Thread: The Series Speedo and Tyre Sizes

The Series Speedo and Tyre Sizes

the red highlight shows where the relevant number is located on the speedo

The main land rover ones are

1408 7.50×16 (235/85 r16)
1504 6.50×16 (205/80 r16)
1536 6.00×16 (205/70 r16)

the number in red is the number of revolutions the speedo cable does to increment the mile wheel

Tyre Outside Diameters
7.50x16 31.6" OD Circumference 99.31" 100% 10.4%+ 5.68%+ 4.62%+
7.00x16 30.2" OD Circumference 94.92" 95.5% 5.6%+ 1.01%+
6.50x16 29.9" OD Circumference 93.97" 94.6% 4.5%+
6.00x16 28.6" OD Circumference 89.89" 90.5%

Series Land Rover have a 4.7 : 1 reduction differential and a 2.2 : 1 speedometer drive gear reduction from propshaft to speedometer.

4.7 divided by 2.2 = 2.136 which means a 1 : 2.136 step up from rear wheels to speedometer.

For every revolution of the road wheels we get 2.136 revolutions in the speedometer. This is a constant relationship that can be used in every speedometer calculation.

Attached Images

• speedoshow.jpg (50.2 KB, 476 views)

Last edited by incisor; 14th August 2012 at 09:01 AM.

2007 Discovery 3 SE7 TDV6 2.7
2012 SZ Territory TX 2.7 TDCi

"Make the lie big, make it simple, keep saying it, and eventually they will believe it." -- a warning from Adolf Hitler
"If you don't have a sense of humour, you probably don't have any sense at all!" -- a wise observation by someone else
'If everyone colludes in believing that war is the norm, nobody will recognize the imperative of peace." -- Anne Deveson
“What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others.” - Pericles
"We can ignore reality, but we cannot ignore the consequences of ignoring reality.” – Ayn Rand
"The happiness of your life depends upon the quality of your thoughts." Marcus Aurelius

1974 S3 88 Holden 186.
1971 S2A 88
1971 S2A 109 6 cyl. tray back.
1964 S2A 88 "Starfire Four" engine!
1972 S3 88 x 2
1959 S2 88 ARN 111-014
1959 S2 88 ARN 111-556
1988 Perentie 110 FFR ARN 48-728 steering now KLR PAS!
REMLR 88
1969 BSA Bantam B175

the plot thickens




here is the speedo from my 1959 swb ( ex army commd recon)

looks to be the reaL as the year of manufacture matches the vehicle

but the rev / speedo mile is 1400 not 1408 as is usual for 7.50x16

any one else with a command recon have the same?

PS if trying to do calculations yourself remember there is a 1 : 2.136 step up from rear wheels to speedometer. For every revolution done by the wheels we get 2.136 revolutions in the speedometer.

Attached Images

• madge-speedo-0022.jpg (20.5 KB, 212 views)

2007 Discovery 3 SE7 TDV6 2.7
2012 SZ Territory TX 2.7 TDCi

"Make the lie big, make it simple, keep saying it, and eventually they will believe it." -- a warning from Adolf Hitler
"If you don't have a sense of humour, you probably don't have any sense at all!" -- a wise observation by someone else
'If everyone colludes in believing that war is the norm, nobody will recognize the imperative of peace." -- Anne Deveson
“What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others.” - Pericles
"We can ignore reality, but we cannot ignore the consequences of ignoring reality.” – Ayn Rand
"The happiness of your life depends upon the quality of your thoughts." Marcus Aurelius

Last edited by gromit; 13th August 2012 at 04:57 PM. Reason: typesetting & additional info

'56 Series 1 with homemade welder
'65 Series IIa Dormobile
'70 SIIa GS
'76 SIII 88" (Isuzu C240)
'81 SIII FFR
'95 Defender Tanami
Motorcycles :-
Vincent Rapide, Panther M100, Norton BIG4, Electra & Navigator, Matchless G80C, Suzuki SV650

1974 S3 88 Holden 186.
1971 S2A 88
1971 S2A 109 6 cyl. tray back.
1964 S2A 88 "Starfire Four" engine!
1972 S3 88 x 2
1959 S2 88 ARN 111-014
1959 S2 88 ARN 111-556
1988 Perentie 110 FFR ARN 48-728 steering now KLR PAS!
REMLR 88
1969 BSA Bantam B175

so one of yours has the 1400 speedo?


your forgetting the 2.2 speedo worm drive ratio and the 4.7 diff ratio

the number on the speedo relates to the revolutions the speedo cable does per increment on the mile wheel.

you have to calculate it back down your drive line.

Attached Files

• speedo.xls (6.5 KB, 18 views)

2007 Discovery 3 SE7 TDV6 2.7
2012 SZ Territory TX 2.7 TDCi

"Make the lie big, make it simple, keep saying it, and eventually they will believe it." -- a warning from Adolf Hitler
"If you don't have a sense of humour, you probably don't have any sense at all!" -- a wise observation by someone else
'If everyone colludes in believing that war is the norm, nobody will recognize the imperative of peace." -- Anne Deveson
“What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others.” - Pericles
"We can ignore reality, but we cannot ignore the consequences of ignoring reality.” – Ayn Rand
"The happiness of your life depends upon the quality of your thoughts." Marcus Aurelius

1974 S3 88 Holden 186.
1971 S2A 88
1971 S2A 109 6 cyl. tray back.
1964 S2A 88 "Starfire Four" engine!
1972 S3 88 x 2
1959 S2 88 ARN 111-014
1959 S2 88 ARN 111-556
1988 Perentie 110 FFR ARN 48-728 steering now KLR PAS!
REMLR 88
1969 BSA Bantam B175

2007 Discovery 3 SE7 TDV6 2.7
2012 SZ Territory TX 2.7 TDCi

"Make the lie big, make it simple, keep saying it, and eventually they will believe it." -- a warning from Adolf Hitler
"If you don't have a sense of humour, you probably don't have any sense at all!" -- a wise observation by someone else
'If everyone colludes in believing that war is the norm, nobody will recognize the imperative of peace." -- Anne Deveson
“What you leave behind is not what is engraved in stone monuments, but what is woven into the lives of others.” - Pericles
"We can ignore reality, but we cannot ignore the consequences of ignoring reality.” – Ayn Rand
"The happiness of your life depends upon the quality of your thoughts." Marcus Aurelius

1974 S3 88 Holden 186.
1971 S2A 88
1971 S2A 109 6 cyl. tray back.
1964 S2A 88 "Starfire Four" engine!
1972 S3 88 x 2
1959 S2 88 ARN 111-014
1959 S2 88 ARN 111-556
1988 Perentie 110 FFR ARN 48-728 steering now KLR PAS!
REMLR 88
1969 BSA Bantam B175