speed and odometer readings

[dick lyons]

my 48 has 15 in. wheels. did the speedo and odometer readings change much? I got the coupe this way. I assume it has the original gear. Thanks.

[V8COOPMAN]

Really has more to do with OUTER DIAMETER of tire than wheel diameter. DD

[JM 35 Sedan]

Originally Posted by dick lyons

my 48 has 15 in. wheels. did the speedo and odometer readings change much? I got the coupe this way. I assume it has the original gear. Thanks.

Are you talking about the ring and pinion gear or the turtle gear being original? What is the number on the turtle housing. What are the numbers on the bottom center web of the banjo housing?

[Mart]

If you can state the exact size of the rear tyres as stated on the sidewall, It is possible to calculate the % difference between stock 6.00:16s and what you have.

Mart.

[Walt Dupont--Me.]

Originally Posted by JM 35 Sedan

Are you talking about the ring and pinion gear or the turtle gear being original? What is the number on the turtle housing. What are the numbers on the bottom center web of the banjo housing?

I installed 3;54 gears in my Model A, I bought a turtle gear to match, installed the gear in the 3:78 turtle. SO, if someone looks at my turtle or reads the no. on the banjo there going to think it's 3:78 but accually my A has 3:54 gears. Walt

[George/Maine]

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I would guess your speedometer reads faster, the tire size should be 600x16 larger.
I run 650x16 for better speed.

[supereal]

Most old speedometers are not very accurate. Most are at least 5-10 percent off. The instrument may be in need of cleaning and lube, or the magnetic discs and spring may be weak. If the needle is jumpy, the input fitting may be worn and loose in the body. My NOS speedo with new cable and sheath is still about five mph off.

[Marv]

Originally Posted by dick lyons

my 48 has 15 in. wheels. did the speedo and odometer readings change much? I got the coupe this way. I assume it has the original gear. Thanks.

It came out with 600-16 and if i remember right 670-15 was the same height 28"

[flatford8]

I have an app on my iphone. It tells speed and distance.....and when to pick up milk and eggs.....MARK

[jake197000]

use a gps thet are very accurate.

[Ross F-1]

Originally Posted by supereal

Most old speedometers are not very accurate. Most are at least 5-10 percent off. ...My NOS speedo with new cable and sheath is still about five mph off.

I swapped a 9" with 3.50 gears into my truck, and am running 235/75-15's, so my speedo/odo ratio is off almost exactly 10%. On a long interstate trip I kept track of the odo readings against the mile markers, and the odo was indeed off 10%. But the speedo is off 10% up to about 50 mph (actual), by the time I get to 55 or 60 it is off 15%. The speedo is an NOS replacement with only 5k miles on it, new cable, etc. You're right, they just aren't designed to be real accurate. I use the tach if I'm worried about going a specific speed.