9.5 Steeda wheels with 45mm offset on the front passenger's side and it cleared everything perfectly, including the sway bar end link stud.. The question is, will the driver's side clear on the front as I forgot about the strut, sway bar link, LCA and steering rack stud are different dimensions from the passenger side..

Guess I won't know for sure until doing another test fitment, but it's just too fucking hot in the garage to mess with it today lol.

Best guess I have is that the bead seat width is the more important measurement technically (from the tire sizing point of view at least, and likely for suspension design/engineering).

Overall width rarely matters, because normally there is at least a little tire peeking out a little further than the extreme width points of the wheel flanges anyway. Plus the fact that mfrs and most of the aftermarket tend to be conservative about their wheel widths (read: narrower than is physically possible).


Norm

Thanks for clarifying Norm, as I have a better understanding where your coming from now..