How correct is speedo?

I'm just wondering how far it's out at high speed??
Say hypothetically somebody found a 5 mile straight just outside Peterborough and possibly maxed out they're thundercat with the speedo reading 160mph (5 mile an hour faster than its even capable of going?)
Realistically what speed would that have been?

It's probably 10% out if not more - so 140 ish

Thanks steve :-)

Thinking Hypothetically about your hypothetical conundrum, I reckon at such a hypothetical speed id have no idea what the speedo would hypothetically read as I'd be far too scared to look at it!!!!!

Digger1981 wrote: . . . as I'd be far too scared to look at it!!!!!

No you wouldn't . . . . trust me, . . . you'd still peek

A group of us from the forum went on a trip to the Nürburgring, and the last straight before the ring exit just begs for wide open throttle. A few of us saw the same sort of readings from the clocks of our Cats. . . but as SteveCat says, after 10%ing the reading (down), we reconed on 140 ~ 145mph.

BUT you do sneak a peek at the speedo

According to the speed awareness course that I recently had to go on (read that as voluntarily signed up for) the newer speedo's are only 2-3 mph out (if your Speedo reads 50 then you are doing 48ish). This could just be them trying to get people to slow down but the guy seemed genuine enough.

Yeah digital ones are meant to be a bit more accurate but my 19 year old analogue one will be quite out I would think. It's not bad at low speeds when I compare it on them 'know your speed' signs.

I do prefer analogue dials for the fact that as long as the needle is around the 30 then as far as I'm concerned I'm doing 30mph (even if it's half way between 30 and 40 lol). Where as with the digital ones as soon as it says 31 you sort of feel like a criminal haha

You also lack an excuse if you drive the older Honda Civics with the digital display. The Cops can clearly read it through the drivers window.

Probably about 5% out at least, but still a good effort, if only in theory

It's been confirmed that my Speedo is at least 5-10mph out as I keep getting asked why I am riding slowly on observed rides when my Speedo is reading the posted limits!! I bet they would complain if I was speeding everywhere lol