Jarlaxle
Well-Known Member
I'm torn between 17s or 18s. I'm thinking 17s, 245/45 (or even 235/50) probably. I was thinking 4.5" backspace on an 8" wheel...you say 5+"?
Yeah, that's too low. I would lose headers in a week that low in this area.
My "new" '74 Duster- or why I need a project like a hole in the head
- Thread starter 72bluNblu
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I've seen you talk a lot about that mod. Thanks for posting some pictures!
DionR
Well-Known Member
I am currently running a 245/45R17 on a 17x8 +30mm wheel. I guess I should just use that as my basis for if a 275/35R18 would fit if it was on a rim with the same offset.
Comparing my current tire to a Falken RT660 275/35R17 doesn't look positive. The RT660 section width is 1.6" wider, so .8" per side on a rim with the same offset as current. Tread with is a full 2" wider. That isn't going to happen without some sheetmetal mods. Even a Conti ExtremeContact Sport 02 is .65" wider per side in section width and tread width, which might work but will use up all of the available room.
Rule of thumb is the section width will change by 0.20" for every 1/2" of rim width, and since the measured rim for the RT660 is 9.5", it would narrow the tire and put it at more like .7" wider than my current tire per side on an 18x9 rim. Maybe? But probably not.
Wow, tire brand really does matter. The RT660 shows a section width of 11.2" and tread width of 10.1" while the Conti shows 10.9" and 9.4". Both for a 275/35R18. That's .7" more tread width for the RT660!
18x9 +30's should be fine for the front. Your brake set up should be about the same as mine for track width, mine are +35's but it's a small difference. The other thing is to look at 18x9.5's, it seems like there's a lot in the +30 to +40 range for aftermarket wheels in 18x9.5". And that should be fine too, I'd lean more to +35 with those. If I buy another set of wheels for the front they'll probably be 18x10's.
Really the 275's aren't that big of a deal as long as you've got 6" of backspace. Maybe a trim on the corner and a little lip rolling, the rest is ride height dependent and most folks don't run as low as I do.
Yeah the suspension isn't the issue for me in going any lower, the wheels hit the body and that would be true of any kind of suspension up front. Maybe even more so with the HDK, the way I'm set up with my QA1 LCA's and bumpstop I should be on the bumpstop at about the same time my tires touch the inner fender. Apparently there is a little bit of overlap there...
This will be my next major bodywork modification, I'll add the tub to raise the inner fender (72BBswingers old ride)
Yeah an 8" wheel with 4.5" backspace isn't enough. For a 245 the minimum would be about 5.25" of backspace, and that would put the outer face of the wheel in the same place as my 275's. Ideally you'd want more like 5.5"-5.7" if you wanted to avoid doing any trimming/fitting. With a 17" rim ~5.7" is the maximum backspace too, just FYI. A 17" rim doesn't clear the outer tie rod end much beyond that. With an 18" rim the outer tie rod end fits inside the lip of the rim, so you can run more backspace (6"+) which is what you need to step up to 275's.
My Doug's headers sit around 3.75" to the flange on the low side. It's not bad as long as I take it easy on speed bumps.
DionR
Well-Known Member
I fight with the tire rubbing on my frame rail and z-bar bracket. Just got done drilled a small hole in the lower control arm for a 6mm bolt for the steering stops to hit and now I am clear, but not 0.6" clear. So a wheel with more backspacing and a wider tire is only going to be worse. Not really sure why my car rubs when I know of others that don't have that issue, but it is what it is.
The additional 5mm of positive offset would probably make that RT660 clear the top of my fender with a 9" rim. Really doubt it will work on a 30mm offset rim unless I start pushing the fender around. Not the end of the world to do that, just need to accept it before I do anything. Car is painted but it's not like it doesn't need to be straightened and painted again.
Worst case, I guess I could do like the guy that put +12mm offset Enki's on his Duster. Somehow he got it to work. And I think he even ran a 285 tire.
Yeah I pretty sure I didn’t put the lower bump stops on when I installed my suspension, and add in the fact that I was at 23.5”, it definitely rubbed pretty good! Enough actually that it discolored the paint on the engine bay side of the inner fender. Some type of front mini tub is definitely in my long term plans as well!
DionR
Well-Known Member
Good grief.
