18" wheels

72bluNblu

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I realize I'm digging an old thread up, but there's some great info here... wanted to see if anyone could shoot holes in my thoughts?

I've got a 76 Scamp currently with 10" drums and a 7.25 rear end. I just bought used some OEM disc spindles. Also just ordered a ton of suspension components to rebuild the front (tubular UCA's, rebuild kit for LCA's, sway bar, adjustable strut rods, new torsion bars, and about every rod end and bushing imaginable)... also have the Wilwood Dynalite Big Brake kit on its way.

The car currently has SBP but I'll be swapping the front to LBP with the Wilwood kit. For the rear, I anticipate pulling my axles and drums and running them up to the machine shop to have the LBP added to them.

But now I've gotta figure out wheels/tires... I'm leaning toward this set of 18x8 with 4.5" backspace...American Racing 51088012400: VN510 Draft Series Vintage Silver Wheel 18" x 8" - JEGS High Performance. my point of concern is that the car currently has the SBP 14x5.5 rallys on it (they appear to be about 3.5" backspace) and I've had a time or two where I've been backing out of the garage at full lock (kinda uphill) and heard the front tire scrape I believe the top of the fender lip...

If I'm doing the math right, the new wheels would be 2.5" wider than my existing ones. 1" of that would be to the inside (difference between 3.5 and 4.5 backspace) and the remaining 1.5" would be to the outside, which theoretically would make my steering lock/tire scrape issue worse... however, I also tend to think the lower profile tires probably don't bulge out as much beyond the width of the wheel as the current 14" (215/70/14) ones do, so maybe it will be less than 1.5" closer once it's up to the outer diameter of the tire? Sound right, or am I completely off base?

Which Wilwood kit? Some alter the track width, which will change the backspace you need. Also, some of their kits have a VERY large hub diameter, which will seriously limit wheel options.

In general, if you want to run an 8" wide wheel up front and put a tire on it that's worthwhile, you need at least a 5" backspace. 18x8" with a 4.5" backspace will probably be too close to the fenders on most cars even with a fairly modest 245/40/18. That combo would be 15mm further out than the 275/35/18's I run on 18x9's, and my fenders are rolled and pushed.
 

72bluNblu

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This one: Wilwood Disc Brakes - 1976 Plymouth Scamp All - Front Brake Kit No.: 140-15468-DR

It appears to not alter track width, but I don't see any info about the hub diameter.

The hub dimensions are right on that page. That’s the one I was talking about, the hub diameter is 3.1”. Which is gigantic, even the factory hubs limit wheel selection some and they’re only 2.7”.

A923272D-ED63-4875-9055-0FDD9867D54E.jpeg
 

72bluNblu

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Honestly, I’m not much of a Wilwood fan. You can run the 11.75” Mopar rotors and calipers and get every bit as much braking as with the Wilwoods. DoctorDiff also has some larger diameter brake kits available. If you have the 73+ Mopar rotors you can use any of his disk kits. The 11.75’s are just later B/R body Mopar parts but DoctorDiff sells them as his stage II kit. I run his 13” cobra kit on my Duster at the moment, will have the 13” Viper kit on there shortly.

Only way to get a normal size hub from Wilwood is with their 6 piston kit.
 

rich_mc

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Hmmm... I looked at the Dr Diff stuff but didn't care fir the caliper used in the 11.75 dia kit... the Cobra 13" caliper is pretty nice though... I'll have to call them to see about hub diameter dimensions as it may make sense to swap to a different kit before I even open the Wilwood one that arrived today...
 

72bluNblu

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Hmmm... I looked at the Dr Diff stuff but didn't care fir the caliper used in the 11.75 dia kit... the Cobra 13" caliper is pretty nice though... I'll have to call them to see about hub diameter dimensions as it may make sense to swap to a different kit before I even open the Wilwood one that arrived today...

The caliper with the 11.75” kit is just a stock Mopar single piston. But it’s a 2.75” piston, which is gigantic, and from a math standpoint anyway it has way more clamp force than the Wilwood calipers. Some of that is lost in translation because its a single piston slider vs a fixed.

The hubs with the 13” kits are just under 2.7”, they’re basically an aluminum version of the 73+ Mopar hubs without the rotor attached.
 

