Wheel Back Space For A 1970 Mercury Cougar

I am thinking of replacing the wheels and tires on my '70 Cougar. Drum brakes all around and stock suspension, although it does have traction bars on the rear. Currently it has 14 inch wheels (P225 70 R14) on plain Ford wheels with Eliminator center caps and beauty rings.

I plan on going with 15" x 7" for the front and 15" x 8" in the rear. I have been told 3.75 backspace for the front and anywhere from 3.75 to 4.50 backspace for the rear.

Short of actually going in and doing the measurements myself in a few more weeks when the snow all melts, do YOU guys have any recommendations for back spacing in my car?

Thanks,

Steve  
Member of COUGAR CLUB OF NEW ENGLAND (#25) www.necougarclub.com
Member of DODGE TRUCK WORLD (Maine Chapter) http://dodgetruckworld.tenmagazines....ry.asp?id=4871

2006 Ford Mustang
1970 Mercury Cougar (19,300 miles )
2003 Dodge Ram 4x4 Quadcab
1994 S-10 Blazer Tahoe
1968 Mercury Cougar DGS (Parting Out)

Retired Navy (Submarine Service) E-7 MMC(SS)
USS Simon Bolivar SSBN-641 (B)
USS Henry M. Jackson SSBN-730 (B)
USS Gurnard SSN-662

Shipfitter @ Bath Iron Works in Bath, Maine. Building Aegis class destroye

Since a 70 Mustang and a 70 Cougar are related enough for the rear housings to swap, I'd think that - depending on the tire you choose - 4 to 4.5" will be what you end up with.  If you run a fairly fat tire like a 295-50 or so on the back, then 4.5.  If you use just a tall 60 series type tire, then 4" should be fine.  That's my 1/50th of a buck on that  
1967 Falcon 4 door 351C-4V
1970 Mustang 351C-2V
http://raceabilene.com/kelly/hotrod
Owner built, owner abused.

Thanks Falcon67.

I have yet to decide on the rims. I am pretty partial to AR Torq Thrust II's, then distant second are Cragar S/S's, AR 200s (Daisys), generic 5 spokes, Supremes.

I want to fill out the wheel wells in the car. That is the goal. I know I can get by with 15 x 7's in the front, possibly 15 x 8's, but I don't want to create any rubbing or steering issues. For the rear, at least 15 x 8's, maybe even 15 x 10's if they will fit without clearance rubbing issues.

Another reason for me to get out and do the measurements myself. I just have to wait for the weather to warm up and the rest of the snow to melt. I am sure that you do not have those issues down in Abilene. Lucky!!!

Thanks again,

Steve  
Member of COUGAR CLUB OF NEW ENGLAND (#25) www.necougarclub.com
Member of DODGE TRUCK WORLD (Maine Chapter) http://dodgetruckworld.tenmagazines....ry.asp?id=4871

2006 Ford Mustang
1970 Mercury Cougar (19,300 miles )
2003 Dodge Ram 4x4 Quadcab
1994 S-10 Blazer Tahoe
1968 Mercury Cougar DGS (Parting Out)

Retired Navy (Submarine Service) E-7 MMC(SS)
USS Simon Bolivar SSBN-641 (B)
USS Henry M. Jackson SSBN-730 (B)
USS Gurnard SSN-662

Shipfitter @ Bath Iron Works in Bath, Maine. Building Aegis class destroye

Today - no issues.  83F and sunny.  Tomorrow - issues.  10~12" snow to the north - maybe as close as a county to us, high only mid 40s, wind NW at 35 gusting to 40+.  Race day Saturday, maybe 60.  Nice on Sunday - go figure.  But I'll not trade you  

Note that the wider the wheel, the more the section width will be on a given tire.  Read the specs carefully and try to get the rim size the mfg uses for stating the dimensions.  Pay particular attention to the section width because that's where you'll get the rub.  On the Falcon I use MT #3055 28-10.5 x 15 MT which are 28" diameter, 11.7 section with a 10" tread.  The measuring rim is stated as 10".  To fit the tire, I had to roll the fender lips and mash the ends of the rocker panels.  ( the older 28's were really 27ish and cleared the rockers, MT must have redone the molds in 2006 ) These are run on a 15 x 8 x 4.5" back space wheel to clear. The slicks just skim the leaf springs with a 1/8" spacer behind the wheel.  The tires leave rubber on the leading edge of the fender well when they swell on the top end.  I really should be running them on a 9" or 10" rim, but the increased section would cause me to do some more hammer work LOL.  

The exact same tire on the 70 Mustang with the same wheel dimensions clears the springs by an inch and there are no issues with the fenders or rockers.  Plenty of clearance.  The tire does not tuck up in the fenders on that car like it does some on the Falcon, so there is a difference there.  
1967 Falcon 4 door 351C-4V
1970 Mustang 351C-2V
http://raceabilene.com/kelly/hotrod
Owner built, owner abused.