A Conti EC Sport 02 275/35R18 spec's out at 9.4" tread width. My current Cooper tires spec at 8.1". An RT660 245/45R18 spec's out as 9" tread width. Not far off the 275 and almost an inch more than my current tire. And a Rival S 1.5 is a full inch wider in tread width than my current tire.
So depending on which brand 275/35R18 you compare, there are some 245/40R18 tires that are almost as wide.
A Conti EC Sport 02 275/35R18 spec's out at 9.4" tread width. My current Cooper tires spec at 8.1". An RT660 245/45R18 spec's out as 9" tread width. Not far off the 275 and almost an inch more than my current tire. And a Rival S 1.5 is a full inch wider in tread width than my current tire.
So depending on which brand 275/35R18 you compare, there are some 245/40R18 tires that are almost as wide.
Jarlaxle
Well-Known Member
Don't you have a wider track in front due to your brakes?
The steering stops being cast into the lower ball joints is kind of a crap shoot. After talking to 72BBSwinger about running a 6.4" backspace on his car, he said he never had any issues with the frame rub, which surprised the heck out of me because even with ~6.1" I had the wheel touch at full lock (when I still had stock LCA's). So I gathered up all the lower ball joints I had from collecting spindles at the local yard and replacing them on all my cars, and found that the height of the steering stops was wildly different between them. Some were barely a bump, others were a 1/2" protrusion. So I stopped putting as much weight on the tire touching the frame at full lock and started looking at steering angle instead.
Now, I run QA1 LCA's so I have no steering stop at all because the lower ball joint doesn't touch anything. But the tires aren't touching the frame yet in this picture...
Older picture, this is with the old set of 275's and before I went to the LED headlights.
Yes, tire specs actually change as much or more by model/manufacturer than by specs sometimes. A 275 should be ~10.8" at the section, but I've seen them go all the way up to 11.2". The Fallen Azeni RT615's on my car now are 10.8" at the section and 9.7" at the tread. The other thing is that the rim makes a big difference too. A 275/35/18 is squeezed on a 9" rim, that's the minimum width. The math would say that I should have .4" hanging over the lip of the rim with 18x9's (they're 10" outside to outside), but really the overhang is closer to a 1/4". So, even with a wider 275 if you're running a 9" rim there's a limit to how wide the section width will really be. The "measuring width" for a 275/35/18 is an 18x9.5". So on a 9" rim you will have a narrower section than the spec, and on a 10" wide rim you might have a wider section than the spec.
It gets even crazier as the tires get taller, the 295/40/18's on my car now are noticeably wider than the 275/35/18's that were on there before. The extra sidewall height allows them to flex out more. I didn't have any rubbing in the quarter with the 295/35/18's, when I went to the 295/40/18's I ended up rubbing a bit on large bumps (which is why I did the reverse tub).
Yes, but it's only about 5mm. It's just the thickness of the rotor at the hub. With the DoctorDiff hub the floating rotor sits on the face of the hub, where with the '73+ disks it's flush. The DoctorDiff hub is basically an aluminum version of a turned down 73+ rotor/hub. DionR has a similar brake set up, he just actually turned his hubs from a set of 73+ rotors.
DionR
Well-Known Member
Jarlaxle
Well-Known Member
So...17x8, 5.25" backspacing, 245/45R17?
Jarlaxle
Well-Known Member
What does a 4'5" backspace wheel interfere with in front? There is a guy near me selling a complete set of Year One 17" Rally wheels with Conti tires-17x9, 5" backspace, 275/40, and 17x8, 4.5" backspace, 245/40.
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Yep, that should work
The fender. A 17x8 with a 4.5” backspace and a 245/40/17 will stick out 15mm further than my 275’s do.
People have done it, I’ve seen those YO rallye’s on A-bodies. You basically need to run the front high enough that they clear. Ends up looking like a 4x4 though, in my opinion anyway.
Jarlaxle
Well-Known Member
I think I need to test fit this...
DionR
Well-Known Member
Any updates?
JBrian
Well-Known Member
For me, and what I wanted to build, this has been the longest and best A-Body thread anywhere! A bunch of build pictures from the past couple of years
JBrian
Well-Known Member
Couple pictures from STL autocross and MoParty 2023. This thread, along with a full complement of parts from Bergman Autocraft has allowed me to build a 52 year old car that I can thrash around an autocross course with impunity, it looks pretty good too! I added a Hellwig rear swaybar last week after these pictures were taken.
