Speedometer

[Logan]

The speedometer on my 53 Dragon registers about 10-15 miles (I think) over actual speed.  The engine and transmission (hydramatic) are from a 53 Manhattan.  I know the Dragon had different sized tires, 7.10 x 15, than the Manhattan, 6.70 x 15, and the tires I am using are (bias ply) G78s, which according to comparison charts should be equivalent to 7.10 x 15.  I actually don't know much about tire size, but are 7.10's taller than 6.70's?  Were there different gearing ratios for the speedometer gauge?  If both of the above statements are true, I am still confused, because it seems that if I have a speedometer geered for shorter tires (standard Manhattan issue) and am driving around on taller ones, I should actually be going FASTER than the speedometer registers, not the opposite.  Any ideas on this?

[joefrazer]

Believe it or not, your car is about on par with most Kaisers. The speedometer does read higher than actual road speed on most and this was even noted in road tests back when they were new. The tire size does have a little bearing on the reading, but not that much given what you're using against what it should be. All hydrmatic equipped 53 Kaisers used the same rear end gear ratio (3.31) so the speedometer gear in the transmission should be the same from car to car. It is possible, tho, that a 1951 speedometer gear could have been substituted in at one time. The 51s used a 3.54 rear axle and this could cause an incorrect speedometer reading. The easiest way to tell is to pull the speedometer cable out of the transmission and count the teeth on the gear. A 51 unit will have 7 teeth and the 52-up units have 8.

[ben-tex]

Our family 51 K standard with OD would clock close to 120 on the speedometer which may have been a true 90 or so. Joe is right about the optimistic speedometers in Ks.

[Logan]

Scary in a Kaiser at a true 120 mph!  Thanks for the info, I susptect that this is how it has been since new.