workout out wheel offset?

[kurbn]

I have searched 3 times and I am sure there used to be a thread about how to do this but I am unable to find it.. the closest thing is a picture that says

A measurement - B measurement = offset and I keep getting a weird number

Rear measurement to a straight peice of dowl I am using across the top of the rim is 163mm

Front side of the rim measurement is 74mm.

A - B = 89mm/3.5"

I buffed back the powdercoat off the back of my rims to have a look and I can read the 17x9 embossed into the rim, but the stamp is not clear, seems sandblasting has taken most of it away, I can see what looks like 3 / not sure if that's a 31 or a 37.

rather confused haha

[mitchy]

check the other rim?

89 is NOT right. 17x9 +37 was a common size for P1's

[kurbn]

one rim I can make out 3 and half a stroke and that is it, and the other rim I can make out a 3 and a / so could either be a 31 or a 37

how do you measure them mitchy? this is what I am doing

1 - Lay rim on its face
2 - run a long dowl along the top of the rim inc the lip
3 - measure from the base of the dowl through the centre hole of the rim but measuring align with the flat section bolts against the hub

and flipping the rim on its back and measuring the front the same way, but measuring it to the flat section where your wheel nuts go on instead of going right through to the rear where it bolts up... hope that makes sense. Must be doing something wrong.

[iluv2moan]

measure the total width of the rim then half that value

measure the distance from the hub face to the back of the rim

subtract the two values

[mitchy]

then take the front measurement from the rear measurement, and divide by 2, so you end up with 45mm.

rims are actually measured from inside the bead, not the outside, so as a rough guess i'd go with 17x9 +37, as thats the closest.

[kurbn]

measure the total width of the rim then half that value

measure the distance from the hub face to the back of the rim

subtract the two values

total width of the rim is 9" aka 229mm = 114.5
hub face to back of rim 158 if you remove the lip measurement
= -43.5

:S

seeing my rim is stamped with a 3 and a slash, I am going just pray they did not make a 31 or 39 lol, guards needed a little bit of a lip fold slightly to run the 235's on the back with -3 camber..

when you say rims are measured from the inside of the bead, do you mean the start of the inside of the rim where the tyre is pressed up against the lip? as the backside of the rim has quite a larger bead sealing area than the front of the rim

[reNEGade]

Don't you measure the wheel from the inside of the lip where the tyre sits to the other side of the lip across the wheel. Then measure the distance to the where the hub sits in one way and the measure the distance the other way.
So then you have a 9 inch wheel with 37mm offset from center of the wheel.
http://www.rx7.org/Robinette/images/wheel_offset.gif

[mitchy]

total width of the rim is 9" aka 229mm = 114.5
hub face to back of rim 158 if you remove the lip measurement
= -43.5

:S

seeing my rim is stamped with a 3 and a slash, I am going just pray they did not make a 31 or 39 lol, guards needed a little bit of a lip fold slightly to run the 235's on the back with -3 camber..

when you say rims are measured from the inside of the bead, do you mean the start of the inside of the rim where the tyre is pressed up against the lip? as the backside of the rim has quite a larger bead sealing area than the front of the rim

yup.. like my 18x10's were about 11.5" wide overall

that larger rear lip would account for the extra ~5mm you get too.

9 +37 was a pretty common size with P1's, go compare them with kims (my old rims) if you want to be sure, they were definately 17x9 +37 on the rear, so should measure up the same if you do it overall.

[kurbn]

cool, thanks a lot for your help mitchy :)

Just wanted to make sure I do not order a rim in the wrong offset

[Milhouse]

be sure the other wheels havent been repaired in teh past aswell, otherwise ordering one wheel might be a waste of time

[kurbn]

the wheel that cracked is the only one with any curb damage, other ones are spotless, the backside of the rim had hit a curb as well at some point as some of the lip was missing on the back.. so should just be an issue with that rim.

[mitchy]

be sure the other wheels havent been repaired in teh past aswell, otherwise ordering one wheel might be a waste of time

surprised you'd even look in a thread, let alone reply, where such high offsets are involved. :p

[Milhouse]

someones gotta help the less fortunate. think of me as the jesus of wheels :D

[mitchy]

i dont think anyone with rims under 10" wide can even THINK about calling themselves the jesus of wheels. :p

take your pizza cutters elsewhere!