Tire size v. MPH - Ford Powerstroke Diesel Forum
Wheels, Tires, and Brakes Here's where you can post all your topics and questions about wheels, tires and brakes.
Sponsored by Discount Tire

User Tag List

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 15 Old 06-23-2013, 05:40 PM Thread Starter
Compression Ignition Addict
 
jesilvas's Avatar
 
Join Date: Feb 2009
Location: Nacogdoches, TX
Posts: 11,148
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 0
Thanked 27 Times in 25 Posts
Feedback Score: 0 reviews
Tire size v. MPH

Ok, since you guys are experts, tell me if I'm right.

Wifes truck, 2000 F150 Lariat.

Currently has P235 70 17. 63MPH on speedo means 60MPH real.
Door sticker says P275 60 17. That would be the same sidewall, which would be 63MPH speedo and 60MPH real correct?

Tire Size for 2000 Ford F-150 Lariat
Using that website, it gives me a list of possible OEM sizes.
Using the P265 70 17, I think I used the calculators right and it would actually correct my speedo, right?




General question, MY truck states 215 85 16 or something like that is OEM size. But using 235 85 16, my speedo is actually right. Is that common?



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
jesilvas is offline  
post #2 of 15 Old 06-23-2013, 06:37 PM
WWW.COMPIGNTECH.COM

 
Join Date: Oct 2011
Posts: 9,369
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 98
Thanked 103 Times in 82 Posts
Feedback Score: 10 reviews
No your speedo is incorrect. The 60,70,85 etc is the percentage of the tire width. So for instance if you have 275/60r20's the sidewall is 60% as tall as the tire is wide. Make sense?

l BRYAN l


WWW. COMPIGNTECH .COM

Look us up on Facebook
COMPRESSION IGNITION TECHNOLOGIES

l 2005 l Ford F250 l FTX l
[A Few Odds-N-Ends]

Tuscany is offline  
post #3 of 15 Old 06-23-2013, 06:43 PM Thread Starter
Compression Ignition Addict
 
jesilvas's Avatar
 
Join Date: Feb 2009
Location: Nacogdoches, TX
Posts: 11,148
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 0
Thanked 27 Times in 25 Posts
Feedback Score: 0 reviews
No I understand that. I'm saying right now, on 235 70 17, it says 63MPH and is GPS rated right about 60MPH.



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
jesilvas is offline  
post #4 of 15 Old 06-23-2013, 06:50 PM
WWW.COMPIGNTECH.COM

 
Join Date: Oct 2011
Posts: 9,369
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 98
Thanked 103 Times in 82 Posts
Feedback Score: 10 reviews
Then your speedo needs recalibrated.

l BRYAN l


WWW. COMPIGNTECH .COM

Look us up on Facebook
COMPRESSION IGNITION TECHNOLOGIES

l 2005 l Ford F250 l FTX l
[A Few Odds-N-Ends]

Tuscany is offline  
post #5 of 15 Old 06-23-2013, 06:54 PM
Powerstroke.org Sponsor

 
Corey@CNCFAB's Avatar
 
Join Date: Apr 2010
Location: Defiance, OH
Posts: 9,127
Mentioned: 127 Post(s)
Tagged: 1 Thread(s)
Quoted: 353 Post(s)
Thanks: 751
Thanked 485 Times in 441 Posts
Feedback Score: 1 reviews
Quote:
Originally Posted by Tuscany View Post
No your speedo is incorrect. The 60,70,85 etc is the percentage of the tire width. So for instance if you have 275/60r20's the sidewall is 60% as tall as the tire is wide. Make sense?
X2

First number is in mm. Second is % of first. Conversion is divide by 25.4 to get inches, then double that plus rim.

So. Your door says correct tire size, specifically height, must be 30".

275.6=165 165/25.4=6.49 round up 6.5x2 13+rim17=30"

Whatever tire/wheel setup you want without recalibrating pcm to keep mph correct, just plug in the numbers to get as close to 30"

Sent from AutoGuide.com Free App

E99CCLB 250/200s,STG1cam, KC38R, 4" exh,CNC FAB fuel&oil lines,140vIDM,BTS,S&B

97 ECLB F250 4x4 all stock
96 CCLB F350 4x4 D60 swap stock



EDGE,S&B,SCT,PHP Hydra,TS-Perf,OEM parts,Sam Wyse trans,VB's,LED's,MBRP,ISSPRO,ICON,FOX,KC TURBOs,SD 7.3 fuel kits, HPOP lines

www.cncfab.us or email sales@cncfab.us

Corey@CNCFAB is offline  
post #6 of 15 Old 06-23-2013, 06:55 PM
Compression Ignition Addict
 
Wannabitawerm's Avatar
 
Join Date: Feb 2012
Posts: 289
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Maybe this will help. My stock tire size is 265/75r16. I have 315/75r16 and my speedo difference is 9.3% over my reading. There are charts on google that will tell you the percentage. You put in stick tire size and the other size and it will tell you over or under percentage. Can't find the link or I'd post it.


