correct speedo

[eddiegrimes]

Would anybody know if there is a mini speedo that I could fit to correct my problem that is I have a ford 5 speed gearbox,standard 1098 4.22-1 diff and 14" wheels and the speedo is running approximately 8 mph slow , I really don't want to get my speedo re-calibrated as I intend to fit 13" wheels after the body work has been sorted and resprayed.[frame][/frame]

[bmcecosse]

You say it's 8 mph slow - but is that a steady offset all the way up the range ? Or just at a specific speed.....? Better to compare the accuracy of the mileometer against a sat nav - or just a distance that you KNOW to be correct. And - what tpm speedo is in your car at the moment?? I have a Mini speedo in my car - 4 speed box but 3.7 final drive, and it is deadly accurate on miles and speed. I think it's 1249 tpm - I would need to check at the week-end since th car is not easily accessible at the moment! And - my opinion - 13" wheels look pretty much 'lost' on a Minor - better to stick with 14" or even go up to 15"!

[welshrat]

Its a 1248 BMC, have one sitting on my shelf waiting to be fitted. Took your sound advice some time ago as had the same problem, took a while to find the right one mind as most people don't bother saying what the tpm is when selling on ebay, had several weeks of either copying the pics and enlarging the very small tpm number or sending messages asking for it. Managed to pick one up for about £20 in the end. Follow this link to read the thread. http://www.mmoc.org.uk/viewtopic.php?f= ... 8&start=15

[bmcecosse]

£20 !!!!!!!!!!!!!! Crikey.. Mine was £5 plus a bit of postage......

[IslipMinor]

1248 or 9 is spot on for a 3.7 diff with a standard Minor 948/1098 gearbox and standard overall diameter tyres.

With a 4.2 diff, you would need a 2.94 speedo ratio for a 1248 speedo head, which in Ford speak means the closest is either the 24/8 (3:1) speedo drive ratio, which will be ~2% slow or 23/8 (2.875:1) which will be ~2% fast. Do you know what the speedo drive ratio is in your T9 gearbox? Many of the mainshaft gears are 8T, so by just pulling out the speedo gear itself could give the most likely ratio.

With wider 13" rims, at least 4.5", you can fit 165/80x13 tyres, which fill the arches pretty well, particularly if the car is lowered a bit, and are within 1% of the same overall diamteter as the standard 145/80x14's. Ours are 185/70x13 on 5.5" rims, which also give virtually the same o/d. Depends what 'look' you want?

If you do go the 13" route, then I would choose the 23/8 speedo drive, as 165/80x13 tyres are 1% bigger o/d than the standard 14", so the speedo drive error would be down to 1% also, which is pretty good!

[eddiegrimes]

Took it out today and according to the sat nav journey was 14 miles, mileometer read 10.1, travel time was 28 mins! hope this helps

[bmcecosse]

So - it's under reading by 30% - and you won't fix that with a Mini speedo! As Richard details above - you will need to get a more suitable speedo gear drive for the gearbox.