Here's my dilemma.....I've read in several different places all about backspacing and offset. I'm wanting to fit some great looking tires on my '70 GS. Now, from what I can tell, it seems that if I want to put on a 15x8 wheel, then the offset should be zero, (0) right? In some places, I've read that you could actually get away with, say, -12 offset.??? I'm confused! The wheel I want to use is steel, matte black, and generally used on off-road vehicles. I'm thinking 225 60 15 front, and 255 60 15 rear. I think the U.S.Wheel "Stealth Star" would look great, and give a "road racer" look to my car. The problem is that they only offer it in a -12 backspace without custom-making it at a way higher price. (One of the reasons I like this wheel is it's affordability!) So what do you think? BS & OS wise? Any insight on this is greatly appreciated !
THANK YOU!!! That's pretty much what I was after....so this means that a negative offset would push the tire ...."outward" away from the car? Would there be detrimental effects by having that offset, or just how much offset can the axle/wheel bearings stand?... I'm determined to get this wormed into my head!!
Here is an attached pic for you to see. Typically if you go with a 15X8 wheel then you go with a 4.5" backspace. This gives enough room for a 275/60/15 tire in most 70-72 Skylarks or GS cars. Or if you go with a 15X10 wheel you want a 5.5" backspace so that you can center the wheel in the wheel wells. My 15X10 wheels with 5.5" backspace put the wheels RIGHT in the middle of the wheel well for max tire room. Keep in mind not all cars are the same and many cars are 1/2" out from side to side if you measure. My point from all this banter is that with a 10" wheel you need a backspace of 5.5" to center the wheel in the wheel well. This is also called a positive 0.5" offset. Where as a negative offset is going to take away your clearance on the outside of the wheel well. Remember, if you change the wheel width the backspace and offset numbers are different than with a different width wheel. The safe bet is the 15X8 wheels and a tire about 9" wide and 28" tall, something like a 275/60/15... The more tricky way is with 15X10 wheels and 325/50/15 tires which can fit in the wheel wells without major mods just a bit of trimming the trim and upper wheel lip.
I run a 15x10 wheel with a 325/50R15 tire on my car. My backspacing was 5-5/8". These cars weren't built to exactling standards. That's what centered the wheel in my car. And plus if I did need to adjust the wheel with a spacer, I would be able to. But none was needed. Good luck.
I'm really just trying to get good handling and looks, and of course I'd like my tires to last long. This is a mildly modified GS350, as fast as I'll ever wanna go. I've added boxed rear control arms, fat sway bars front & rear, and polyurethane bushings throughout. Some of the "pro's" may feel differently, but I think this thing handles like a dream. The tire/wheel combo thing started getting complicated when I looked into backspacing and offsets, but I think I've just about got a handle on it now. I'm still not quite sure about the amount of offset these wheel/axle bearings can stand. When you search for 8" wheels with 4.5" backspace and zero offset, the choices are few.....unless one has lot's of cash. My car is a driver, and I just want to get there quick, in style, and on a budget.
Beautiful car there, Curtis......one question before I shoe this horse.....I found the wheel I want, and it's available in 15x8. The BS is 3 3/4", and the offset is -19. I'm pretty sure this will fit my '70 GS, but does anybody know of any other problems this wheel might cause?
3 3/4 BS may be a bit better That would move the tire in. Mine are close to the fender, so you'd have a little more room.. but you may hit the sway bar or chassis at full lock.
Wait......now I'm confused again. Wouldn't "less" BS move the tire out.......and "more" BS moves the tire in?
You're right.. Now Im confused LOL But yes..you are right...Less BS will move the tire out In that case...take the opposite of what I said above. My 255 60 15 on 4.5" BS just clear the fenders I think if they were out another inch, you'd be in for some fender trimming
That is a nice looking wheel, but boy howdy it is a terrible looking web page. He needs to lighten up that background so that you can read the text he put on it. The GS stage one and tri shield should be about 1/4 as dark/opaque.
I can see that's kinda tight there Curtis.....I sure appreciate you helping me out with this!....So do you suppose the 19mm negative offset will cause any problems with the wheel or axle bearings? Oh yeah, ....are there any offsets on your wheels?
19 mm is approx 3/4" Thats not much Guys put spacers on their wheels all the time effectively making an offset I dont think its a big deal. If the BS is 3 3/4, I believe that puts the center of the wheel at the same as having 0 offset and 4.5" BS?
Just take the rim width, divide it by two and add the offset (if positive offset) to get the backspace. A positive offset puts the wheel further into the wheel well and a negative puts the wheel further in the wheel well.
