What Does Off-Set Mean? (Wheels)
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What Does Off-Set Mean? (Wheels)
My 72 Coupe has P255 60R15 tires. I want to buy wheels, but cannot figure out this off-set stuff. Will any of the American Racing wheels fit my car? :confused:
Thread Starter
Team Owner
Joined: Dec 1999
Posts: 26,555
Likes: 257
From: Florida
2021 C2 of the Year Finalist - Modified
C2 of the Year Finalist - Modified 2020
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St. Jude Donor '03 thru '26
Re: What Does Off-Set Mean? (pats406nitrovette)
Please tell me more! :)
Le Mans Master
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From: San Diego CA
Re: What Does Off-Set Mean? (OHSIXX)
Offset (as I understand it) is often confused with backspacing - both measure the same.
They both measure the location of the inside face of the mounting point on your wheel.
Backspacing locates this point from the inside edge of the rim (inside meaning that edge of the rim pointing into the car. If you have an 8" wide wheel - 4" backspacing would mean that the mounting location is in the exact center of the 8" width of the wheel (i.e. 4" from the inside face of the rim)
Offset measures from the Neutral point of the wheel (i.e. the center of the width...4" on a 8" whell 5" on a 10" and so forth) it is them measured in inches nagative (towards outside of car) and positive (inside of car) so a wheel with 0 offset has the mounting flange down the centerline of the wheel. 1/2" negative would mean 1/2" off the centerline towards the outside.
OK now the disclaimer...All this was described to me just the other day by the Ricer Driving son of a freind who works at Discount tire - So all this could be out the door - but it makes sense to me.
The big thing is that they both locate the bolting surface in relation to some point on the wheel.
They both measure the location of the inside face of the mounting point on your wheel.
Backspacing locates this point from the inside edge of the rim (inside meaning that edge of the rim pointing into the car. If you have an 8" wide wheel - 4" backspacing would mean that the mounting location is in the exact center of the 8" width of the wheel (i.e. 4" from the inside face of the rim)
Offset measures from the Neutral point of the wheel (i.e. the center of the width...4" on a 8" whell 5" on a 10" and so forth) it is them measured in inches nagative (towards outside of car) and positive (inside of car) so a wheel with 0 offset has the mounting flange down the centerline of the wheel. 1/2" negative would mean 1/2" off the centerline towards the outside.
OK now the disclaimer...All this was described to me just the other day by the Ricer Driving son of a freind who works at Discount tire - So all this could be out the door - but it makes sense to me.
The big thing is that they both locate the bolting surface in relation to some point on the wheel.
Melting Slicks
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From: The cure for the blues is eight cylinders roaring
Re: What Does Off-Set Mean? (OHSIXX)
The back spacing is the depth from the mounting surface of the wheel to the hub to the inside rim of the wheel. An 8in. wide wheel on a vette is 4in. backspace and I think you want to stay within a 1/4 in. of that.
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Le Mans Master
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From: San Diego CA
Re: What Does Off-Set Mean? (PrarieShark)
Fauxers just proved his point. :D
So there is a difference between Offset and Backspacing...they still measure the same thing. I suspect that offset didnt enter into the equation until Front wheel Drive became prevaleant but I have no proff of that.
So the Ricer was right - put that into your V8 and smoke it :lol:
I should have mentioned that little ricer kid drools over my vette, so he cant be half bad. :jester
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From: Orange Park Florida
Re: What Does Off-Set Mean? (OHSIXX)
Way I read the comments by the ricer kid is that he is correct to a point, but way I read the engineering tome on the topic, is to draw an imaginary line from center to top balljoint, through the center of the bottom ball joint with wheels straight ahead, and continue that down to the road surface....
it SHOULD be damn near the center of the tire tread.....
and when putting new wheels on the car, that's the point you do not want to change.....
now the rear point should be the centerline of the bearing hub as related to the center of the tire.....otherwise loading of hubs is stressing to the bearings....constantly, not just intermittantly as in when cornering....look at typical ricer with top inwards on the wheels to see what I mean....corners like mad, but totally unsafe condition , not to mention tire wear....
GENE
it SHOULD be damn near the center of the tire tread.....
and when putting new wheels on the car, that's the point you do not want to change.....
now the rear point should be the centerline of the bearing hub as related to the center of the tire.....otherwise loading of hubs is stressing to the bearings....constantly, not just intermittantly as in when cornering....look at typical ricer with top inwards on the wheels to see what I mean....corners like mad, but totally unsafe condition , not to mention tire wear....
GENE
Le Mans Master
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From: San Diego CA
Re: What Does Off-Set Mean? (mrvette)
Way I read the comments by the ricer kid is that he is correct to a point
But I think the method you have described is correct for SELECTING the correct offset, but your description does not DEFINE offset. (sorry for the caps - used to highlight - not shout)
Team Owner
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From: Orange Park Florida
Re: What Does Off-Set Mean? (fauxrs)
fauxrs, you could very well be right as the manual was very thick and full of equations I could never understand...'weak in math' is an understatement...anything further than electronic algebra is beyond me...
at any rate, I kept the same offsets with my new wheels as the old one's...
simple to figger with a bit of measuring and thought...keep centerline the same and rest is easy....
so for ME, on the rear of my '72 that meant only 3/4 inch PER SIDE was widest my car with stock t-arms would take....translate to 9.5 inch wheel...
and that required moving E-brake tab....I just used the same spacers in front....
GENE
at any rate, I kept the same offsets with my new wheels as the old one's...
simple to figger with a bit of measuring and thought...keep centerline the same and rest is easy....
so for ME, on the rear of my '72 that meant only 3/4 inch PER SIDE was widest my car with stock t-arms would take....translate to 9.5 inch wheel...
and that required moving E-brake tab....I just used the same spacers in front....
GENE
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Re: What Does Off-Set Mean? (OHSIXX)
OHSIXX.. Discount tire has the centerline wheels I'm getting.. 250/wheel the centerline thruster 806's I bet they can get the lexy or lasers around 300
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Re: What Does Off-Set Mean? (mrvette)
Way I read the comments by the ricer kid is that he is correct to a point, but way I read the engineering tome on the topic, is to draw an imaginary line from center to top balljoint, through the center of the bottom ball joint with wheels straight ahead, and continue that down to the road surface....
it SHOULD be damn near the center of the tire tread.....
and when putting new wheels on the car, that's the point you do not want to change.....
now the rear point should be the centerline of the bearing hub as related to the center of the tire.....otherwise loading of hubs is stressing to the bearings....constantly, not just intermittantly as in when cornering....look at typical ricer with top inwards on the wheels to see what I mean....corners like mad, but totally unsafe condition , not to mention tire wear....
GENE
it SHOULD be damn near the center of the tire tread.....
and when putting new wheels on the car, that's the point you do not want to change.....
now the rear point should be the centerline of the bearing hub as related to the center of the tire.....otherwise loading of hubs is stressing to the bearings....constantly, not just intermittantly as in when cornering....look at typical ricer with top inwards on the wheels to see what I mean....corners like mad, but totally unsafe condition , not to mention tire wear....
GENE
Significantly widening the track of a vehicle through messing with the wheel offset is a bad thing. I see ricers and I just want to cry for the poor bearings that are being stressed so much.
