rim size and offset for newport

swisherred

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just checking...someone has a nice set of rims that are 8" wide with a 3" offset...will that fit my 67 newport with the skirts?
 
I was able to fit 18x8 with 4.5" backspace and 0 offset on my 68.
 
I'm rather confused on measuring this stuff...don't understand the difference between backspace and offset. Measuring from the back of the rim to the mounting flats is 3" on an 8" rim.
 
I'm rather confused on measuring this stuff...don't understand the difference between backspace and offset. Measuring from the back of the rim to the mounting flats is 3" on an 8" rim.
Offset/backspace difference

wheel-offset-backspacing.jpg
 
In the modern world, worry about "Backspacing" more than "Offset", from what I've seen.

When the "backspacing" orientation started, back in the '70s I believe, I was against that as "offset" was a more engineering-based measurement which would relate to wheel bearing loading issues. As "offset" would relate to the centerline of the wheel to where the wheel bearings were located in the mix of things. Positive offset would put more loadings on the bearings, due to the greater leverage involved . . . which seemed to matter on VWs with "chrome reverse" wheels on them. "Backspacing" means you can move the mounting flange around inside of the rim width to place the tire where it will fit under what you want it to fit. BTAIM

CBODY67
 
There's a pretty lengthy thread somewhere on this site all about the different wheels that guys are using on their C bodies. Maybe someone can post a link to it.

Jeff
 
Anyone know the stock specs for comparison?

There's probably something somewhere. Here's what I have on my '67 Newport. 14x6.5" Chrysler station wagon wheels. P245/70R-14 BFG Advantage T/A whitewalls (which were NOS when I bought them in the earlier '80s from Coker). On the left side, I can remove the fender skirts and use a normal scrub brush to do the whitewalls with about 1/8" clearance. On the rh side, it barely clears to do that. With the stock 8.55x14 Goodyears (stock 14x5.5 wheels) or the P225/75R-14 Kelly-Springfield radials I first put on it after I got it, it was close, but not that close. With the BFGs, there is, maybe, 1/2" clearance between the inner sidewalls and the leaf spring. The two "hard points" will be the leaf springs and the quarter panel inner wheelhouse.

What I plan to ultimately put on it are the repro Magnum 500s in 15x7 and 4.25" backspacing. But 4" backspacing might work, too?

Just some thoughts,
CBODY67
 
In the modern world, worry about "Backspacing" more than "Offset", from what I've seen.

When the "backspacing" orientation started, back in the '70s I believe, I was against that as "offset" was a more engineering-based measurement which would relate to wheel bearing loading issues. As "offset" would relate to the centerline of the wheel to where the wheel bearings were located in the mix of things. Positive offset would put more loadings on the bearings, due to the greater leverage involved . . . which seemed to matter on VWs with "chrome reverse" wheels on them. "Backspacing" means you can move the mounting flange around inside of the rim width to place the tire where it will fit under what you want it to fit. BTAIM

CBODY67

Thank you for the explanation. I've been wondering what all the talk about backspacing and offset was all about. When I got the reverse chrome wheels and then replaced them with the Magnum 500 repros I just went to the tire shop, ordered them, they put them on, and I never had a problem with anything rubbing anywhere. So I am wondering if any competent tire shop will already know what needs to be done?
 
Just put 17x7 front, 17x8 rear on my 66 Polara. ZERO offset. The standard size recommended by American Racing.

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The goal is to not have the tire rub against the inner wheel tub or the leaf spring. I removed the wheel and using a straight edge measured the distance to the spring and to the wheel opening.
Using those measurements and 300rag's drawing you can figure out max rim width and offset. Remember the tire is wider than the rim in most situations. Go at least one inch less than the spring to wheel opening distance. You need to make a drawing and check the math to make sure it will work or you will have an expensive mess on your hands. Start with your measurements. The mounting point on the drum is zero, mark the distances to the spring and wheel opening and subtract at least 3/4" on each side to be safe. The total distance is max rim width. The mounting flange to spring distance is back spacing, the other is front spacing. Offset is the distance from mounting flange to rim center. Negative moves the tire outward, positive inward.
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Front wheels are more complicated since they turn. If you max out the rear wheel width you need to make the front narrower. At least 2-3 inches or they will rub the inner fender when turning and hitting bumps.
 
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