Wheel/tire specs (rear):

18x10 +20 295/35

I spoke to the local shop and he told me to research how many degrees to roll the fender lip. He said the standard roll is 45 degrees, but for me to check with people running the same setup, or those knowledgeable about this type of fitment on a Z. I guess 45 degrees is the cutoff (from the lip's original position at about 90 degrees) before the paint starts really cracking.

I greatly appreciate insight into this.

 

roll just enough to clear the tire without rubbing. 45 is a good place to start, and then determine if you need to go further. This will vary with each setup, and the further you roll, the greater the likelyhood of cracking

 

Thanks for the response.

Unfortunately, I will not have the wheel and tire package on my car for some time to use the trial and error method you are proposing. I have the oem 17x8 rear wheels with 255/45 tires and 25mm spacers, and I am flush with the outer fender. I have not rubbed yet with this setup, but I fear that as the suspension wears, on hard bumps/dips/turns I will begin to have some rubbing. I figured since I will be getting the wheel and tire package detailed in the firs post down the road, I may as well kill two birds with one stone by getting a roll done sooner than later.

I will be using POR-15 paint on the fender lip once it is rolled, regardless of how far they roll it, to seal any obvious or not so obvious cracks in the paint, so maybe I should just have them roll the lip almost to the max since I will be "sealing" it anyway?

 

Or you could run a perfectly-fit 285/30/18 and not worry about rolling the fender (probably).

 

When cracks occur after fender rolling and you use touch-up paint to fix such cracks, these cracks won't "run" to the outside, will they? Like a windshield crack?

 

The standard 45 degree should be fine. You may need a could extra, but you'll find out once you get them on.

 

I think I'm just having trouble making sense of wheel fitment and how much travel the wheel and tire makes over bumps and around turns and everything.

I'm just looking at the pictures of the setup I want on wheeldude's car, and I'm trying to visualize the tire going up into the rear quarter panel, and if it will hit anything. How much travel would these wheels/tires really have given my suspension (Hotchkis).

You know what....I'll stop talking. You all know what my concerns are....please enlighten me! lol

 

Read / Comment on post 7, but maybe seeing the exact-sized setup I am looking at will be helpful to determine how much to roll?

I am dropped on Hotchkis (.75"), and he is dropped on Eibach Pro-Kit (1").





Oh yes, here is my current setup out back. This is also why I am rolling early before I even get my bigger wheels.

17x8 OE wheels + 255/45 tires + 25mm spacer = a finger and a half between the top of the tire and the un-rolled fender lip. Seem pretty damn close to me, especially in the event I have 2 people, a full tank, of gas and maybe some cargo. Hasn't happened yet, knock on wood, but it looks like it could, right?

 

I am running 18x10 +22 with a 295/35 and have no issues with rubbing. I am lowered on coilovers and running -1.7 degrees camber. I had them at -1 degree and still didn't rub. I wouldn't roll the fenders unless you had to. I would think you will be fine without rolling

 

I PMed WheelDude.com and he said I would have to if I wanted to run the 18x10 +20 w/ 295/35s w/out having to compensate any rubbing with a fair amount of negative camber. He also said I will have no problem running 18x9 front (+20) w/ 275/35s.

He said I may be able to get away with not rolling them and running some camber.

But, the issue still remains about my current setup, which does not rub, but is only a finger and a half away from rubbing.

I should probably just do a mild roll to be safe. I guess I shouldn't go too extreme, though, given what you're telling me about your past/present setup.

Note: I'm aiming to run camber as close to stock as possible.

 

Where did you guys get your fender roll professionally though?
like auto body shop?

 

I'm going to do it myself, most likely. A friend of mine has a fender rolling tool. It is pretty expensive, so if you don't have a friend like me who has one, you should get it professionally done for about $100 ($50 / fender)

Some body shops may do it, but most likely a performance shop will be able to.

 

Mild roll should be just fine.

 

Alright.

I guess I really still am not understanding the whole story about rolling. Maybe because I can't wrap my head around how I would not rub with any wheel/tire setup that sits flush with the fender, regardless of a roll or not. In my mind, physics would still say under hard cornering it would scrape.

These two images are what are tripping me up:

My BMW w/ 5 people in it...look at the wheel going into the fender. This won't happen to any degree on the Z under a hard turn, or with weight, or as the suspension wears? Even with mild fender rolling, it won't allow the wheels in the specs I want to do this. But the question is, will it ever? (again, NOOB)




See the tuck-age? No rubbing? How?! Fenders cut? I don't get it

 

Is your car lowered? If not then you won't have to roll the fender lip. If the car is really low you will have to roll the fender flat. The paint won't crack if it's done right with a heat gun.

 

I think I mentioned it is lowered on Hotchkis coils above.

Will someone please explain to me the physics that allow the wheels and tires not to rub (even with a fender roll), as seen in the pic of the Z under a hard turn, above?

 

There's nothing to explain really. As the suspension compresses the wheel follows a curved arc around the suspensions instant center.

 

My gut feeling tells me that the hub shifts up and in as the suspension compresses, thus allowing for the wheel and tire to "tuck up and under" the fender lip.

I still feel like the fender lip would interrupt that travel...less so if you're rolled, of course.

Half the reason I want to roll isn't even for the new setup, but for my current one. I read on here that if I was lowered 1/2" more in the rear (w/ the 25mm spacers on the stock 17s), I would rub on a hard launch or in hard cornering. My logic is that the suspension will wear (naturally) over time, which may cause maybe another 1/2 or so of "play" due to this wear. Of course, that's an indication that the shocks are on their way out, but I'd rather not have to make that decision to replace because my car's rubbing the wheels against it's fenders, if you catch my drift.

Again, for reference (this is my car. i hate the little ad at the bottom too, but that's what i get for using imageshack):




...that's a serious inward angle that hub is taking in order to allow the top of that tire to clear that fender lip. The edge is only about and inch and a quarter away from the top of the tire at rest, so while cornering, hitting a bump, or with weight, how am I not rubbing? I guess I'm just lucky now, but like I said, when those shocks start to go...

 

WTF with all the questions!? If you're concerned about it, just freakin' do it!

 

I didn't think that trying to learn was a bad thing. That's the whole point of me being on forums for all of my cars, and working on them myself. If I have a project in front of me, I research it as much as I can and ask questions when I have a question. Usually, those who reply to my threads are very helpful.

Also, the wheel and tire package I'm looking at will cost me $3,000. I think it's in my best interest to see if it will fit with no issues before I shell out that kind of money.