which speedo

Post by **dustyfog** » Tue Sep 01, 2009 10:09 pm

i have a 948 engine with the 955-1 diff with a 1098 gearbox, which speedo would i need to get a true reading? the standard 80mph silver faced speedo or the 90 mph 1098 speedo

regards dusty

Post by **bmcecosse** » Tue Sep 01, 2009 10:10 pm

Speedo with 1508 tpm - any colour face you fancy - but must be ~ 1508.

Post by **dustyfog** » Tue Sep 01, 2009 10:16 pm

hi bmc where would this info be mate

Post by **bmcecosse** » Tue Sep 01, 2009 10:20 pm

Tiny numerals on the dial face - sometimes near the mileage readout - but always shown on the face, near the serial number.

Post by **dustyfog** » Tue Sep 01, 2009 10:50 pm

hi i had a look, none of them say 1508 ( i gather this number is the last four digits on the right above the milage reading) i have 2 cars the same age 67 both with black faced a 63 1098 and the 948 and this number dos'nt appear on any of them, what are the chances of getting a clock with this number on. any more ideas what model this 1508 speedo would appear

Post by **bmcecosse** » Tue Sep 01, 2009 10:53 pm

What do your's say then ?? It's the common speedo for car with 4.55 diff.

Post by **dustyfog** » Tue Sep 01, 2009 11:01 pm

its to dark at tha moment. will look again tomorrow ang give all details then, thanks for you help

Post by **mike.perry** » Tue Sep 01, 2009 11:07 pm

Go to the Series MM website http://seriesmm.mmoc.org.uk. click on car ident and scroll down to the table on speedometers.
The gearbox does not make any difference to the speedo gearing, it is the diff ratio that counts.
It is worth checking the readings with a sat nav, you may be surprised at the results.

Post by **flowersGTR** » Wed Sep 02, 2009 3:27 pm

i have a 4.22 diff and i have a 1508 tpm speedo, using my satnav i found the speedo to be spot on
ie 40mph on the speedo equals 40 mph on the sat nav

what should be the tpm for a 1098 4.22 diff speedo out of intrest?
its not the original speedo in my morris i dont think, but i didnt change it

Post by **mike.perry** » Wed Sep 02, 2009 5:42 pm

The usual TPM for a 4.22 diff is 1408. As you have found out the standard speedo is rather optimistic. My 1408 speedo reads correct with a 3.9 diff.

Post by **bmcecosse** » Wed Sep 02, 2009 7:20 pm

I'm VERY surprised at that - should be 1305 to be correct with 3.9 diff - NO idea if there is a speedo at that setting - but that would be the correct tpm for a 3.9 diff.

Post by **PSL184** » Wed Sep 02, 2009 7:38 pm

The above statement based on the assumption that original size crossply tyres were fitted of course ;-)

Post by **bmcecosse** » Wed Sep 02, 2009 8:42 pm

No - based on radials 155 x14!

Post by **mike.perry** » Wed Sep 02, 2009 11:51 pm

I am running a 3.9 diff, 175/80x13 tyres and a 1408 speedo. Checked the readings with a sat nav this evening on the way to the branch meeting.
Results :- speedo under reads by 1mph at 30 and 70 mph and is spot on at 50 and 60mph.

Post by **bmcecosse** » Thu Sep 03, 2009 8:49 am

Ahh - non standard wheels tyres - anything goes!

Post by **mike.perry** » Thu Sep 03, 2009 8:57 am

The circumference of 175/80x13 tyres is slightly larger than 155x14 tyres so it should make the speedo under read by even more.