Correcting Speedo

John Roach · Post by **John Roach** » Sun Dec 14, 2008 5:07 pm

Hi,

Have just purchased a Stage 1...which has been fitted with a standard 109" speedo. Have posted a request for a proper one, but in the meantime was wondering how to calculate true mph/mpg etc. Do I divide by 3.54 then multiply by 4.7 (diff ratios) or, as I expect, is there more to it? Tyres are standard.

Regards,

John

olliebarrett_92 · Post by **olliebarrett_92** » Sun Dec 14, 2008 6:06 pm

Hi, just reading your post, do the Stage Ones not have a standard speedo?! How would I know if mine has the correct one, or if mine too has a standard 109 speedo?
Thanks
Ollie

John Roach · Post by **John Roach** » Sun Dec 14, 2008 6:43 pm

Hi Ollie,

As I understand it, the Stage 1 has a unique speedometer. Seems logical as the diff ratios are different to other Series models. As you look at your speedo you will see a four digit number towards the lower right edge. All Stage 1's should be "1376". Hope this helps.

Regards,

John

redtailhawk · Post by **redtailhawk** » Sun Dec 14, 2008 9:37 pm

hi had a look in the parts book it gives two part no for 109 x 7.50 tyres and two part no for 109 x 9.00 tyres which means with trip or with out doesn,t mention stage 1 but i am sure i read some where if you put 3.54 diffs in normal 109 and change the speedo drive to a stage 1 one your speedo would read right? Have checked mine and it does have the digits 1376 in the bottom right.
Darren

map1275 · Post by **map1275** » Mon Dec 15, 2008 8:34 am

The drive gears are the difference to make it all work.

Otherwise the Stage One uses the standard Ser III speedo for 109" with 7.50 x 16" tyres.

There are about three variants of this depending on what the face reads in: KPH, MPH, both, and which ever one is dominant.

The Jaeger coding at the bottom of the dial is the identifier. However I haven't found a comprehensive Land-Rover listing of these.

sebking · Post by **sebking** » Mon Dec 15, 2008 11:04 am

This may help - looks like speedos are the same

John Roach · Post by **John Roach** » Tue Dec 16, 2008 5:25 pm

Before reading the last two posts I posted this in Sales/Wants..."Having done some research have learnt that the four digit number represents the turns, or revs, per mile...in other words a 1376 speedo requires 1376 turns of the cable for it to register exactly one mile. There are several variables to consider before being able to determine whether or not a correct speedo is fitted: tyre size, diff ratio and speedo drive gear ratio (the ratio between speedo cable and propshaft turns). There is a formula to calculate the required TPM for any vehicle:

TPM = (inches in a mile/circumfrerence of tyre)*(diff ratio/speedo drive ratio)

One should use the rolling circumference of the tyre (at correct pressure), rather than simply calculating from the tyre size. Do this by measuring either the distance from the centre of the hub to the ground then 2*pi*r or how far vehicle moves with one complete revolution of a (rear) wheel.

Also, found this company http://speedograph-richfield.com For a small fee (but more than a secondhand Series speedo!) they can recalibrate any Land Rover speedo. They give instructions on their site regarding the info required to do this...how far vehicle moves for one revolution of speedo cable, I think. This does mean that any speedo of unknown history may have been recalibrated, therefore not corresponding to its original TPM number. I am told that if one is sure what the correct TPM of a speedo should be then no other info is required."

According to the Haynes manual a standard Series 3 has a speedo drive ratio of 2.2:1, not sure on Stage 1's.

Thanks again.

Regards,

John

map1275 · Post by **map1275** » Thu Dec 18, 2008 11:06 am

That's not entirely correct. Though the idea is there.

As the speedo's have their own internal gearing, you are reliant on having (or your repairer having) a correct gear set. As most UK Jaeger/Smiths internal components are built to a standard format, you can raid and swap as required. The repairer's final operation is to check the calibration (indication).
Therefore you could also have your Land-rover odometre modified to indicate six digits instead of five.

Using Minis as an example, all cars up to the very late 70's used the same gearbox drive gears. This was regardless of application, engine size, tyre rolling diametre or gearbox ratios. The correct speedo was fitted to suit the application.
This then changed to a standardised speedo and various gearbox drive gears.

But all speedos do have an error margin that increases with speed/rpm.

In the case of Land-Rover, where parts availability is pretty damn good, its easier to buy the correct part. My original speedo cost more to repair than it did to buy a new unit.

olliebarrett_92 · Post by **olliebarrett_92** » Sat Dec 20, 2008 9:28 pm

Hi there,
Could anyone possible tell me, on a stage one speedo what do the markings go up to?
I think my speedo may be a 109 series 3 speedo for two reasons, 1)I think the number is incorrect, 2)it only goes up to 70mph?
Thanks for you help,
Ollie

map1275 · Post by **map1275** » Sat Dec 20, 2008 9:39 pm

Original for my car:
Marked 140 KPH
Slashes up to 150 KPH

Replacement:
Outer ring:
Marked 140 KPH
Slashes up to 150 KPH
Inner ring:
Marked 90 MPH
Slashes up to about 95 MPH

Davo · Post by **Davo** » Sat Dec 27, 2008 8:28 am

Wow, that's getting pretty complicated.

I already looked into this as I'm turning my SIIA into a Stage I.

I found the the 109" speedos are all the same. It's the drive gears in the gearbox that are different. That's why there's no mention of a particular Stage I speedo in the parts book, which threw me until I put a post on here and someone pointed me in the right direction.

landdani · Post by **landdani** » Sat Dec 27, 2008 2:37 pm

Hi, can I say that the result is (the stage1 speedo is the same as standard serieIII ) ?
it is:
Made in UK IP3231/08
560744
JAGER

I am puting a photo:

[/img]

map1275 · Post by **map1275** » Sat Dec 27, 2008 10:35 pm

Well no, that isn't the conclusion as there are different speedo's for Series III.

The answer is: A Stage One speedo is the same as a Series III with 7.50 x 16" tyres.

You have posted a picture of the fuel/temp cluster.

landdani · Post by **landdani** » Sun Dec 28, 2008 1:14 am

Ok, thank you map1275.

John Roach · Post by **John Roach** » Sun Dec 28, 2008 12:50 pm

Seasons Greetings,

I opened this can of worms as the speedo in my Stage 1 seems to be reading too slow, by quite a margin, and I wanted to calculate my true mph/mpg. Having looked into it I discover all (UK) Stage 1's should have a 1376, yet mine has a 1408. map1275, surely a 1376 (Stage 1?) is not the same as a 1408 (4cyl on 7.50's?)? Having said that, they might as well be: a difference of less than 2mph at 70mph...well within a speedo's natural margin of error. If this is the case, then I reckon the transfer box speedo drive ratio must be the issue with my vehicle...assuming that it's all working properly, of course! Does anybody know what this ratio is on a Stage 1: it's 2.2:1 on all 4cyl Series 3's? If my maths is good I think it might be about 1.6 or 1.7:1. Alternatively, anyone know how many teeth are on the Stage 1 speedo pinion drive? They look like this...http://cgi.ebay.co.uk/Land-Rover-Stage- ... 240%3A1318 Will check this afternoon, but if I have one of these fitted in mine I will be very suprised as 60 feels more like 80...and 14mpg!!!??? Or I have just forgotten what Series 3's are like?

Much thanks for all input.

Regards,

John

Stage 1 V8

Correcting Speedo

Correcting Speedo

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