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Sorry to ask a dumb question which seems to have been discussed a lot on this forum. But I have confusion on some of the posts, but I seem to have figured out what I need.
I am looking at a set of 17" wheels. Up front 8" wide with 0mm offset (4.5" BS) and 9" in rear with 0mm offset (5" BS). I have a 1969 Cutlass S that came with all drum brakes, but the fronts have been converted to factory stock disc brakes that came off a 1970 Chevelle. Has 1" lowering springs from Eibach.
My concern is the back space/offset correct? I think it is, but just want to verify. I thought off running 235/50 up front and 275/50 in rear. I see people running 245 up front and wider in rear. What are your opinions? I dont want to rub and dont plan on trimming fender.
275/50/17 diameter is 27.78” in a Nitto. I’m running a 285/40/18 which is exactly 27” diameter and my 9” wheel with a 5.29” backspace would barely rub on the right rear until I installed adjustable lower control arms. I adjusted them in to bring the springs back into plumb. That centered the wheel in the opening and now there’s no rubbing.
I think if you’re going to run that large of a diameter tire, you need 6” of backspace. I have plenty of room between the inside of my rear tire and the frame/inner fender but I’m as far out with a 285 and 5.29” backspace on a 9” wheel as you can get without rubbing.
A 9" wide wheel with zero offset would have about 4.75" to 5.0" backspace, depending on the exact shape of the inboard lip (which is why backspace is such a useless number). More than that will push the tire inboard, towards the frame.
Thanks.
I was using the information on people running the the Year One SSII 17" x 9" wheels with 5.125" BS / +3mm offset. That is only a 1/8" difference to what I am looking at, 17" x 9" with 5" BS / 0mm offset Americam Racing VN501 / Magnum 500 wheel. I would think Year One specifically designed these for the Cutlass's. They did their testing with a 275/40R17 tire.
Also, I found someone posted a 9" wide wheel with 5.5" BS and he says has only a 1/2" from the wheel edge to the inside, tires will rub. Will have to use spacers or send wheels back to change BS to 5".
American Racing does make this size wheel with a 5.5" BS / +12mm offset.
Currently I am running 235/60R15 all four corners on a 7" wide wheel. Car is lowered 1" with Eibach springs. Looks good except for the space between the tire and wheel opening in the rear.
Posts that I read seems contradictory to one another, unless I am not understanding them. I know more back space brings wheel in and less back spacing pushes wheel out.
My second question is for the front. 17"x8" with 0 offset / 4.5" BS. Thinking of running 235/50s or do I run 245/50s.
Here’s the frame to tire gap on my ‘69 Cutlass S running 285’s on a 9” wheel with 5.25 backspace. It measures 1 1/2” at the rearmost of the tire.
on the face of tire at the center point of the wheel well, I measure 1 3/4”. Of course the way a Cutlass’s openings are shaped in and out, that drastically changes from front, middle to rear.
Something you need to pay attention to on tire choice is the diameter difference between brands. A Nitto 245/50/17 is almost 1 inch bigger in diameter than a Michelin of the same size. I would keep your front tires under 27” and you’ll have no rubbing issues with a 17x8 with 4.5” backspace.
Here’s the frame to tire gap on my ‘69 Cutlass S running 285’s on a 9” wheel with 5.25 backspace. It measures 1 1/2” at the rearmost of the tire.
on the face of tire at the center point of the wheel well, I measure 1 3/4”. Of course the way a Cutlass’s openings are shaped in and out, that drastically changes from front, middle to rear.
Something you need to pay attention to on tire choice is the diameter difference between brands. A Nitto 245/50/17 is almost 1 inch bigger in diameter than a Michelin of the same size. I would keep your front tires under 27” and you’ll have no rubbing issues with a 17x8 with 4.5” backspace.
Are those measurements of the outside face of the tire to the fender?
Thanks of the info.
Last edited by Bradley Dougherty; Jul 13, 2020 at 10:37 AM.
The factory literature has the top of the tire hidden but other factory adds look like the top of the tire is even with the wheel arch. Possible the Olds art department was trying to mimic the Pontiacs wide track campaign. Seems today’s aftermarket springs make the rede height too tall or people aren’t torquing the suspension bolts with a loaded chassis during assembly. Dustin
