Speedo gear

[Hawklord]

Hi

When going through villages with speed recorders the figure shown on the roadside display always appears to be lower than what my speedo shows. Can anyone tell me which colour (teeth number) speedo drive gear I should have in my 300TDI defender 90 fitted with 235/85 R16 tyres and discovery 1.2 ratio transfer box.

Thanks

 

 

[MR-HIPPO]

Here you go.

 

Land Rover 90/110 speedo drive gears

• Colour: blue/20 teeth - Part number: FRC3310 - Tyres: 7.50/16 or 235/85/16
• Colour: green/21 teeth - Part number: FRC3311
• Colour: yellow/22 teeth - Part number: FRC3312 - Tyres: 205/16 tyres
• Colour: red/24 teeth - Part number: FRC3313

Taken from THIS page.

 

Transfer box ratio does not affect this, as the speedo drive is driven from the output side of the box.

Edited July 26, 2019 by MR-HIPPO

[Retroanaconda]

With the blue one and 235/85R16 it will over-read by around 5% which is just about ideal.

Transfer box ratio makes no difference. Only diff ratio and tyre size.

[Hawklord]

Thanks for your replies and I have the blue 20T gear fitted so will just accept the error, but at least it reads higher.

 

 

[Pappa Smurf]

Why would the reading be off? If they are the standard size tyres, surely it just needs calibrating.

[western]

I wouldn't rely on those speed signs being 100% accurate. 

check your speedo readings against a GPS unit.

 

I run 255/85 with a standard 110 transfer box of 1.410:1 & its very accurate when compared to my gps speed 

[Retroanaconda]

2 hours ago, Pappa Smurf said:

Why would the reading be off? If they are the standard size tyres, surely it just needs calibrating.

Speedos are designed to over-read slightly - usually by 5-10%.

They are not allowed to under-read, so manufacturers err on the side of caution. It also gives you a useful safety margin of a few mph for those speed traps 

[steve b]

Is that with the standard drive gear Ralph?

As James says the speedo should read correct or over  , pretty much every vehicle I've driven with a separate GPS shows this , the closest is my Forester but that over reads by a couple of mph .

One of the quirks I found driving around NZ was fairly frequent odometer check signs on the roads either a measured 1km or 10km .

cheers

Steve b

[Pappa Smurf]

Fair enough, I can see the logic.

[western]

23 minutes ago, steve b said:

Is that with the standard drive gear Ralph?

As James says the speedo should read correct or over  , pretty much every vehicle I've driven with a separate GPS shows this , the closest is my Forester but that over reads by a couple of mph .

One of the quirks I found driving around NZ was fairly frequent odometer check signs on the roads either a measured 1km or 10km .

cheers

Steve b

Yes, in my 110 the blue frc3310 gear. 

[cackshifter]

On 7/27/2019 at 1:57 PM, steve b said:

 

One of the quirks I found driving around NZ was fairly frequent odometer check signs on the roads either a measured 1km or 10km .

 

Because tourist hunting is the national sport of the NZ constabulary in their unmarked Commodores

[steve b]

I did 15000km north and south Island and never had any problems at all , back then on the south Island particularly we could drive for 2 or 3 hours and not see another vehicle , 20 years ago though .

One of my favourite places and road tours so far , what would have made it even better would have been an early RRC in place of the Mitsi Mirage although it coped totally with around 7000km of dirt roads and still did high 30's mpg

Saw several Series 1's and 2/2a's around

cheers

Steve b