Sent from AutoGuide.com App
Wannabitawerm is offline  
post #7 of 15 Old 06-24-2013, 03:57 PM Thread Starter
Compression Ignition Addict
 
jesilvas's Avatar
 
Join Date: Feb 2009
Location: Nacogdoches, TX
Posts: 11,148
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 0
Thanked 27 Times in 25 Posts
Feedback Score: 0 reviews
Speedometer Calibration / Tire Size Change Calculator
I used this and another.

From Tire Size for 2000 Ford F-150 Lariat <- that website, it lists three possible OEM sizes. 235 70 17 and 275 60 17 have the same sidewall size.
The other, 265 70 17 has a larger sidewall.
Basically, I'm making sure that if I run a larger sidewall, my speedo will drop in displayed speed.



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
jesilvas is offline  
post #8 of 15 Old 06-24-2013, 06:02 PM
Compression Ignition Addict
 
Join Date: Jan 2012
Location: Fallon, Nv
Posts: 2,403
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks: 54
Thanked 11 Times in 10 Posts
Feedback Score: 0 reviews
Quote:
Originally Posted by jesilvas View Post
No I understand that. I'm saying right now, on 235 70 17, it says 63MPH and is GPS rated right about 60MPH.
Quote:
Originally Posted by jesilvas View Post
Speedometer Calibration / Tire Size Change Calculator
I used this and another.

From Tire Size for 2000 Ford F-150 Lariat <- that website, it lists three possible OEM sizes. 235 70 17 and 275 60 17 have the same sidewall size.
The other, 265 70 17 has a larger sidewall.
Basically, I'm making sure that if I run a larger sidewall, my speedo will drop in displayed speed.
235 70 17 is 29.95" tall
275 60 17 is 29.99" tall
265 70 17 is 31.61" tall

In total, there is only a 5% difference between these tires. 31.61/29.99=1.05 Guess what? Your speedo is...wait for it.... 5% off 63/60=1.05. Everything is working like it is supposed to.

In short, your speedo was calibrated for the tallest of the three tires. Ford most likely did it because it's better to go slower than indicated than to go faster than indicated.

Karl and his 2003 6.0

Barefoot Accelerator Pedal
TRICO Force wiper blades
Yellow Military Aircraft Valve Stem Caps
Offensive "Stick Family" Decal
Big Ol'Honkin 1 1/4" Shank Receiver Hitch


WHAT!?! I was trying to list stuff that everyone else
hasn't already listed for their truck!




Karls03 is offline  
post #9 of 15 Old 06-24-2013, 06:14 PM Thread Starter
Compression Ignition Addict
 
jesilvas's Avatar
 
Join Date: Feb 2009
Location: Nacogdoches, TX
Posts: 11,148
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 0
Thanked 27 Times in 25 Posts
Feedback Score: 0 reviews
Ok cool, just wanted to make sure I thought it all through right.

That's so dumb, because my truck is also the same way.
215 85 16 = 182.75mm sidewall is sticker oem.
235 85 16 = 199.75mm sidewall is what makes speedo right.



2000 F-350 Lariat Super Duty, Dually, CCLB, 7.3L
4R100, 2wd
330,000 + miles
jesilvas is offline  
post #10 of 15 Old 06-24-2013, 06:24 PM
Compression Ignition Addict
 
Join Date: Jan 2012
Location: Fallon, Nv
Posts: 2,403
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks: 54
Thanked 11 Times in 10 Posts
Feedback Score: 0 reviews
Keep in mind that different tire manufactures can have a different OD for the same size tire, hence why I'll never buy tires at Pep Boys ever again.

Karl and his 2003 6.0

Barefoot Accelerator Pedal
TRICO Force wiper blades
Yellow Military Aircraft Valve Stem Caps
Offensive "Stick Family" Decal
Big Ol'Honkin 1 1/4" Shank Receiver Hitch


WHAT!?! I was trying to list stuff that everyone else
hasn't already listed for their truck!




Karls03 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ford Powerstroke Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome