Please Double-Check My Offset Math...

[iloveredmeat]

Oh my gosh, this seems like it should be so simple... but the internet confounds...

I'm trying to calculate the offset on my Revolution wheels.

A quick google yields this method:

1. Measure total width, bead to bead. Cinchy.
2. Divide that measurement by 2 to find the centerline value. Easy peasy.
3. Measure the backspace - the distance from the inside lip of the bead to the mounting face of the rim. No probs.
4. Subtract the centerline value from the backspace value, and that is your offset. Positive or negative. Positive means the wheel is closer to the center of the car.

Correct?

But, if I plug my info into various 'online calculators', I get wildly different results.

So different, in fact, that I no longer believe everything I read on the internet.

Here is what I scribbled on my chalkboard:

Total width = 6.875 in

6.875 in / 2 = 3.4375 in = center point

Backspacing = 4 in

4 in - 3.4375 in = .5625 in

.5625 in = 14.25 mm

14.25 mm offset, right?

And if it is 14-ish mm, these wheels should work just fine, yes?

Thank you,
Peter

roadster wheel width.jpg

roadster wheel backspace.jpg

Anthrocite Revolutions.jpeg

Silver Revolutions.jpeg

[Pjackb]

Peter measurements are correct, offsets is probably sold as +15

And these specs would be what I consider perfect fit for a 67.5 running a 195/65/14 tire size
However since you will be running a custom lowered suspension and will have a LOT of power I would highly recommend getting 195/60/14 Falken Azenis tires , they fat and sticky and a perfect California tire in my opinion.

These pictures are same specs wheels with 195/60/14s





Finally you can use this calculator to check how different wheel size and offsets will interact
https://tiresize.com/wheel-offset-calculator/

[iloveredmeat]

Awesome! Thanks Jacques!

I love the look of yours, and I searched through the Gallery of Wheels, and I really like the look of a 60 aspect ratio, so I will take your advice and look into those tires.

I bought those two sets of Revolution wheels with a teeny bit of uncertainty on whether or not they would fit a Roadster. I bought one set for me and the other for my brother's 510, but he just sold that... and then I bought the libre styles wheels as a backup and because I love them... so, including my stock steelies, I now have 4 sets of wheels.

And I'm good enough at math to know that's too many.

Looks like I will be selling some wheels soon.

Thanks again.

[Bwk2000]

… Looks like I will be selling some wheels soon …

I love those libre wheels of yours (previously posted) … shipping & duty would kill me though

[iloveredmeat]

… Looks like I will be selling some wheels soon …

I love those libre wheels of yours (previously posted) … shipping & duty would kill me though

Hey Kai,

I love 'em too, and at some point, I'm going to have to decide between the grey Revolutions and the Libre styles...

And even then, if I do run the Revolutions, I'll be reluctant to sell the Libres. A lot of pride and elbow grease in those beauties.

If the time does come to sell, I always hope the stuff I work on finds a good home, so we'll at least try to find a way.

You do have giant Bluefin Tuna up there, right?

[Bwk2000]

… You do have giant Bluefin Tuna up there, right?

Lol … Oh ya! Including the largest one ever caught.

[Pjackb]

so, including my stock steelies, I now have 4 sets of wheels.

And I'm good enough at math to know that's too many.

Presently I’m at 8 sets Never too many

Looks like I will be selling some wheels soon.

Thanks again.

I’ll take first refusal on the Revolutions

[iloveredmeat]

so, including my stock steelies, I now have 4 sets of wheels.

And I'm good enough at math to know that's too many.

Presently I’m at 8 sets Never too many

Looks like I will be selling some wheels soon.

Thanks again.

I’ll take first refusal on the Revolutions

8???!!!

Would I be enabling your addiction if I sell you the silver Revolutions??? You can't tell your wife it was me...