Here is one for the Gurus

**Gippslander** · 24th April 2021, 05:50 PM

I recently purchased 225/95/16 tyres for my Series 3 and I am trying to work out revs at 80 kilometres an hour, the tyres rotate 369 times per Kilometer and my final gear ratio I believe to be 7.19 : 1 in the 109” 1 ton Ute. From that I deduce I will be running the engine at around 3550 RPM. My question is not having owned a Land Rover powered Land Rover (past vehicle was Series 1 with a Valiant slant six) is this normal engine operating conditions or am I missing something in the calculation.
Thanks in advance Gippy

**Tins** · 24th April 2021, 06:26 PM

Originally Posted by Gippslander

gear ratio I believe to be 7.19 : 1

Where did that figure come from? Diff ratio should be 4.7. Am I missing something?

**pop058** · 24th April 2021, 06:32 PM

225/95-16 has a circumference of 2619mm (according to goggle)

In 1Km they would rotate 381 times

In 80Kms they would rotate 30,557 times. ( in one hour)

tailshaft would rotate 145,661 times in that hour (4.77 diff ratio)

tailshaft would rotate 2,427 times in a minute

engine would rotate at 2,110 RPM ( 1:15 hi range ratio)

my line of thought anyway.

Edited to include transfercase Hi Range ratio

**101RRS** · 24th April 2021, 07:26 PM

Originally Posted by Gippslander

I recently purchased 225/95/16 tyres for my Series 3 and I am trying to work out revs at 80 kilometres an hour, the tyres rotate 369 times per Kilometer and my final gear ratio I believe to be 7.19 : 1 in the 109” 1 ton Ute. From that I deduce I will be running the engine at around 3550 RPM. My question is not having owned a Land Rover powered Land Rover (past vehicle was Series 1 with a Valiant slant six) is this normal engine operating conditions or am I missing something in the calculation.
Thanks in advance Gippy

If you have a 1 Ton Ute (very rare here - " Only 170 IIA and 238 series IIIs (1 Ton) were built for the home market. Export markets had even fewer examples, making this one of the rarest types of Land-Rover ever built" then you will need bigger tyres as they ran 9.00 x 16 tyres so a metric equivalent of 255/100 x16 - basically 35" tyres.

I guess you actually mean a Standard 109 Series 3 rather than a 1 Ton 109.

Garry

**Gippslander** · 25th April 2021, 08:42 AM

Thanks for the replies I do appreciate the information, I thought the six cylinder version was a 1 ton but if that is not so I am fine with that, as the gear ratio is then higher as indicated on this web site.(Land Rover gear ratios)
From that I get 5.4:1 final ratio which brings the revs required to 2,060 or there abouts and I think that is much better.
Thanks again for the help.
Gippy

**pop058** · 25th April 2021, 04:10 PM

Originally Posted by pop058

225/95-16 has a circumference of 2619mm (according to goggle)

In 1Km they would rotate 381 times

In 80Kms they would rotate 30,557 times. ( in one hour)

tailshaft would rotate 145,661 times in that hour (4.77 diff ratio)

tailshaft would rotate 2,427 times in a minute

engine would also rotate at 2,427 RPM ( 1:1 top gear ratio)

my line of thought anyway.

Originally Posted by Gippslander

Thanks for the replies I do appreciate the information, I thought the six cylinder version was a 1 ton but if that is not so I am fine with that, as the gear ratio is then higher as indicated on this web site.(Land Rover gear ratios)
From that I get 5.4:1 final ratio which brings the revs required to 2,060 or there abouts and I think that is much better.
Thanks again for the help.
Gippy

Forgot about the transfercase ratio. So low 2000s would be close.

**JDNSW** · 25th April 2021, 08:50 PM

My calculations come out somewhat differently.

Tyre circumference (nominal) = ((225x0.95x2)+400)x3.1428 = 2600mm or 2.6m

Turns per kilometre = 1000/2.6 = 384

Turns per 80km = 80x384 = 30720

Prop shaft turns/80km = 30720 x 4.7 = 144384

Prop shaft rpm = 144384/60 = 2406

Engine rpm in 4th high = 2406 x 1.148 = 2762

Notes:-

Actual effective tyre circumference will vary a little between brands. For radial tyres it depends on the properties of the belt and how far it is below the tread, at least for all reasonable tyre pressures.

Diff ratio is 4.7 for all Series Landrovers except Stage 1 and some very early 80 inch. (that is what they left the factory with, anyway!)

High range for all Series 2/2a/3 (and most Series 1) except Stage 1 and One Ton transfer cases is 1.48 reduction.

The One Ton Landrover was a variant of the six cylinder Series 2a/3. It used a similar chassis to the Australian military 2a (actually copied from it) with extended hangers for the springs and with extended shackles. It had ENV or Salisbury axles front and rear, and a different transfer case, with constant mesh low range as well as high, and a high ratio of 1.53 reduction. Their standard tyre size was 9.00x16. Production numbers were very low as mentioned earlier, and they were sold in the home market only. None are known to have come to Australia although it is possible. Nearly all were apparently sold to commercial buyers and flogged to death. The One Ton transfer case was optional on standard 109s, but as far as I know, not in Australia, and I have never seen or heard of one.

Rover engines of this period are in general quite happy to operate at high rpm by the standards of Australian six cylinder cars (or later larger and more powerful Landrover engines), and while they are very flexible, using full throttle for long periods at lower rpm is asking for engine trouble.

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