speedo calibration

Hi All,

Me again with yet another question. Here is my yet another "minor"
problem. I have 165/45R15s tires on the front (droped from 195/50) and
now my speedo is way off, by which I mean i am reading 70 while going
around 50. And 80 while in the right lane on the freeway. Which looks
totaly cool and all, but I would like to be able to tell my actual
speed. Is there anyway to recalibrate stock speedo? Or the only way to
remedy this problem is to replace it with an electronic unit? Car is
64 T1.

Thanks again,
Anton

P.S. I had to go this small on the tires, because previous size was
rubbing on the fenders and I want it low. (droped spindles, cb wide 5
disk breaks, 2" narrowed beam).

anton wrote:
> Hi All,
>
> Me again with yet another question. Here is my yet another "minor"
> problem. I have 165/45R15s tires on the front (droped from 195/50) and
> now my speedo is way off, by which I mean i am reading 70 while going
> around 50. And 80 while in the right lane on the freeway. Which looks
> totaly cool and all, but I would like to be able to tell my actual
> speed. Is there anyway to recalibrate stock speedo? Or the only way to
> remedy this problem is to replace it with an electronic unit? Car is
> 64 T1.
>
> Thanks again,
> Anton
>
> P.S. I had to go this small on the tires, because previous size was
> rubbing on the fenders and I want it low. (droped spindles, cb wide 5
> disk breaks, 2" narrowed beam).
>

Go electronic and put your old one away in the vault.

To calibrate it requires watchmaker skills in manipulating
the hairspring.

Speedy Jim
http://www.nls.net/mp/volks/

Speedy Jim,
My 65 came with 135's on the stock rims. Do you know how much that puts my
speedo off by? Greater or less than the actual speed?

Thanks
Eddie

"Speedy Jim" > wrote in message
om...
| anton wrote:
| > Hi All,
| >
| > Me again with yet another question. Here is my yet another "minor"
| > problem. I have 165/45R15s tires on the front (droped from 195/50) and
| > now my speedo is way off, by which I mean i am reading 70 while going
| > around 50. And 80 while in the right lane on the freeway. Which looks
| > totaly cool and all, but I would like to be able to tell my actual
| > speed. Is there anyway to recalibrate stock speedo? Or the only way to
| > remedy this problem is to replace it with an electronic unit? Car is
| > 64 T1.
| >
| > Thanks again,
| > Anton
| >
| > P.S. I had to go this small on the tires, because previous size was
| > rubbing on the fenders and I want it low. (droped spindles, cb wide 5
| > disk breaks, 2" narrowed beam).
| >
|
| Go electronic and put your old one away in the vault.
|
| To calibrate it requires watchmaker skills in manipulating
| the hairspring.
|
| Speedy Jim
| http://www.nls.net/mp/volks/
|

Eddie wrote:

> Speedy Jim,
> My 65 came with 135's on the stock rims. Do you know how much that puts my
> speedo off by? Greater or less than the actual speed?
>
> Thanks
> Eddie
>

I'm not an expert on tires. Best way is to measure
the tire radius (as it sits on the road). Compare that
to a stock tire radius.

Here's a very handy calculator for gear ratios and
tire dimension influence:
http://www.johnmaherracing.co.uk/gearcalc.htm

This site may help too:
http://www.torquecars.co.uk/Tuning/alloy-wheels.php

and
http://www.carbibles.com/tyre_bible.html

Jim

Thanks, I just don't have any stock tires unless the back 165's are close to
the stock size.

"Speedy Jim" > wrote in message
et...
| Eddie wrote:
|
| > Speedy Jim,
| > My 65 came with 135's on the stock rims. Do you know how much that puts
my
| > speedo off by? Greater or less than the actual speed?
| >
| > Thanks
| > Eddie
| >
|
| I'm not an expert on tires. Best way is to measure
| the tire radius (as it sits on the road). Compare that
| to a stock tire radius.
|
| Here's a very handy calculator for gear ratios and
| tire dimension influence:
| http://www.johnmaherracing.co.uk/gearcalc.htm
|
| This site may help too:
| http://www.torquecars.co.uk/Tuning/alloy-wheels.php
|
| and
| http://www.carbibles.com/tyre_bible.html
|
| Jim

Hi Jim,

Well I do realize the intricacies of the speedo mechanics, floats and
magnets etc. So I wouldn't dare going inside of it myself. I was
thinking more along the lines of who can do it for me? I cannot find
ccspeedometers and don't know if there is anybody else that is capable
of doing this.

Thanks
Anton


Speedy Jim wrote:
> anton wrote:
> > Hi All,
> >
> > Me again with yet another question. Here is my yet another "minor"
> > problem. I have 165/45R15s tires on the front (droped from 195/50) and
> > now my speedo is way off, by which I mean i am reading 70 while going
> > around 50. And 80 while in the right lane on the freeway. Which looks
> > totaly cool and all, but I would like to be able to tell my actual
> > speed. Is there anyway to recalibrate stock speedo? Or the only way to
> > remedy this problem is to replace it with an electronic unit? Car is
> > 64 T1.
> >
> > Thanks again,
> > Anton
> >
> > P.S. I had to go this small on the tires, because previous size was
> > rubbing on the fenders and I want it low. (droped spindles, cb wide 5
> > disk breaks, 2" narrowed beam).
> >
>
> Go electronic and put your old one away in the vault.
>
> To calibrate it requires watchmaker skills in manipulating
> the hairspring.
>
> Speedy Jim
> http://www.nls.net/mp/volks/

Many years ago I had a GM car (I won't go into the specific model
because it is not important here). It was necessary to replace the
transmission (it broke). The new tranny had a different speedometer
gear and so the speedo read slower than actual vehicle speed.

