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Spare tire |
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1973gts 
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Joined: 05-March-2018 Location: Grand Rapids Mi Status: Offline Points: 720 |
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 Topic: Spare tirePosted: 19-July-2025 at 7:54AM |
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I currently have Cooper Cobra P225 70R 15 tires on my car and have an older set of BF Goodrich Radial T/A P225 70R 14 tires mounted on an original set of Magnum 500's which I put on for winter storage. I need a spare for the trunk and need to know if the size difference will create a possible problem if the smaller tire was used on the rear for short distances due to it being a limited slip rear end. thanks - dave
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Dave - 1973 GTS N code
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72 RS 351
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Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 3443 |
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Posted: 19-July-2025 at 8:55AM |
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Yeah, no don't use that one, it's one inch shorter than the 15" tire. That 225/70R15 is a very common size, I used to buy those for years on my two old Crown Vics. I'd find a decent used tire in the size you want, for a 15" wheel. The jack question is tough. I've been living with my late 90's Fords that have the cute bottle jack, which I've used once. I repair my tires on my vehicle without needing a jack. I don't know what I'll do with my Ranchero's.
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Don
73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000 rpm 351 stroker 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W |
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72FordGTS
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GTS.org Admin Joined: 06-September-2005 Location: Ontario, Canada Status: Offline Points: 6780 |
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Posted: 20-July-2025 at 6:10AM |
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I have 245/60-15s on my car and a 225/70R-14 spare. Even though these tires are only about 0.2" shorter than my tires on the car, I would probably not run it on the rear if I got a flat on the rear. I'd put the spare on the front and take the front and put it on the rear. Maybe that is over cautious, but I wouldn't want to cause issue with the trac-lok.
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Vince
1972 Ford GTS Sportsroof - Survivor, One Family car GTS.org Admin |
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72 RS 351
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Joined: 04-September-2014 Location: Knoxville TN Status: Offline Points: 3443 |
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Posted: 20-July-2025 at 7:25AM |
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Yeah, less than a 1/4" difference won't hurt the diff, but try not to let the tires get that far apart. The clutches aren't that expensive, but it is a big job to R&R the diff, and change the clutches. What you can do is install a True Trac differential, they have no clutches to wear out. Different tire sizes do not effect them at all. I just removed a Torsen diff, from my 98 Explorer which had bad pinion bearings, which ate the gears finally. I swapped the entire rear from my 98 Mounty(identical parts), and removed the Torsen first which I put in about 150k miles earlier. The used diff looks like new, typical appearance of the many gears. In normal applications they should last a lifetime, they aren't for very high power drag racing etc.
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Don
73 Ranchero "Sport 72 front end", floor shift/console, planning EFI 7000 rpm 351 stroker 73 Ranchero GT 351C-4V &4R70W for sale later. 92 Lincoln Mark VII SE GTC, OBDII 347/4R70W |
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