Rpm

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
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BLACKJACKф
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Rpm

Post by BLACKJACKф »

This might be kind of weird question or topic my car does not have a tachometer. My car is a complete stock 1275 Cooper S. I am wondering what is a good cruising speed on Highway. Measured in mph or kph and what RPMs would I be at? I've looked through books watched videos and can't seem to find anything for a safe cruising speed on Highway. Any information would be helpful please and thank you
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timmy201
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Re: Rpm

Post by timmy201 »

Tachometers weren’t standard fitment on mk1 minis. On a Cooper S the maximum shift points are marked on the speedo with some Roman numerals - I, II, III

It should be happy to sit on 60-70mph all day which is around 4000rpm
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mk1
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Re: Rpm

Post by mk1 »

Agreed, a decent one should pull that sort of speed all day every day.
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MiNiKiN
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Re: Rpm

Post by MiNiKiN »

BLACKJACKф wrote: ↑Wed Sep 13, 2023 6:45 pm This might be kind of weird question or topic my car does not have a tachometer. My car is a complete stock 1275 Cooper S. I am wondering what is a good cruising speed on Highway. Measured in mph or kph and what RPMs would I be at? I've looked through books watched videos and can't seem to find anything for a safe cruising speed on Highway. Any information would be helpful please and thank you
Here you find graphs for a Cooper S close ratio with 3.44 and 3.76 final drive. Speed on the Y-axis is in kph

Cooper S_CR_3.44-vs-3.76.jpg
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If only I knew the power of the Dark Side...I wouldn't have made contact with an Innocenti :mrgreen:
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Exminiman
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Re: Rpm

Post by Exminiman »

here you go - you can try out different ratios, tyres etc...here

http://www.guess-works.com/Tech/ratio.htm

If you want to find out what ratio diff you have this is as good a description as I have seen of what to do https://www.theminiforum.co.uk/forums/t ... ?p=2107153
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BAD942B
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Re: Rpm

Post by BAD942B »

And here is kmh to mph converter https://www.unitconverters.net/speed/kph-to-mph.htm
Chris A
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BLACKJACKф
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Re: Rpm

Post by BLACKJACKф »

Okay thank you so much that information. Is the engine very reliable at 4000 RPM? It is 55 years old . Lol I do know about the three orange colored lines on the speedometer I have never come close to an RPM that high . So maybe I should change my final drive to a 3.1
Last edited by BLACKJACKф on Sat Sep 23, 2023 7:03 pm, edited 2 times in total.
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mk1
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Re: Rpm

Post by mk1 »

A 3.1 will decrease cruising RPM, but will have a proportional impact on acceleration.
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BLACKJACKф
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Re: Rpm

Post by BLACKJACKф »

Yes I understand that about swapping to a 3.1. Thanks for the information again. Jack.
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