JustRob

Hi all-

I'm having a devil of time understanding wheel fitment. I've gone through a few threads here and in the wheel and tire forum and am more confused than ever. Hopefully someone with more knowledge than I have attained can answer this. I have a base 2005 C2 with 18x8 offset 57 and 18x10 offset 58 on the car now and have found a set that are 19x8.5 offset 52 and 19x11 offset 67. I from what I've read I believe the rears will fit as is, but I'm not sure about the front. They're a half inch wider but the offset changes from 52 to 57. Will these work on my car? Spacers needed at either end?

Thanks!
Rob

qikqbn

One thing to keep in mind for offset numbers. The "Smaller" the offset number the closer the hub is to the center of the wheel, which is equivalent to push the face of the wheel further out. The "larger" the offset number the closer the hub of the wheel gets to the face/spokes of the wheel, which is the equivalent of the face of the wheel getting closer to the brakes/rotors/hub . Offset numbers work in reverse for "negative" offset numbers, For example an offset of -25mm means the face of the wheel is being pushed out and away from the car 25mm. You don't have to worry about negative numbers which I have never seen used on a 997.

So imagine the hub of the wheel reached all the way to the exact center of the wheel. That would equal "0" offset. An offset of 50mm et would basically mean that 50mm were cut off that hub and moved the mounting points 50mm away from the center of the wheel and towards the Face of the wheel.

This video explains a lot.


So to answer your original question...

19x8.5 offset 52 ..... YES, this will look great on your car. Going from your original 18x8 et 57 to a new offset of 52 is the equivalent of add a 5mm spacer to your 57mm offset. Adding a spacer is like adding meat/metal back to the center hub of the wheel offset et.

19x11 offset 67 .... YES, this will look great on your car. Going from your origianal 18x10 et 58 to a new offset of 67 is a bit different on the rear, because you have to consider that you are adding 1 inch wider (25mm) to the wheel width. The manufacturer now needs to offset that center line by 9mm (0.35 inches) to allow the new wider wheel to not go beyond the wheel wells.

The above wheels will probably look great and stock with a standard stock suspension. Even with a standard stock suspension some people like to use 5mm spacers all around for a conservative, but wider stance.
So with that said... another big question to answer is if you car is on a lowered sport suspension. If it is lowered then adding wheel spacers will probably help the look a bit more. On a lowered suspension the tires will seem to tuck a bit more under the wheel well, so the common spacers for those 19 inch wheels are spacers of 7mm-10mm in the front and about 15mm on the rear. Some people like 15mm spacers all around, but then you may get the front wheels poking out beyond the wheel well. You also need to increase the length of your wheel bolts by however deep your new spacers are. Adding a 15mm spacer requires wheel bolts that are 15mm longer than stock. Also to note, when adding spacers larger than 5mm, it is recommended to add spacers that have a center bore lip built in to the spacer. This will help center the wheel on the hub better and avoid vibrations from the slightest little offset that can happen when the center bore does not have enough meat to sit well on the hub.

Hope that all makes sense and helps!

JustRob

Yes! Thank you! That helps a lot. Funny what some visual aids can do to help you better understand something.

PelicanParts.com

In addition to the helpful info above, take a look at the link below for another helpful guide on wheel fitment and offset/spacing.

Wheel Fitment & Spacing Guide

Petza914

Another simple thing is to go to www.willtheyfit.com and enter the specs for the two wheels you want to compare. It will then give you s nice graphic showing them superimposed on each other with a description of how far it moves out or in.

Apex Wheels

Yes, those specifications will work for your 997. Feel free to use our 997 fitment guide as a reference.

gjarvie

I have a 2022 C4S arriving this week and looking to order some new wheels for the winter. Anyone know the offset of the stock wheels, I got the spyder design. Thanks.

Apex Wheels

I'm fairly certain the specs are as follows:

F: 20x8.5" ET53 - 245/35-20
R: 21x11.5" ET67 - 305/30-21

- Ryan

gjarvie

Thanks for the info