Do I need to reset my speedo?

Thunderscrash · February 5th, 2012, 06:03 PM

First, please don't bite my head off for not using the search because I did but I was getting all kinda of confused from all the things being said.

I just got some 17x10.5 bullitts with 315-35-17 555r's the front are still 245-24-17. Do I need to recalibrate the speedo for these? I've heard yes and I've heard no because it's still the same overall or something and I've heard it needs to be set according to the rear tires only and I've heard to average the front and rear size for what to set it at. So if anyone can shed some light on this for me that would be great.

Also I have an sct live wire with the free tunes through am. Can I reset the speedo through that or do I need them to write me a new tune?

1_nice_03_gt · February 5th, 2012, 06:10 PM

you can put in the tire info on there tune sheet of whats done to your car

Thunderscrash · February 5th, 2012, 07:34 PM

Ok I'll do that I was just hoping it was something I could do myself because it takes a few days for them to do everything and I just got a new tune for all my stuff haha but thanks.

N20zuki · February 5th, 2012, 07:55 PM

Look up information before giving advice... You need to do NOTHING, 245/45-17 and 315/35-17 are BOTH 25.7in in diameter... So you are fine and do not need to calibrate your speedo...

Tire size calculator

cliffyk · February 5th, 2012, 07:59 PM

^+1, they have the same OD--no change of anything is needed...

Thunderscrash · February 5th, 2012, 08:27 PM

Yea that's what I thought thanks guys

Eagle2000GT · February 5th, 2012, 10:31 PM

N20zuki is correct. The tires have exactly the same diameter. If you have further questions you can use the tire size calculator:
Tire Size Calculator - tire & wheel plus sizing

February 5th, 2012, 06:03 PM	#1
Thunderscrash Regular 2000 GT N/A Join Date: Oct 2010 Location: Delaware? Posts: 478 iTrader: 0 reviews	Do I need to reset my speedo? First, please don't bite my head off for not using the search because I did but I was getting all kinda of confused from all the things being said. I just got some 17x10.5 bullitts with 315-35-17 555r's the front are still 245-24-17. Do I need to recalibrate the speedo for these? I've heard yes and I've heard no because it's still the same overall or something and I've heard it needs to be set according to the rear tires only and I've heard to average the front and rear size for what to set it at. So if anyone can shed some light on this for me that would be great. Also I have an sct live wire with the free tunes through am. Can I reset the speedo through that or do I need them to write me a new tune?

February 5th, 2012, 06:10 PM	#2
1_nice_03_gt Hardcore Enthusiast 2003 ford mustang gt 13.9 stock Join Date: Sep 2010 Location: bay area Posts: 1,473 iTrader: 1 reviews	you can put in the tire info on there tune sheet of whats done to your car __________________ k&n cai, mangaflows exhaust, summit udp's, 24lb injectors, 78mm bbk plenun, tri-ax s/s, a/c delete,3.73's, aluminum drive shaft, upr upper/lower control arms, solid motor mounts, bbk heades, upr xpipe,bbk cc plates, camber bolts.bama tune

February 5th, 2012, 07:55 PM	#4
N20zuki Regular 2004 Mustang GT Join Date: Dec 2011 Location: Elizabeth City, NC Posts: 84 iTrader: 0 reviews	Look up information before giving advice... You need to do NOTHING, 245/45-17 and 315/35-17 are BOTH 25.7in in diameter... So you are fine and do not need to calibrate your speedo... Tire size calculator __________________ 2004 Mustang GT 40th Aniv 5spd, Stock for now. 2005 Joe Gibbs Silverado #0396 1986 Monte Carlo SS

February 5th, 2012, 07:59 PM	#5
cliffyk Hardcore Enthusiast Join Date: Feb 2007 Location: Saint Augustine, FL Posts: 1,808 iTrader: 1 reviews	^+1, they have the same OD--no change of anything is needed... __________________ -cliff knight- My Mustang 2003 GT, UPR X, 24lb/h injectors, Magnaflow, 180° stat, PP 70mm TB & plenum, DF Commando, Steeda UDPs, Ralco RZ_flywheel, RAM HDX clutch, WX EFX COPs 3.73s, 262 rwHP/305 lb-ft. Flex-fuel: burns gas and rubber...

February 5th, 2012, 10:31 PM	#7
Eagle2000GT I Post Entirely Way Too Much 2000 Mustang GT 12.73@111.36 Join Date: Aug 2007 Location: Shelbyville, IN Posts: 5,311 iTrader: 1 reviews	N20zuki is correct. The tires have exactly the same diameter. If you have further questions you can use the tire size calculator: Tire Size Calculator - tire & wheel plus sizing __________________ ProCharger P-1SC, 9 psi, STD 396/383; Uncorrected 388/375; SAE 383/370 Mods list in Garage.

February 5th, 2012, 07:34 PM	#3
Thunderscrash Regular 2000 GT N/A Join Date: Oct 2010 Location: Delaware? Posts: 478 iTrader: 0 reviews	Ok I'll do that I was just hoping it was something I could do myself because it takes a few days for them to do everything and I just got a new tune for all my stuff haha but thanks.

February 5th, 2012, 08:27 PM	#6
Thunderscrash Regular 2000 GT N/A Join Date: Oct 2010 Location: Delaware? Posts: 478 iTrader: 0 reviews	Yea that's what I thought thanks guys

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