63 Dodge Dart, now let me see;)

[Johnny Dart]

Good lord, the information you are getting is terrible imo.
Where do we start ? For starters 235/245/255 series tires are
waaay to big and heavy for your little slant motor. You will lug that poor motor to death. More on tires in a minute.
Air shocks ? He'll no !!!! Nice little set of KYB's or Monroe's is all you need. 355 gear ? Going from a 355 gear to a 323 gear makes absolutely no sense. Keep the money in your pocket, and stay with the 355. That's a great gear and it's already in your car. Now the elephant in the room. Your tires are rubbing. Yes, because you have to big a tire and wheels with the wrong offset !!!!! I'm not sure if you have a money tree in the backyard, maybe you do. But you are getting horrible advice at the tire shop as well. An 8-in wheel on the back of that car is not the answer, or needed. What you need is a nice Wheel and Tire setup, that is light, looks good, and doesn't kill the performance of your little Slant six motor. Without reading all the pages in your post, I'm assuming you have big bolt pattern all around ? My advice to you would be to get a Chrysler 14-in steel wheel ( black or body color) with a 205 70 14 or 215 70 14 BFG Tire all the way around. Top it off with a early A dog dish cap, or no Cap at all. No rubbing, no nothing.
But heck, what do I know. Your money, your car.
All the best.

 

[GGs66GT]

The 8” not going to cut it . 7 x 15 wheel is the max for you . With more back spacing .

 

[Killer6]

Hi Glen;) 4" on the back spacing and 8" width. I could be off a tad on the back spacing, possibly 3 3/4;)

I agree, 8" wide is out unless You have the perfect offset/backspace & downsized tires, 14" rims in the same sizes are going to drop You down ~1/2" from the tubs....that may help.
Keeping in mind, if You want to gain 1/2" of clearance w/o changing offset/backspace, going to a 225 from a 255 would get You 9/16",...235 would only get You a tick over 3/8".
It looks like You did a great job centering-up that rear axle, so whatever route You choose should be good, if it's a tad tight but enough.
And You can thank @72bluNblu for taking the initiative to start that Sticky Thread, even when I've known or measured that stuff, I can't always count on My memory anymore,........or find the notes where I scribbled them down..!!!

 

[GGs66GT]

She is running 73-76 disc brakes with BBP so 14” wheels are out .

Hay guys check out tremic.com it has a gear ratio rpm calculator and a tire size calculator . The 2 interact , you can even change the gear ratio on the 4 speed trans to torque flight ratios just change the 1st and 2nd numbers and use the 1to1 for 3rd .

 

[72bluNblu]

Good grief! So much terrible information.

• A 255/60/15 fits perfectly fine on a 7" wheel. It's literally still in the recommended range from the manufacturer, which is typically pretty conservative (lawyers!)
• The 8 1/4 is narrower than A-body 8 3/4's, as already mentioned. It's a BETTER rear end for width on an early A.
• Air shocks are terrible. So are KYB's.
• It looks like there is PLENTY of room for a 255/60/15 on that car. You need a 15x7" with at least 4" of backspace. About the max on an 8 1/4 is a 15x7 with 4.25" of backspace, that's actually a mopar dimension, cop wheels are 15x7 and 4.25" backspace. With a 255 the 4.25" backspace will be pushing it for spring clearance, but a small wheel spacer is easier to add than extra room to the quarter!
• 255's are heavy. They will slow your 0-60 but once you're rolling it doesn't make all that much difference. If you're not drag racing it won't matter.
• 14" wheels do work with 73+ disks as long as they're the 10.95" disks and not the 11.75's. 14's were still stock on 73+ BBP cars.

I don't know who was doing the math on your engine RPMS, but, it's wrong.

With a 3.55 rear gear, a 26" tall tire (235/60/15), and a 1:1 4th gear at 3,500 RPM you get 75 mph.

with a 26.5" tall tire (245/60/15) at 3,500 you get 77 mph

with a 27" tall tire (255/60/15) at 3,500 you get 79 mph

3,500 rpm is perfectly doable for these engines. Maybe not what you'd want for an 8 hour freeway drive, but it works just fine and 75mph will be ok on the freeways as well. Heck with the 255's you're only at 3,200 for 72 mph, that's not bad at all.
You can play with all of that with the Tremec calculator mentioned above, but here's a good link for it Gear Ratio Calculator | TREMEC

 

[Johnny Dart]

She is running 73-76 disc brakes with BBP so 14” wheels are out .

