et confusion

Post by **2088 bob** » Sun Mar 05, 2006 4:56 am

looking for a little help here i would like to buy some new wheels
the wheels are 17x9 45et so 0et on this wheel would be 4 1/2 " correct so 45 et means the hub mounting flange on the wheel moves toward the front or the rear face so if 45 et means the hub mtding moves towards the front of the wheel then this means 4 1/2" + 45mm(which =approx 1 13/16") so if i lay a straight edge across the back of the wheel i should come up with

4 1/2 + 1 13/16 = 6 5/16" back spacing or to put it another way if i lay a straight edge across back of the wheel and measure to the hub mtding surface my measurement should be approx 6 5/16"

do i have this right or is it the other way around to make a really dumb statement is -45et the opposite then
i have allways bought previous wheels by inches of backspacing
regards 2088bob
i know that this has been covered before but i have never given it much thought until now and when you are used to buying wheels at jegs and summit racing the et thing never comes up

Chris V · Post by **Chris V** » Sun Mar 05, 2006 6:48 am

ET is derived from a wheel's advertised width - a measurement from bead-to-bead.

Backspace takes into account the material beyond the bead.

Follow? A steel wheel advertised 5.5" is usually 6.5" wide...an alloy rim is usually ~5/8" wider than the advertised width.

Your 17x9 is really ~9.625 wide so the backspace would measure more like 6-9/16"

You’re correct about positive and negative offset.

Post by **2088 bob** » Sun Mar 05, 2006 12:22 pm

thanks chris