Backspacing on 16 x 8 Wheels?

[BGBronco]

76, cut fenders, disc brakes, 1.5 BL.

I'm planning on moving from my current 15x8 / 33x12.5x15 wheels / tires to a 16x8 with an ~ 33x10.5x16 set up. It looks like that will be a 285x75x16.

I'm trying to wrap my head around backspacing and it's not working. My current wheels are Pro Comps with 3.75" backspace. Do I need more or less backspacing with the 16x8s and does 'more backspacing mean it goes to, for example, 4" and does the higher number mean the wheels stick out further or tuck in closer.

These are the wheels I'm looking at.

4" BS

https://www.4wd.com/p/pro-comp-69-series-vintage-16x8-wheel-with-5-on-5-5-bolt-pattern-polished-1069-6885/_/R-BKBQ-1069-6885

4.5" BS
https://www.4wd.com/p/mickey-thomps...shed-2368402-90000001771/_/R-BFLW-90000001771

Thank you.

 

[Yeller]

More back spacing makes the wheel stick out less further from the inside of the fender.

 

[DirtDonk]

Yep, the more backspacing the more of the wheel and tire are tucked in.
And on your 76 that means the closer they are to the steering arms and tie-rod ends.

There’s no guarantee that a 16 will clear your steering arms. Depends on the design of the wheel. A 17 is virtually a shoe in, but a 16 is borderline.
If you have any opportunity to test out before mounting a tire, then by all means do so.
If you’re set on a particular wheel and it does not clear the steering arm or tie rod end, you can use spacers to get it back out a little further. That does give you more leeway with wheel choices too, since a lot of 16s have even more than four inch backspacing.

And I kind of disagree with your estimate of width. A 265 is very similar to an 11.50 where a 285 is getting close to a 12 1/2. Maybe between an 11 1/2 and 12 1/2? Remember that flotation sizes were rarely actual sizes in the real world.

Measure your current 12 1/2 just as a comparison. Or the next time you’re near a tire shop roll a 285 up next to yours.
When GM first started putting 265/75 16‘s on their ‘88 and newer trucks, we put them side-by-side with standard 33 12 1/2 tires and they were virtually the same diameter but slightly narrower.

 

[BGBronco]

Yep, the more backspacing the more of the wheel and tire are tucked in.
And on your 76 that means the closer they are to the steering arms and tie-rod ends.

There’s no guarantee that a 16 will clear your steering arms. Depends on the design of the wheel. A 17 is virtually a shoe in, but a 16 is borderline.
If you have any opportunity to test out before mounting a tire, then by all means do so.
If you’re set on a particular wheel and it does not clear the steering arm or tie rod end, you can use spacers to get it back out a little further. That does give you more leeway with wheel choices too, since a lot of 16s have even more than four inch backspacing.

And I kind of disagree with your estimate of width. A 265 is very similar to an 11.50 where a 285 is getting close to a 12 1/2. Maybe between an 11 1/2 and 12 1/2? Remember that flotation sizes were rarely actual sizes in the real world.

Measure your current 12 1/2 just as a comparison. Or the next time you’re near a tire shop roll a 285 up next to yours.
When GM first started putting 265/75 16‘s on their ‘88 and newer trucks, we put them side-by-side with standard 33 12 1/2 tires and they were virtually the same diameter but slightly narrower.

Yep, the more backspacing the more of the wheel and tire are tucked in.
And on your 76 that means the closer they are to the steering arms and tie-rod ends.

There’s no guarantee that a 16 will clear your steering arms. Depends on the design of the wheel. A 17 is virtually a shoe in, but a 16 is borderline.
If you have any opportunity to test out before mounting a tire, then by all means do so.
If you’re set on a particular wheel and it does not clear the steering arm or tie rod end, you can use spacers to get it back out a little further. That does give you more leeway with wheel choices too, since a lot of 16s have even more than four inch backspacing.

And I kind of disagree with your estimate of width. A 265 is very similar to an 11.50 where a 285 is getting close to a 12 1/2. Maybe between an 11 1/2 and 12 1/2? Remember that flotation sizes were rarely actual sizes in the real world.

Measure your current 12 1/2 just as a comparison. Or the next time you’re near a tire shop roll a 285 up next to yours.
When GM first started putting 265/75 16‘s on their ‘88 and newer trucks, we put them side-by-side with standard 33 12 1/2 tires and they were virtually the same diameter but slightly narrower.

So I understand this, I currently have the Pro Comp Vintage 69s. If I go with the same wheel and move from a 15" (3.75 BS) to a 16" (4" BS) it may not fit because of the extra .25 of BS?

If I went with the M/T Classic III in a 16x8 with 3.65 BS I should be in good shape?

Yes, I meant to say 265 not 285, thank you.

 

[DirtDonk]

That is potentially correct. The 76 and 77 bronco steering system gets extremely close to the edge of the rim. Many people even with as little as 3 3/4 inch backspacing have experienced rubbing. Here again that minor difference between rubbing and not rubbing is the profile of the individual wheel. Some cast aluminum wheels are quite thick and can rub it where a thinner steel wheel might not.

A 16 inch wheel does put that rim edge farther away, but it’s not guaranteed to fit with four inch backspacing. That’s why I recommended seeing if the tire place will let you trial fit one wheel on the front before your mount the tire.

 

[BGBronco]

That is potentially correct. The 76 and 77 bronco steering system gets extremely close to the edge of the rim. Many people even with as little as 3 3/4 inch backspacing have experienced rubbing. Here again that minor difference between rubbing and not rubbing is the profile of the individual wheel. Some cast aluminum wheels are quite thick and can rub it where a thinner steel wheel might not.

A 16 inch wheel does put that rim edge farther away, but it’s not guaranteed to fit with four inch backspacing. That’s why I recommended seeing if the tire place will let you trial fit one wheel on the front before your mount the tire.

For simplicity, I know a 3.75 works. If I go upwards to 4, I'm taking chances and if I go down to 3.65, I should be good. Is that correct? Thank you.

 

[DirtDonk]

In a nutshell, yes.
There are always exceptions of course ( which is why you rarely get a simple answer around here), and we used to say three and five eights was the maximum. But in your case since you know 3 3/4 works at least with that wheel, chances are other wheels with similar specs would fit too.