18's with 275s on a Duster

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Scat

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I've read soo many threads its mind numbing but, with that said. Stock 73 Duster Disc Brakes up front and A body rear Rear axle currently.
18x9 with a +35 Offset for 275/35/18 fronts
18x9 with a +35 offset For 275/40/18 Rear

I'm thinking ill need a spacer in the front but wasn't sure yet.

Can someone confirm my thinking?
 
I dont understand, or care to understand this plus/minus metric offset bulls#!t. What is the backspace, in inches, like the rest of the wheel measurements.
Is the wheel advertised as a 45.8cm x 22.9 cm. wheel?
 
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In the front a 245/45/17 will fit fine, the 17x8 with +25 offset is perfect. Backspace is right at 5.5” so it will be tight to the outer tie rod end but should clear. If you wanted you could probably run a 255/45/17 up front, that would be 26” tall though which is about the upper limit for height with a tire that wide. Might have to adjust the front lower corner of the fender a bit, depends on the car and the ride height.

A 275/40/18 on an 18x9 with 0 offset should work as well. It will be tight to the quarter lip, but if you’re not lowered it should be ok on most cars. I think a +6 would be about perfect for a 9” rim with a BBP 8 3/4 and the stock spring location, it would be tight to the springs but that can be adjusted with a small spacer if need be. The shorter sidewalls can run tighter to the springs, but if you end up too close to the quarters you have to cut stuff. Plus it gives you a little room if you do a rear disk kit later (they add like 3/16” usually), so you can go disks without buying new wheels.

I do run 275/35/18’s on the front of my Duster (now Demon) but they’re on 18x9’s with about +30 for offset. That’s a 6” backspace, which you need for 9’s and 275’s. But you need 18’s to do it, most 17” rims end up with tie rod end interference around 5.6” to 5.7” of backspace. Depends on the rim, some do better but I’d say any time you need to go past 5.7” for backspace on a 17” it’s not likely to clear the tie rod end.

This is straight from the the guy who knows way more about tire fitment than most of us ever will.
Good luck and thanks to @72bluNblu
 
This is straight from the the guy who knows way more about tire fitment than most of us ever will.
Good luck and thanks to @72bluNblu


I’ve read it a few times. I keep finding wheels I like but sizes that won’t fit. I like a few sets that us mag has but they are 18x9.5 with a 5.29 back spacing. So better to ask then gamble I suppose. I’m really digging the Enkui wheels too but some are like hens teeth to find currently.
 
72blunblu, you can disagree if you want, but even in your post quoted above, you talk about offset plus or minus this or that , but then TO BE CLEAR,you explain what the backspace is.
If offset is so self explanatory, why mention the backspace?
The op says the wheels he is looking at are +35 mm offset. That dont mean dick to me, unless i convert to inches, and then try to figure out which way "+" is. Tell me the backspace, and i KNOW what the wheel looks like.
 
I've read soo many threads its mind numbing but, with that said. Stock 73 Duster Disc Brakes up front and A body rear Rear axle currently.
18x9 with a +35 Offset for 275/35/18 fronts
18x9 with a +35 offset For 275/40/18 Rear

I'm thinking ill need a spacer in the front but wasn't sure yet.

Can someone confirm my thinking?

In the front you’ll probably be fine, you might need a small spacer (5mm or less) depending on your steering stop situation.

In the back that’s too much offset for an A-body width 8 3/4, even with BBP axles and brakes. If your springs are in the stock location, you’ll need more like +6 to +13


I dont understand, or care to understand this plus/minus metric offset bulls#!t. What is the backspace, in inches, like the rest of the wheel measurements.
Is the wheel advertised as a 45.8cm x 22.9 cm. wheel?

Blah blah blah, the entire rest of the world is wrong using a 10 based measurement system that makes perfect logical sense and makes pretty much every calculation past basic arithmetic easier. Why we still insist on using a bastardized measurement system that wasn’t ours to begin with I still don’t understand. It’s not “American”, we stole it from the Brits and even they were smart enough to get rid of it.

Offset is easy, it uses the centerline of the wheel which can be a very helpful measurement if you’re changing rim widths but want to keep the wheel centered. It’s just the distance of the wheel mounting face from the centerline of the wheel, measured in mm’s.

C41277E5-D887-4808-86FF-2831C57287C0.jpeg


72blunblu, you can disagree if you want, but even in your post quoted above, you talk about offset plus or minus this or that , but then TO BE CLEAR,you explain what the backspace is.
If offset is so self explanatory, why mention the backspace?

Two reasons. One, not all wheels list offset in their advertised specs. Most do, but not all. And two, I know from over ten years of posting here that there are plenty of people that don’t understand offset, regardless of how straightforward it is, so posting the backspace as well just makes it more clear. Know your audience.

