Backspacing Actual Width vs Stated Width

[ADiCarlo]

Hi Guys,

When backspacing is measured it's take from the actual width of the wheel not the stated correct?

So a 10 inch wheels center line would be 5.5 instead of 5 to account for the added 1 inch difference between stated and actual.

I'm trying to work with some European wheels that use offset so to calculate the backspacing i'm taking the stated size + 1 inch (for actual) /2 + the mm offset converted into inches.

Also whats the maximum recommended spacer to run on the front wheels?

[SWAPMEETCRAZY]

Simply, it is the distance from back of center wheel hub to back edge of wheel...here's a good diagram....jim

http://www.google.com/imgres?imgurl=http://www.sizeitup.com/images/wheel_offset_diagram.gif&imgrefurl=http://www.sizeitup.com/tech-center.html&h=670&w=600&sz=16&tbnid=k_ZsCbpCA0dH-M:&tbnh=136&tbnw=122&zoom=1&usg=__SojQZum1rcc6SSASJB6Ys0EGn3Y=&docid=boB_RD8fd7xYZM&sa=X&ei=fdSfUqyYHeSj2QXwpIDAAQ&ved=0CEEQ9QEwAQ

[Apogee]

...Also whats the maximum recommended spacer to run on the front wheels?

Most people wouldn't recommend running a spacer, however considering that a slip on rotor is generall 1/4" to 3/8" through the hat, it would stand to reason that anything 1/2" or less properly designed and installed shouldn't create any problems. Avoid the cheap die-cast aluminum spacers as they're prone to failing, usually when you really can't afford for them to fail. Stick with quality 6061 or 7075 spacers and all should be well.

FWIW, I have a friend who runs 1.4" loose spacers on a 4200# car with no issues for several years and many 10's of thousands of miles, however they're hub-centric with ~.002" slip fit and he runs M14 wheel studs torqued to 135 ft-lb. The spacers themselves also have reliefs around the wheel studs holes to maintain as even a stress concentration between the spacer and hub/rotor as possible, minimizing the chance to lose lug nut preload/torque due to localized material failure around the stud, something relatively common with inexpensive bolt-on type wheel adapters.

In general, for any spacer at or over 1" thick, 7/8" if you can fit the lug nuts on the inner pattern, I would be looking at a bolt-on type adapter/spacer.

Tobin
KORE3

[ADiCarlo]

Thanks guys!

From my calculations a 10 inch wheel with 25mm offset equals a backspace of 6.484 and when using tru-turn the recommended backspacing is 5.75 but I've read that 6 1/4 will also work.

I think with the 10 inch wheel and the 25mm offset I should get away with less 1/4 spacer to hit below the 6 1/4 sizing.

This is based upon a 10/2 = 5 + .5 for actual width and 25mm equaling .984 inches.

yay math! :waveflag:

[Forgeline Wheel]

When backspacing is measured it's take from the actual width of the wheel not the stated correct?

So a 10 inch wheels center line would be 5.5 instead of 5 to account for the added 1 inch difference between stated and actual.


That is correct. Here is Dave explaining it:
2K1lUlv9ZOA#t=12

[ADiCarlo]

That is correct. Here is Dave explaining it:
2K1lUlv9ZOA#t=12

Awesome - thanks for confirming.

I saw the video but when trying to calculate backspacing off of offset I wasn't sure which one to use.

[Forgeline Wheel]

Awesome - thanks for confirming.

I saw the video but when trying to calculate backspacing off of offset I wasn't sure which one to use.

Well in this case, it is an 11 inch wheel with a total width of 12 inches. So the center of the wheel is 6 inches as measured from the outermost edge.

The backspace on this wheel was 6.5 inches, which means that the center of the wheel is 0.5 inches inboard of the hub mounting surface. Hence 0.5 inch offset. Converted to mm is 0.5in * 25.4mm/in = 12.7mm.