Help with offset math

[TheOtherMe]

Are there aftermarket 8-8.5” rims with stock offset of 44.5mm? I haven’t seen anything higher than 25mm.
Not sure why you’d want to stick with stock offset either way. You’ll run into clearance issues if you go with bigger tires.

I don't plan on sticking with stock offset. I just wanted to use an equal offset to take that factor out of the equation for for my question. I'll probably end up somewhere in the +25 range. I'm looking for a mostly tucked look with most if not all of the tread covered. I'm still on the fence about tire size as well, so I'm just gathering data. Thanks.

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[GATORB8]

Are there aftermarket 8-8.5” rims with stock offset of 44.5mm? I haven’t seen anything higher than 25mm.
Not sure why you’d want to stick with stock offset either way. You’ll run into clearance issues if you go with bigger tires.

Tough task, +40 mm:
https://www.discounttire.com/buy-wheels/voxx-nova/p/48806

 

[Swisskidd]

I'm not personally a fan of using backspace. In the majority of our builds tire sidewall is the controlling clearance point. While wheel width does impact section width to a degree (industry standard is 0.2" in overall tire section width change per 1/2" change in wheel width) that really needs to be added/subtracted regardless of whether you locate the tire with BS of Offset.

Since offset directly locates the centerline of the tire, it's a good static locating metric. Backspace is dependent on width, so you can't locate the tire without knowing the width.

Just for an example of why this can be frustrating, let's look at the difference between using backspace and offset. For ease of calculation, let's use a baseline of a 8.5" wheel with 0 offset /4.75" backspace.

Change to 10" width, but maintain 0 offset:

Change to 10" width, but maintain 4.75" backspace:

In both cases, the change of wheel width would impact the section width the same. Using a BFG KO2 37x12.50R17, their data shows a 13" section width on a 10" wheel, so you'd want to consider that in your use of the tiresize.com offset comparison if you are comparing changing tire sizes with the wheel change. Using the industry standard, the section width on the 8.5" wheel should be closer to 0.6" thinner, or just over a 1/4" more clearance either side with the 8.5. I don't put a ton of weight in the standard, but at least gives you an idea.

Great illustrations!
Changing the wheel size while maintaining the Offset (and tire size) will only affect tire bulge (within reason).
Changing wheel size while maintaining BS and tire size will affect tire poke and bulge.

Most who look for wheel upgrades also change their tire size.

It also appears as there are typically two main concerns owners have. The Off-Roader is mainly concerned about suspension and fender clearances during suspension articulation; while others may have be more concerned to comply with laws regarding wheel/tire poke (depending on region or country they live in).

If I remember correctly, the Offset terminology was heavily used by the German manufacturers starting in the 1980’s. It slowly crept its way over here, once car manufacturers started using large brake systems on their offerings.

 

[Bryce]

I've seen that calculator. However, I don't see an option for before and after wheel width. Am I missing it?

try this one. it let's you put in wheel width and offset along with tire size
https://www.willtheyfit.com/

 

[TheOtherMe]

try this one. it let's you put in wheel width and offset along with tire size
https://www.willtheyfit.com/

Bookmarked it. Thank you.

 

[GATORB8]

Great illustrations!
Changing the wheel size while maintaining the Offset (and tire size) will only affect tire bulge (within reason).
Changing wheel size while maintaining BS and tire size will affect tire poke and bulge.

Most who look for wheel upgrades also change their tire size.

It also appears as there are typically two main concerns owners have. The Off-Roader is mainly concerned about suspension and fender clearances during suspension articulation; while others may have be more concerned to comply with laws regarding wheel/tire poke (depending on region or country they live in).

If I remember correctly, the Offset terminology was heavily used by the German manufacturers starting in the 1980’s. It slowly crept its way over here, once car manufacturers started using large brake systems on their offerings.

I bet you're right. I had a BMW I tracked and that's where I was really introduced to offset.

I tend to dive in on the technical side of things, I certainly understand that lift manufacturers have to have a simple way to communicate wheel requirements. By setting a minimum backspace they can expect there will be a minimum offset/tire combo.

Unfortunately in setting a single standard, they have to account for the worst case scenario. Narrowest axles, maximum tire size, "maximum" offset. All three play in our case with probably the first clearance concern on most being front tire to LCA contact.

 

[Swisskidd]

try this one. it let's you put in wheel width and offset along with tire size
https://www.willtheyfit.com/

Great source! Thank you for sharing.

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