speedo out.

[exosteve]

my terrano is relatively new ( to us that is) 12 years old lol.
I found out the speedo is out by 8 mph. 30 is actually 38 confirmed by my sat nav.
would this be due to the tyres? they are 235/17r16
steve

[rustic]

Originally Posted by exosteve

my terrano is relatively new ( to us that is) 12 years old lol.
I found out the speedo is out by 8 mph. 30 is actually 38 confirmed by my sat nav.
would this be due to the tyres? they are 235/17r16
steve

Could you re quote the tyre size, what does the 17 represent 17% of the width?? I don't think so.

If you measure the circumference, then you can compare.

In fact there are sites that give you this information.

However 8 mph in 30 is huge, you would need bus tyres for that error?


edit...
It's not an import is it, with a label stuck over the dial?
Is the odometer in miles?

[jims-terrano]

Hmm good one but people often compare Sat Nav's to Speedo's which is a pet hate of mine. Normally Speedo's say you are doing 30 but Sat Nav's say 25. Personally I'd rather trust the speedo. Not heard of one reading over and to that extent. What year is your Terrano? I'm sure someone will come back and tell you about tyre/wheel sizes but yes they can cause speedo to read incorrect but unsure to what extent.

Can a garage with MOT Brake test pop it on and test speed against your speedo perhaps?

A friend with another car perhaps run at exactly 30 in front of you perhaps compare?

[theron]

Speedo's by law can over-read but they are not allowed to under-read. GPS (sat-nav) speed will be slower to update but will be 100% accurate.

[AD Ent]

It's normal.
Police cars have calibrated speedos, T2's don't, GPS is calibrated. Terrano speedo is a joke, of all the cars I've tested a GPS App in, It's by far the worse. Mine is on standard 16" wheels and tyres, 235/70/16. 90=80 80mph=70mph 60mph=53mph Bigger the tyres the better it will be.
'Makeitfit' will be along soon with a cure.....

The Big question is.... Have our T2's done LESS Miles than it shows??????? I'm testing this tomorrow.....

[rustic]

Here's one to try...

http://www.alloywheels.com/Tyre_Calculator


Rustic

[AD Ent]

This too, from the download links

http://www.kouki.co.uk/utilities/vis...ize-calculator

[R1cho]

I run 33's and my speedo according to the street speeds radars, my satnav and a local traffic plod i know is spot on 30mph when the speedo says 30mph, for it to be doing 38 at 30 on standard tyres is an odd one to me

[R1cho]

Originally Posted by rustic

Could you re quote the tyre size, what does the 17 represent 17% of the width?? I don't think so.

i think he means 75

[AD Ent]

mine is not far off 38 at 30. I'll check and report back.

[AD Ent]

Originally Posted by AD Ent

mine is not far off 38 at 30. I'll check and report back.

Just tested using Samsung Galaxy 2 and the GPS speedometer App:

At Indicated 40mph the GPS showed 33mph
At Indicated 37mph the GPS showed 30mph
At Indicated 30mph the GPS showed 22mph

[Lazy-Ferret]

Originally Posted by AD Ent

Just tested using Samsung Galaxy 2 and the GPS speedometer App:

The thing it, I thought I read somewhere that by law they are not supposed to be more than 10% out

So worst case

At Indicated 40mph the GPS showed 33mph Speedo should show 36
At Indicated 37mph the GPS showed 30mph Speedo should show 33
At Indicated 30mph the GPS showed 22mph Speedo should show 24

Still, on the plus side, we have no excuses to get pulled for speeding, and I now feel bad for harassing so many T2's in the past, that were only doing 22 in a 30...

[micktheshed]

I thought this was a common problem with several 4x4's.
My 2004, 3L Terrano reads 36 @ 30mph this is 20% error! (legal max error +10%). It improves the faster I go: maybe reads correct at about 120? LOL. Strangely the milometer is nowhere near as bad. This is on standard (original) tyres.
My previous Frontera was just as bad, but at least it's stopped me getting done by the cameras LOL. At one time (when the sender unit was playing up) it would occasionally display up to 50mph standing still!
I know use a sat nav all the time just for the speed reading.

Don't understand how Nissan etc. get away with it. Technically I (we!) could be prosecuted for this error.

[exosteve]

thanks for the comments.
the only reason i new the speedo was out to start with was the thingy at the side of the road you get telling you your speed.
it was telling me i was doing about 23 at 30 on the clock and the sat nav confirmed it.
im not too concerned about it. but I will look into it more as I do want my truck in tip top running order but not that bothered about cosmetics. as i brought it with the idea that 4x4s are meant for a bit of rough and tumble.
steve

[danielj]

Originally Posted by exosteve

thanks for the comments.
the only reason i new the speedo was out to start with was the thingy at the side of the road you get telling you your speed.
it was telling me i was doing about 23 at 30 on the clock and the sat nav confirmed it.
im not too concerned about it. but I will look into it more as I do want my truck in tip top running order but not that bothered about cosmetics. as i brought it with the idea that 4x4s are meant for a bit of rough and tumble.
steve

Same here. Thingy at the side of the road is always about 8 mph lower than my speedo. Speedo on an 92 micra I use is the same. Mazda b2500 I used to use same also. It can be handy though as I don't know how many times I have passed a speed camera a few miles over the limit and breathed a sigh of relief when I remembered that my speedo is over-reading by 8 mph or so and I'm in the clear.