issue with Porsche 914 speedo readings

[itHaKa]

Hi All
i have a porsche 914 speedometer, it is in KMPH , front tires are
205-45-17 and compared with a gps and my friend´s car , the speed reads 10 kilometers higher that real , if speedo marks 100 km, i am really running at 90 kmph , any options to solve this ?
i think changing to a bigger profile on the front tires, but i am not sure, and dont want to end up with a big 4x4 tire...

any clues or thoughts are welcome
thanks !!

[NO_H2O]

You can send it to North Hollywood Speedometer and they can calibrate it for your tire size.

[Steve C]

Hi

My work ute is a nearly new Toyota Hi Lux, its about 10 ks out 100 kph, must be a safety feature.

Steve

[evilC]

Your tyre size should make it read 4-6% high depending on new or worn tyres. Also, different makes of tyre have different rolling radius for the same size. Then on top of that mechanical speedos on european vehicles have an allowable tolerence of -0/+10% in reading so that it can read up to 10% higher given all other factors are perfectly sized. Its a safety thing so that you ought not to exceed any speed limits if you adhere to what your speedo reads. In general you can see that your speedo only shows an indicative reading, it can't be accurate because there are too many variables.

Clive

[itHaKa]

thank you guys,
will send an email to North Hollywood Speedometer to see if they can help , the problem is that i am from Argentina,
and i am not sure if i have to send them my speedo..
about the safety feature, not sure, because running at 30 km/h , it still shows 40 km/h, so error is > to 10 %,
i didn´t test the accuracy of the odometer yet ,

for the 914 speedo users ,i know there are a lot ,like sandeep, aartjan , and other users :
is the speedo working fine , is it accurate, no issues ?

[NO_H2O]

Mine reads a bit faster than it is running but I live with it.

[evilC]

If the error is a consistant 10 kph or thereabouts are you sure the needle is correctly positioned? It was certainly possible on the Smiths speedos to take the needle off and reposition it - there is like a preload against the stop, it may be that your needle is incorrectly positioned.

Clive

[vdubzack]

Originally Posted by evilC

If the error is a consistant 10 kph or thereabouts are you sure the needle is correctly positioned? It was certainly possible on the Smiths speedos to take the needle off and reposition it - there is like a preload against the stop, it may be that your needle is incorrectly positioned.

Clive

Yeah, what he said. Thats exactly what I had to do.

[Sandeep]

I am not sure how accurate my speedo was, I usually based my speed on the gear I was in, along with engine RPM.

My new dash will be digital, taking the data from the DTA S60 Pro. I'm programming it in visual basic and displaying it on a 7" LCD.

Sandeep

[KAFUR1]

My 914 speedo was right on the money with 16 inch fuch with stock size.

[itHaKa]

Yes , At the end , i bought another 914 speedo to compare, and this one is working perfectly, so i think the other one had an issue with a spring
i am very happy because it is very accurate, still need to connect the trip cable.