Converting back and forth between them isn’t as straightforward, because lots of people forget that backspace is measured from the OUTSIDE lip of the rim, and so their conversions end up being wrong by a 1/2”. So yeah, people screw up backspace too.
 
72blunblu, you can disagree if you want, but even in your post quoted above, you talk about offset plus or minus this or that , but then TO BE CLEAR,you explain what the backspace is.
If offset is so self explanatory, why mention the backspace?
The op says the wheels he is looking at are +35 mm offset. That dont mean dick to me, unless i convert to inches, and then try to figure out which way "+" is. Tell me the backspace, and i KNOW what the wheel looks like.
Soo. 9” wide wheel is 4.5” with zero offset so when someone says +35 they are adding 35mm what’s roughly 1.375 so what would give a total backspace of 5.857 roughly. Not that hard to figure out.
 
Soo. 9” wide wheel is 4.5” with zero offset so when someone says +35 they are adding 35mm what’s roughly 1.375 so what would give a total backspace of 5.857 roughly. Not that hard to figure out.

Nope. That’s exactly what I was talking about. A 9” wide wheel has a 5” backspace with 0 offset. It’s 10” wide outside to outside.
 
I do have a b body housing laying here I could just order some axles and be set with no issues.

I just for got about the lip like you stated above as well
 
I do have a b body housing laying here I could just order some axles and be set with no issues.

I just for got about the lip like you stated above as well

What year B-body housing? A 68-70 with a 1/2” spring offset would basically make a 18x9 +35mm a perfect wheel. And since you’d have to move the spring perches on a B-body housing it’s the perfect time to install a 1/2” spring offset.
 
What year B-body housing? A 68-70 with a 1/2” spring offset would basically make a 18x9 +35mm a perfect wheel. And since you’d have to move the spring perches on a B-body housing it’s the perfect time to install a 1/2” spring offset.

I have quite a few here actually I think I have a 69 for sure here that could get some new perches. Make life easier in the long run and wheels would be more available too.
 
I have quite a few here actually I think I have a 69 for sure here that could get some new perches. Make life easier in the long run and wheels would be more available too.

Yeah if you want to run a square set up on a Duster/Demon/Dart Sport without doing a bunch of bodywork the 68-70 B-body rear is just about perfect for making the wheel offset the same front and rear. And there’s a decent selection of wheels in the 18x9, 18x9.5” sizes with a +35 offset. 18x9.5’s are better with a tubular UCA in the front because of rim to UCA clearance at full steering lock and full suspension extension. With with a “V” shaped tubular UCA (vs a “U” shape) you can run 18x9.5’s or even 18x10’s up front. 10’s would be easier with some fender lip rolling though, and a 275/35/18 is still about as wide as you’re gonna go so the 18x10’s aren’t really necessary, 18x9.5’s would be great.

The funny part is when you get to 18x10’s or 18x11’s the A-body rear is better to have, because for some reason once you go past 10” wide rims the popular offset goes back to like +10-15.
 
So, even the guy trying to buy the wheels doesn't know what he is looking at?

Pretty common. There's a longtime member here that to this day will argue with me because he refuses to believe that backspace is measured from the outside lip of the wheel (on the backside) to the mounting surface.
 
What i like about backspace is that it can be measured with a tape measure and a straight edge. And i dont even have to know how wide the wheel is.
I have several wide wheels with very wide tires, that makes it hard to tell if they are 12" 13" or 14"wide. Without knowing the width, how do you calculate the offset?
If i look at my wheel, and one has 5 1/2 bs, and the other has 3 1/2, i know which one will fit on my car.
Tell me you think that wheel is a 14", you think, and you think the offset is +50mm, or whatever, i have no clue whether that will fit.
 
What i like about backspace is that it can be measured with a tape measure and a straight edge. And i dont even have to know how wide the wheel is.
I have several wide wheels with very wide tires, that makes it hard to tell if they are 12" 13" or 14"wide. Without knowing the width, how do you calculate the offset?
If i look at my wheel, and one has 5 1/2 bs, and the other has 3 1/2, i know which one will fit on my car.
Tell me you think that wheel is a 14", you think, and you think the offset is +50mm, or whatever, i have no clue whether that will fit.

First, if you can't tell how wide the wheel is then you don't know if it will fit with only the backspace measurement, because you don't know how far it will stick out. You still need more information. If you have that information, then you can come up with the offset.

Meanwhile, if you tell me the offset I can tell you exactly whether or not it will fit. You're just not understanding how to use offset, and you don't use it enough to be familiar with it.

And finally, the offset is cast directly into most modern wheels. So, you just need to look at the backside of the wheel for the "ET" number. Backspace usually is not and has to be measured.

