Speedo accuracy?

[MikeO996]

Was driving everywhere today with my sat nat which just confirmed how much out my speedo is.

At an indicated 70, according to my sat nav I'm only doing 56.

I'm running 13 inch wheels , could I have a 15 inch speedo?

[sjmmarsh]

With that difference in speed it sounds more like you are running the wrong diff, or more likely the speedo has been calibrated incorrectly. If I is a more recent car then there should be some dip switches on the back of the speedo.

Wheels normallly one make at most 5% difference in the reading, unless you have massively low profile tyres on the 13" wheels.

Steve

[2slo]

It seems Caterham tends to set them 5mph optomistic, i.e. at an indicated 75 I'm doing 70mph. A couple of other owners I've spoken to have said similar.

[MikeO996]

Curious observation, the rev counter and speedo needles are perfectly aligned with each other in 6th gear, which surely means that it's set up as the factory intended - or am I missing something?

It's a K series R300 btw

[jackh707]

Ours is spot on, identical to GPS readings, if my dad driving the caterham and indicating 40, I will be showing 45 on the bike.

[kenno78]

Pull the speedo out. They'll be a rubber bung covering the calibration switches. Caterham should be able to tell you which combination suits your wheel size/diff setting.

[coppice]

Buy a Stack if you want serious pace though; mine once told me I was doing 535mph past WH Smiths. Managed to stop before Iceland though - hellish good brakes.