Speedo/milage correction for new tires
01-17-2010, 10:08 AM
#11
1st Gear Member
Join Date: Feb 2009
Location: Chicagoland IL
Posts: 133
245mm / 25.4 = 9.64in; * 45% = 4.34in; * 2 = 8.68in total sidewall;
8.68in + 17in = 25.68in overall diameter;
The working diameter, because of loading, will be about 97% of this. 24.9in or so.
For the OP, here's my How Fast Can I Go in Each Gear? calculator, you can select you tranny, rear-end gears, and tire size and see what's what...
8.68in + 17in = 25.68in overall diameter;
The working diameter, because of loading, will be about 97% of this. 24.9in or so.
For the OP, here's my How Fast Can I Go in Each Gear? calculator, you can select you tranny, rear-end gears, and tire size and see what's what...
Now can you make another one, that has standard tire sizes and a drop down menu for PSI? So we can use it for the track for guys running slicks.
And while your in there, another RPM colum for gt and cobra redlines.
01-17-2010, 11:29 AM
#12
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
You can however do a forced entry of the tire diameter, just click on the displayed value and you can enter whatever you like.
And while your in there, another RPM colum for gt and cobra redlines.
01-17-2010, 12:06 PM
#13
Retired Moderator
Join Date: Jun 2006
Location: SF Bay Area
Posts: 9,235
245mm / 25.4 = 9.64in; * 45% = 4.34in; * 2 = 8.68in total sidewall;
8.68in + 17in = 25.68in overall diameter;
The working diameter, because of loading, will be about 97% of this. 24.9in or so.
For the OP, here's my How Fast Can I Go in Each Gear? calculator, you can select you tranny, rear-end gears, and tire size and see what's what...
8.68in + 17in = 25.68in overall diameter;
The working diameter, because of loading, will be about 97% of this. 24.9in or so.
For the OP, here's my How Fast Can I Go in Each Gear? calculator, you can select you tranny, rear-end gears, and tire size and see what's what...
Jazzer now looks foolish
PS. Good calcs though
01-17-2010, 01:09 PM
#16
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
Both the odometer and speedometer will be affected by running tires that have a different diameter than the stock tires (245/45-17, 25.7" dia unloaded, 24.9" dia loaded).
The amount of the error will be roughly 0.4% for each 0.1" difference in diameter, smaller tires will make the speedometer read fast (as compared to actual speed), larger tires will make it read slower than real speed.
The odometer is similarly affected, smaller tires will make it rack up miles faster, larger tires slow it down...
01-17-2010, 01:10 PM
#17
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
01-17-2010, 01:48 PM
#18
1st Gear Member
Join Date: Feb 2009
Location: Chicagoland IL
Posts: 133
There are too many other factors, other than inflation pressure, that would impact effective tire diameter, making calculation of same from tire size and PSI a very inexact exercise.
You can however do a forced entry of the tire diameter, just click on the displayed value and you can enter whatever you like.
I added two columns, took it out to 8 grand...
You can however do a forced entry of the tire diameter, just click on the displayed value and you can enter whatever you like.
I added two columns, took it out to 8 grand...
And thanks for the added column, I just meant one for red line (5750) so I could figure best ratio/tire combo in the 1/4. No biggy though,I just thought it would be easier than splitting the difference between 5500 and 6000.
Last edited by 01 P-51G t; 01-17-2010 at 01:51 PM.
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