One day I got stopped for speeding. I explained to the officer that
the tranny had been replaced and I was sure the speedo wasn't reading
correctly and so I really "...didn't know how fast I was going".
To avoid the fine and the insurance points I took the car to a
speedometer recalibration shop. This shop had a huge roller drum
(similar to a dyno) where they could measure the true speed vs the
speedometer reading.
Based on the results, they built a "ratio adapter". Basically a geared
box w/ male/female speedo connectors on each end. This geared up my
speedo cable RPMs and resulted in my speedo reading the correct speed.


I did a quick Google search and found a company in CA that builds the
same things. I'm sure there are others places out there. Maybe
someone else can recommend one?
http://www.speedometershop.com/ratio.html
I can't speak for their quality or if they even have the parts to build
an adapter for a VW, but if you have no choice but to run non-stock
tire diameters, this is another alternative to replacing your speedo w/
an electronic one, or giving your original speedo a "root canal".

Such an adapter would connect behind the dash between the speedo and
the cable, gearing down the RPMs. Total service cost to build a "ratio
adapter" and test it in the car (many ago)... ~$250 !!!! Well, I
didn't say it was a cheap solution :-)



AshMan

Could you not get a freind to drive with you and tell you your correct
speed - at 10mph intervals (for example) . Then print yourself a new dial
onto acetate ?

Rich

"anton" > wrote in message
oups.com...
> Hi All,
>
> Me again with yet another question. Here is my yet another "minor"
> problem. I have 165/45R15s tires on the front (droped from 195/50) and
> now my speedo is way off, by which I mean i am reading 70 while going
> around 50. And 80 while in the right lane on the freeway. Which looks
> totaly cool and all, but I would like to be able to tell my actual
> speed. Is there anyway to recalibrate stock speedo? Or the only way to
> remedy this problem is to replace it with an electronic unit? Car is
> 64 T1.
>
> Thanks again,
> Anton
>
> P.S. I had to go this small on the tires, because previous size was
> rubbing on the fenders and I want it low. (droped spindles, cb wide 5
> disk breaks, 2" narrowed beam).
>

Try this site http://www.miata.net/garage/tirecalc.html

Eric 62 Ghia 68 Bug

"anton" > wrote in message
oups.com...
> Hi All,
>
> Me again with yet another question. Here is my yet another "minor"
> problem. I have 165/45R15s tires on the front (droped from 195/50) and
> now my speedo is way off, by which I mean i am reading 70 while going
> around 50. And 80 while in the right lane on the freeway. Which looks
> totaly cool and all, but I would like to be able to tell my actual
> speed. Is there anyway to recalibrate stock speedo? Or the only way to
> remedy this problem is to replace it with an electronic unit? Car is
> 64 T1.
>
> Thanks again,
> Anton
>
> P.S. I had to go this small on the tires, because previous size was
> rubbing on the fenders and I want it low. (droped spindles, cb wide 5
> disk breaks, 2" narrowed beam).
>

"anton" > wrote in message
oups.com...
> Hi All,
>
> Me again with yet another question. Here is my yet another "minor"
> problem. I have 165/45R15s tires on the front (droped from 195/50) and
> now my speedo is way off, by which I mean i am reading 70 while going
> around 50. And 80 while in the right lane on the freeway. Which looks
> totaly cool and all, but I would like to be able to tell my actual
> speed. Is there anyway to recalibrate stock speedo? Or the only way to
> remedy this problem is to replace it with an electronic unit? Car is
> 64 T1.
>
> Thanks again,
> Anton
>
> P.S. I had to go this small on the tires, because previous size was
> rubbing on the fenders and I want it low. (droped spindles, cb wide 5
> disk breaks, 2" narrowed beam).
>

your 195/50's also made your speedometer read "fast"....assuming your
speedometer was accurate with the stock sized tires, 195/50's are
approximately 10.5% smaller than stock..therefor your speedometer will read
10.5% fast....
the 165/45's are tiny little fellows....according to an internet tire size
calculator( http://www.miata.net/garage/tirecalc.html ) they are 17.9%
smaller....therefor your speedometer will read 17.9% faster than you are
going....any shop that does certified speedometer checks(for verification of
speed readings...ask any local police officer they can refer you to the
closest one) can make a componet up that increases or decreases indicated
speed based on the percentage it is off...it is an add on piece that is put
inline between the speedometer and the cable....i have one on my chevy
pickup after re-gearing and adding larger tires...was about 20 percent slow
on indicated readings....that is a bad thing...well unless you like
tickets....