offsets

[Riptide]

You have two wheels.

17x9 +45 offset
18x9 +45 offset

Do both wheels stick out the same distance from the car? Does the extra diameter have any effect given the same offset?

 

[psfracer]

The extra diameter could affect fitment with regards to brakes or shocks As far as the edge of the wheel with regards to the fender, they are the same width with the same offset so they would be the same.

Wheel with no offset:

Wheel with positive offset:

Wheel with negative offset:

 

[Riptide]

Thank you that helps.

So width would make it stick out more. For instance a 17x9 sticks out more than a 17x8.

About how much width can you go with given the stock offset before you start having it poke past the fender? Gracias

 

[csamsh]

You can do an 11" wheel, but you can't use the stock offset

 

[SlowJim]

http://www.willtheyfit.com/

 

[Norm Peterson]

So width would make it stick out more. For instance a 17x9 sticks out more than a 17x8.

The simple answer is "yes" - and the simple illustration to go with that is to assume that both of those wheels have the same offset. In that situation, half of the "extra" width goes on the outside and the other half goes on the inside.

If the offsets are different, all bets are off. The wider wheel could either stick out more on the outside than the narrower wheel, less than the narrower wheel, or even be exactly the same depending on how much smaller of a +offset it had.


Norm

 

[Riptide]

Much appreciated.

There is a certain set of 17x9 wheels I want to go with that are +48 offset. They are supposed to clear big brakes. Sounds like they should fit fine. Wanted to make sure I understood how this worked. It gets expensive exchanging things like this.

 

[Norm Peterson]

You'll be fine as far as clearances to the strut on the inside and the sheetmetal on the outside are concerned. Relative to a +45 GT500 wheel, your +48 steals 3mm away from about 10mm clearance, but the 1/2" narrower width buys you back about half of 12mm, so you'll be 3mm better off (~13mm wheel to strut clearance, which *should* be enough to fit a 275/xx tire). On the outside, you'll have 3 + 6 mm more clearance than with a GT500 wheel.

For rotor clearance there are two other clearances involved.

One is radial clearance to the barrel of the wheel. The *safe* assumption is for the nominal wheel size to be 4" greater than the nominal rotor size, though tighter fitments are possible depending on the actual rotor diameter and caliper dimensions and the actual thickness and contour of the wheel's barrel itself. My guess is that a steel wheel can be a little thinner and flatter for greater clearance.

The other is clearance to the back sides of the wheel's spokes. Brembo calipers in particular require more room this way, so the shape of the back sides of the spokes and/or the mounting pad height matter for this one.


Norm

 

[irishpwr46]

what is the measurement from the face of the brakes to the fender lip on the front and back of the car?

 

[csamsh]

what is the measurement from the face of the brakes to the fender lip on the front and back of the car?

given the variability in the answer here, the best way for you to determine that will be to grab a tape measure and a plumb line

 

[Riptide]

Well gentlemen. I am feeling a bit impulsive right now.

I have four of these guys in a shopping cart ready to be ordered.
http://www.good-win-racing.com/Mazda-Performance-Part/61-1315.html

Rear tires:
http://www.mandhtires.com/275-50R17#.VLweukfF8mc

Front tires:
http://www.discounttiredirect.com/direct/findTireDetail.do?v=008857|2006&pc=32893&ar=55&rd=17&cs=235

Any reason not to do this?

 

[irishpwr46]

that looks like a lot of sidewall

 

[Riptide]

EDIT:

Change of plans. I can get a PF01 in 17x8 +50 offset. Weighs even less. I can't find the +45 offset model in black unfortunately. The difference is only 5mm which should be barely noticeable.

 

[Norm Peterson]

You might want to check the load rating for those wheels. A Mustang is a bit heavier than a Miata.


Norm

 

[Riptide]

Rated at 1530lbs.

 

[Norm Peterson]

That should be OK - I just dug out one of my new Forgestars and found that it has a 1520 lb rating. I was concerned that a Miata wheel might have been rated somewhat lower, like maybe somewhere down in the 1300's.

Incidentally, Load Index 97 SL and 101 XL tires are rated at 1511 lbs @ 32 psi . . . and I doubt that wheel ratings slightly above that are coincidental.


Norm

 

[warpath06]

Riptide,
I assume you know some people that are running these 17" wheels already with no issues. I realize that you are aware of the larger front brakes on non-brembo 2014 GT's, but I was under the impression that 17" wheels won't fit on 2011-up GT's because of the diameter, not just the offset. I know on 2005-2010 GT's I can't even get a sponge compressed enough to clean the wheel around the smaller brake setups with 17" wheels. Just throwin it out there..

 

[Riptide]

These should clear the calipers. They are designed with bigger brakes in mind.

I examined the rotors on the car and to the eye anyway it looks like a 17" wheel ought to be OK. I know people run 17" racing wheels up front on these cars all the time.

I'll be surprised if it doesn't fit but I am a guinea pig on this one. Nobody else has tried this combo that I am aware of.

 

[Riptide]

Just an FYI guys. This turned out to be a no-go. The inside of the wheel will not clear the calipers. Looks like there are precious few 17" wheels that can be run on a non brembo car. Only ones I'm aware of actually working for certain are the racing wheels like welds, darkstars, etc..

Very disappointed. Looks like I'm stuck with an 18" on this car unless I want to go with welds or something else like that.

 

[2011/5.0]

Or iirc you can put a 10 caliper mounting bracket and 10 rotor i beleive thats how they ran 15s skinneys up front on a 11