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What is the largest tire size that can be used on the original Ford Cobra R wheels?

Thanks

Mitch
 

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245 in the front due to spindle clearance issues and 275 or 285's in the back.

Are you talking 17" or 18" Cobra R's? I think the originals were 17 ...
 

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And there's a few flavors of originals as well, there's the original 1995 Cobra R wheel used on the... Cobra R at 17x9, the SVE Thunderbird Cobra R style wheel at 17x7, and the unique 2000 Cobra R wheel at 18x9(I assume this isn't the one).

255s fit in the front with room to spare, tire to spindle clearance is much more a tire height issue, the wheel width/offset is more critical when it comes to width.
 

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I've got 255/45/17 up front on 9" rims; those are due for replacement and I'm probably going to keep that size. Rears are 255/50/17; I'd like to go wider but finding the right combo leaves very limited options that aren't obnoxiously wide and recommended for 10" or wider rims.
 

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Discussion Starter #5
These are the 17" that were sold by Ford for a short time made specifically for the TBird.

Mitch
 

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255/45/17s here on the rear . Works great keeps the birds tail pretty much straight ;)
 

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I've got 255/45/17 up front on 9" rims; those are due for replacement and I'm probably going to keep that size. Rears are 255/50/17; I'd like to go wider but finding the right combo leaves very limited options that aren't obnoxiously wide and recommended for 10" or wider rims.
275's fit cleanly on 9" rims and 285's don't look bad either. I've run both on my 18 x 9 imitation Cobra R's.

Anything higher than 285 and you'll need a 10" rim and you'll need to move the e-brake cable back out of the way.
 

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Any photos of a 285 out back? My concern is that it'll stick out and look obnoxious. The 255s look pretty nicely tucked in on the back. The 255s up front stick out a little and I'm not too keen on how it looks, but there's not much to be done regarding that with a 9" rim. I like the cornering grip too much to switch to a narrower wheel or tire. :D
 

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245 front / 285 Rear on 18 x 9" rims. I'm pretty sure the offset on those rims is 36 mm.

The 285's stick out just a hair but don't look obnoxious.

The fronts are Sumo and the rears are Nitto NT05R's





 

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235/55/17 is a good size for a 7 inch wide wheel. slightly taller than OEM.

245/50/17 is dead on diameterwise but not very good selection.

245/45/17 are pretty short. Even lowered they look small, and the wheel wells on our cars are HUGE front to back.

255/45/17 are great all around with a proper backspacing 9 inch wide wheel (I have 3/16 spacer in front so I have 3/16 gap with spindle, tire is just short of the upper ball joint shaft where it mounts to the top of the spindle).
 

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235/55/17 is a good size for a 7 inch wide wheel. slightly taller than OEM.

245/50/17 is dead on diameterwise but not very good selection.

245/45/17 are pretty short. Even lowered they look small, and the wheel wells on our cars are HUGE front to back.

255/45/17 are great all around with a proper backspacing 9 inch wide wheel (I have 3/16 spacer in front so I have 3/16 gap with spindle, tire is just short of the upper ball joint shaft where it mounts to the top of the spindle).
What wheels are you running and what backspacing on them? I'm running 255/50/16 o my stock 16x7 Sport wheels, and was going to go 255/40/18, which is the same diameter and width, but going to be on a wheel that is 18x9 with a 35 offset which should offer plenty of clearance.
 

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I don't know what backspacing my wheels have. They are SUPPOSED to be 36mm offset on 9 inch wide Bullitts but they hit the 93+ front spindles. They were fine on my 89 Cougar until I did the spindle swap, then they hit on the 89 Cougar, 97 Cougar, and 97 Mark VIII without the 3/16 spacer. As it is now, when they put on hammer on weights on the inside rim edge (I ask before they do any work with my list of requirements, including stick on weights) the get knocked off by the spindle (WITH THE SPACER).

An 18 inch wheel can be slightly more backspacing due to the way the spindle is angled, but not much. On an 18 inch wheel, that 255/40/18 is .6 inches less in diameter than OEM, should be fine as far as clearance for the spindle, fender, and upper ball joint.
 

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255/50/17 are perfect in my opinion however fitment does require trimming the excess off of the upper control arm ball joint stud.
 

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I don't know what backspacing my wheels have. They are SUPPOSED to be 36mm offset on 9 inch wide Bullitts but they hit the 93+ front spindles. They were fine on my 89 Cougar until I did the spindle swap, then they hit on the 89 Cougar, 97 Cougar, and 97 Mark VIII without the 3/16 spacer. As it is now, when they put on hammer on weights on the inside rim edge (I ask before they do any work with my list of requirements, including stick on weights) the get knocked off by the spindle (WITH THE SPACER).

An 18 inch wheel can be slightly more backspacing due to the way the spindle is angled, but not much. On an 18 inch wheel, that 255/40/18 is .6 inches less in diameter than OEM, should be fine as far as clearance for the spindle, fender, and upper ball joint.
Yeah, I need the shorter tires due to my 3.73 gears. Not sure what gear is in my transmission for the speedo calibration, but it's dead on with my 255/50/16 which is also .5" smaller than stock. In the 18's it'll be .1mph low at 60, I'll live with it. :) I'm going with a 35mm offset, should leave plenty of room without needing spacers.
 
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