question about wheels. plz help.
Thread Starter
Cruising
Joined: Jul 2012
Posts: 11
Likes: 0
question about wheels. plz help.
i have a chance to buy some rims that are 18x8 with 4.5 backspacing all the way around. will this create any problems with clearance any where? Hope this set works i am getting a really good deal on these. Any help please. Thank you
Pro
Joined: Aug 2010
Posts: 698
Likes: 8
From: Stockholm Sweden
The stock 8x15" ralley wheels have 0 offset = 4" backspacing.
I run 9x16" with 0 offset = 4,5" backspacing and it works fine but i had to move the bracket for the parking brake wire from the outside to the top of the trailingarm.
//Ricky.
I run 9x16" with 0 offset = 4,5" backspacing and it works fine but i had to move the bracket for the parking brake wire from the outside to the top of the trailingarm.
//Ricky.
Le Mans Master
Joined: Oct 2010
Posts: 6,936
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From: melbourne florida
2023 C3 of the Year Finalist - Modified
Melting Slicks
Joined: Jan 2004
Posts: 3,247
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From: Detroit MI
9" wheel with 0 offset = 5" backspace because the wheel is about 10" overall width. 9" wheel with 4.5" backspace is -12 mm offset.
This link has a handy table for converting backspace and offset:
https://rsracing.com/tech-wheel.html#backspace
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Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
Not exactly. Wheel offset is calculated using the overall width of the wheel, which is usually about 1" wider than the advertised width. An 8" wheel is really about 9" wide overall from inner flange to outer flange(advertised widths are measured between the bead seats). 0 offset of an 8" wheel is 4.5" backspace, and stock rally wheels with 4" backspace are -12mm offset.
9" wheel with 0 offset = 5" backspace because the wheel is about 10" overall width. 9" wheel with 4.5" backspace is -12 mm offset.
This link has a handy table for converting backspace and offset:
https://rsracing.com/tech-wheel.html#backspace
9" wheel with 0 offset = 5" backspace because the wheel is about 10" overall width. 9" wheel with 4.5" backspace is -12 mm offset.
This link has a handy table for converting backspace and offset:
https://rsracing.com/tech-wheel.html#backspace
Scott
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
One of our sons is a CNC machinist, so I had him make me a set of 3/8" spacers with an integrated hub centric adapter ring. (Original Corvette wheels are hub centric and after market wheels are lug centric. Adapters make after market wheels hub centric.)
No more rubbing, and the wheels come out to just about where the original wheels were in the wheel well. BTW, I chose 3/8" thick spacers instead of the full 1/2" difference so I wouldn't have to replace the original lugs with longers lugs.
Burning Brakes
Joined: Mar 2011
Posts: 969
Likes: 1
From: NJ
I have 18x18 wheels with 4.5" backspacing and 255/45-18 tires on my '80. I had very minor rubbing at full lock.
One of our sons is a CNC machinist, so I had him make me a set of 3/8" spacers with an integrated hub centric adapter ring. (Original Corvette wheels are hub centric and after market wheels are lug centric. Adapters make after market wheels hub centric.)
No more rubbing, and the wheels come out to just about where the original wheels were in the wheel well. BTW, I chose 3/8" thick spacers instead of the full 1/2" difference so I wouldn't have to replace the original lugs with longers lugs.
One of our sons is a CNC machinist, so I had him make me a set of 3/8" spacers with an integrated hub centric adapter ring. (Original Corvette wheels are hub centric and after market wheels are lug centric. Adapters make after market wheels hub centric.)
No more rubbing, and the wheels come out to just about where the original wheels were in the wheel well. BTW, I chose 3/8" thick spacers instead of the full 1/2" difference so I wouldn't have to replace the original lugs with longers lugs.
Pro
Joined: Aug 2010
Posts: 698
Likes: 8
From: Stockholm Sweden
Not exactly. Wheel offset is calculated using the overall width of the wheel, which is usually about 1" wider than the advertised width. An 8" wheel is really about 9" wide overall from inner flange to outer flange(advertised widths are measured between the bead seats). 0 offset of an 8" wheel is 4.5" backspace, and stock rally wheels with 4" backspace are -12mm offset.
9" wheel with 0 offset = 5" backspace because the wheel is about 10" overall width. 9" wheel with 4.5" backspace is -12 mm offset.
This link has a handy table for converting backspace and offset:
https://rsracing.com/tech-wheel.html#backspace
9" wheel with 0 offset = 5" backspace because the wheel is about 10" overall width. 9" wheel with 4.5" backspace is -12 mm offset.
This link has a handy table for converting backspace and offset:
https://rsracing.com/tech-wheel.html#backspace
I measure my wheels from the inner surface of the center and to the inboard flange and to the outboard flange. If these measures are the same the wheel has a 0 offset.
One offcourse also need to consider the tyre bulking out outside the rim with a posability of rubbing the trailingarm.
Last edited by RickyBerg; Nov 30, 2012 at 10:22 AM.
Instructor
Joined: Aug 2012
Posts: 146
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From: Arlington VA
Need spacers too
Agreed - would be interested in that as well.
Pro
Joined: Dec 2006
Posts: 695
Likes: 5
From: tx
72blkstingray: measure twice and then measure once more. Don't take anything for granted as these cars can be slightly different car-2-car. Also consider the tire sidewall sticking out past the wheel lip. The measurements for most tires can be found on the manufacturer web site(s). This is all simple math - just take your time and measure properly. Here is a link to a web site showing how to measure BS:
http://www.vintagewheelworks.com/tech-backspace.php
Gary
http://www.vintagewheelworks.com/tech-backspace.php
Gary
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
Yes, he will make more. He can make 1/2" spacers too if you have longer lugs than stock or you are willing to take a chance with stock lugs and less than the lug diameter in threads inside the nut.
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
72blkstingray: measure twice and then measure once more. Don't take anything for granted as these cars can be slightly different car-2-car. Also consider the tire sidewall sticking out past the wheel lip. The measurements for most tires can be found on the manufacturer web site(s). This is all simple math - just take your time and measure properly. Here is a link to a web site showing how to measure BS:
http://www.vintagewheelworks.com/tech-backspace.php
Gary
http://www.vintagewheelworks.com/tech-backspace.php
Gary
We have dimensions to fit BOSS 338 and TT2 wheels now. He can make adapters-only (if you don't need a spacer but want hub centric) or spacer-adapters for other brands if you have the specs.
A CF member who bought the first set for TT2 had a little difficulty getting them on the front hubs and had to dress the front hugs. C3 front and rear hubs have slightly different diameters.
Anyone measuring a different wheel needs to remember that machinists work 3 places to the right of the decimal point. Cast hubs are not very precise. The fit of these adapters or spacer-adapters are at least as precise as stock wheels on the hubs.
Race Director
Joined: Jan 2007
Posts: 14,948
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From: NYC NY
