Will 255/45 tires fit on my '98 Cobra?

DEPete · 07-01-2002, 10:13 AM

Stock size is 245/45/17. Will I have any problems jumping to a 255/45/17?

07-01-2002, 12:06 PM

my friend has that size on his 99 gt , I gave him my old pony 17 that came on my gt and he is very un happpy with that size of tire !!

GTJim · 07-01-2002, 05:36 PM

You won't have any problems with the width, but your height will increase .65" over stock, which may create some rubbing problems in the front, but I'm not sure.

blue00gt · 07-01-2002, 06:40 PM

Actually, the height of the tire only increases by less than 0.2" (I think it's the circumference that increases by .6"). Both the width and the height should be fine.

GTJim · 07-02-2002, 10:02 AM

My bad, I miscalculated.... here are the actuals:

Stock Diameter = [245 (.45) (2)] + [17 (25.4)] = 652.3mm

New Diameter = [255 (.45) (2)] + [17 (25.4)] = 661.3mm

So, 661.3 - 652.3 = 9mm/25.4mm = .35" difference in tire height

New circumference would be 3.14 (661.3) = 2076.5mm

Old circumference is 3.14 (652.3) = 2048.2

So, 2076.5 - 2048.2 = 28.3mm/25.4 = 1.1" difference in circumference

Whew, been a while since i took geometry

blue00gt · 07-02-2002, 11:48 AM

I guess I need to correct myself also - the amount of space between the tire and fenderwell would change by less than 0.2" (half of your 0.35" difference in overall height), not the tire height.

DEPete · 07-02-2002, 01:51 PM

Thanks all. 255/45/17 BFG G-Force KDW's will be installed tomorrow!

MiracleMax · 07-05-2002, 09:04 PM

245/45R17 BFG KDW O.D. = 25.7 inches
255/45r17 BFG KDW O.D. = 26.1 inches

afeezor97 · 07-05-2002, 10:37 PM

I got 17x8 cobra wheels with 245/45 on the front and 275/40 on the back. With 2" lowering springs the back rub a little on extreme bumps (like speed bumps at 30mph). Front rub slightly during hard cornering, thats why i didnt go with 255s. The 275/40s put my speedo off by 5mph. So without getting all technical, you shouldnt have a problem making the jump...

07-01-2002, 10:13 AM	#1
DEPete Registered Member Join Date: Mar 2001 Location: Wilmington, DE Posts: 13	Will 255/45 tires fit on my '98 Cobra? Stock size is 245/45/17. Will I have any problems jumping to a 255/45/17? __________________ '98 Cobra Convertible - Triple Black Bassani X-Pipe with cats Magnaflow Cat-back Ford 3.73 Gears B&M Pro-Ripper Densecharger

07-01-2002, 12:06 PM	#2
southernstang97 Guest Posts: n/a	wouldn't my friend has that size on his 99 gt , I gave him my old pony 17 that came on my gt and he is very un happpy with that size of tire !!

07-01-2002, 05:36 PM	#3
GTJim Registered Member Join Date: Mar 2000 Location: Rio Rancho, NM Posts: 32	You won't have any problems with the width, but your height will increase .65" over stock, which may create some rubbing problems in the front, but I'm not sure. __________________ 2001 Mineral Grey Cobra - #2277 of 3867 - MM SFC's, Bilsteins, Rear: H&R race springs, PHP IRS brace, Steeda IRS bushings, Front: MM Coilover conversion w/ Hypercoils - JBA Headers, Bassani X-pipe, Dynomax Ultra-Flow catback - Procharger P-1SC Stage II

07-01-2002, 06:40 PM	#4
blue00gt Mustang Addict Join Date: Jan 2001 Location: McKinney, TX Posts: 1,294	Actually, the height of the tire only increases by less than 0.2" (I think it's the circumference that increases by .6"). Both the width and the height should be fine. __________________ Strike down the unroadworthy! 2000 GT Atl. Blue: '03 Cobra motor - 465rwhp/473rwtq, T-56 6-speed, full MM TA/PH & tubular K-member suspension, Saleen body, 17" Torq-Thrust II's, M/T ET Street radials, and lots more '94 Rio Red Cobra: All the bolt-ons, 3.73s

07-02-2002, 10:02 AM	#5
GTJim Registered Member Join Date: Mar 2000 Location: Rio Rancho, NM Posts: 32	My bad, I miscalculated.... here are the actuals: Stock Diameter = [245 (.45) (2)] + [17 (25.4)] = 652.3mm New Diameter = [255 (.45) (2)] + [17 (25.4)] = 661.3mm So, 661.3 - 652.3 = 9mm/25.4mm = .35" difference in tire height New circumference would be 3.14 (661.3) = 2076.5mm Old circumference is 3.14 (652.3) = 2048.2 So, 2076.5 - 2048.2 = 28.3mm/25.4 = 1.1" difference in circumference Whew, been a while since i took geometry __________________ 2001 Mineral Grey Cobra - #2277 of 3867 - MM SFC's, Bilsteins, Rear: H&R race springs, PHP IRS brace, Steeda IRS bushings, Front: MM Coilover conversion w/ Hypercoils - JBA Headers, Bassani X-pipe, Dynomax Ultra-Flow catback - Procharger P-1SC Stage II

07-02-2002, 11:48 AM	#6
blue00gt Mustang Addict Join Date: Jan 2001 Location: McKinney, TX Posts: 1,294	I guess I need to correct myself also - the amount of space between the tire and fenderwell would change by less than 0.2" (half of your 0.35" difference in overall height), not the tire height. __________________ Strike down the unroadworthy! 2000 GT Atl. Blue: '03 Cobra motor - 465rwhp/473rwtq, T-56 6-speed, full MM TA/PH & tubular K-member suspension, Saleen body, 17" Torq-Thrust II's, M/T ET Street radials, and lots more '94 Rio Red Cobra: All the bolt-ons, 3.73s

07-02-2002, 01:51 PM	#7
DEPete Registered Member Join Date: Mar 2001 Location: Wilmington, DE Posts: 13	Thanks all. 255/45/17 BFG G-Force KDW's will be installed tomorrow! __________________ '98 Cobra Convertible - Triple Black Bassani X-Pipe with cats Magnaflow Cat-back Ford 3.73 Gears B&M Pro-Ripper Densecharger

07-05-2002, 09:04 PM	#8
MiracleMax Registered Member Join Date: Apr 1999 Location: Hayes, Va, USA Posts: 798	245/45R17 BFG KDW O.D. = 25.7 inches 255/45r17 BFG KDW O.D. = 26.1 inches __________________ 2002 5M GT (99% stock) 1991 5M LX (30% stock) patiently awaiting my satin silver 07 Mach 1, and don't forget the shaker

07-05-2002, 10:37 PM	#9
afeezor97 GRNSNAK Join Date: Jun 2002 Location: Slidell Louisiana Posts: 65	I got 17x8 cobra wheels with 245/45 on the front and 275/40 on the back. With 2" lowering springs the back rub a little on extreme bumps (like speed bumps at 30mph). Front rub slightly during hard cornering, thats why i didnt go with 255s. The 275/40s put my speedo off by 5mph. So without getting all technical, you shouldnt have a problem making the jump... __________________ 1997 Cobra SVT & 2012 Shelby GT500

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