Changed from Hoosiers to Bridgestones. Have question...

[BAT]

Yesterday I took off the Hoosiers and put on the Bridgestones Potenzas. Unless traffic was moving along quicker than usual yesterday, my speedometer is incorrectly reading a higher speed. Because I am too lazy to go drive with my hand held GPS, how much of "speed error" is there between the stockers (Firestone) and the Bridgestones?

Stock:

235/45/18 (F)
315/40/19 (R)


Bridgestones:

265/40/18 (F)
345/35/19 (R)




Thanks,
Brian

 

[Xcentric]

I measured the circumference of the Goodyears and Bridgestones with a tape measure. Not precision, but good enough. Rear Bridgestone is 1% smaller than rear Goodyear.

The speed sensor is in the transaxle...front tires don't matter for speed.

Treadwear will make a bigger difference in speedometer readings than nominal tire size difference.

More tire and wheel measurements here: http://www.fordgtforum.com/forums/showthread.php/12372-THE-Tire-Thread/page48?highlight=tire+thread, post 477.

 

[tmcphail]

That can be handled through proper recalibration of the tire revolutions per mile

 

[texas mongrel]

Bridgestones give 1.4% variation, in other words, negligible; at 70mph the error would be 1mph.

 

[tpraceman]

Her you go Michigander http://www.offroaders.com/info/tech-corner/reading/mph-rpm.htm

 

[The Grey Ghost]

To make it even easier, here is a calculator for comparisons

www.net-comber.com/tirecalc.html

 

[Fubar]

The correct answer it is... it depends (tire pressure/temp on one tire verus the other/manufacturing imperfections/the mass of the 13 moon of Jupiter on it 10th bi-annual orbit). I can't believe you're to lazy to use the GPS but you would spend 45 minutes (of potential GT time) doing calculations. GO DRIVE!

 

[roketman]

The correct answer it is... it depends (tire pressure/temp on one tire verus the other/manufacturing imperfections/the mass of the 13 moon of Jupiter on it 10th bi-annual orbit). I can't believe you're to lazy to use the GPS but you would spend 45 minutes (of potential GT time) doing calculations. GO DRIVE!

+1

 

[BAT]

+1

Ha. Very true. I am juuuuuust getting comfy driving this thing now so I will hit the roads tonight with a gps. BTW, the Hoosier's traction are so much better than the Bridgstones (of course) but I find the road noise is better with the Bridgestones.


B

 

[SteveA]

When I went to 19's and 20's the rear was about 7% smaller. It was important to figure this out because I wanted to correct the speedo, it's one thing to put miles on your car it's another to put 7% more than your are actually enjoying.