Hay guys check out tremic.com it has a gear ratio rpm calculator and a tire size calculator . The 2 interact , you can even change the gear ratio on the 4 speed trans to torque flight ratios just change the 1st and 2nd numbers and use the 1to1 for 3rd .

Why are 14" wheels out ?

 

[Killer6]

I want to be sure to point out that, when I compare the size changes, that it applies to the same Brand & Model of tire only. I had at one point 3 sets of 225/50R-15's; Falls Mastercraft Avenger GTH's, Hoosier GT's(H), & Uniroyal Rallye GTH's. There was a whopping inch and a quarter difference in width between them, the Hoosiers were the narrowest, the Uniroyals were probably closest to being correct, & the Avengers were so wide I couldn't put them on My '88 ShelbyZ.

 

[72bluNblu]

Why are 14" wheels out ?

Yeah they're not. 14" wheels fit 73+ 10.95" disks just fine

 

[petty437]

You have done an AMAZING job on what you started with. It looks great, Dne'! Drive that thing and be proud!

BTW, I ended up buying Sof Seal door seals as I was having the same issue with other manufacturers.

 

[Dne007]

Good morning, gee I go away for just a few hours and loads of information pops up here;)
The advice/recommendations is wonderful, of course ultimately I have to make the decisions. You know the only thing I had to source out was when having my engine work done $, oh and having a driveshaft made, oh and having the dart sandblasted, other than that I did everything else. We all know that working on old cars can be an expensive ordeal, and time consuming. I'm retired and have a husband which supports my crazy habit and I do love it so and I admit I'm not an expert and rely on forums and the internet, otherwise I'd probably never have gotten into this hobby. I have done some remarkable "restorations" since 2006, accumulated tools and equipment which would make a professional mechanic jealous.
If I were to have taken my Dart to a restoration facility/shop, it would have easily cost a phenomenal amount of money, however, my labor is dirt cheap, much like most here. there are unknown variables which I've encountered along this challenging journey including the tire thing. IT will be resolved probably at a cost, but I have the money to absorb it. Not long from now, we'll be driving it to car gatherings for show n tell and enjoying the other builders. I can say I'm a builder, a mechanic, fabricator, experimenter, a decent welder, can do body work, replace panels, troubleshoot, etc.
Have no idea where I'm going with this, other than I'm having fun in my garage and that gives me peace of mind and lowers my blood pressure I'm sure. Months from now I'll fade off and most will wonder what happened to dne007.
So, hang in there with me, I want you guys to have fun along with me

 

[Johnny Dart]

Yeah they're not. 14" wheels fit 73+ 10.95" disks just fine

Well yah. A-body big bolt steel and rallye wheels from 73 on.
Still waiting for a response.

 

[barbee6043]

I am sure, when I say we all admire and appreciate your work here, it is fact... and bottom line is never be a stranger on this site.

Advice?? I always remember back some 50 odd years when my father in law said this " I will offer advice but realize, you are the one that must decide whether to add it to your arsenal or not!"

 

[GGs66GT]

Why are 14" wheels out ?

In her case it would require buying new wheels and tires .

 

[GGs66GT]

Yeah they're not. 14" wheels fit 73+ 10.95" disks just fine

Gee you learn something new everyday .

 

[George Jets]

I want to see a video of @Dne007 when she gets zeroed in on the rear gears and rear tire final fit sizes.

Pulling gears and working that Slant 6 for what it is worth. Smooth operation, all components complimenting each other.



As an Example....☆☆☆

 

[Dne007]

Wow, that sounds great! I wish!!

I want to see a video of @Dne007 when she gets zeroed in on the rear gears and rear tire final fit sizes.

Pulling gears and working that Slant 6 for what it is worth. Smooth operation, all components complimenting each other.



