Okay, here's the deal...

I wouldn't be surpised if this wasn't answered somewhere else but if it is, I haven't been able to find it. Forgive me if it is out there and I just missed it.

I am going to go with a set of 18s...9.5" in the front and 10.5" in the rear. This is going to go on my lowered (about 1.25 inches with DMS springs) 2002 Camaro SS.

I am looking to find the perfect offset where there is as little clearance issues as possible, but still fit relatively flush. I think I would rather roll the fender than do the BFH mod, but I want to avoid both if possible.

If I read correctly, the front offset should be +38 (for an 18 x 9.5) and the rear offset should be +50 (for an 18 x 10.5). Is my thinking correct or is there a better f-body offset that I should be using for the look and clearance that I need? I just want to make sure I have it as perfect as possible as I am having a set of custom wheels made and I will only get one shot at it.

Thanks!

 

Custom wheels? Pics? Similar to...?

 

You are probably pushing the envelope with the 38mm offset in the front. They will be very close to the outer edge of the fender. The TT II 9.5" wide wheel is a 45 or 46mm offset, so you would be out about 1/4" further than the front wheel on this car:

http://www.kellydrown.com/showcase/120-2036_crw_std.jpg

And another reference... the OZ MOnte Carlo had a 49mm offset, so you would be about 1/2" further out than those wheels of the front of my Formula:

http://cjcfo.fbody.com/members/injun...sD/3_4View.jpg
http://cjcfo.fbody.com/members/injun...210Full02a.jpg

I think the early Enkei wheels, pushed by LG Motorsports were 17x9.5 38mm offset, and they tended to sit out a ways. I think there is a set on the car next to mine in this pic:

http://cjcfo.fbody.com/members/injun...osD/SLP27a.jpg

In the back, I think you have it right with the 50mm offset. That means, compared to the typical 17x11 50mm offset wheel, you will have reduced the "front space" by 1/4", minimizing interference with the fender lip, and reduced the backspace by 1/4" minimizing the need for taking the 3# BFH to the inner fenders.

 

Right now...the design exists 75% in my head. Not for long. Preliminary designs are being developed in 3D, I need to approve them when they are done. They will be forged, modular and 5-spoke. Similar to the higher-end 5-spoke forged wheels out there. I cannot give out any more info than that at the moment.

Well, I definitely do not want them to stick out. I need them to look just right. Like I said, I really only get one shot at this and if I don't get it right, more R&D will have to happen and I am trying to avoid that at all costs. So, I am trying to absorb as much info as possible.

Thanks, guys! Keep feeding me info if possible!

 

Jason -
I would contact Todd @ Pro Dyno as he's great with these and should be able to provide excellent help. I'm currently running 18x9.5s up front and 19x10.5s in the rear. Although the rear sticks out some (fine with me, but sounds like you want it flush). Here is some info from a post of his..



"WIDTH OFFSET WIDTH OF TIRE
7.0 +35/+40 215/225/235
7.5 +35/+45 215/225/235
8.0 +38/+55 225/235/245
8.5 +38/+45 235/245/255
9.0 +38/+56 255/265/275
9.5 +38/+56 255/265/275
10.0 +38/+48 265/275
REAR ONLY
10.0 +45/+54 275/285/315
11.0 +50/+56 275/285/315


Z06 replicas:
17x9.5 +50 to +56 no problems. 275 or 285-40-17s.

18x9.5 +50 to +56 275-35-18 or 285-35-18.

18x10.5 +50 to +53. Higher than 53 will require the BFH mod. 285-35-18s thru 315-30-18. Over 285 will require rolling the fenderlip and BFH.

Y2k Replicas:
17x8.5 +56

17x9.5 +50 to +56

18x9.5 +50 to +56

17x11's. Always a possibility of needing the BFH and fender rolling mods with 315s. If lowered an Adj Panhard rod comes in very handy. Some have used the +38 offsets with 11" but it does stick outside the fender and is definitly not recommended on lowered vehicles. +50 and +56 are the two most common. +50 is the best fit. for race only applications a 17x11 at all 4 corners can be made to fit.

17x10 +38offset is very aggressive but fits all 4 corners...even lowered 1.5". "

 

Yep, I posting in that thread asking the same thing. The odd thing is, I keep finding ranges of offset, and not a solid proven number. I cannot give my wheel builder a range, he needs an exact number.

I only have one shot at this. Due to the nature of this project, if it doesn't fit, I am stuck with some very expensive wheels that don't fit properly.

No biggie, though. Things like this are never easy. I am just going to keep digging and asking around.

 

Ahh...sorry, didn't know you posted in that thread. It was worth a shot. In your efforts to continue digging for info...I suggest maybe you call a few rim Manufacturers that you know deal with F-body offsets (i.e. HRE and a few other high end companies). I say a few because as you mentioned, you're getting varying information on offsets. Hopefully that will help bring you closer to your custom rims! Good luck. Can't wait to see a pic of them when they're done

 

But you are looking for a "flush" appearance, so you use the lower end of the "range". Note that he cites 38 - 56mm for the 9.5" wide wheels. 38mm puts it "very" flush with the outside of the fender, 56mm pushes it in 0.70" from the edge of the fender. It's simple math at that point, not rocket science

In the back, you have to balance the wheel position with interfering with the fender lip (flush with fender) or too deep and rubbing on the inner fender liner, behind the tire. There isn't much "range" when you get to 10.5" or 11.0" wheels. The 50mm number is going to be the best for either, IMHO. With a 10.5" wide wheel, you gain 1/4" on each side of the tire, compared to the common 11" 50mm ZR1 wheel/tire combo. Should eliminate both fender lip and inner fender rubbing problems.

A couple things that do "cloud" the issue..... not all tires with the same "size" are the same dimensions.... even though a tire is labeled 285mm (11.22") it doesn't mean the tire will be exactly 11.22" wide for every manufacturer, and when mounted on a 10.5" side wheel. The wider the wheel, the wider the tire cross-section. And, to complicate things even further, one manufacturer's 285 on a 10.5" wide wheel may be wider or narrower than some other manufacturer's tire.

Then there is the method for calculating "backspace" from "offset". The thickness of the bead retention flange on the wheel enters into the equation. While 0.50" is a typical flange width used in the calculations, not all wheels use this dimension. My Pro-Stars use 0.50". The AFS ZR1 replicas use approx 0.46". Your wheel manufacturer will have to account for this.

 

Not to hijack, but I had a quick question. What offset would you guys recommend for a 18x10.5 zo6 motorsport wheels with 335/30/18 tires?

I want the rear tires to either line right up to the top of the fender lip or just a little past it.

The tires are michelin pilots if that helps

Sorry Jason


-Archie

 

Thanks, guys. I think I got it all straightened out.

I spoke with someone who was very knowledgeable and had a great deal of experience fitting the exact size I am going with on a 4th gen f-car.

More details to come...this wheels is gonna be awesome.

Thanks again.

 

Jason -
Awesome bro..can't wait to see the rims

Archie - I wouldn't put 335's on a 10.5 rim. That's way too much tire for rim. If you want 335's done right you should put them on a 12 or 13" rim. For example, the new Z06's have a 19x12 rim rim in the rear with 335's.

 

Then what offset would you suggest for 315's or just a 10.5 inch rim in general so it lines up with the fender or just a little past is fine