What to do about speedo error

guards73/2.0 · guards73/2.0's Garage

My teener has 195 60 15's on it right now and the speedo reads low. Is this somthing that can be adjusted or comped for by changing the speedo gearing or something at any reasonable cost, or do I just have to do the math and think about that while driving?

Rot 911 · 08-29-2002, 11:37 AM

Before I even start, I will admit my ignorance about teeners. If you have a mechanical speedo, you will need a different gear. If you have an electric tach, there is a potentiometer screw that can be adjusted. Do a search on the 911 board for info on how to do this. When I had my '72E, and for my Sprite, both of which are notoriously inaccurate, I went to Walmart and bought a $99 GPS which tells you the speed you are going along with direction. I just turn it on and set it standing up in the ash tray.

JWest · 08-29-2002, 11:48 AM

So Kurt V, when are you going to buy a teener so you can see how a performance car SHOULD handle? A nice '73 2.0 in your garage would go a long way toward curing your ignorance.

guards73 - I am suprised it reads low. 195/60/15 are shorter than original, so the speedo should read high. The speedo is mechanical, so readjustment by a speedo shop is the only real solution I know of. There are other theoretical solutions (different speedo gear, inline ratio adapter) but I have not seen real sources for these parts.

Since yours reads low it may be on its way out anyway - excessive drag in the cable or the speedo head maybe.

Rot 911 · 08-29-2002, 12:01 PM

Quote:

Originally posted by James Adams
So Kurt V, when are you going to buy a teener so you can see how a performance car SHOULD handle?

Ah, master, the Force is strong in this one! Actually I've been doing a bit of ebay and other online car ad perusing. There is this open space in my garage. . .

JWest · 08-29-2002, 12:05 PM

You're learning well, young Jedi...

karlp · 08-29-2002, 01:29 PM

I use the same tire combination. Mine reads high. I kind of like it:
"What do you mean it's a POS, we're going 100mph and it only feels like 90?!"

guards73/2.0 · guards73/2.0's Garage

Woops....it actually reads HIGH...I noticed people becoming impatient behind me in 30 mph zones....then went through a
stationary radar trap and it read lower than 30 (25 or so I think)
But it's definitely off...

Dave at Pelican Parts · Dave at Pelican Parts's Garage

I only know three ways you can change the reading.

One, put different size tires on it.
Two, put a small "gear box" in between the tranny and the speedo. (This also includes different gears in the tranny, etc.)
The third way only changes the speedometer, and leaves the odometer reading high. That is to open up the gauge and mess with the little spring that pushes the needle back toward zero. If you can bend it just right, you can probably get closer to your actual speed. If you bend it just wrong, you'll break the spring. Oops. Anything other than those two, and you'll have a very non-linear speedometer...

None of the above are worth it, IMHO.

--DD

red-beard · red-beard's Garage

I was concerned about this for a little while and I finally gave up and bought the GPS unit. Uniden makes a combination GPS and Radar detector for about $225. It's my primary speedo for the car. I did end up changing the tires which made the speedo read better, but I did this to reduce the RPMs on the highway.

205 65 15 or 195 70 15 should make the speedo read right. They are both a shade over 25 inches.

Tirerack is closing out the AVS Intermediate - $45 each!

http://www.tirerack.com/tires/Spec.jsp?make=Yokohama&model=AVS+Intermediate

James

bander · 08-30-2002, 11:39 AM

I was considering making a new stick on label for the speedo which would have the correct spacing for the numbers. It would just take a little thinking to figure out the new scale but shouldnt be that bad. Then draw up a pretty picture and stick it on. Done.

red-beard · red-beard's Garage

A CD Labler should be able to do it.

James

yoh!!! · yoh!!!'s Garage

Hi,

I tried two things that were mentioned before successfully...
For my Vanagon with Km/h speedo I created a new scale with paintshop pro and printed the thing on photo paper and stuck it on top of the existing speedo... this work now for a couple of years. Its not pealing nor does the paper have wrinkles ...
My 914 has tires in the dimension 195/55 15. The speedo should be more off than yours. In the case of the 914 I used the the GPS method to check the tolerance at the critical speeds (like 55, 70). IMO it seems to be good enough to develop some sort of idea what the tolerance is. The GPS is also good to meassure top speed. The receivers save the highest speed so you can read the meassurement after you slowed down, you can reset it and try again!!! :-)

patrick