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Largest Diameter Front Tires? - 70 Plymouth B-body

PurpleBeeper

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I'm sure this question has been asked a 100 times, but I don't know the answer. What is the largest front diameter tire you can run on a '70 Road Runner?

I'm not sure if I'm keeping my "factory" steel wheels & poverty hub caps (I think 15x6 in front & definitely 15x8 reproduction "steelies" in back) OR I "might" start looking for some aftermarket wheels/tires, maybe 17" or 18", with lower profile tires???

Regardless, I want to have ONE spare tire that I can use on both front & back (same diameter all around). I really need to get the largest tire I can in back since I'm running 3.91's with no overdrive....so, what IS the largest diameter front tire I can run without any clearance issues turning, etc?

(fyi- I have rolled the rear quarter panel fender lips) THANKS FOR THE HELP!
 
I'm sure this question has been asked a 100 times, but I don't know the answer. What is the largest front diameter tire you can run on a '70 Road Runner?

I'm not sure if I'm keeping my "factory" steel wheels & poverty hub caps (I think 15x6 in front & definitely 15x8 reproduction "steelies" in back) OR I "might" start looking for some aftermarket wheels/tires, maybe 17" or 18", with lower profile tires???

Regardless, I want to have ONE spare tire that I can use on both front & back (same diameter all around). I really need to get the largest tire I can in back since I'm running 3.91's with no overdrive....so, what IS the largest diameter front tire I can run without any clearance issues turning, etc?

(fyi- I have rolled the rear quarter panel fender lips) THANKS FOR THE HELP!

I have Dr. Diff's 13" Brembo brake setup on the front, and a Baer 11.65" setup on the rear. 18x9's (6.38" BS / +35mm offset) with 255/45r18's on the front. Under full lock, with Wilwood .200" wheel spacers, I have maybe an 1/8-1/4" clearance. On the rear, I run 295/45r18's. 18x10's (6.36" BS / +22mm offset). Also, have a .375" Baer wheel spacers to give adequate clearance off the leafs. These were some of the largest (diameter) tires available, as they're a 45 series. You're going to have a tough time deciding if a spare tire is worth not going with a wider width/diameter tire in the rear. I would guess, 27-27.5 x 10" would be were you'll end up for front and rear with 18" wheels (if you want a square setup).

basically;
front 27x10r18
rear 28.5x11.6r18
 
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I run 29" tires on all my old cars, to get that period look.
 
Like mmissile, on a 63 Belvedere and a 68 GTX 29'' was as big as we could without rubbing.
 
I have Dr. Diff's 13" Brembo brake setup on the front, and a Baer 11.65" setup on the rear. 18x9's (6.38" BS / +35mm offset) with 255/45r18's on the front. Under full lock, with Wilwood .200" wheel spacers, I have maybe an 1/8-1/4" clearance. On the rear, I run 295/45r18's. 18x10's (6.36" BS / +22mm offset). Also, have a .375" Baer wheel spacers to give adequate clearance off the leafs. These were some of the largest (diameter) tires available, as they're a 45 series. You're going to have a tough time deciding if a spare tire is worth not going with a wider width/diameter tire in the rear. I would guess, 27-27.5 x 10" would be were you'll end up for front and rear with 18" wheels (if you want a square setup).

I'm running nearly the same setup as Sweet5Ltr with a 1.5" dropped spindle in front and lowered rear springs with no problem. It's close in front under full lock but, as was pointed out to me when I started: How fast will you be going at full lock anyway!
 
Check with Darius. He had a minor issue on his 70 under certain circumstances. Turning, load, backing, not sure.
 
Mine are 26.5 and are 8.5 wide. My rub was solved via an adjustment to where the fender stiffening/support bar attaches to the bumper support bracket.
 
This is just a tough question, we really need to know;

Do you plan on upgrading your brakes? Not every 17-18" wheel is going to work with thicker calipers, such as the Brembo style. You need to have the correct offset, and once you have the correct offset, then, backspacing must be checked. I'm running stock style, upgraded Hotchkis suspension. Someone may post here with an aftermarket k-member or coil-over setup, and could have completely different recommendations. If you're on the fence, just purchase Dr. Diffs 13" Cobra (2-piston) front and (1-piston) 11.7" rear. These work amazing together and have a plethora of pad options. It's still a good idea to install an adjustable proportioning valve, even though some say you don't need to with this setup. You'll also need a 15/16" bore master cylinder if running manual brakes (Dr. Diff will recommend a size for power). Also, be aware that Dr. Diff will refund you the pad price if you choose to order your own. I run the Hawk HPS series for the street. Please don't be 'that guy' with 18" wheels and 11" drums! :rolleyes:

Just more things to think about!!! What do you plan on doing with the car? Just cruising?
 
in my opinion 28" is about the safe limit. wheel offset and width will come into play. at 28" with a stock ride height the tire will contact the sub frame and may come very close to the fender front corner when turning. keep in mind everything is in motion when driving so clearance when the car isn't moving may be contact when moving.
 
I’m running 28”x7.5” M/T front runners with no issue. Though you’d be nuts to try them in the rear. :)
 
Please don't be 'that guy' with 18" wheels and 11" drums! :rolleyes:

Yes, nothing dumber looking than huge *** rims with silver dollar sized discs!
 
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