Like this
img_1741-jpg.jpg

Or this (not the best picture or stamping, its a 0 )
img_3647-jpg.jpg
 
If i cant measure the wheel width, its cause its got a tire on it, and i can measure the tire. An 18" section width tire with a 3 1/2 bs will fit, with 5 1/2 it wont. Dont know, or care, what the offset is.
Edit: curious why it is"ET" and not something self explanatory, like "offset ", or "off" or a simple + or - number?
 
If i cant measure the wheel width, its cause its got a tire on it, and i can measure the tire. An 18" section width tire with a 3 1/2 bs will fit, with 5 1/2 it wont. Dont know, or care, what the offset is.
Edit: curious why it is"ET" and not something self explanatory, like "offset ", or "off" or a simple + or - number?

And yet you're talking about a wheel that will in no way, shape or form fit one of these cars without massive modifications, making the whole thing moot. That little bit of info is good for your car alone. Not very helpful to anyone else. Which is why there are standardized ways to measure this stuff.

And again, just look at the wheel!!! If it was made in the last ten years, the specs are stamped or cast right into it.

As far as ET, it's German. It's short form of the German word 'Einpresstiefe' which translates as 'insertion depth'
 
If i cant measure the wheel width, its cause its got a tire on it, and i can measure the tire.

That's exactly why I like to know the offset. If I know the width of the tire, all I have to do is divide it in half and add the offset to know how far the inside of the tire is from the mounting surface. The backspacing only tells me where the inside of the wheel is and I have to go through several more calculations to figure out where the tire would land.

Add that backspacing uses some unknown number (the thickness of the lip) so it's kind of a guess as to where the inside of the tire is. Like Blu mentioned above, 1/2" works and is close enough but it's still just an approximation. On the other hand, the tire is always centered on the rim so using the offset is easy.

And generally it is the tire that hits before the rim. In most cases anyway.
 
That's exactly why I like to know the offset. If I know the width of the tire, all I have to do is divide it in half and add the offset to know how far the inside of the tire is from the mounting surface. The backspacing only tells me where the inside of the wheel is and I have to go through several more calculations to figure out where the tire would land.

Add that backspacing uses some unknown number (the thickness of the lip) so it's kind of a guess as to where the inside of the tire is. Like Blu mentioned above, 1/2" works and is close enough but it's still just an approximation. On the other hand, the tire is always centered on the rim so using the offset is easy.

And generally it is the tire that hits before the rim. In most cases anyway.
Uh, if the rim has a tire on it, you can put a straightedge across the tire and measure to the wheel mount face, and know exactly where the tire is, without any calculations or knowing what the offset is, or how wide the rim is.
 
I would like to make a note. Not all 275mm tires are the same width. A lot of the 200TW tires that have come out in the past year or so are actually wider (by approx. 10mm) than their predecessor's at the same size. While they are wider, most tires aren't taller for the same size. Notice the size difference between a Falken RT660 and RT615K+.

RT660 (11.2" wide on 9.5" wide wheel): https://www.tirerack.com/tires/tire...ewall=Blackwall&partnum=735WR8RT660&tab=Sizes
RT615K+ (10.8" wide on 9.5" wide wheel): https://www.tirerack.com/tires/tire...all=Blackwall&partnum=735WR8RT615KP&tab=Sizes

My main point... Measure, measure, measure. And even after that, you might still rub.
 
I would like to make a note. Not all 275mm tires are the same width. A lot of the 200TW tires that have come out in the past year or so are actually wider (by approx. 10mm) than their predecessor's at the same size. While they are wider, most tires aren't taller for the same size. Notice the size difference between a Falken RT660 and RT615K+.

RT660 (11.2" wide on 9.5" wide wheel): https://www.tirerack.com/tires/tire...ewall=Blackwall&partnum=735WR8RT660&tab=Sizes
RT615K+ (10.8" wide on 9.5" wide wheel): https://www.tirerack.com/tires/tires.jsp?tireMake=Falken&tireModel=Azenis+RT615K+&sidewall=Blackwall&partnum=735WR8RT615KP&tab=Sizes

My main point... Measure, measure, measure. And even after that, you might still rub.
Section widths vary widely with manufacturer but should be pretty close with a low profile sidewall tire. The sidewall bulge is what gets you.
 
well I splurged a little bit.. Wheels are ordered but in the need of updating and treating myself. I got the full cobra disc brake set up from Dr diff Front and Rear. Got everything to redo the rear axle for a B body plus a tur trac sure grip with some 3.91 gears to go with it. Plan on driving the car a lot this year and enjoying it handling better other then straight burst of speed with the skinnys. Ill post more once I get going.
 
I’ve always had a soft spot for Enkei wheels ever since a friends EVO had them soo I joined the gang
17CCAC67-2CE4-49E4-98F5-F9559ACB6E75.jpeg
 
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