As an Example....☆☆☆

 

[Dne007]

I had ordered a single wheel from the tire store, just out of curiosity sakes. Unfortunately the wheel is a 4 3/4 and wouldn't bolt up. But I was able to do a comparison. The BS was indeed 4.5", but the outer lip is the same as what I have. We all kind of new that. Tomorrow I'll discuss the option of a custom wheel with more than likely a 5" Back spacing. The Tire store guy and I will be talking with American Racing to discuss the details. If they will indeed do it. Don't try to talk me out of this, this is special

 

[Dne007]

This idea placed the tire I have dead center of the wheel well, it would be perfect with the back spacing of ~ 5" or 4 3/4, let's see what happens

omg, that's exciting seeing that wide tire!! That's why I mini tubbed and relocated the leaf springs, plus it was "educational"

Here the tire is deep within well and probably would never go that deep unless pulling Smokey and the Bandit stuff

 

[George Jets]

The ball is in your court now, my brain is all maxed out with all this "Numbers Crunching".

Rocket 1963 you are clear to land... God Speed !


☆☆☆☆☆

 

[George Jets]

This idea placed the tire I have dead center of the wheel well, it would be perfect with the back spacing of ~ 5" or 4 3/4, let's see what happens

View attachment 1716474680

omg, that's exciting seeing that wide tire!! That's why I mini tubbed and relocated the leaf springs, plus it was "educational"
View attachment 1716474681

Here the tire is deep within well and probably would never go that deep unless pulling Smokey and the Bandit stuff
View attachment 1716474682

I did not know you Mini-Tubbed this and relocated the rear leafs inward.

You have the room you need, just need 3/4" less offset on the outer face, then push everything else to the inside.


☆☆☆☆☆

 

[72bluNblu]

This idea placed the tire I have dead center of the wheel well, it would be perfect with the back spacing of ~ 5" or 4 3/4, let's see what happens

View attachment 1716474680

omg, that's exciting seeing that wide tire!! That's why I mini tubbed and relocated the leaf springs, plus it was "educational"
View attachment 1716474681

Here the tire is deep within well and probably would never go that deep unless pulling Smokey and the Bandit stuff
View attachment 1716474682

Relocated and mini-tubbed?

Well heck, I should have paid more attention, you have inches of extra room in there. You should run at least 5" of backspace.

I tried 275/40/17's on my Duster when it had a 7.25" rear axle and stock spring locations, those were on 17x9's and it would have needed a little less than 4.75" of backspace to clear those. A BBP 7.25 is the same width as an 8 1/4", so, yeah at least 5" of backspace. Set your tire up so you have at least a 1/2" clearance to the outer wheel tub/quarter lip.

 

[mygasser]

if the outer lip measures the same on both 7" and 8" wheels you may just get away with the 255 tyre you have. that's because the extra 1" in width is on the inside so the tyre and sidewall bulge will be 'pulled' inward away from the outer wheel house. hope that makes sense and is at least worth a mockup
neil.

 

[Dne007]

Darn, I should have brought that back up about the mini tub and leaf spring relocation
I am going to see if the tire store has the same rim with the correct wheel spacing and 7”, just for educational purposes;)

But I believe I’ll be ordering the new wheel , made to order for sure, it will be unique

 

[barbee6043]

Yea I missed that mini tub/rear leaf deal also.
That 63 has pro street wrote all over it! Take us back to the 80s' Scotty! or was it 90s!??? Can't recall!

 

[Dne007]

Pro street! I like that!!

I spent part of this morning at the tire store~ Dereck the sales guy loaned a this measuring device. Set the wheel spacing, wheel width, back spacing, then mount to the axle, and can set the tire in it too. Actually, I think the way I measured was pretty good. He was just trying to lessen the chance for mistakes.

I'm going with the 9" (total width outside to outside of the rim or an 8" wheel), 5 1/4 back spacing. 5 1/4 was as deep at they could go, if it had been a 7" wheel, only 4.5" So, six weeks from now I'll drive over there to have them mount the tires, in the meantime, I have plenty going on, we have fence we need to address, about 60', got blown down and is propped up. We really need to get on that.

It doesn't work so well with the tire resting on it

This is the one I'd be going with, but the contraption here was set at 5", it will be 5 1/4. If for some reason the 255 doesn't work, I'll buy other tires.

Found this !!

Not looking forward to the other half