Wheel back space/offset question
Thread Starter
Instructor
Joined: Mar 2002
Posts: 212
Likes: 0
From: Elko New Market MN
Wheel back space/offset question
Okay - looking at some AR wheels for my 75 and, paying close attention to back spacing. my logic would say that an 8" wheel with 4" back space would have 0 offset. Not so, some 8" wheels with 4" back space actually have a positve(+) or negative(-) offset. How can this be? If there is offset my logic tells me the back space on an 8" wheel can not be 4". Who can explain?
Burning Brakes
Joined: Sep 2002
Posts: 1,179
Likes: 3
From: SF East Bay CA
Re: Wheel back space/offset question (Bobbyg75)
What are you looking at? TTII's have a 4" offset, or 0 as you say.. NO PROBLEM calearing the calipers.
Do the math.l;. or you WILL be sorry
Do the math.l;. or you WILL be sorry
Senior Member since 1492
Joined: Aug 2000
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From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
Re: Wheel back space/offset question (timbo79)
On a 15 or 16 inch wheel, stick to a maximum of 4.125 inch back spacing.
More than that and the wheel may hit into the rear spring/parking brake cable bracket. I'm using 16 inch wheels w/4 inch BS. :chevy
More than that and the wheel may hit into the rear spring/parking brake cable bracket. I'm using 16 inch wheels w/4 inch BS. :chevy
Intermediate
Joined: Sep 2002
Posts: 33
Likes: 0
From: Lancaster PA
Re: Wheel back space/offset question (Bobbyg75)
The reason offset and backspace get so confusing is because wheel size (width) is measured from the inside of the wheel flange, but backspacing is measured from the outside of the flange. For a good illustration go to http://www.wheelsforless.com and click on the tech folder
Melting Slicks
Joined: Jun 2002
Posts: 2,842
Likes: 99
From: Orrtanna Pa.
Re: Wheel back space/offset question (1970 Stingray)
Take a look at the actual wheel before you buy if at all possible. I went with Welds and figured I could sqeeze 10" rims on the back with a 4 1/2" baskset.
Wrong!
The mounting flange was flat to the wheel center and hit the caliper.The outter rim edge was 1 1/2" past the fender lip. I had to return the rims,order 9" with 5 1/2" backset(Because they didn't make a 4 1/2" backset on a 9" rim) and then run 1 1/4" VB wheel adapters. The fit is perfect now,but I was fuming at the time. Nobody sells Welds but Summit,and I could not actually see the wheel before I ordered. The wheel specs do not reflect all the critical measurements that pertain to Vettes. This explains why most Vettes still run stock rims for sure. :banghead:
Wrong!
The mounting flange was flat to the wheel center and hit the caliper.The outter rim edge was 1 1/2" past the fender lip. I had to return the rims,order 9" with 5 1/2" backset(Because they didn't make a 4 1/2" backset on a 9" rim) and then run 1 1/4" VB wheel adapters. The fit is perfect now,but I was fuming at the time. Nobody sells Welds but Summit,and I could not actually see the wheel before I ordered. The wheel specs do not reflect all the critical measurements that pertain to Vettes. This explains why most Vettes still run stock rims for sure. :banghead:
Senior Member since 1492
Joined: Aug 2000
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From: Just because I'm paranoid doesn't mean people aren't out to get me...
St. Jude Donor '09
Re: Wheel back space/offset question (The Money Pit)
Backspacing is just one of the considerations for a wheel to clear the calipers. The shape and angle of the spokes or back of the wheel also comes into play. The Torque Thrust D's spokes curve in more from the center of the wheel to the rim than the TT2's. That's why the TTD's won't fit without a spacer or machining the back of the spokes. On the D's, the spokes hit the caliper.
Here's another related topic: http://forums.corvetteforum.com/zerothread?id=226531
Here's another related topic: http://forums.corvetteforum.com/zerothread?id=226531
