Wheel Adapters and Backspacing

[Super Birthday Snake 11]

Hey,

 

Looking to get some Wheel Adapters for my 18" rims. These are 18x7.5 with a backspacing of 6"

 

So I understood that I would need about 1.5" backspacing to fit with the recommended backspacing of 4.5"

 

However, when measuring the back it seemed like it would be around 2" which I thought seemed a lot. Does this seem right? I also have a Heidts Mustang II front end if that would make any difference to the front?

[buening 63]

FWIW, you don't technically need spacers for the back for them to fit but you will not have the same track width in the rear as you would up front.

 

If it were me, I'd measure the distance from face of rotor hub to face of rotor hub on the front, and measure the same for the rear (use a nut tied to a string dangling below and measure between strings). Ideally you want a similar track width, so take the difference in your front and rear measurements and that will be approximately the difference in your wheel spacers. Unfortunately there isn't a single answer when you get into aftermarket suspensions. With stock, between 4.5 and 4.75" backspacing is ideal before you hit the UCA balljoint. With the Heidts, I don't know if the same concern is present (I assume it is). For the rear, typically the wheel tubs get in the way when you get to about 6.25" backspace. My rears are 6.8" backspace with 1/2" spacers, for a net backspace of 6.3"....but I had to use a hammer to clearance the wheelhouse. My wheels are also 10.5", so I need them to tuck in as much as possible. You likely won't want that much backspace since the wheels are narrower.

[Super Birthday Snake 11]

FWIW, you don't technically need spacers for the back for them to fit but you will not have the same track width in the rear as you would up front.

 

If it were me, I'd measure the distance from face of rotor hub to face of rotor hub on the front, and measure the same for the rear (use a nut tied to a string dangling below and measure between strings). Ideally you want a similar track width, so take the difference in your front and rear measurements and that will be approximately the difference in your wheel spacers. Unfortunately there isn't a single answer when you get into aftermarket suspensions. With stock, between 4.5 and 4.75" backspacing is ideal before you hit the UCA balljoint. With the Heidts, I don't know if the same concern is present (I assume it is). For the rear, typically the wheel tubs get in the way when you get to about 6.25" backspace. My rears are 6.8" backspace with 1/2" spacers, for a net backspace of 6.3"....but I had to use a hammer to clearance the wheelhouse. My wheels are also 10.5", so I need them to tuck in as much as possible. You likely won't want that much backspace since the wheels are narrower.

 

Thanks very much for that really helpful, particularly about the tracking as it's not something I'd thought of!

[mustangmike6996 34]

When you are checking for backspacing make sure the suspension has a load on it (IE jack it up from the control arm) If the wheels you have now have enough open space between the spoke you can do the tape measure/ plumb bob trick with ease

[buening 63]

Also check the widths from fender lip to fender lip as well as the quarters. I don't recall if there is a difference. You don't want the fronts close to the wheel lips and the rears sucked in. Its all a balancing act.

[Boogerschnot 12]

I read somewhere that you could just use a crap load of washers, space the wheel out to where it fits, then measure the thinkness of your washers.. Then you can order the spacer that you need.

 

I run 1.5 inch spacers on the front of my car with 17x8 mustang 05 GT wheels.. 1.25 on the rear. The 1.25 didnt have the wheel clearing the upper a arm.. but just barely. In my opinion the rear looks better with the 1.5 also, but I didnt feel like buying another set.

[buening 63]

I read somewhere that you could just use a crap load of washers, space the wheel out to where it fits, then measure the thinkness of your washers.. Then you can order the spacer that you need.

 

 

I did exactly that. It works fine for thinner spacers, but your wheel lugs are only so long and when you need thick spacers you eventually run out of whee lug length for the washers and wheel. Here is my thread with pics of the washer method I used on the rear (post #4):

 

www.1969stang.com/mustang/forum/showthread.php?t=9551

[Super Birthday Snake 11]

Thanks very much for the help guys, will give it a go over the weekend