8" wide wheel, 4" backspace - question

Quick question....

I found a set of 16x8 Pro Comp wheels on Craigslist for dirt cheap. The back space on them is 4" (or -12 offset).

I've spent most of my day at work researching this set up and havent come up with too much other than a half full of pictures.

I started running numbers and I came up with this -

From what I've found, the stock 16" TRD wheels are 7" wide et32, which is 5.25" backspace. Can anyone verify this??

I have 1.25" Spidertrax spacers on my 16" TRD wheels. 1.25" = 31.75mm.

If my math is right, the specs of the stock 16" TRD wheels w/ the spacers
is 7" wide roughly et0.

So I plugged in the numbers and came up with this....



According to this, 8" et -12 (4" backspace) sticks out 12mm (1/2") further the the 7" et 0. Does this seam right?


Or if its easier, is there anyone running 8" wide wheels with a 4" backspace (et-12) ??

This is the only shot I can find which really shows the wheel poke from head on -



And for comparison, these are 8" et-25 (3.5" backspace), which should stick out 1/2" further than 8" et-12 -



:beer:

 

I think they will stick out a full inch more. A 7" wheel with 5.25" BS and 1.25" spacers will have a 4" BS overall. Go to an 8" wheel with the same BS and it should stick out 1" more.

A 7" wheel with 4" BS will have 4" of the wheel on the inside of the wheel mounting surface and 3" out, 4+3=7. An 8" wheel with 4" BS will have 4" inside of the wheel mounting surface and 4" out, 4+4=8.


I have 8" wheels with 4.5" BS. I'm running 255/85R16 KM2's. The wider the tire is the more it will stick out as well.

 

OP, what size tires are you plan on running with the Procomps? The 8" wheel will stick out a tad wider but with a wider tire, turn radius also increases, which could result in rubbing possibly the cab mount.

 

I have 265/75 Cooper AT3s on the stock wheels, which I'd run on the Pro Comps. I'd eventually step up to either 255/85s or 285/75s.

The truck has 5100s set at 1.75 right now, but I plan on ordering Eibachs and top plates to get a full 3". Im not opposed to chopping the cab mount and trimming some things.

Ultimately, Id probably just be keeping the 265s with the 3" lift since they are brand new tires.



:beer:

 

any other thoughts?

 

If I'm reading and understanding your first post right, then if you go with the pro comps and keep your spacers, then they should stick out 2 1/4 inches further than they already do. If you get rid of the spacers then you'll stick out one inch further than your current set up. That's if I'm understanding what you're saying which I'm not sure if I am. Best of luck!

 

Im not sure. I hate converting from backspace to offset. I was able to nail the perfect offset on my VW, but calculating the offset for this truck seems to be a pain.

 

So forget about offset and just think of everything in backspacing. Much easier. You just have to remember to add an inch to each wheel to get it right.

ie 4.5" BS is the center of an 8" wide wheel because the measure BS from the wheel mounting surface to the furthest out lip of the wheel. The lip appears to had a 1/2" to each side of the wheel.

 

I re ran the number and it looks like the 8" wide 4" backspace wheels will sit out a 1/2' further than my current set up

 

Unless I am missing something I stand by my answer of 1 inch.

You said the 7" wheels have a 5.25" BS and with 1.25" spacers gives it a total BS of 4"
The 8" wheels will have 4" BS with no spacers so 4" BS total.

4" BS means that 4" of the wheel will be tucked inside the wheel mounting surface. So with a 7" wheel that means 3" will be sticking out and with an 8" wheel 4" will be sticking out. So 1" more as shown in my pic I made real quick in paint below.



This is why I prefer backspacing to offset. Offset isn't very comparable from wheel to wheel unless you are trying to get a certain inside to outside ratio. Backspacing is really easy to compare different width wheels and how they will stick out just like you are trying to do.

 

Id rather mess w/ offset actually.

Im gonna scoop the wheels up tonight after work. If they dont fit, I'll refinish em and flip em.

 

I'm sure they will still fit. Lots of guys on here are running 10" wheels with 12.5" wide tires on them with less than 4" of BS. It all comes down to how much you want to trim.

I doubt you will have to trim much if any.

 

Running 1.25" spacers on top of the pro comp wheels with a 4" BS is totally unnecessary in your application (265/75 or 285/75s) and will result in rubbing issues.

 

I do NOT plan on running the spacers.

8" wide 4" backspace with a 265/75 and 3" of lift, it shouldnt be too bad. If not, Ill flip em

 

ok, it'll work but will look better when you go with 285's vs. the 265s.

 

Are you planning on running the spacers with the wheels? I got the impression you were not.


If you do, that will give you 2.75" backspacing and those tires will stick out 2.25" wider than they do now. With your 265/75's, you will likely have to do some good trimming to prevent rub while turning. You may even have to do a cab mount chop.


EDIT: you ninja edited your post on me while I was writing mine. And with that, you will be just fine with those wheels and your tires.

 

NO spacers. 285s are planned for them if I can make them fit.

 

Welp. Picked em up after work yesterday.

They are actually Eagle Alloy 187s, not Pro Comps.

After searching, I was able to come up with a few people running these wheels.

Just to answer my own question, and to answer the question for anyone searching, here are some pictures of said size wheel / tire on another truck -

8" wide 4" bs 165/75 Duratracs -







And for what its worth, I measured the backspacing of the stock wheels with the spacers added on and its 4". The 8" wide 4" bs stick out an inch father than spaced out stock TRD 16s.

:beer:

 

Called it!




They look great though man!

 

:beer:

No idea how I fucked that one up. I've been building 3 piece wheels for VWs for years now calculating offset, spacer, adapter, lip, and barrel sizes, but couldnt convert from offset to backspace.....