Joeycurl
‘72 Demon 440
Very nice! What was your tire/wheel combo?
DionR
Well-Known Member
Completely agree. @72bluNblu has built one of the top cars I want my car to emulate, and done a great job of documenting it and being willing to help me when I have questions. Love the car, love the way he uses it and how he built it, and a great guy.
JBrian, have you done a build thread for your car? If not, might be something to work up.
I started a Word document over a year ago documenting my build (not that it would be of the caliber of Blu's), but still haven't even started the thread.
DionR
Well-Known Member
Who are you asking?
Dartsun
Mopar Dude
Thanks guys! I appreciate the kind words! Although to be completely honest even my car is pretty heavily based on a few earlier builds, like Steve @autoxcuda 's barracuda, or @72BBSwinger 's "blue blur" Dart. Some of it was definitely a "next step" from my '72 Challenger build, although that one took cues from the Green Brick, and some help from Firm Feel and @DoctorDiff.
That Duster is awesome @JBrian , and it's great to see you getting it out there at the events and kicking ***. One of these years I'm going to have to actually start taking mine to stuff, it always seems like I'm at work for any of the big events though. I may have to paint it eventually too!
Not a lot in the update department, at least not in terms of my car. My new shop building has been the priority lately, although that's getting a lot closer. Had 30 yards of concrete put down a couple weeks ago, with a new 30'x42' building on the way. I did finally get around to putting the DoctorDiff 13" Viper kit on it though, so that was a nice improvement in the stopping department even from the 13" Cobra style kit that was on there before.
The old 13" cobra style kit
The new rotors. Same overall diameter, but
Much thicker rotors, lots more meat on these
The new caliper brackets with the aluminum DoctorDiff hubs
The MUCH larger GIII Viper calipers
JBrian
Well-Known Member
Thanks guys! I appreciate the kind words! Although to be completely honest even my car is pretty heavily based on a few earlier builds, like Steve @autoxcuda 's barracuda, or @72BBSwinger 's "blue blur" Dart. Some of it was definitely a "next step" from my '72 Challenger build, although that one took cues from the Green Brick, and some help from Firm Feel and @DoctorDiff.
That Duster is awesome @JBrian , and it's great to see you getting it out there at the events and kicking ***. One of these years I'm going to have to actually start taking mine to stuff, it always seems like I'm at work for any of the big events though. I may have to paint it eventually too!
Not a lot in the update department, at least not in terms of my car. My new shop building has been the priority lately, although that's getting a lot closer. Had 30 yards of concrete put down a couple weeks ago, with a new 30'x42' building on the way. I did finally get around to putting the DoctorDiff 13" Viper kit on it though, so that was a nice improvement in the stopping department even from the 13" Cobra style kit that was on there before.
The old 13" cobra style kit
View attachment 1716150271
The new rotors. Same overall diameter, but
View attachment 1716150272
Much thicker rotors, lots more meat on these
View attachment 1716150273
The new caliper brackets with the aluminum DoctorDiff hubs
View attachment 1716150274
The MUCH larger GIII Viper calipers
View attachment 1716150275
I'm pretty sure for any road or autocross, those 13" rotors will stop with my 14.25" rotors. I do have a Hydroboost as well. A couple of other things to consider with our builds. I'm a little bit older than you and this was my last build. I was green lighted by the boss to do whatever I wanted to do. I assembled this car in my little 20x22 garage over about 2 years of weekends. I did use your Duster as inspiration, just kind of when all in, and added the warmed over 6.1 Hemi, EFISource Goldbox, American Autowire harness, Vintage A/C kit with my own design Sanden 7176 brackets seen above, a Passion 5-speed, flawless body work by a friend in Conroe, TX that is now deceased, rolled all four fenders for clearance, a 67 B-Body rear so I can run modern offset wheels, and the modern Challenger gas cap along with a murdered out triple black V24 rendition.
The car can be driven (like you!), drag raced, abused on an autocross and when I become a better driver (autocross forces you to become a better driver than most couldn't comprehend) on a road course. My goal was to make it look tasteful, and as stock as possible inside and out. I also apologize and don't mean to hijack the best thread on building a tossable A-Body anywhere!
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