Morris 1100 wrote:
phillb wrote:
Morris 1100 wrote:
I just run the Cooper S gear ratio and tyre size into
Gearcalc.
16.51mph per 1000rpm.
33.02 at 2000
49.53 at 3000
65.74 at 4000
82.25 at 5000
98.76 at 6000
But the actual tyre size will make a difference. So if you mark the sidewall of the tyre at the bottom and place a mark on the ground. Then push the car one revolution of the tyre and place another mark on the ground. Measure the distance between the two marks and feed that into gearcalc it will give a more accurate reading.
Yeah, Thanks heaps Morris, thats very close to what I'm seeing with the Navman, so that confirms my Gearbox/Diff is standard.
Thanks for the recommendation of repairer also.
The Australian workshop manual gives 16.00mph per 1000rpm not the 16.51 that Gearcalc worked out. It could be the difference in tyres or it could be bad info! If you could give me the circumference (or even the dia) of the tyre I could run it again.
I have not used that instrument repairer but the bloke at work used him on an old Falcon and I think he might have used him for his Cooper S as well.
Well the 16/1000 rpm gives almost exactly what I am getting so I guess that confirms I have a standard diff etc.
I also measured my circumference on the garage floor and its 1475mm* so if you like you can put that into Gearcalc and see what comes up.
EDIT: *they are pretty worn, due to be replaced
That Guessworks site is good also, thanks MINImal effort
Either way its only a couple of mph difference and I'm sure new vs worn tyres could give that kind of variation.
Anyway at least now I can ask the instrument repairer to set it back to 1280 TPM and it should read correct (or very close) for my car.
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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)
(mostly Morris 1100 stuff that is missing so I guess it won't worry most of you! 
)
