Speedo Calibration
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Speedo Calibration
Hey guys, Im going from 295/35r18 in the rear to 315/30r18 tires 
. These will be around 1/2in shorter. Will that warrant the need to calibrate my speedo? Thnx.
Btw, for now, my fronts are 25.6-7in tall while the rears will be 25.5in tall. Will it be noticeable?
. These will be around 1/2in shorter. Will that warrant the need to calibrate my speedo? Thnx.Btw, for now, my fronts are 25.6-7in tall while the rears will be 25.5in tall. Will it be noticeable?
Last edited by C5Natie; Dec 23, 2010 at 09:30 AM.
Burning Brakes
Joined: Nov 2007
Posts: 951
Likes: 2
From: Rochester MN
Burning Brakes
Joined: Mar 2008
Posts: 983
Likes: 36
From: Middle Of Kali CA
Racer
Joined: Nov 2006
Posts: 297
Likes: 26
From: San Jose California
Speedo calibration
Since your tires heat up and expand, monitor the tire pressures (on your drivers info screen). When they stabilize (after a half hour), drive on a straight road and hold your speed steady. Read your TRUE speed on a portable GPS unit and compare the two. You should repeat this at various speeds(50, 75,100....). It helps to have a passenger read the GPS true speed while you concentrate on maintaining a steady speed.
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
Than guys. Im looking at 255/35r18 for the front now so the rears will be 1/2in taller than the fronts. I turn off the tc a lot but I still use it when it rains and I dont wanna see service tc codes all the time. Thnx.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
A 1/2" shorter tire on the rear won't affect the speedo that much--You will be going a little slower than what the speedo reads without correcting it--On a 6 speed there isn't a need to do anything else but on an A4 a small shift-point correction will help it shift at the proper times
HOWEVER---altering the split between the front heights and rears different that the stock 1" differnence, will affect the traction control and more importantly the ABS brakes--The ABS may NOT work---This is NOT correctable---I would try to keep the 1" split
HOWEVER---altering the split between the front heights and rears different that the stock 1" differnence, will affect the traction control and more importantly the ABS brakes--The ABS may NOT work---This is NOT correctable---I would try to keep the 1" split
Thread Starter
Safety Car
Joined: Apr 2007
Posts: 3,582
Likes: 137
From: SoCal CA
A 1/2" shorter tire on the rear won't affect the speedo that much--You will be going a little slower than what the speedo reads without correcting it--On a 6 speed there isn't a need to do anything else but on an A4 a small shift-point correction will help it shift at the proper times
HOWEVER---altering the split between the front heights and rears different that the stock 1" differnence, will affect the traction control and more importantly the ABS brakes--The ABS may NOT work---This is NOT correctable---I would try to keep the 1" split
HOWEVER---altering the split between the front heights and rears different that the stock 1" differnence, will affect the traction control and more importantly the ABS brakes--The ABS may NOT work---This is NOT correctable---I would try to keep the 1" split
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