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| Speedo Calibration https://www.ausmini.com/forums/viewtopic.php?f=2&t=63519 |
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| Author: | phillb [ Sat Jun 05, 2010 6:26 pm ] |
| Post subject: | Speedo Calibration |
I am thinking of getting my speedo serviced/calibated as it reads about 8-10mph too fast and the needle shakes around a bit (2-4mph) Before I do this I want to make sure my gearbox/diff is correct ratio for this speedo. It is a Mk1 Cooper S fitted with a Mk2 gearbox. Speedo is Cooper S 130mph speedo marked as 1280TPM Car has 10inch wheels According to Navman.... When I do 3000 rpm in top gear I am doing 78kph (48mph) according to navman When I do 4000 rpm in top gear I am doing 102kph (63mph) according to navman If the g/box and diff are standard do these figures sound about right? Am I better off measuring one wheel rotation and comparing it to the speedo cable rotation? |
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| Author: | GT mowog [ Sat Jun 05, 2010 6:41 pm ] |
| Post subject: | Re: Speedo Calibration |
phillb wrote: According to Navman.... When I do 3000 rpm in top gear I am doing 78kph (48mph) according to navman When I do 4000 rpm in top gear I am doing 102kph (63mph) according to navman If the g/box and diff are standard do these figures sound about right? Those numbers sound pretty spot on. Diff is 3.44. |
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| Author: | phillb [ Sat Jun 05, 2010 6:51 pm ] |
| Post subject: | Re: Speedo Calibration |
GT mowog wrote: phillb wrote: According to Navman.... When I do 3000 rpm in top gear I am doing 78kph (48mph) according to navman When I do 4000 rpm in top gear I am doing 102kph (63mph) according to navman If the g/box and diff are standard do these figures sound about right? Those numbers sound pretty spot on. Diff is 3.44. Ok, thanks GT, I guess my next question is can anyone recommend an instrument repairer in Sydney with experience with Smiths Speedos? |
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| Author: | Morris 1100 [ Sat Jun 05, 2010 6:54 pm ] |
| Post subject: | |
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. |
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| Author: | Morris 1100 [ Sat Jun 05, 2010 6:57 pm ] |
| Post subject: | Re: Speedo Calibration |
phillb wrote: GT mowog wrote: phillb wrote: According to Navman.... When I do 3000 rpm in top gear I am doing 78kph (48mph) according to navman When I do 4000 rpm in top gear I am doing 102kph (63mph) according to navman If the g/box and diff are standard do these figures sound about right? Those numbers sound pretty spot on. Diff is 3.44. Ok, thanks GT, I guess my next question is can anyone recommend an instrument repairer in Sydney with experience with Smiths Speedos? A bloke from work told me that there was good instrument repairer at Unanderra. Quote: Humphrey Instruments Sales & Service
Instruments--General - Unanderra, NSW (02) 4272 6014 Address Unit 2/ 235 Princes Hwy, Unanderra NSW 2526, Australia Give them a call. |
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| Author: | BBY755 [ Sat Jun 05, 2010 7:25 pm ] |
| Post subject: | |
Had my Cooper S speedo calibrated and checked out and serviced at a place on Carter Rd Brookvale: Manly Auto instruments 19 Carter Rd Brookvale NSW 2100, Australia (02) 9938 4114 Nice guy and good service - knows his stuff. Also apparently does all Mini and Moke World's instruments. |
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| Author: | phillb [ Sat Jun 05, 2010 7:30 pm ] |
| Post subject: | |
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. |
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| Author: | Morris 1100 [ Sat Jun 05, 2010 7:36 pm ] |
| Post subject: | |
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. |
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| Author: | MINImal effort [ Sat Jun 05, 2010 9:02 pm ] |
| Post subject: | |
This site has a good online calculator that is mini specific ... and useful for looking at speedo variations http://www.guess-works.com/Gearbox/Technical/ratio.htm |
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| Author: | Morris 1100 [ Sat Jun 05, 2010 9:25 pm ] |
| Post subject: | |
MINImal effort wrote: This site has a good online calculator that is mini specific ... and useful for looking at speedo variations
http://www.guess-works.com/Gearbox/Technical/ratio.htm Not bad. I got some good info from there. 
