Speedo Accuracy?

[bogie]

Anyone elses speedo read a bit high - I think ours is out by a good 10-20mph?

[rjosborne]

On average, they are accurate. By that, what I mean is that mine under-reads by at least 10mph, cancelling out your over-reading.

[bogie]

maybe I'll get it checked out at the dealer...Im sure its like reading 50Mph when Im doing 30mph and 110Mph at 85Mph etc !

anyone know the gearing - mph/revs so I could could check for definate?

[powerlord]

if you know anyone with a GPS that's worth a go ?

My GPS seem to show accurate to 1-2mph at speed.

I'm in Ipswich if that's any use to ya.

stu

[bogie]

thanks - Ive got one in the Elise, but its hard wired in - I think we'll just go out in both cars and sse what its like in comparison

[Chim450]

On Vmax last weekend my speedo read 165mph and the speedtrap 164mph, pretty accurate I would say.

[J_S_G]

My analogue reading is fooked at times... some times it's spot on, some times it's a constant 10mph out (always reads low). If you switch off the engine and restart it, it'll be a different amount out. I've even switched the engine off when it was reading 80 on the motorway, then restarted it whilst coasting to fix it.

However the digital readout has always been spot on - verified by GPS up to, erm, "substantial" speeds.

I'll be having that sorted out along with the other 14 things (no, really) on the list when I drop the car off tomorrow!

I've even kept the private plate ready to transfer onto it for when it returns, I'm that sure it'll feel like a different car after all this...

[Bob the Planner]

I think the ratios are in the handbook and you should be able to work it out from there. MPH per 1000 revs for 245/40/ZR18 Toyo it should be something like

1st 6.8mph
2nd 10.2
3rd 14.9
4th 19.9
5th 24.9

[bogie]

thanks chaps - is the correct tyre size 225/40 and 255/40 then ? (handbook only gives sizes for 16") - our Tuscan has 225/35 and 255/35's - just wondering if this is why it seems out a bit

[bogie]

sussed it now - the analogue speedo always shows approx 5-10mph more than the digital one. The digital one is about 5-7mph out...pretty sure this is down to the /35 profile tyres - with 40/45 profile tyres it would be spot on.