If I am running the set-up below, will I encounter any problems if I lower my car.
And will I have to roll my fenders.

Sizes
Wheels (All around)
18x9.5 +20 offset

Tires
Front:255/40/18
Rear:275/40/18

 

maybe is really the only answer anyone can honestly give you - only way to know is to try it, as every car is different

 

You can't roll the front fenders they come rolled from the factory. you could cut/pull them though, if needed. but I doubt it.

I am running in the front:

17x9 +20 255/40/17 < no rubbing, but pretty darn flush. (lowered 1 + inch)

I have run in the rear:

- 19x10.5 +20 275-35-19 < no rubbing, unrolled fenders (lowered 1 + inch)

and currently run:
- 18x10 +18 275/35/18 < no rubbing, unrolled fenders (lowered 1 + inch)

I will be lowering the car another 1/2 inch soon and don't see any issues at the front, but might need to roll the rear.

your fronts would be the only thing I would question. you have 1/2 inch extra on me so your +20 is 12mm farther out from mine... and mine seem really flush, even with a little camber.

 

My car with 18x9.5 +20 and 275/40 tires rubbed horribly - I had to heavily roll my rear fenders to cure it. Or I could run -3.5 degrees of camber, and then it barely rubbed (which sucks for handling)...so either way, rolling was needed.

Every car is different. Every car reacts to lowering different, and every car comes from the factory with different alignment settings - where your car starts off, will determine if it is more or less likely to rub after its lowered

 

We already did this: https://my350z.com/forum/wheels-and-tires/326738-very-quick-question.html.

 

seems we do it everyday.....but I guess no one likes the answers they get, or they don't know who to listen to

so, let's end this finally - these are the facts:

Some people will need rolling with those sizes, and some people won't - to find out which category you fall into, you have to first lower the car and install your wheels and tires, and the answer will reveal itself for your particular car/situation. There are too many variables involved to give a definitive yes or no answer. Unfortunately, there is no magic answer to give beyond that.

 

- how low were you?
- were you running positive camber?? lol, I keed.

 

I don't remember what the height was set at, it was a few years, and a few setups ago, but here were pics. I've always run slightly more negative camber than the outer limit of stock range

 

9.5 +20 all around isn't aggressive at all. you'll be fine.

 

I was lowered 1.2 inches or so with

19X9.5+22 front 255/35/19
19x10.5+22 Rear 275/35/19

No rubbing, but I had -2.5 camber in rear and around -2 in the front... Like Z1auto said it will depend on your car and especially how low you plan to go later....

Worse case you have to roll your fenders for $100 after you lower.... Big deal.

 

doesnt that cause problems

 

Not really, if your toe is in spec then you can still get a decent amount of life out of the tires...

The Z comes stock with a slight bit of neg camber anyway.... Most track cars are using some sort of neg camber on their cars.

 

slightly out of range isn't a big deal. it's the -3+ camber that kills ya

 

Amen to that brotha!!