Via Veloce by Wille R.  Internet since November 1995 and still here. alfa romeo spares

The speedometer, happy reading or true speed?

The speedometer is notoriously known to be reading too high figures. The same goes for the tacho as the main principals of the speedometer and tachometer are essentially the same. Speeding too fast is not so popular according to the law, so why don't you check your speedo. Besides, imagine to drive with your 'spouse or girlfriend at 140 kph with the speedo reading 110 kph! "Notice how cool and calm I'm driving, eh?"

What about new tires? Check how your speed will change with a different tire option. The new tires you're looking for might perhaps have some great effects on your speedo reading. If it turns out that you tire size will lead to miss calculating the speed, it is quite easy to adjust a mechanical instrument. Just follow the instructions below.

Enter your current tire size :
/ - R
Enter tire size :
/ - R
Enter your current speedometer reading: KM/H or MPH

True or happy reading?

When your speedometer indicates KM/H or MPH, you would be cruising at KM/H or MPH.

There are also some other car manufacturers that have steel rims and wheels that will fit your 105 Alfa Romeo. It's all here.

In order to check the tachometer, use an electronic one to confirm the discrepancy. Electronic tachos are inexpensive and easy to install. I use one in the engine bay when I tune the engine.

The final ratio and engine revs, Giulia 105-series.

The Roundtail spiders have different final ratios like any other Alfa Romeo. Check the table to find out your speed at 2.000 revs and then you may have to adjust your instrument. The figures are approx. naturally, so use your common sense. The tires have some influence too on the speed. The table shows the speed in 5th gear with the standard wheels. However, this does not effect the relationship between the engine revs and the speed.

Model Final ratio Final ratio, metric Approx. kph at 2.000 revsand 5th gear Approx. mph at 2.000 revs and 5th gear
and 1600 GT
9 / 41 4,55 66 kph 41 Mph
1750 Spider Veloce
and GTV
10 / 41 4,10 70 kph 44 Mph
1300 Spider
and GT Junior
9 / 41 4,55 59 kph 37 Mph
2000 Spider
and GTV
10 / 41 4,10 70 kph 44 Mph
1750 and
2000 Berlina
10 / 43 4,30 68 kph 43 Mph

Assuming your tacho is reading correct, just cruse along at 2.000 revs in 5th gear and see if you need to increase or decrease the speedometer. When you have verified the discrepancy, go back to you garage and remove your speedo. There are two nuts to undo at the back of the instrument before you take the whole unit out from the dash.

This is how I do it. The procedure is for the Jaeger instruments, common on AR Spiders. I have however not tried this on Veglia Borlettis, but I assume that they are much alike. Then just cool down and turn on some good music like Duane Eddy or Jerry Lee Lewis.




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