Courtshark

Here's the specs:

Sport Edition Cup 4s (Tire Rack sells them; I bought them here for less, way less). Chuck Z has them on his GTS and they look stellar. Alas, I do not have a GTS.

19 x 8.5" fronts, et 54, 235/35/19 tires

19 x 11" rears, et 62, 285/30/19 tires

Fronts fit just fine; no spacers needed. The 19x11 rears will fit, though they needed a 4mm spacer to not rub the suspension, and are too close for comfort on the outside without rolling the fenders. I am not opposed to rolling the fenders, but I also do not like the super-stretched look of the 285/30 tire.

So... Tire Rack sells the same rim in a 19 x 10, but with a et42. Per the fitment calculator, using the same tire sizes (I figure the 285/30 will look better with 1" less rim to wrap around) , these should fit. But I thought 47mm was the lowest we could get away with on the rear. Thoughts? Thanks in advance.

EDIT: this calculator suggests they will fit: http://www.gtsparkplugs.com/WheelOffsetCalc.html Calc is at the bottom of the page

Courtshark

bump; if anyone knows the outer limits (and inner limits!) for offsets, I'd appreciate it. I know there's been a million threads on this but my searches are not turning up that key piece of info.

Ispeed

I am running 275 rears with a 52 offset and no rubbing, decent fender clearance as well.

DougM

Look at it this way. If your current rears were 10" with the same offset, they would lose 1/2" inside and 1/2" outside. Take that rim and slide it outward 20mm which is about 3/4". (1"=25.4mm). Essentially, the new wheel face will stick out even more @1/4-1/8".

I have some OEM hollow spoke 993tt wheels on mine which are 10" with the 42 offset and they fit fine...

heinrich

I would get wider tyres, see if you can machine the spacers a little so the wheels JUST clear your suspension, and roll your fenders a little. Remember, if your wheel clears the suspension by a few microns, they are fine. They don't flex or move (perceptibly) and neither does the suspension in that direction. And if you can get your little finger between the tyre and fender, you're cleared because the wheel does not move upward linearly, it comes away from the fender as it moves up. COOL so now we know definitively that a 295 on an 11" ET62 will work perfectly and looks like about as much as you can go. I like it.

James Bailey

When comparing 295 width tires which is the width of the sidewall bulge and NOT tread width it is good to see under the tire specifications what width rim was used by that tire company when THEY measured it. There is no standard for the rim used which means tires of a nominal width on 295 will vary somewhat. Also the tire can rub on the front part of the rear lower control arm and the tires do deflect quite a bit under load so some clearance is needed.

Courtshark

Thanks all; the tires on there now are 285s. Too stretched-looking to me, though they do fit under the fender. I'm concerned, though, by DougM's analysis (which looks correct); I don't have 1/4" to spare, or even 1/8", as pictured. However, those photos were with a 4mm spacer in place, which I would not need with these 1" narrower wheels. The 10s should not come anywhere near the inside suspension.

Heinrich, not sure this is conclusive evidence re: 295s fitting. IMHO, that tire would absolutely require fender rolling. Try plugging it into AO's wheel fitment calculator and it will balk. I think it will tell you to roll the fender, anyway. I believe AO's shorted the available space the rear wheel well, however. I measured 305mm; I believe he has it at about 300mm if my math is right, which might be the result of an unknown-to-me difference between the S4 and the GT rear suspension geometry. Or maybe something is wonky with my rear end! (or my math; but I doubt that).

James, I agree, tires and wheels sizes are surprisingly not as standard as one would think. On my 9-5, I purchased Dunlops in the stock size and they looked goofy-big, almost like the tires were stamped with the wrong size. This actually came up, too, when I installed my 18s. I put 265/35s on the 18x10 rears and they looked fine; another rennlister had an absurd amount of space left (to the point of not even being able to seat I bead, I believe).

Fikse Wheels

Here is the wheel math. The wheel you have pictured on the car, 11" 62mm offset, has a net offset of 58mm when using the spacer. If you remove 1" from the inside of the wheel the result would be a 10" 45.3mm offset. The 10" 42mm offset wheel will be 3.3mm closer to the fender. Your greater issue will be with the tire as you will push the outside of the tire even farther out than it is now as you are using a narrower wheel, therefore a less stretched tire. This will be around 1/4". Add this to the 3.3mm offset change and your tire will be at least 3/8" closer to the fender.

Courtshark

Thanks, I'm not sure I follow you entirely (see bolded part). Here's my math:

1" = 25.4mm.

I am assuming (famous last words) that 1/2" comes from each side of the wheel to take it from a 10" to an 11". (FWIW, 10" = 254mm (which shohuld easily fit within the available 300+ mm of wheel well space)).

Current offet (with spacer) = 58mm; spacer was absolutely needed to clear the rear suspension

New offset = 42mm, = 16mm less than 58mm

= New wheel will be 16mm more toward the fender than the current 11" is, BUT with 12.7mm (1/2") less overall width, resulting in the wheel being 3.3mm (16 - 12.7) closer to the fender (as you found, too).

So I think we're saying the same thing. And do I have 3.3mm to spare? Not without rolling the fenders, I don't think, and especially because of the tire flex issue you mentioned.

JPTL

Mike,
When you get this whole thing figured out, wheels mounted & car settled, please post pics of the new look. I agree...these look great on our cars.

Courtshark

JP, you might want to change that "when" to "if"!!! I'm hopeful I can make it work, though it looks like fender rolling is inevitable.

DougM

I missed the 4mm spacer part in your first post. Your analysis in the previous post is correct.

Courtshark

Thanks, Doug. What size tires are you running? And I assume you did not need to roll your fenders.

DougM

I have 285s on the rear. I did not roll the fender, but it is possible that a PO did?

Ispeed

One problem with 295/35/19 rear tires is the diameter of 26.1", when stock is 24.7" The height alone may make it rub when a smaller diameter 295 wouldn't.