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Speedo Recalibration
Posted: Sun Oct 19, 2008 8:34 pm
by d_harris
Who does it?
What info do they need and how much does it cost?
I've discovered that my speedo reads stupidly quick (i.e. it reads 85 when the speedo reads 70)
Posted: Sun Oct 19, 2008 8:39 pm
by Judge
Posted: Sun Oct 19, 2008 8:43 pm
by d_harris
I don't know what you mean
Posted: Sun Oct 19, 2008 8:48 pm
by bmcecosse
What tpm does your speedo have Dan ? There are a range of speedos about (mostly ex Mini) with different tpm - there may be one to suit you rather better! That will be a MUCH less expensive way to go.
Posted: Sun Oct 19, 2008 8:55 pm
by d_harris
tpm being?
Posted: Sun Oct 19, 2008 8:56 pm
by alex_holden
Turns Per Mile, I think.
Posted: Sun Oct 19, 2008 8:59 pm
by d_harris
aaah. That would make sense. How can I find that out?
Posted: Sun Oct 19, 2008 9:31 pm
by Matt
it will be whatever is standard for a 1098 with standard wheels and 1098 diff
Posted: Sun Oct 19, 2008 10:51 pm
by bmcecosse
It's written on the speedo - just above the mileometer readout - a 4 digit number probably something like 1408 for a 1098 with 4.22 diff, if it still has the original speedo fitted of course. You really need to do a mileometer accuracy check against a known distance or a GPS. Then decide what tpm you need to put that right. The actual Speed reading can be 'adjusted' by tweaking the spring - although obviously it will be best matched if you can get a unit where the mileometer reads close to correct.
Posted: Sun Oct 19, 2008 11:06 pm
by d_harris
so is 1408 the correct figure for standard 1098?
The difference comes from my wheels I suspect
Specification...Revs/Mile..Difference
145/80-14......872...........0.0%
175/65-13......919..........-5.1%
Therefore I would be looking for TPM of 1325?
Posted: Mon Oct 20, 2008 12:20 am
by jock299
Posted: Mon Oct 20, 2008 10:13 am
by Matt
you need to add that 5.1% Dan. The smaller wheels are doing more tpm and therefore the speedo should do more tpm too
Posted: Mon Oct 20, 2008 2:20 pm
by bmcecosse
Yes - somthing more like 1480 - that's IF your speedo is 1408 - is it ?? Of course if you go for a 3.9 diff that would near enough cancel out the difference! I would think that's a better way to spend the money than recalibrating the speedo!
Posted: Mon Oct 20, 2008 8:51 pm
by d_harris
Yep, but I don't have a spare £150.00 odd lying around!
and on the TPM adjustment. D'oh!
Posted: Mon Oct 20, 2008 10:12 pm
by Mogwai
is this a useful manual
http://tr6.danielsonfamily.org/Files/SpeedoRepair.pdf has a bit about calibration near the end
Posted: Tue Oct 21, 2008 12:13 am
by mrbenn
These people seem to be mentioned pretty regularly in Practical Classics
