Reply to "Larger diameter wheels. Upgrading wheels and tires. Resizing wheels and tires. Modernizing wheels and tires. Campy clones, etc."

I have read this post multiple times and every time I get dizzy! I use to work with dimensions and rattling off reams of figures was the norm, but nothing as boggling as this.

I think I have begun to grasp the concept of wheel offsets, tire widths and possibility of scrubbing, but I just wanted to verify the few basics, please correct me if I am wrong

To me, offset is the value of a wheel I am interested in and to determine it, I can easily measure wheel width and backspace.
offset = backspace - wheel width/2.

The wheels bolt to the lug stud flanges and this width should be the starting point for any wheel evaluations. From online sources, I found the front track given as 57” with the OEM 7” Campy’s and their 0.25” offset. From this I gather the front flange to flange width would be 57.5”. Is this correct thinking?
Track = 57.5” - 2 X offset

Using the track and the tire sectional width, I can figure a tire outside width. For the OEM with 185s, that would be 64.3”.
Outside = Track + sectional/25.4

If correct in my thinking, I can use the flange width and the offset of the desired wheel to figure the new track. For example, in George’s post with the wheel table, he stated the 8” clone Campy’s had an offset of 0.86”, thus given a new track of 55.8”. With a 245 tire, one can expect rubs. This combo would have a width of 65.4” (or have the tire about 0.6” farther out than OEM combo). Going with the 9” clone and its 1” offset, the outside width would reduce to 65.1” and be OK.

My comparison of using the OEM 8” with their 0.75 offset reduces the track to 56” and with the OEM 225 tires had the outside width of only 64.9”.

So it appears to me that an outside tire width of less than 65.4” is the limit. I am still dreaming I’ll use the OEM wheels, but this implies that the BFGoodrich TA 215/60r15 93S for 7” I was considering might scrub with its outside width of 65.5”

(oh, I did make an excel sheet to do the crunching)

track_offset

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