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PostPosted: Fri Aug 15, 2008 2:13 pm 
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EFI Slant 6
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Location: Western Maryland
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Hey All,

I am getting ready to purchase some tires for my \6 4d 73 Dart driver. I want to do this right the first time.

Right now the car has 195/75/14 's on stock steel lbp wheels. I also have a set of 15" lbp wheels at my disposal

I have not figured out what gear is in the rear yet (l'll do that this weekend) but I assume it is a highway gear.

I am trying to find out what the ideal tire height will be for a daily driver with fuel mileage being the goal. I was thinking I could use a lower profile tire with the 15" rims vs. the 14's and get a bit of handling back to boot.

I will update this post when I figure out the rear end ratio. For now, does anyone have a combo they have had good luck with. Or maybe a rule of thumb for figuring out the best height for my purposes?

Thanks,

CE

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-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!

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PostPosted: Fri Aug 15, 2008 2:37 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
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Location: Fircrest, WA
Car Model: 76 D100
For mileage you want the largest total diameter tire and the skinniest tire width that will safely fit.


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PostPosted: Fri Aug 15, 2008 2:55 pm 
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How wide are your 14" wheels?

"Tallest tires possible for best possible mileage" is not necessarily correct. If you effectively undergear the car by making the tires too tall, you'll have your foot well into the carburetor's power valve all the time just trying to make the car get out of its own way, and that uses up a lot of gasoline. The optimal tire diameter depends not only on rear axle ratio and engine/transmission configuration, but also whether you use the car mostly in town, mostly on the freeway (and if so at what cruise speed) or an even mix of both.

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PostPosted: Sat Aug 16, 2008 4:04 am 
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EFI Slant 6
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Joined: Tue Aug 14, 2007 11:04 am
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Location: Western Maryland
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Quote:
How wide are your 14" wheels?

"Tallest tires possible for best possible mileage" is not necessarily correct. If you effectively undergear the car by making the tires too tall, you'll have your foot well into the carburetor's power valve all the time just trying to make the car get out of its own way, and that uses up a lot of gasoline. The optimal tire diameter depends not only on rear axle ratio and engine/transmission configuration, but also whether you use the car mostly in town, mostly on the freeway (and if so at what cruise speed) or an even mix of both.
Exactly. A friend of mine got better mileage after switching to a steeper gear (went from a 3:90 something to a 4:10) because his foot wasn't down hard trying to keep his speed up.

today I will get out and get the rear ratio, wheel width and so forth

Thanks,

_________________
-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!

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 Post subject: optimal tire size
PostPosted: Sat Aug 16, 2008 6:31 am 
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Turbo Slant 6
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Joined: Sat Oct 25, 2003 12:41 am
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Location: wichita ks
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go to (www.tirerack.com) I think that is the correct site. They have an upgrade garage. It will assist you in determining the 15" tire size that matches your factory 14"--- It also has the formula -- so you can plug in other sizes.


Lawrence


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PostPosted: Sun Aug 17, 2008 7:45 am 
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EFI Slant 6
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Joined: Tue Aug 14, 2007 11:04 am
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Location: Western Maryland
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Ok, I pulled the diff cover while changing the gear oil yesterday. Here are my specs.

-Holley 1 bbl carb (engine is getting a super six upgrade in the near future)
-Stock 73, 904 trans
-2:76 rear gears

The rims I have to choose from are
-14 X 5.5 LBP ralleys
-15 X 5.5 LBP steelies

about 50/50 highway vs. city driving. I am looking for mileage in this car. So what would be my ideal tire height?

Thanks for any info!!!!

CE

_________________
-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!

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PostPosted: Sun Aug 17, 2008 9:35 am 
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Supercharged
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Location: Portland-ish
Car Model: Fiat 500e
Well, 205/65R15 is the same 25.5" diameter as the 195/75R14. Trading an inch of sidewall for an inch of wheel improves steering response and the lower profile usually has a greater tread width. This is the Plus Size Concept. Plus one is nice, but I'm about to do +3 on my Valiant with 255/40R17 on the back and 235/35R17 on the front.

