Novak Conversions Jeep Wrangler TJ engine mounts

Struggling with offset for wrangler TJ on 33's

Roger Dunning

Roger Dunning

TJ Enthusiast
Original poster
Joined
May 9, 2025
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111
Location
Chichester, West Sussex, UK
Hi all,
I've struggling to calculate offset when ordering new wheels. I'm replacing wheels with 15" or 16" modular steel wheels in Bronze. I will have 33" AT wheels such as BFG K02. I want them to sit with the tyre right on the edge of the fender or just past.

Any help or advice much appreciated.

My car is on the left. Big ass 33's on the right.
 
That’s because offset is stupid. Try to get the backspace. Backspace is the distance from the inner edge of the wheel to the mounting face of the wheel.

Then measure the distance from the mounting surface on the rotor to the edge of the flare (I think you don’t mean fender since that’s the metal part). That distance tells you what backspace you want.
 
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If you're wanting to keep the tires inline with the flares, then really only stock wheels will accomplish that. Aftermarket wheels in almost all sizes will push the tire significantly outside of the flare, like 1.5-2". You currently have stock 7" wheels, but the 8" stock wheels would be better for this.

Something like the American Racing AR172 with 5.29" backspacing would move the tire out very slightly, so that would also work. Not very many options when wanting to keep things under the fenders.

Since you said steel wheels, if you can find something with 4.75" backspacing, that would also work but with a bit more stickout...3/4" stickout vs stock.
 
Which width of tire? 10.5 or 12.5

The pizza cutter 33x10.5 tires on OEM Ravine wheels with 5.5" backspacing fit perfectly under my LJ (slightly wider) flares, with essentially no rubbing (after tweaking the steering stops). Wider tires will need shallower backspacing.
 
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machoheadgames said:
If you're wanting to keep the tires inline with the flares, then really only stock wheels will accomplish that. Aftermarket wheels in almost all sizes will push the tire significantly outside of the flare, like 1.5-2". You currently have stock 7" wheels, but the 8" stock wheels would be better for this.

Something like the American Racing AR172 with 5.29" backspacing would move the tire out very slightly, so that would also work. Not very many options when wanting to keep things under the fenders.

Since you said steel wheels, if you can find something with 4.75" backspacing, that would also work but with a bit more stickout...3/4" stickout vs stock.
Click to expand...

That sounds perfect. I'm in the UK and many don't seem to show backspacing. I'll see what I can find.
 
Roger Dunning said:
That sounds perfect. I'm in the UK and many don't seem to show backspacing. I'll see what I can find.
Click to expand...
Black Rock brand has 15x8 steel wheels with 4.75” BS if you are able to get those over there.

I’d suggest 33x10.5 tires if you can get them. They will fit quite a bit better than 33x12.5.
 
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Not exactly what Rut Row has but close for reference. 33x10.5-r15 KO2s on 15x8 rims with 3.75" back spacing and factory flares. Zoom in and you'll see ~1.5" sticking out past the flares.

20240301_102517.jpg
 
Roger Dunning said:
That sounds perfect. I'm in the UK and many don't seem to show backspacing. I'll see what I can find.
Click to expand...

Here you go. Use the two factors you have to find the one you don't.

You are going to struggle to find what you are after though. Manufacturers make wheels in certain (and few) common options. Most common on TJs in an 8" wheel is going to be around the 3.75" backspace (or more). There's not a lot of options between factory backspace (5.25 to 5.5") and 3.75". There are some, you'll just be very limited when it comes to style and price.
EDU_wheel-offset-backspacing-conversion-chart.webp
 
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Roger Dunning said:
Hi all,
I've struggling to calculate offset when ordering new wheels. I'm replacing wheels with 15" or 16" modular steel wheels in Bronze. I will have 33" AT wheels such as BFG K02. I want them to sit with the tyre right on the edge of the fender or just past.

Any help or advice much appreciated.

My car is on the left. Big ass 33's on the right.
Click to expand...

Backspacing and offset are directly related. I believe all the stock wheels are 5-5.25" backspacing and I think all 7" or 8" wheels. The chart posted by NskLJ is really helpful.

If you are concerned with fender coverage for legal/MOT reasons, there are fender flares available that are 3" wider than stock. I know shipping to UK is a fun time, but it will open more options.

I have a Rubicon with it's 16" Moab wheels. I run a 285/75R16 Duratrac which is 11.25" width roughly. The Moab wheels on here are 5" backspacing on an 8" width. This is with the trackbars as centered as I can get them and I have roughly 2.5" lift. We don't have a fender coverage law here, but I think this would pass anywhere.

If you're running a 33x12.5R15, if using a 5" backspacing they're going to stick out with the stock backspacing period and you're going to rub the factory control arms when turning, period.

If you are running a 33x10.5R15 or a 225/85R16 on your TJ with +12mm offset they will be covered by the fenders.
20241230_152822.jpg
 
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GoldenGorilla said:
Backspacing and offset are directly related. I believe all the stock wheels are 5-5.25" backspacing and I think all 7" or 8" wheels. The chart posted by NskLJ is really helpful.

If you are concerned with fender coverage for legal/MOT reasons, there are fender flares available that are 3" wider than stock. I know shipping to UK is a fun time, but it will open more options.

I have a Rubicon with it's 16" Moab wheels. I run a 285/75R16 Duratrac which is 11.25" width roughly. The Moab wheels on here are 5" backspacing on an 8" width. This is with the trackbars as centered as I can get them and I have roughly 2.5" lift. We don't have a fender coverage law here, but I think this would pass anywhere.

If you're running a 33x12.5R15, if using a 5" backspacing they're going to stick out with the stock backspacing period and you're going to rub the factory control arms when turning, period.

If you are running a 33x10.5R15 or a 225/85R16 on your TJ with +12mm offset they will be covered by the fenders.View attachment 639465
Click to expand...

What you have in this picture is exactly what I'm thinking. Perfect. I'll be going 10.5 for sure.
 
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TheBoogieman said:
You are wrong. 🤫

View attachment 639477
Click to expand...

I was talking specifically about the 5" backspace reference I provided so the OP would have that visual reference.

That's a 5.5" backspaced (+25.4 offset) Gambler or clone. There are a few other 5.5s. There's a good sticky with the stock wheels. The 5.5" (+25 offset) backspace wheels are right on the edge with a 12.5" tire and now we have the alternating lugs that generally stick out a bit further than in the OG TAKO days. Probably enough to have an issue if you encounter inspection Officer Stickler in one of those fender coverage states. Which I called out because I think that's a UK issue for the OP, but wasn't certain.

You can't tell me that didn't rub like crazy on stock control arms in that configuration at full lock. Not without a massive stack of washers behind the steering stops. I mean you could, but then we'd both know your job title is politician.

On that note, my 11.2" Duratracs rubbed a good amount at full lock on 5" backspace with stock arms even with some washers stacked behind the stops. They don't rub with aftermarket tube shaped arms. The 255/85R16s also rubbed with no stops but did not with some washers. I don't want to give the impession that you will not some clearance issues.

Nice Sahara though!
 
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