speedometer problem

[rwcstang 201]

well i guess its spining and not accurate when at cruising speeds or freeway speeds lol checked the gear teeth to the tranny looks fine maybe i have to recalibrate the speedometer? are there any tech articles on fixing it? thanks

[rwcstang 201]

well i guess its spining and not accurate when at cruising speeds or freeway speeds lol checked the gear teeth to the tranny looks fine maybe i have to recalibrate the speedometer? are there any tech articles on fixing it? thanks

[bnickel 10,004]

how do you know it's not accurate? have you checked it? and how did you check it? have you changed the rear gears or drastically changed the erar tire size? generally, you'll need to know the rear gear ratio, tire diameter and number of teeth on the speedo drive gear (the one inside the trans), once you have all that info you can usually find a speedo gear selector by doing a google search.

[bnickel 10,004]

how do you know it's not accurate? have you checked it? and how did you check it? have you changed the rear gears or drastically changed the erar tire size? generally, you'll need to know the rear gear ratio, tire diameter and number of teeth on the speedo drive gear (the one inside the trans), once you have all that info you can usually find a speedo gear selector by doing a google search.

[rwcstang 201]

well we have a street that has a sign that checks how fast ur going so i checked and it read my car doing 25mph but my cluster shows it was at 30pmh everything is stock my rear end gears are low 2:79 and im running 235's in the rear.

[bnickel 10,004]

well we have a street that has a sign that checks how fast ur going so i checked and it read my car doing 25mph but my cluster shows it was at 30pmh everything is stock my rear end gears are low 2:79 and im running 235's in the rear.

 

 

every car i have reads fast according to those road side radar trailer things. even my wife's 02 escape reads fast according to that thing.

[rwcstang 201]

hrm i dunno cuz i drove in others cars and they are fairly accurate with the radar, so im just thinking to take a look at it.

[bnickel 10,004]

what size tires do you have right now? i know you said 235 but is that like 235/60-15 or 235/60-14 or 235/70-14

[Protowrxs 111]

Back in the day (when the car actually ran) I would drive off a mile section around here and check the odometer for exactly where it ended up, turn around and recheck and then adjust by getting a different speedo gear. Obviously that may not be an option elsewhere but worked here. You could do the same on the interstate with mile markers but that would be quite dangerous anymore.

 

-Stephen

[rwcstang 201]

235/60-14 in the rears i took off my mags cuz of the weather over here

[bnickel 10,004]

235/60-14 in the rears i took off my mags cuz of the weather over here

 

 

well that's the problem right there. your 235/60-14's are about an inch smaller than stock diameter.

[rwcstang 201]

well that's the problem right there. your 235/60-14's are about an inch smaller than stock diameter.

 

oh okay but wait didnt some wheels that came on the mustang were 14?? or the actuall stock diameter is 15?

[bnickel 10,004]

oh okay but wait didnt some wheels that came on the mustang were 14?? or the actuall stock diameter is 15?

 

 

most mustangs had 14" wheels stock, the difference is that you go by tire diameter not wheel diameter. stock size for a 69 would either be an E70-14 or an F70-14 both of which are around 26" tall tires or thereabouts. the modern metric tire size eguivalents would be a 215/70-14 for E tire and 225/70-14 for the F tire the same diameter tire for a 15" wheel would be a 225/60-15 for the E tire and 235/60-15 for the F tire the 235/60-15 is exactly 1" taller than a 235/60-14 or 225/70-14 or the stock size F70-14. the E series tire and it's eguivalent sizes are approximately 1/4" to 1/2" smaller in diameter than the F series tires but still taller then the 235/60-14.

 

just for comparison purposes the stock tire size on a 69 Boss 302 was an F60-15 which is the same size as a 235/60-15 so even back then they still tried to keep the overall diameter of the tires approximately the same size