need back spacing on 18X9 fronts and 19X12 rears

[sixty-niner]

I have 18X9 and 19X12s.  tires are 275 40r18 and 345 35r19  the company I bought the rims from measured my car and did the back spacing but when I put the wheels on I could not even turn it cuz of the rub on the bottom outside .  Gonna have to re-due it and not looking forward to that but since the company measured it I should not be charged anything.  Just want to know what backspacing to tell them.  I know there are people who have put on 9 inch wide rims on the front without problems,
Anyone have any clue on the fronts?? I did a mini tubb and relocated the springs for clearance in the rear
for now I have factory discs in the front.
ant ideas?

[sixty-niner]

I need some backspacing help.  I have 18X9s with 275 40 r18 tires in front.  what should the back spacing be?  also I have stock discs

thanks need help

[randy73]

What car?

[sixty-niner]

a 69 charger

[WHITE AND RED 69]

for the front it should be 5" or 0 offset. I run a 8" wide front with 4.75" and it has plenty of room.   

[Kern Dog]

My 70 has 18x9 front wheels with 4 7/8 backspacing. SAME size tire as you have. My fender hangs over the tire nicely and only rubs during one scenario: Backing up while turning, and then only when rolling off of a curb. Wierd.
The rear on my car are 18x10 with the same 4 7/8 B.S. the tires are 295 45 18. they cleared fine when the ride height was taller, but in the current height, they rubbed the OUTER wheel house. My wheelwells are totally stock. I have a narrowed C body 8 3/4 in the car, since it was cheaper to buy and narrow the housing than it was to buy new rims. To fit my rims in the car with a stock 68-70 B housing, I'd need at least 6" of backspacing.

[sixty-niner]

really?  now I am worried.  the rims have 5 inches of back spacing and rub like crazy!!  unless I am measuring wrong.  the thing isnt even lowered yet.

[v21hemicharger]

I have 18 x 9 on mine with 4 1/2 inch backspacing.  I do have wilwood hubs on it.  This is the only way to measure in my opinion.

[sixty-niner]

its the offset.  I have a negative .25 offset or an inch.  so I think I will need to get that to 0  I think.   

[Kern Dog]

its the offset.  I have a negative .25 offset or an inch.  so I think I will need to get that to 0  I think.   

Your method of measurement differs from what I have used. I see that to YOU, "offset" is in reference to the where the center of the wheel is?
The backspacing method makes far more sense to me. It allows the user to measure to what will most likely pose a problem...Suspension components. I also use my own method of FRONTspacing to determine clearance around the body.
In all cases, a wheel will be wider than advertised, since the measurement is taken at the inside bead of the wheel. On Steel wheels, the actual width is often 3/4 inch wider. Aluminum wheels are often a full inch wider. THIS is why you need to be extra diligent when trying to stuff the widest tire in the car.

[MSRacing89]

really?  now I am worried.  the rims have 5 inches of back spacing and rub like crazy!!  unless I am measuring wrong.  the thing isnt even lowered yet.

Yeah.....hmmmmmm.  I think you are going to have a hard time making those fit.  We run 4¾" BS with 19x10's.  Doing the quick math you would need at least 5¾"BS with all things being equal on a 12" rim. Then you may have some issue inboard with the springs also?

OOPS...you were referring to the fronts.  I run 18x9 with 4¾" BS and no issues.

[Kern Dog]

MSracing.....
How do your tires clear? The sig pic shows a Blue car with the tires close to the outside edge. My tires rubbed the outer section of the wheelhouse when I was set up like that. I had to narrow the axle to suck the tires in. Your stance looks great, but I wonder how you fit them in without interference.

[HPP]

Good explanation of offset vs backspace.

http://www.chevellestuff.com/tech/wheel_offset.htm

[MSRacing89]

MSracing.....
How do your tires clear? The sig pic shows a Blue car with the tires close to the outside edge. My tires rubbed the outer section of the wheelhouse when I was set up like that. I had to narrow the axle to suck the tires in. Your stance looks great, but I wonder how you fit them in without interference.

The sig pic is my car with 19x10's in the rear.  I just took the time to do all the measuring.  I do some rally racing and road racing so I found the 4¾" BS to be the best with no modifications necessary.   The choice you made to go with the 12" rim is what gave you some problems.  Not sure what other info to give you. 

[Kern Dog]

Here are pics of my car.  Sorry I do not have close ups.  I'm also sorry if this posts more than once, I keep receiving error messages.

[Kern Dog]

There was a little confusion . I have 18x10 on the rear with 4 7/8 backspace along with a cut down C body axle that is 1 1/2" narrower per side than a stock 68-70 B housing.  When I first bought the wheels and tires, I HAD a 66 B housing in it that had my tires pushed out 3/4". I LOVED the look, but tire rub is annoying.