Hey guys, I want to run a 15x8 wheel from weld racing..either the draglites or the prostars when i decide. I am gonna put the wheels on my sport coupe which has a drum brake rear and i know that the bolt pattern for our cars are 5/4.75 but my question is: for the 15x8 wheel, which is a better b.s 4.5" or 5.5" I want to run a 275/50/15 dr but do not want them to stick out too much...i'd really appreciate some input guys, thanks.

 

I have 17 x9.5 with a 275 tire. My backspacing is 5.5 and all fits well.

The backspacing should be the same regardless of the wheel size.

I dont know about your front. My car has baer brakes which offest the hub to allow 5.5 bk **** there too.

 

I have 17 x9.5 with a 275 tire. My backspacing is 5.5 and all fits well.

The backspacing should be the same regardless of the wheel size.

I dont know about your front. My car has baer brakes which offest the hub to allow 5.5 bk **** there too.

 

Backspacing should not be the same no matter the wheel size. The offset should be the same to keep the wheels fitting the same. Backspacing will change with the wheel width to keep the offset the same, you just have to make sure that the backspacing doesn’t end up too big and hit suspension or brake parts on the back side…

FWIW, you’re looking for about ˝(12mm) offset on the back, which unfortunately falls right between the two wheels you listed.

 

I have used Super Lites and Drag Stars, both were 15x8 with 4.5" backspacing and 265-50-15's all the way around. The front would rub a little on the inner fender when the wheel was turned all the way to either side, but it never damaged anything in 15 years and countless sets of tires. The rears never rubbed at all.

When I ran 295-50-15's in the back they would rub the outer fender a little when cornering, but never when launching.

I also have used 15x10 Drag Stars in the back with 5.5" backspacing. Other than the disk brake parking cable bracked having to be bent VERY slightly they were a perfect fit with 265-50-15's. I currently have ET Streets (26x11.5) mounted on these rims, but I have not raced with them yet. They look like that fit well.

I have also used a couple of 15x10 rims with 5" backspacing in the rear. They fit fine.


I would not run 15x8 with 5" backspacing in the front.
I would/have run 18x8 with 4.5" backspacing in the front.
I would/have run 15x8 with 4.5" backspacing in the rear.
If you don't intend to ever run the rim in front, 15x8 with 5" backspacing should be fine (I think). It may even be better with a tire bigger than 265-50-15.

In summary:
If you are doing all 4 wheels I would go with 4.5" so they will be the same. If you are doing rear only I would probably go with 5".

HTH

 

Backspacing should not be the same no matter the wheel size. The offset should be the same to keep the wheels fitting the same. Backspacing will change with the wheel width to keep the offset the same, you just have to make sure that the backspacing doesn’t end up too big and hit suspension or brake parts on the back side…

If the backspace is 5.5 on a 15 X 10 and 5.5 on a 17 x9.5 how is the backspacing different?

If the wheel's hub(mounting surface) is 5.5 off the axle, brake roter, drum etc. it is 5.5 off regardless of the offset.

In the front there is suspension to clear and the diameter of the wheel will make a difference, but in the rear I do not understand the difference?

Please educate me as to you comment.

 

This comment confuses me.

 

excuse me, please Leave out the "not"

 

Huh? I’m not sure I’m following what you’re saying.

Nutshell, a 10” wheel with 6” BS will have .5” offset and will allow you to fit a pretty big tire on the back of an f-body (from what I understand may cause some minor clearance problems with the parking brake), an 8” wheel with 6” BS will have a 1.5” offset and most tires will hit the inner wheel well.

 

I believe that 6" bs would actually be 1" offset, since 5" bs on a 10" rim would be 0 offset.

Other than that I think you have it right. The narrower rim w/ same BS as wider rim (will have more offset and) move tire SLIGHTLY in, and potentially cause a problem.

Back to the origional post: The 275-50-15 on a 15x8 with 4.5" or 5" bs.
With 4.5" bs there will be a .5" offset (close to stock). The 5" bs will be a 1" offset (more than stock), but I expect it will fit fine anyway.

 

SDIF, do you have the Baer track kit - its on my car and was wondering if it really moves the mounting surface of the brakes out 1/4" like I heard.

 

It does move it out. It is real close to the rear axle lenght because my front and rear and rear track width is within 1/8 inch which the same wheel size and offset.

I used to know how much; because I measured it when ordering wheels.

One real advantage is the ability to rotate wheels with same offset.

I could measure it next week and get back to you if you like. The car is 100 mile away. I recently moved and have not yet built a shop.

 

In a perfect world, yea, but in this one, the companies that make any of their measurements match something that is actually on the rim usually include the lip thickness (usually 3/8” for steel rims and ˝” or more for aluminum rims) in the backspacing measurement, so a 10” rim will actually be 11” or more wide, which would make a 5.5” BS a 0 offset rim.

Of course, some wheel companies call their rims something that makes no sense WRT to their actual sizing and you can’t really predict what you’ll get until you try it.

 

In a perfect world, yea, but in this one, the companies that make any of their measurements match something that is actually on the rim usually include the lip thickness (usually 3/8” for steel rims and ˝” or more for aluminum rims) in the backspacing measurement, so a 10” rim will actually be 11” or more wide, which would make a 5.5” BS a 0 offset rim.

Of course, some wheel companies call their rims something that makes no sense WRT to their actual sizing and you can’t really predict what you’ll get until you try it.