Tell me that I'm crazy and I'll agree. The Fiat was built for 13 inch wheels 10 inches wide. They had 6 inches of backspacing so that puts me at -25ET correct? It was built for 20 inch tall tires front and 23 inch tall tires rear. My thought is it needs to be be raised for the street anyway so how about go to 23 inch tall tires front and 26 inch tall rear? That leads me to thinking 15 inch rim front and 17 inch rear. I can't find anything that works. Some Rota's are like -15 or -20 but can't find the same wheel in 15 inch and 17 inch. Most wheels aren't even offered in negative offset. Any thoughts?
Care to share more details or a link to this Fiat project? Because all of these wheel specs do sound crazy, but maybe I'm missing something.
I might do something like call the guys at Diamond Racing Wheels and see what they can put together for you, since they do a lot of low offset circle track stuff and build it all in house they would probably be able to come up with something for you. They can do as small as 13" and as big as 16", and you could always mix and match tire sizes to complete the difference too.
Otherwise I would probably be looking more at like the Jegs/Summit type vendors as opposed to the import-oriented Rota type manufacturers, since low/negative offset is a lot more common on old domestic stuff.
dps214
SuperDork
11/16/23 8:35 p.m.
10" width with 6" backspacing makes +25 offset, not -25.
In reply to dps214 :
Well Harold says setback and -1 inch from centerline. I should ask ojannen to measure for me. I have Miata wheels on it right now. I should see how lock to lock goes and I know the rears could come out more.
The wheels I'm using on my corolla are 15x10,approximately 12mm offset, Bassetts. 23" tires are plentiful, just use usual Miata stuff. When Harold says "setback" was he measuring from the front or the back? Bassett makes the 10" wheels with backspacing from 1", up to 6" on their website, but mine are more than that (I think). I'll try and measure tomorrow or Saturday.
dps214
SuperDork
11/16/23 10:36 p.m.
Stampie said:
In reply to dps214 :
Well Harold says setback and -1 inch from centerline. I should ask ojannen to measure for me. I have Miata wheels on it right now. I should see how lock to lock goes and I know the rears could come out more.
Okay yes, what's on the spec sheet does come out to -25mm, I didn't look at that originally.
For reference backspacing is measured from the backside of the wheel, so what you described in your original post would be +25.
Second Bassett, they were one of the few places with negative offset for my Europa. I think they look decent too
Yeah double check the actual measurements then start searching. Here is a helpful link.
https://www.discounttire.com/learn/offset-backspace
Double-double check the 10" wide especially if it was a dimension given by a guy who measures wheels backward as evident by the information provided so far. 10" wide outside to outside is usually a 9" or 9.5" wide rim since rim width is measured as minimum dimension inside lip to inside lip (bead seat to bead seat).
Remember that offset is the distance of the hub mounting face relative to tire mounting face centerline, a 0 offset wheel has the hub mounting face right at tire centerline. Negative offset is closer to the rear of the wheel, positive offset is closer to the face of the wheel.
Backspace measurements are from the rearmost surface of the wheel to the hub face, so its best to stick with backface for all measurements or offset for all measurements unless you have the wheel with the tire dismounted and can figure out the width of the rim lips, especially if you are really down to the last mm for fitment.
