General Speedo Reading

[jaspernina]

Hello

Happened to notice that the speedo isn't very accurate. I fitted a Snooper to my Seicento, when it reads 28mph, the car speedo says 32, at 60mph, the car is nearer 68. Though it was the Snooper, however, when I tried A Garmin sat nav it gave the same results as the Snooper. Have you noticed this?

Stephen

 

[fingers99]

Yes, on stock tyres they over read.

 

[jaspernina]

Yes, on stock tyres they over read.

So I've 14" Abarth wheels does this make it worse?

Thanks

Stephen

 

[fingers99]

So I've 14" Abarth wheels does this make it worse?

"

It'll probably depend on the gearbox (and the tyres).

On the MPI Abarth box, I'd expect it to under read, on the "standard" box, to be fairly accurate.

 

[Most Easterly Pandas]

Has the same read out difference as our Panda's. All cars are designed to over read

Jon.

 

[fingers99]

Yes, under reading is illegal. You can get it close to being accurate by sticking bigger wheels and tyres on (and thus raising the overall gearing), but expect that to have an impact on acceleration and even (actual) top speed.

I've encountered cars which under read by much more than the Centos, especially a 1.8 BMW which read 110 at about 85!

 

[Slosei]

Yes and if you get large enough wheels to get your speedo close to accurate with enough top end torque its rather funny when over taking larger cars lol on my 14s with a (195-45-14 contis) iirc doing 100mph on speedo sav nav would read around 92mph ish
tried both sets of wheels (14s 16s) on drag strip and and the difference i saw was 0.3seconds slower with the 16s starting off and finishing but with the 16s i crossed the line with just 91.8mph n with 14s i crossed line with 90.9mph little differences imo