ryanater

iTrader: (2)

I have a set of 17"x9.5" C5 Z06 replica wheels that I am installing on a '69 Camaro. I need to run spacers in order to get a 5.5" backspacing and I'm having trouble trying to figure out what size spacer to run.

The thing I don't understand is that the website shows that they are 9.5" wide, 54mm offset, and a 7.38" Backspacing. How is that possible?

If the wheel is 9.5" wide with a 0"/0mm offset, wouldn't the backspacing be 4.75"?

So if the offset is 54mm/2.125", wouldn't the backspacing be 6.875"? (4.75"+2.125")

I also measured the width of the wheel and it seems like it is actually over 10" in width.

redtan

iTrader: (5)

Sorry can't help with the other questions, but this is common for most if not all wheels.

Advertised width measurement it not actually from outer edge to outer edge, it's really from the beads inside. So all wheels will technically be wider than they are advertised as if you measure the entire width.

ryanater

iTrader: (2)

Ok so I assume that the backspacing does account for the entire width then? That would make sense. I measured the entire wheel to be about 10.5" wide.

So 10.5" wide with a 54mm/2.13" offset that would be exactly 7.38" backspacing. (10.5"/2)+2.13"=7.38"

crimson_bird

iTrader: (4)

backspacing is the distance from the hub mounting surface to the rear lip of the rim. lay the wheel on the ground, face down, and lay a straightedge across the top of the rim (not on the tire) and measure the distance from the mounting surface to the straightedge. this is the backspace.

offset is the distance from the hub mounting surface to the actual center of the wheel

no, because that advertised "9.5" is not the "overall rim width", it is the width BETWEEN the beads. the general rule is to measure the total rim width and then take off an inch, and that would be the advertised width. so you cant just divide the advertised width in half to get the backspacing on a 0 offset wheel.

if you want to find the actual overall rim width, subtract the offset from the backspacing (converted to mm), and then multiply that by 2, and then convert back to inches.

for your wheels...

backspacing = 7.38 inches = 187.45mm

offset = 54mm

187.45 - 54 = 133.45mm = 5.20 inches

5.2 x 2 = 10.4 inches (overall rim width)

9.5" (rim width between the beads)


Its a lot easier to do this stuff converting everything to metric.


backspacing = 7.38 inches = 187.45mm

backspacing you need = 5.5 inches = 139.70mm

187.45 - 139.7 = 47.75mm = 1.86 inches

adapter/spacer you need = 47.75mm = 1.86 inches

I highly recommend www.motorsport-tech.com for custom adapters. they'll make one up in that exact size, both hub centric (made to fit snug with the hub mount) and also wheel-centric (to fit snug with the wheels). Essentially none of the cheap spacers/adapters will offer these things for your specific needs, and those universal style adapters are what give people issues. spend the extra money and get the proper stuff!



pic for reference

ryanater

iTrader: (2)

Thanks for all of the info!