Speedo Difference??? - Ford Explorer Ranger Enthusiasts "Serious Explorations"®

Jason94sport · 05-02-2001, 10:09 AM

How off will my speedo be if I change the stock 235-75-15's to 30X9.5's?? I have several tire cal programs, & websites, but I can't find any sizes in that range.
Thanks

Rob Slade · 05-02-2001, 11:54 AM

Go to www.4lo.com. This place has the calculators that will tell you your difference. You shouldn't notice anything but about 2-3 mph difference.

914x4sport · 05-02-2001, 12:33 PM

I have a calculator that works pretty good..I figured it out for you...235-75-15 = 28.9" diameter
I compared that diameter with a 30" tire and came up wth the following figures for ya....
Speedo says= Actual speed:
20=20.8mph
35=36.3mph
45=46.7mph
55=57.1mph
65=67.5mph
75=77.9mph
85=88.2mph

npearman · 05-04-2001, 03:22 PM

What if you go from a 235-75-15 to a 31x10.50 r15? I know you just love sitting around figuring this stuff out for slackers like me

Thanks

Nate

ACBlessing · 05-07-2001, 02:23 PM

Great online calulator:

http://www.miata.net/garage/tirecalc.html?clkd=iwm

*FMExplorer* · 05-07-2001, 02:35 PM

Nate,
If you got to 31's you will find a 10% difference (speedo says 50, really 55)

Checked it with a gps...

Jon

**Dannyboy** · 05-07-2001, 03:06 PM

I sat by a guy in a class that got pulled over in a taurus and the speedo was off by 8-9mph at 70 mph. A mechanic told him that he could get out of the ticket because Ford speedos are only gaurenteed for 10% accuracy. When we had 10 Explorers and Matt Adam's F150 in a line( granted we had all sorts of tire sizes) at 65 mph we were all over the place. So Matt said "I have the correct speed with stock size tires" and it was not what I expected so I fired up the GPS and even his was off by a few MPH so just to let you know it may not be accurate from the start. All to make it a little more of a challenge

914x4sport · 05-07-2001, 03:19 PM

Funny thing about speedo calculation is that you may be off by 5mph at 70, but not necessarily at 55...thats why I wrote it at differant speeds for the first guy...for you...
speedo says : new tires
20=21.5mph
35=37.5mph
45=48.3mph
55=59mph
65=69.7mph
75=80.4mph
85=91.2mph
any higher than that and I would worry about other things if your riding on 31" meats
Hope that helps...

05-02-2001, 10:09 AM	#1
Jason94sport Wannabe Elite Explorer South FL 94 XLT Auto ----Sold Join Date: Apr 2001 Posts: 2,778 Vehicle Specs	Speedo Difference??? How off will my speedo be if I change the stock 235-75-15's to 30X9.5's?? I have several tire cal programs, & websites, but I can't find any sizes in that range. Thanks

05-02-2001, 11:54 AM	#2
Rob Slade Wannabe Elite Explorer Wake Forest, NC 03 Tacoma DoubleCab Join Date: Feb 2000 Posts: 540 Vehicle Specs	Go to www.4lo.com. This place has the calculators that will tell you your difference. You shouldn't notice anything but about 2-3 mph difference. __________________ Rob Slade 2003 Toyota Tacoma DoubleCab Lots of Mods on the way! http://home.earthlink.net/~muddyexpl...20Website.html http://community.webshots.com/user/03trdblack

05-02-2001, 12:33 PM	#3
914x4sport Wannabe Elite Explorer St. Petersburg,Fl 91 4x4 sport Join Date: Jan 2001 Posts: 292 Vehicle Specs	I have a calculator that works pretty good..I figured it out for you...235-75-15 = 28.9" diameter I compared that diameter with a 30" tire and came up wth the following figures for ya.... Speedo says= Actual speed: 20=20.8mph 35=36.3mph 45=46.7mph 55=57.1mph 65=67.5mph 75=77.9mph 85=88.2mph __________________ Ex X-Owner

05-04-2001, 03:22 PM	#4
npearman Wannabe Elite Explorer Join Date: Dec 2000 Posts: 37 Vehicle Specs	914x4sport What if you go from a 235-75-15 to a 31x10.50 r15? I know you just love sitting around figuring this stuff out for slackers like me Thanks Nate

05-07-2001, 02:23 PM	#5
ACBlessing Wannabe Elite Explorer Spokane, WA (eastern Washington state) 2000 Mercury Mountaineer Join Date: Apr 2001 Posts: 277 Vehicle Specs	Great online calulator: http://www.miata.net/garage/tirecalc.html?clkd=iwm __________________ ACBlessing, Spokane, WA 2000 Merc Mountaineer V8

05-07-2001, 02:35 PM	#6
FMExplorer the original tramp Fort Myers, FL '99 Explorer EB Join Date: Feb 2000 Posts: 1,996 Vehicle Specs	Nate, If you got to 31's you will find a 10% difference (speedo says 50, really 55) Checked it with a gps... Jon __________________ Jon McLeod 2002 Harley Davidson F150 #6792 visit Florida Explorer Club

05-07-2001, 03:06 PM	#7
Dannyboy Asian Thunder #2 Scottsdale, AZ(WI native) 91 4 do' Join Date: Feb 2001 Posts: 5,007 Vehicle Specs	Just my 2 cents I sat by a guy in a class that got pulled over in a taurus and the speedo was off by 8-9mph at 70 mph. A mechanic told him that he could get out of the ticket because Ford speedos are only gaurenteed for 10% accuracy. When we had 10 Explorers and Matt Adam's F150 in a line( granted we had all sorts of tire sizes) at 65 mph we were all over the place. So Matt said "I have the correct speed with stock size tires" and it was not what I expected so I fired up the GPS and even his was off by a few MPH so just to let you know it may not be accurate from the start. All to make it a little more of a challenge __________________ In chatrooms I'm a 14 year old girl 91 long travel 4x4 '06 Superduty PSD 94 Limited The Diva

05-07-2001, 03:19 PM	#8
914x4sport Wannabe Elite Explorer St. Petersburg,Fl 91 4x4 sport Join Date: Jan 2001 Posts: 292 Vehicle Specs	Funny thing about speedo calculation is that you may be off by 5mph at 70, but not necessarily at 55...thats why I wrote it at differant speeds for the first guy...for you... speedo says : new tires 20=21.5mph 35=37.5mph 45=48.3mph 55=59mph 65=69.7mph 75=80.4mph 85=91.2mph any higher than that and I would worry about other things if your riding on 31" meats Hope that helps... __________________ Ex X-Owner