Tire height calculated vs. installed???

Reply Subscribe

Thread Tools

Search this Thread

Apr 7, 2005 | 09:37 AM

1CAMWNDR

Thread Starter

TECH Veteran

iTrader: (21)

Joined: Nov 2001

Posts: 4,247

Likes: 2

Tire height calculated vs. installed???

My stock pcm says it is set fot a stock 245 50 16 tire as 24.95xx inches (even thought I have 315s on there now). The calculator in HP Tuners says it is 25.6".
Now, my 315 35 17 tires in the HP Tuners calculator comes to 25.7" which is only .1" difference. Do I plug in 25.7" for the new speedometer calibration, or the stock pcm reading (24.95") plus the .1" difference (25.05")??
Thanks.

Apr 7, 2005 | 10:48 AM

1CAMWNDR

Thread Starter

TECH Veteran

iTrader: (21)

Joined: Nov 2001

Posts: 4,247

Likes: 2

TTT. Anyone know which one to use?

Apr 7, 2005 | 01:16 PM

foff667

LS1TECH Sponsor

iTrader: (2)

Joined: Jul 2003

Posts: 7,986

Likes: 3

From: Clermont, FL

i would usually just set it somewhere in between like 25.10

Apr 7, 2005 | 06:44 PM

1CAMWNDR

Thread Starter

TECH Veteran

iTrader: (21)

Joined: Nov 2001

Posts: 4,247

Likes: 2

25.3???
Maybe?

Apr 8, 2005 | 07:49 AM

jimmyblue

Moderator

iTrader: (11)

Joined: Mar 2002

Posts: 12,604

Likes: 7

From: East Central Florida

Best is to drive over a tape measure, wrap it around the
tire and back-figure height from the circumference. The
manufacturers' size ratings are loosely coupled to reality.

Apr 8, 2005 | 02:56 PM

1CAMWNDR

Thread Starter

TECH Veteran

iTrader: (21)

Joined: Nov 2001

Posts: 4,247

Likes: 2

Cool. Thanks. I have debated using the "Mark the tire and pavement, roll one revolution and mark the pavement, measure circumference, calculate height." thing.

Apr 8, 2005 | 03:11 PM

MrDude_1

TECH Junkie

iTrader: (4)

Joined: Feb 2002

Posts: 3,368

Likes: 5

From: Charleston, SC

Quote:

Originally Posted by 1CAMWNDR

Cool. Thanks. I have debated using the "Mark the tire and pavement, roll one revolution and mark the pavement, measure circumference, calculate height." thing.

thats what i did... works great.

i also do the same thing for my bicycle computer....