If my 275s rub with stock 4" BS, how could 4.5" BS work on wider rims?

[2QUIK6]

My current 275/50/15s rub the inside frame with the stock GN rims which have 4" Backspacing. I'm thinking of getting some new rims and I've read a bunch of posts that with 9 to 10" wide rims its recommended to have 4 or 4.5" backspacing.

Can someone explain how more backspacing like 4.5" would cause the rubbing problem to be worse since thats bringing the rim even closer to the frame?

I was thinking 3.75" BS on 8.5 or 9" rims. I don't see how a wider rim would cause the sidewall not to stick out any less, it would appear not to "Buldge" as much with wider rims but would still be the same overall width if not wider I would think and not allow you to run more backspacing than the stock 4".??

 

[charlloots]

275 50 15 requires a spacer with stock wheels. 1/4 in should work fine . jegs or summit sells them .

 

[Red Regal T]

If you put on a 4.5" backspace wheel on your car, the rim itself will not rub. The bulging part of the tire is what would rub. with a 9.5" rim, YES, the sidewall will not bulge as much, thus giving you clearance. Worse comes to worse, install 2" lug studs and use a 1/4" or 7/16" spacer. Something else that will give you more clearance would be aluminum brake drums.

 

[2QUIK6]

I think I see now how 4.5" BS would work, just have to make sure I don't get a tire thats wider than the rim like the 275's are now with the stockers.
I know I have to use spacers with the 275's on stock wheels, thats what I have now. The whole point in trying to figure out what BS works best is so when I custom order my new wheels I'll get them with the correct BS so no spacers have to be used.

 

[Zurn]

worried about tire size...

Some tire and wheel shops have a tool that will mesure the amout of b/s and the amount of room you have for tire clearance. These tools are some what expesive, so you may have to call around and ask if the shops near you have one. The other choice is to make a cardboard cutout. There is a good thread here somewhere that explains how to do this. The card board will end up looking like a dog bone, and then you can use it to mesure how much room you have to work with. Hope this helps. -Gabe

 

[Dusty Bradford]

I recently went through this discussion with a wheel manufacturer. My current wheel is a 15x8 with 4 inch BS. I wanted a 10 inch wheel but keep the outside of the wheel in the same place. In other words I wanted all of the extra 2 inches to the inside so I could notch my frame. My redneck math told me I wanted a 15x10 with 6 inch bs, thinking if I went with a rim 2 inches wider then all of the extra rim would go to the inside. According to the wheel guy that is the wrong thinking. A 15x10 with 6 inch bs would really move the outside of the wheel inside the fenderlip an inch when compared to my current 15x8. It don't add up in my head but this is what he said.

I believe if you went with a 9 inch wheel with 4 inch bs then the tire would actually move away from the frame 1/2 inch. I would call and speak with the wheel manufacturer personally to get what you want. Not all may do the math the same. It all just confused me.

 

[Zurn]

try this link...

There are a few web sites that do a really good job explaining how bs on rims work with pictures and everything. Try looking at the links below to see if these help. Otherwise, try doing a search on google, I've come across some very good articles about bs and rim size along with tire size. -Gabe

http://www.tirerack.com/wheels/tech/fitmentdrawing.jsp

http://www.tirerack.com/wheels/tech/offset.jsp

 

[2QUIK6]

I've read a dozen articles on wheel dimenisions, but none explain just what Dusty is saying above. After reading all of the articles and measuring the Backspacing an wheels I have, I came to the conclusion that if I had 4.5" BS, the rim would rub the frame, as I have exactly 1/2" clearance betweem the rim lip and the frame rail with the current 4" BS now, but appearently that is not how it works as Dusty explains, and the fact there are a lot of folks running 4.5" BS on a TR without problems.

 

[Zurn]

some cars are different

That's kind of weird. I was always under the impression that if you go to 10" wide rims 4.5" bs is what you want on the GN. I know that some of our cars are different, some will take a 10" rim and some won't. Maybe you are just one of the ones that can't take a 10" rim? Some tire shops will let you "test fit" a rim and tire combo to see if it will work, maybe call some of your local shops to see if they have a 15x10 with 4.5" bs and see if they will let you bolt them up to see if they will clear the frame. You might try 4x4 shops; this is a pretty popular truck rim size. That would be the only other thing I could suggest, besides talking to the wheel manufacture themselves. Also, I know that Gbodyparts.com widens the factory GN wheels to 10" and they use a 4.5" bs, maybe they could explain it better? -Gabe

http://www.gbodyparts.com/wheels.htm