Hey guys. Would changing over from 245/60 tires to 245/50 change the speedo accuracy in any way ?

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

Assuming you have 16" rims. The 245/60 tires are 27.57" tall. The 245/50 tires are 25.64" tall. You're decreasing the total height of the tire 2". Your speedo will say your are going faster than you really are. Overall gear ratio will change also. Lets say you have 3.45 gears. Decreasing that tire size would be like putting 3.73 gears in with the old tires (not exact but you get the idea).

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Stephen's racing page

87 IROC-Z Pro ET Bracket Race Car and knocking on the SuperPro ET class
383 stroker (carbed) with double hump cast iron heads and pump gas
LS6 Big Block buildup now in progress

Best results before the engine blew up
Best ET on a time slip: 11.857
Best corrected ET: 11.163
Best MPH on a time slip: 117.87
Best corrected MPH: 126.10
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!

Member of the Calgary Drag Racing Association