Mojoe9955

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No extra height, the car is lowered almost 2" in the front compared to stock. All of the modifications were to fit the wide 275's, with a narrower tire nothing would have been necessary. The width of the tires meant I had to trim the lip on the back of the front fender wheel opening, and I extended the fender to bumper brace to push the front corner out further. I also run tubular UCA's to clear the 9" wide front rim at full lock. But all of that was because of the tire width. Even with a 245 up front none of that would have been necessary.

The car is not tubbed, I have a 1/2" spring offset kit installed and about a 1/2" trimmed from the quarter lips, but the wheel tubs are stock. You don't have that much room on a dart though.

As long as you keep your front tire height at or below 26" not much is needed for modifications, it depends more on the tire width and backspacing below that.
I have a 8.25 rear and later a body disc conversion with 10.75 rotors. I really like how those Enkis. I'm looking at some 18x8.5's on FB.
As long as I stay with less then 26"/ 45 tires I should ok?
Thanks
 
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Jarlaxle

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No extra height, the car is lowered almost 2" in the front compared to stock. All of the modifications were to fit the wide 275's, with a narrower tire nothing would have been necessary. The width of the tires meant I had to trim the lip on the back of the front fender wheel opening, and I extended the fender to bumper brace to push the front corner out further. I also run tubular UCA's to clear the 9" wide front rim at full lock. But all of that was because of the tire width. Even with a 245 up front none of that would have been necessary.

The car is not tubbed, I have a 1/2" spring offset kit installed and about a 1/2" trimmed from the quarter lips, but the wheel tubs are stock. You don't have that much room on a dart though.

As long as you keep your front tire height at or below 26" not much is needed for modifications, it depends more on the tire width and backspacing below that.
I know this is a very old post, but I'm planning on 17 or 18" wheels on my 73. (See avatar.) Would your sizing here work for 17" wheels, as well? Say...235/50 front? It seems like you're saying even an 8" wheel would clear in front without the tubular UCA swap...right?
 

72bluNblu

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I have a 8.25 rear and later a body disc conversion with 10.75 rotors. I really like how those Enkis. I'm looking at some 18x8.5's on FB.
As long as I stay with less then 26"/ 45 tires I should ok?
Thanks

There’s a lot of things that go into it, the ride height on your car is probably the biggest thing, followed by Ma Mopars relatively loose body tolerances.

But in general, if you keep the height below 26” and don’t go wider than about a 245 or 255 and run between 5.25” and about 5.7” of backspace that should work
I know this is a very old post, but I'm planning on 17 or 18" wheels on my 73. (See avatar.) Would your sizing here work for 17" wheels, as well? Say...235/50 front? It seems like you're saying even an 8" wheel would clear in front without the tubular UCA swap...right?

Only thing with 17’s is the outer tie rod end limits the backspace, about the most you can do with most 17’s is about 5.6”-5.7”. With that backspace and a 17x8 you can manage a 245 or 255
 

Jarlaxle

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There’s a lot of things that go into it, the ride height on your car is probably the biggest thing, followed by Ma Mopars relatively loose body tolerances.

But in general, if you keep the height below 26” and don’t go wider than about a 245 or 255 and run between 5.25” and about 5.7” of backspace that should work


Only thing with 17’s is the outer tie rod end limits the backspace, about the most you can do with most 17’s is about 5.6”-5.7”. With that backspace and a 17x8 you can manage a 245 or 255
My concerns are cost (18s are pricey), and having room for sidewall on an A with the short tires.
 
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72bluNblu

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Mu concerns are cost (18s are pricey), and having room for sidewall on an A with the short tires.

Totally get it. As long as you stay under 26” for the overall tire height and don’t run more than 5.7” of backspace or so a 17x8 will work and shouldn’t hit the UCA at full steering lock and suspend droop. 245’s should clear with 73+ brakes if you run around 5.25” to 5.7” of backspace
 

Jarlaxle

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Totally get it. As long as you stay under 26” for the overall tire height and don’t run more than 5.7” of backspace or so a 17x8 will work and shouldn’t hit the UCA at full steering lock and suspend droop. 245’s should clear with 73+ brakes if you run around 5.25” to 5.7” of backspace
I was thinking 17x7, probably 5" backspace. I think I'll need wildly different backspace I back, with the narrow axle.
 

1971 CY Dodge Dart

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I'm running Ridler 18x8 wheels over my Wilwood brakes. The tires are 235/40-18"s. I bought the car with these and the 18" have grown on me.
IMG_1719.jpg
 
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