But a few of his wheel sizes are wrong and it is missing some of the Australian speedo variants.  (mostly Morris 1100 stuff that is missing so I guess it won't worry most of you!  )
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| Author: | phillb [ Sat Jun 05, 2010 10:11 pm ] |
| Post subject: | |
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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| Author: | Morris 1100 [ Sat Jun 05, 2010 10:33 pm ] |
| Post subject: | |
Funnily enough when I ran it with 1475mm it gives 15.99mph per 1000rpm.
I will give you the full results in a little while. 
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| Author: | Morris 1100 [ Sat Jun 05, 2010 10:44 pm ] |
| Post subject: | |
I hope I got the ratios right! Someone will soon let me know if they are wrong. 
Code: GearCalc v2.0.0.3 Copyright ©2001, Peter Ogden Gear Ratio, Speed and RPM Calculator Gear set: Manually entered values Gear 1 2 3 4 Final Ratios: 3.300 2.070 1.350 1.000 3.440 RPM Limit: 6500 RPM @Peak Power: 5800 Tyre Size: unknown Tyre Diameter: 18.48 in Tyre Circumference: 58.07 in Gear Mph per 1000 RPM Mph @5800 RPM Mph @6500 RPM -------------------------------------------------------- 1 4.84 28 31 2 7.72 45 50 3 11.84 69 77 4 15.99 93 104 Mph RPM (in Gears) ---------------------------------------- 1 2 3 4 ---------------------------------------- 5 1032 647 422 313 10 2064 1295 845 626 15 3097 1942 1267 938 20 4129 2590 1689 1251 25 5161 3237 2111 1564 30 6193 3885 2534 1877 35 4532 2956 2189 40 5180 3378 2502 45 5827 3800 2815 50 6475 4223 3128 55 4645 3441 60 5067 3753 65 5489 4066 70 5912 4379 75 6334 4692 80 5004 85 5317 90 5630 95 5943 100 6256 Gear Change RPM drop (change @5800) RPM drop (change @6500) ------------------------------------------------------------- 1 -> 2 -2162 (to 3638) -2423 (to 4077) 2 -> 3 -2017 (to 3783) -2261 (to 4239) 3 -> 4 -1504 (to 4296) -1685 (to 4815) Code: GearCalc v2.0.0.3 Copyright ©2001, Peter Ogden Gear Ratio, Speed and RPM Calculator Gear set: Manually entered values Gear 1 2 3 4 Final Ratios: 3.300 2.070 1.350 1.000 3.440 RPM Limit: 6500 RPM @Peak Power: 5800 Tyre Size: unknown Tyre Diameter: 469.51 mm Tyre Circumference: 1475.00 mm Gear Km/h per 1000 RPM Km/h @5800 RPM Km/h @6500 RPM -------------------------------------------------------- 1 7.80 45 51 2 12.43 72 81 3 19.06 111 124 4 25.73 149 167 Km/h RPM (in Gears) ---------------------------------------- 1 2 3 4 ---------------------------------------- 10 1283 805 525 389 20 2565 1609 1049 777 30 3848 2414 1574 1166 40 5131 3218 2099 1555 50 6414 4023 2624 1944 60 4828 3148 2332 70 5632 3673 2721 80 6437 4198 3110 90 4723 3498 100 5247 3887 110 5772 4276 120 6297 4664 130 5053 140 5442 150 5831 160 6219 Gear Change RPM drop (change @5800) RPM drop (change @6500) ------------------------------------------------------------- 1 -> 2 -2162 (to 3638) -2423 (to 4077) 2 -> 3 -2017 (to 3783) -2261 (to 4239) 3 -> 4 -1504 (to 4296) -1685 (to 4815) |
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| Author: | doogie [ Sun Jun 06, 2010 9:49 am ] |
| Post subject: | |
Hmmm all these numbers are concerning, my Cooper S is far different, MK2 box, 3.44 diff 10 inch wheels. My car does 1750 rpm at 110ks on the highway. Doogie Oh thats right, its on the trailer at the time.
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| Author: | phillb [ Sun Jun 06, 2010 10:33 am ] |
| Post subject: | |
doogie wrote: Hmmm all these numbers are concerning, my Cooper S is far different, MK2 box, 3.44 diff 10 inch wheels.
My car does 1750 rpm at 110ks on the highway. Doogie Oh thats right, its on the trailer at the time. If only that were true.
Here's a pic which shows how far out my speedo is, should be reading 48mph at those revs not 58. 
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