Stelvio speedometer reading low. - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 6 (permalink) Old 02-19-2018, 07:55 PM Thread Starter
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Stelvio speedometer reading high.

We took delivery of our Stelvio last August. My wife drives it most of the time ( I drive one of our 3 other Alfas', '68 Berlina, 73 Berlina or the '78 Spider), great vehicle, but I have found that the speedometer reads 11% high at 40 km/hr and 11% high at 90 km/hr. I have spoken with the local Alfa service manager and he says that's 'standard for the industry'. I find this is hard believe that most drivers would put up with mentally converting your correct speed all the time, especially Alfa drivers. Our other 3 Alfas all have speedometers that are within + or - .5% accuracy. We have made tests with radar and speed with other vehicles to confirm the discrepancy. Is there a computer adjustment for this? Is it the tire/rim size (it has 18 inch rims)? Any comments would be appreciated.
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Last edited by PietroB; 02-20-2018 at 01:40 PM. Reason: Should have said high instead of low.
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post #2 of 6 (permalink) Old 02-20-2018, 08:05 AM
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how did you measure the real speed? in Europe its in law that its not allowed to show lower value than real speed. Max allowed is + 10% so for example in real 100km/h the speedo can show max 114 km/h

-Antti: --ex Alfas:155 2.0 8V '92,155 2.0 16V '96,156 V6 '98,156 V6 '02
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Last edited by Vsix; 02-20-2018 at 08:09 AM.
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post #3 of 6 (permalink) Old 02-20-2018, 08:55 AM
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Same in US. Speedo may not read low, but is allowed to read high. This, in the US, would be a federally mandated warranty if within a certain amount of time since new.

I bet you could find and print out whatever law pertains in Canadjia.

Don P
Carson City, NV

Past Alfas...
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas

Current Alfas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Oops. Add to the "present" list, 10204 01488, 2000 Touring Roadster project

And past...
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)

And present...
64 Mooney M20E ("Rambo". My faithful steed for over 40 years) Over 55 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird


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post #4 of 6 (permalink) Old 02-20-2018, 09:50 AM Thread Starter
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I may have explained my dilemma incorrectly, when I drive through a 40 km/hr speed limit, my speedometer reads 40km/hr and the radar sign shows 36 km/hr (radar is +/- .5% accurate). Therefore the speedometer is reading 10%+ high. Thanks for your comment.

Last edited by PietroB; 02-20-2018 at 09:57 AM.
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post #5 of 6 (permalink) Old 02-20-2018, 01:05 PM
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It's normal for modern speedo's to over read by 2-3MPH minimum (3-5kph), maybe more at higher speeds. As alluded to earlier, manufacturers cannot allow speedo to read under (think of the potential litigation with refunds on all those speeding fines.....). They need to allow for drivers with worn vs new tyres and low tyre pressure, all of which reduce rolling radius and thus start to reduce the real speed vs indicated.

If you want a more accurate check than radars there are some phone apps which are quite usable to give accurate GPS speed if you can find a straight level stretch at constant speed - just make sure the phone is safely mounted or get an assistant to manage it.
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post #6 of 6 (permalink) Old 02-20-2018, 01:22 PM Thread Starter
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Thank you, I'll try that.
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