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PostPosted: Sun Aug 17, 2008 9:56 am 
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I would buy a set of 205/70R14 BFGoodrich Radial T/A tires, put 'em on the 14" x 5½" wheels, and be happy. I'd probably be happier with more gear than 2.76 — I really like a 3.2 rear axle with 205/70R14 tires — but that can come along down the road sometime if you decide you want it.

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PostPosted: Sun Aug 17, 2008 12:46 pm 
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Turbo EFI
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Joined: Tue Feb 18, 2003 7:34 am
Posts: 2479
Location: Lubbock, Texas
Car Model: 1964 Plymouth Valiant V200 Sedan
Dan's recommendation is a good one, particularly with your 14" Rallye wheels. Reasonably modern tires and good looks!
I went with 205-60R15's on 15X7's, as a Plus Two from the 185-80R13's that my car had when I got it. This is a good size for my '64 with 2.94 gears, essentially duplicating the old tire diameter and keeping the speedometer reasonable accurate.

Here's a TIRE SIZE CALCULATOR so you can compare sizes.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO


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PostPosted: Sun Aug 17, 2008 7:15 pm 
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Turbo Slant 6
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Joined: Sat Aug 02, 2008 8:49 pm
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Location: Bowling Green, KY
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Quote:
I would buy a set of 205/70R14 BFGoodrich Radial T/A tires
Hey, those are the exact tires I want, though no place around here sells them. :(

I have 205/75R14s on the front and rear, mounted on 14" Cragar SS rims, and I think they are just fine, but a little big. I have normal acceleration and handeling, although I do get the accasional "scrape" when im backing out of the driveway.

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels


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PostPosted: Mon Aug 18, 2008 5:29 pm 
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TBI Slant 6
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Joined: Tue Mar 18, 2008 2:50 pm
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Location: Denver Pa
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Hey joshie im all in on your idea of 17". I've be thinking, dreamin, and test fitting for about the last 5 months on which way to go. This is what i came up with. 225-45r17 front 245-45r17 rear the steering responce and control gained is amazing. Not to mention the looks i get.

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_________________
Image75 dart custom, 225, >10.5-1, hurricane, 500holley, erson cam, 904, 8.8 ford 3.55 or 3.91 aussielocked, 17" steelies, and much more.


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PostPosted: Mon Aug 18, 2008 5:38 pm 
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Get those blue phony-zeenon diamond-crystal toy headlites off the car now, please, before you cause a crash and lose your beautiful Dart.

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Too many people who were born on third base actually believe they've hit a triple.

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 Post subject:
PostPosted: Mon Aug 18, 2008 5:41 pm 
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TBI Slant 6
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Joined: Tue Mar 18, 2008 2:50 pm
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Location: Denver Pa
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Dont worry dan they are a show only light never to be lit on the road. Im saving up for a set from you some time in the future. Im getting tired of putting them in and taking them out after shows.

_________________
Image75 dart custom, 225, >10.5-1, hurricane, 500holley, erson cam, 904, 8.8 ford 3.55 or 3.91 aussielocked, 17" steelies, and much more.


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PostPosted: Mon Aug 18, 2008 5:59 pm 
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Quote:
Dont worry dan they are a show only light never to be lit on the road. Im saving up for a set from you some time in the future. Im getting tired of putting them in and taking them out after shows.
OK, cool. I never require that anyone buy any lights from me — I wasn't badgering you to buy lights from me here — it's just that those lights like you have in there are so unsafe that I have to squawk when I see 'em in a car. Glad to read you don't actually use them.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

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 Post subject:
PostPosted: Mon Aug 18, 2008 6:12 pm 
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TBI Slant 6
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Joined: Tue Mar 18, 2008 2:50 pm
Posts: 179
Location: Denver Pa
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I admire your knowledge of lighting and will get in contact with you on a later note about the light. As i was putting the picture onto my post I thought to myself " I wonder how long till dan will comment on my light" and not even five minutes later you noticed.

_________________
Image75 dart custom, 225, >10.5-1, hurricane, 500holley, erson cam, 904, 8.8 ford 3.55 or 3.91 aussielocked, 17" steelies, and much more.


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