I need some help to determining the correct backspacing of offset for the front and rear.

I have sold my 18” Ruff rims that wouldn’t clear the front big C6 Z06 brakes due to the spokes were touching the calipers.

So I have been looking around for some rims that would clear the front big brakes. I was thinking of going with Boze Mesh rims custom make.

I was told that the front would have an 18x9.5” with 5.75” backspacing with 275’s wide tires.

For the rear, would have 18x11” with 20mm offset with 315’s wide tires.

So I try to work my calculation to get backspacing in inches and mm in offset.

So here below what I have done, and hope I did it right:

18x9.5”
To get backspace in inchs:
9.5” Wide rim + 1” lip =10.5” overall width
Offset 12mm

[9.5” width + 1” (lip)] / 2 = 5.25”
To convert from mm to inches divide by 25.4
12mm offset / (25.4mm/in) = 0.472”
Therefore: 5.25” + 0.472” = 5.722” Back space =5.75”

To get offset in mm:
Backspacing is 5.75", rim width is 11"
Offset: 5.75” – [(9.5” width + 1” lip)] / 2
= 0.50”
To convert from inches to mm multiply by 25.4
= 0.50” x (25.4in/mm)
Therefore: = 12.7mm offset

18x11”
To get backspace in inches:
11” Wide rim + 1” lip =12” overall width.
Offset 20mm

[11” width + 1” (lip)] / 2 = 6”
To convert from mm to inches divide by 25.4
20mm offset / (25.4mm/in) = 0.787”
Therefore: 6” + 0.787” = 6.787” Back space

To get offset in mm:
Backspacing is 6.787", rim width is 11"
Offset: 6.787” – [(11” width + 1” lip)] / 2
= 0.787”
To convert from inches to mm multiply by 25.4
= 0.787” x (25.4in/mm)
Therefore: = 19.989mm offset = 20mm

Keep in mind that the big brakes are a little wider than stock brakes here are the Big brake information of the measurement http://www.kore3.com/downloads/fitment_templates/DOC0019.pdf

So would the front and rear Boze Mesh custom rims fit without sticking out or be inline with the fenders or touching the spokes of the calipers using the above correct information size?

As for the rear I was thinking of upgrading my brakes to 4 or 6 pistons C6 Z06 brakes later on and I have the 9 bolt axle.

 

I would suggest checking out those "new" calipers you want out back, to make sure they aren't wider. It would suck to get the wheels made, everything fits right, then change the calipers later only to find out the wheels no longer clear!

 

Call Bruce at Hawk's, he has done alot of custom Boze wheels with offsets. He did mine 18x9 up front and I run 275's with Baer 6 setup. Also have 18x10 in back with 305's. Maybe he can help.

Eric

 

I am working on trynig to figure out the rear C6 Z06 brakes calipers fitment with the new rims. In that case, when I know the correct rear backspacing. I could use a small spacer mm or hope to run without it.


I never thought about Hawk to contact them. I will send them an email.

Thanks.

 

Eric, I send an email to Hawk. The guy replied back told me he doesn't know the correct size that I would need and said that Bruce knows the size and said that Bruce won't tell anyone???? I find that odd that he wouldn't tell anyone.

Do you know his email or how I can reach him?

Let me know thanks.

 

Try calling and ask for him.

Eric

 

PURPLEFORMULA; I am curious what is your front and rear lip size on your rims? Are your rims Chrome or Polished?

Do you have any pics?

Let me know thanks.