Speedo calibration

[mazzerman]

Hey guys, ive had my speedo face changed over to MPH but it doesnt seem right, when im doin 30 it feels more like 40 etc etc.
Can someone confirm what speed i should be doing at 3k RPM?
In D with OD on at 3k RPM im doin 70mph does that sound right to you guys?
Thanks
Marty

[TonyN]

Also depends what size tyres you have, 2nd gens came with 215. 265 or 31" tyres, all with different gear ratios to suit. Its hard to tell what size tyres the truck is geared for originally if some one has changed then later.

A truck with 31's seems to read about 8-10% slow if it came from the factory with smaller tyres.

Just wait for the cameras to flash, then you know your going faster than the clock says!

[rubblebags]

Hi Mazzerman
when my friend and I check my speed on my 2.4Surf it appeared that I was reading 50mph and he was only doing 45mph. It was a digital read speedo. I have now got larger tyres 31x10.5x15 . I now hope that the extra circumference of the tyre will bring me closer to the real speed.?

Geoff.

[mazzerman]

Blimey, it looks as though the speedo isnt very accurate then, oh well will just have to wait for the speeding ticket to arrive, LOL.
I wonder if i can work it out using my GPS sat nav system?
Thanks for the replies guys.

[da SLUG man]

the speedo is checked for accuracy on the SVA test.

i've never found GPS speed indication very accurate

[rubblebags]

the speedo is checked for accuracy on the SVA test.

i've never found GPS speed indication very accurate

Hope its not the same bloke that checks the Tyres or the bloke who moaned about the toe hooks or the bloke that moaned about the Knob protusion. (ooooooo ah ).

Geoff.

[mazzerman]

speedo calibration

Mine never went through the SVA test as its just over 10 years old (last month)
So wouldn't have been checked on MOT.
I'll get the missus the drive behind me and tell me what speed im doin so i can see the difference.

[Linda]

When I swapped mine from 265's to 31" it threw mine out by about 8mph... I'm going faster than the speedo says according to those who have tried to follow me...

Still could just be that they are going slow and I'm doing the right speed???

Anyone know a friendly PC with a speed camera to help us check???

[wibblywobbly]

Gps

I have a surf with oversize wheels, I also took the temporary measure of copying an image of an MPH speedo face from Ebay, blowing it up to real size, printing it, cutting out the centre portion, cutting slits in the white marks to let the light through, and sticking it onto the cover perspex with double sided tape. It cost me nowt and works a treat.

I tested it against my GPS and it was absolutely spot on. Now, the big question is, have the oversize wheels/tyres made the speedo accurate??

Rob G

[Guest]

Checked witha GPS my speedo reads 10% fast using 265/70/15 tyres. i.e. when I am indicating 40MPH ia ma actually doing around 36MPH.

With 31s on I should be close to accurate.

Cheers

[mazzerman]

How did you check using GPS?
Would like to try that.

[Guest]

How did you check using GPS?
Would like to try that.

I have a TomTom Navigator System that I use in the car (based on a Compaq Ipaq PDA). It shows the speed you are doing - it's accurate if you get enough satelites to lock on to and you are going at a constant speed on a straight road. It's a bot slow to catch up as you are accelerating or decelerating but then it uses the doppler effect of the difference in distance to the satelites to calculate the speed.

Cheers

[Muzz67]

Speedo check

Find a section of road with the signs for a speedo check- you know, 1 mile, 2 mile etc,and time exactly how long it takes to travel the mile at any speed (without varying speed). Now, divide 3600 by the seconds it took and that is your exact speed. EG, If it took 40 seconds to travel 1 mile then 3600 divided by 40 equals 90mph. 60 seconds equals 60mph. 90 seconds equals 40 mph. Easy!

[Simon.O.]

Heres 'ow I did it
Drive arround untill you spot one of the local Gendarmes with his hairdrier ( the b@astard radar gun )
Hopped out and said something to the effect of " ullo ullo, fancy checkin me sppedo for us guv?"
Waltz down the road at a dead set 50 on the dial and pass 'im
Go back and says " 'ow was that guv?"
'e says spot on 50 it is
So there is me, one happy camper
BTW I have got 31"s and the speedo is right on the money!!
Happy now!!

[Conker]

I got a GPS snooper that shows your speed.
I got 275/70x16 on mine and the speedo reads slow.
At a steady 70 on the clock on the moorway it is really doing 76
like wise showing 50 actual 55 [ enough for a ticket ]
Cheers
Conker