Having my speeded rebuilt and they are asking for the ratio? I currently have 335/35zr/17 rear and 235/40zr/17 on the front. does anyone have an idea?
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I'm assuming (there is a typo) you are having your speedometer rebuilt.
Which begs the question of just what is being rebuilt / done?
I believe there were two versions of the speedometer, one using a 1:1 ratio and the other at 1:1.1 Others will have to chime in on which is found in what year(s) Pantera.
Be glad to help, but it is very unclear as to what "they" are asking for.
Larry
Which begs the question of just what is being rebuilt / done?
I believe there were two versions of the speedometer, one using a 1:1 ratio and the other at 1:1.1 Others will have to chime in on which is found in what year(s) Pantera.
Be glad to help, but it is very unclear as to what "they" are asking for.
Larry
Yes sorry about typo and here's some more info…
I have a 74 pantera with 17 in rims.
Palo Alto speedometer shop is asking me how many cable turns at the distance of 52 feet and 9 1/2 inches (1/100 of a mile)
the speedometer had 1200 marked on the back of it but was covered with a sticker at some point in its lifetime!? not able to do the cable turn count myself at this time! Any help would be appreciated.
I have a 74 pantera with 17 in rims.
Palo Alto speedometer shop is asking me how many cable turns at the distance of 52 feet and 9 1/2 inches (1/100 of a mile)
the speedometer had 1200 marked on the back of it but was covered with a sticker at some point in its lifetime!? not able to do the cable turn count myself at this time! Any help would be appreciated.
Larry is correct, the angle speedo drive in the ZF is available in four variants two each for VDO and Veglia Borletti (taking different style cables), depending whether your speedo is km/h or mph (ratios are 1.1:1 or 1:1)
The back of your speedo will also be stamped with a ratio either 1600 rev/mile or 1200 rev/mile, so it sounds like you have the 1200 version and 1/100 of a mile would thus be 12 revolutions of the cable. But that is for stock tire diameter, so you will need to calculate the difference in tire diameter for your 335/35-17 to stock and ratio the difference in distance traveled for one revolution of the wheel.
Personally I think the best apporach is to do a number of runs at varying speeds with the car and use a gps to measure speed, write down the speedo reading and gps to get an error.
Julian
The back of your speedo will also be stamped with a ratio either 1600 rev/mile or 1200 rev/mile, so it sounds like you have the 1200 version and 1/100 of a mile would thus be 12 revolutions of the cable. But that is for stock tire diameter, so you will need to calculate the difference in tire diameter for your 335/35-17 to stock and ratio the difference in distance traveled for one revolution of the wheel.
Personally I think the best apporach is to do a number of runs at varying speeds with the car and use a gps to measure speed, write down the speedo reading and gps to get an error.
Julian
this seems like it would be a simple gear ratio calculation, however I could not find all the information needed.
the math I could play with would be determine the tire diameters and revolutions per mile
The original rear tires were 215/70 at 26.9 dia or 255/60 at 27.0 dia
Your tires are 335/35 at 26.2 dia. So the revs per mile will increase by 27/26.2 = 1.03
Now I wanted to reverse to the cable revolutions and here is where I had to make a lot of assumtions.
lets call the original tire diameter 27", this would give 746 tire revolutions per mile.
with a 4.22:1 axle gives 3147 r/m
RBT list two different speedo worm/gear ratios,2.0:1 and 2.4:1
choosing the 2.4:1 worm gear gives 1311 r/m
then using the angle between the two angle head ratios of 1.1:1 and 1:1,
choosing the 1.1:1 angle head gives 1192 r/m as the original cable turns for a speedo labeled 1200.
Using the 26.9" diameter for the original tire it comes to 1197 r/m
(using the 2:1 worm and the 1:1 angle, it comes to 1597 r/m)
for your tires and the same assumptions, that would be 1228 r/m.
Now, I have no ideal if this is correct, but is just me playing around with the calculator. I would appreaciate if those that can fill in the assumptions would either show me my errors or confirm
the math I could play with would be determine the tire diameters and revolutions per mile
The original rear tires were 215/70 at 26.9 dia or 255/60 at 27.0 dia
Your tires are 335/35 at 26.2 dia. So the revs per mile will increase by 27/26.2 = 1.03
Now I wanted to reverse to the cable revolutions and here is where I had to make a lot of assumtions.
lets call the original tire diameter 27", this would give 746 tire revolutions per mile.
with a 4.22:1 axle gives 3147 r/m
RBT list two different speedo worm/gear ratios,2.0:1 and 2.4:1
choosing the 2.4:1 worm gear gives 1311 r/m
then using the angle between the two angle head ratios of 1.1:1 and 1:1,
choosing the 1.1:1 angle head gives 1192 r/m as the original cable turns for a speedo labeled 1200.
Using the 26.9" diameter for the original tire it comes to 1197 r/m
(using the 2:1 worm and the 1:1 angle, it comes to 1597 r/m)
for your tires and the same assumptions, that would be 1228 r/m.
Now, I have no ideal if this is correct, but is just me playing around with the calculator. I would appreaciate if those that can fill in the assumptions would either show me my errors or confirm
thanks guys!
I think I have it!
I think I have it!