I own a 2005 G35 Coupe and i recently traded my wheels for another set and the wheels are XXR 968 however the tire size that on their are 245/35/20 (front) and 275/35/20 (rear). I purchased eibach sport-line springs and they have yet to be installed and the drop estimated to be given would be 1.5"-1.7" front and rear. However, the rear wheels need new tires, so before i purchase the same tire size is their anything i should be concerned about?
The wheels are 20x9.5 and 20x11 offset +15 front and rear.
I see that their is a lot of debate on the rear wheels being 275/35/20 or 275/30/20, I just want a perfect flush fit without potentially rubbing or rolling fenders.

Any insight of sticking with the same 275/35/20 or go 275/30/20.

PS... the previous own for these wheels had them on a g35 coupe with Tein Springs and they didnt look so bad, he said no rubbing or anything, but those were Tein Springs (eibachs would be a different drop) and he had his Fenders rolled and pulled.

after you lower the car, you will 110% rub with the 20x11+15 with a 275. not even up for debate without more neg camber or at very least a roll.

you traded your forged oem 19s for these didnt you.. fess up.

roll and pull your rear fenders and throw a 315 back there. man up lol

I don't think you'll get that much of a drop with those springs. Regardless, you'll be rubbing.
So as JT stated...man up and roll that b**ch

You will need to roll the rear. I have a measly 3/4" drop on Z springs, have 20x10.5 +22 and 285/30/20 tires on the rear and still rubbed on hard corners.

As far as replacement tire sizes, a 275/30/20 will have a slightly smaller rolling diameter than the front tires. A 245/35/20 & 275/35/20 gives the factory "stagger" of 3% difference. You can also bump to a 285/30/20 and have the same rolling diameter as the 245/35/20 fronts (0%) difference.

I run 245/35/20 F & 285/30/20 R on 20x9F & 20x10.5 R wheels.

Haha nah i didnt trade my 19's i actually had a square setup 20x9 Axe Ex12 (lots of curb rash so had to get rid of them)...my car OEM is 17s.....anyhow best bet u all think i should pop the springs on measure the drop, then throw on the wheels and then determine the tire size,and last but not least ROLL THE FENDERS? in that order?

So LoSt180, ur saying stick with tire size that came with the rim that the orignal owner had? the 245/35/20 & 275/35/20??? Sorry if im noobin you all with these questions.

you will be able to tell if you need to roll just by test fitting one rear wheel.
then obviously you factor in lowering with the springs and you can take it from there.
btw a 275 on an 11 will be a tiny stretch (just making you aware lol)

why not just devote 2-3hrs and roll them one saturday and not have to worry about any problems in the future? just take your time and they'll come out fine.

Yes, stick with those tire sizes. If you want a little more meat go to a 285/30/20 rear tire.

Go ahead and roll the rear fenders as soon as you get a chance. Basically any time before, or immediately after mounts up the wheels. You don't want to be rubbing too long as that can mess up your new tires.

@LoSt180 I know you stated before to go ahead and go with the tire size on the rim that the original owner had which was 245/35/20 (20x9) F and 275/35/20 (20x11) R and that would give me a 3% difference in Rolling Diameter from OEM wheels. However my question arises is...

I've see a few people having the same question as me, but not the same answer given.
I've also seen a staggered set-up for tires for sale which are 245/35 and 275/30.
How would this affect Rolling Diameter? & would this be more ideal to work with (even with a tiny stretch).

P.S......I've attached a 2 pictures of the original owner's G35 with the 245/35, 275/35 setup..all he said he experienced was he rubbed on big dips doing 75mph on a bumpy road mainly Downtown Orlando on I-4 (if anyone if familiar with the roads out their)

Just to add to this.
I compared my existing setup both fronts and rear on OEM specs and then compared to the potential specs of tires w/ offset.
I am just trying to come to the conclusion with rolling diameter to be closet to stock but I'm a bit confused.

Use 1010Tires tire calculator to figure out rolling diameter differences...make sure it's within a 3% difference.
http://www.1010tires.com/Tools/Tire-Size-Calculator

I'll try to answer your questions, but playing around with a tire calculator will help you figure this out https://tiresize.com/calculator/

I haven't paid attention to the 275/35 vs 275/30 debate since I run a 285 rear tire, but looking at the numbers: A 275/30 will have a smaller side profile than the 275/35. The rolling diameter will be about 4% smaller and the diameter of a 275/30 is a little over 1% smaller than the 245/35 in the front. Basically you'll have taller tires in the front than the rear, essentially a reverse staggered setup.

When comparing with OEM specs, you want to keep the REAR tires as close to the same diameter to maintain odometer accuracy. A 275/30 is a little shorter than stock and a 275/35 is over 3% taller. I would personally use the size closest to stock (275/30). That said, the 285/30 that I run is a perfect diameter match for my stock 19" wheels (245/40/19).

If you want to run a 275/30 on the rear, then you should reduce the front by the same and use a 245/30, this would maintain a 2.7% diameter stagger. 245/30 & 275/30 are also the recommended upgrade sizes on Tirerack btw.

Hopefully this make sense, I figured breaking it down would be more helpful than just saying "buy these sizes because, reasons."

Again, I run 245/35 & 285/30 on mine. This is essentially a square setup in regards to rolling diameter.

Here is my 245/35/20 285/30/20 setup:




Just after getting the rear rolled:

Since your doing that, from what it looks like in the pictures, the height of the vehicle changes, based on the sidewall of the tires?
For example, your rear tires look smaller than the front. Is this due to the 245/35 and 285/30. The 35mm sidewall and the 30mm sidewall? Or did nothing really change because the 285 corrects this?
For example, wider tires = shorter sidewall?
I guess what i am getting at is, to avoid screwing with the VDC or any sensors realistically, i want my tires to be at a even height. So when i put the eibach sport line springs on, it sits evenly across and I know tire height would give that appearance correct?

35/30 isn't mm, it's a percentage of the width. ie: 35% of width is the sidewall height. For example, when comparing a 275/30 with a 285/30, the 285/30 will have a slightly higher sidewall since the "30" is actually a ratio (3.25" vs 3.37" to be specific).

245/35/20 and 285/30/20 actually have the same sidewall height of 3.4". That's probably a crappy pic due to shadows, and the rear has a little bit more of a "stretch" than the front tires.

To avoid screwing with the VDC, you want the overall tire diameter/circumference to have a LESS than 3% difference between the front and rear. Both 245/45/18 & 245/35/20 tires have the same diameter as a 285/30/20 tire. To the sensors, they're the same since they spin at the same speed.

Your lowering springs will have zero effect on this ratio.