I'm an old school drag racer (still racing a Vette) and used to working with the advertised "backspacing" to achieve my desired outside wheel position.. Is there a simple method for determining wheel position using "Offset" since all the wheels I'm looking at for my Z only list the "offset"? I have read about what offset means but its just not sinking in and I'm getting a headache trying to calculate every wheel because they all have different "offsets..

My current stock wheels are listed below, along with the offset.. If I go wider on my wheels, how can I calculate what the offset should be if I want the "outside" of the wheel in the same position as the factory wheels?

Factory Wheels
18x8 +30mm (front)
18x8.5 +33 (rear)

Thanks!!

 

http://www.1010tires.com/wheeloffsetcalculator.asp

 

Thank you, thats perfect!!
So here's what I come up with then.. If I want to widen my stance over factory by +25mm in the rear and +22mm in the front and using wider aftermarket wheels, here's what i come up with (please correct me if I'm wrong)

Factory Wheels
18x8 +30mm (front)
18x8.5 +33mm (rear)


Aftermarket Wheels
18x9 +20mm (front)
18x9.5 +21mm (rear)

 

found on this vette link (if that helps):
http://www.corvettepartsblog.com/cor...-back-spacing/

 

Clearance on the inside of the wheel is tight. If you are going to move the wheel I recommend that you move it towards the fender.

 

Very acceptable setup, we can get wider wheels in there without suspension or body modifications.

 

I thought my aftermarket choice and offset listed was moving it towards the fender? My goal is to make the outside of my wheel choice sit flush with the outside of the fender.. Did I go backwards?

 

no you went the right way..

positive offset moves the face of the wheel further outward and negative moves the face inward (on a flat faced wheel this will create the "deep dish" look because more of the wheel is pushed out past the face like on a -20 offset wheel). from what ive seen, if you want flush without any serious fender modification a +12 offset and a slight stretch in the tires will do it, with your setup at +21 and +20 you can put beefier tires on and it will me great.

YES i could be wrong, but i know its not all wrong and i hope it helps some....

 

9.5 +22
10.5 +22

Should sit perfect without fender modification. And still allow you to run wide tires. What size tires are you thinking?

 

Thanks for clearing that up!!
Your right, the calculation shows that a 18x8.5 with +12 offset will push the wheel out 21mm over the stock wheel.. Now I have to figure out what size tires to put on that are wider but also without making it look like a 4x4 since I wont be installing a drop at this time.

 

The calculator on the below link shows that if I use a 10.5 on the rear with +22, I will extend out 36mm over stock.. Wont that be to much, especially since everyone is only recommending a 25mm spacer on a stock rim to sit flush with the fender?

http://www.1010tires.com/wheeloffsetcalculator.asp

I dont think that calculator is working right because I just found a car that has 10.5's in the back with +19 and its sits perfectlly flush..

 

I have 25mm on front and 30mm back spacers and they r barley getting to beeing flush with the fenders. Oem wheels btw

 

You do realize that only a 3mm difference. Roughly a 2 credit cards thick, not much at all. Also +22 could be flush on one car at stock height, and -1.5 camber, then the next car is sitting at -1.8 and it will not sit flush on it. Camber playes a huge roll.

 

Yes, but that is also highly dependent on tire size, drop, fenders rolled (or not), camber, actual tire width, etc. What works conservatively on one car probably works on all cars; however, what works aggressively on one car certainly may not work on another. If the wheels you are looking at don't change their configuration by adding width (like the Enkei wheel series), then there is little reason to go to a huge wheel (like 10.5) and run a small tire versus using a smaller wheel (which looks the same) with an appropriately-sized tire. Does that make sense?

For example, many people run the Enkei RPF1 18x10.5 +15 all around, but put a 265 tire on it. To me, that's silly; to others, that's achieving a "look" but one doesn't need a 10.5" wheel for a 265 tire (I put 265 tires on 8.5-9" wheels myself).

 

Yes, thats makes perfect sence.. I would assume a larger tire on a narrower rim would give the side-wall a little more bubble. Ok, I'll pick my rims and report back to make sure it will work and then start on tire selection..

Thanks for all the help!!

 

Ok, I already have another queston. One of the biggest issues I'm running into when searching rims is the choices on the other 2 rims.. For example, I am finding some rims that will work perfectly on the back but they dont make anything matching for the front in a slightly smaller size and with the correct offset.. It seems alot of brands planned on customers using the same size on all 4 corners....

 

Ok, after looking at thousands of wheels, here's what I narrowed it down too.. My price range is somewhat limited and in order to get into something similar with the perfect offset, it would triple the price.. Offsets and sizes are very limited so I have no choice but to run spacers with them... My goal is to make them sit flush (or close to it) with the outside of the fenders.. Just so you know, the outside edge of the rim is machined and not a trim ring.. I personally think they would look sweet on my White 2006 Z.. Please let me know if something doesn't look right..

Front
19x8.5 +30 offset (with 20mm spacers)

Rear
19x9.5 +35 offset (15mm spacers)

 

So you are saying that you'll net a 19x8.5 +10 front and 19x9.5 +20 rear? Those net offsets DO work, however, there is enough room to bump up the size to 9 or 9.5" in the front and 10 or 10.5" in the rear. You could even run that 9.5 +35 in the front (and add a 10mm spacer).

Regardless, where are you looking for wheels? There are so many wheels out there for these Zs it's ridiculous. Take a look through a bunch of the threads in this wheels Tires forum and see what else people are running. What is your budget for wheels? What about for tires? People change their minds so damn often, that's it's often worthwhile to consider buying a used set.

For example, I just picked up a set of "premium" Volks for the wife's ZR at about 50 cents on the dollar. They are free of any curb rash, and have just a few typical nicks from road use. Alternatively, wheels like the Enkei series of wheels are popular (fact), offer good offsets for Zs (subjective), and cheap (opinion). Take a look: http://enkei.com/racing.html

 

These rims are discontinued but dealers still have them in stock. The sizes available are very limited and the ones i listed are the only ones that would even come close so I cant bump them up in size even if I wanted too.. I can get the entire set of 4 I listed for about $700 delivered..

Your right though, I will take a look around for something possibly used.. However, my budget wont be much more than these since I want new tires too.. I really like the sliver trim with gunmetal or gray in the middle like the ones in the picture.. I also dont like thin spokes so it might be hard trying to find something I like used.. Heck, it took me a good 30 hours of browsing and all I found was one style I like I found others but they were all well over $2k..

 

I am not a fan of spacers, but they do allow lots of options. Put the wheels tires on the car. You can judge spacer size later.