Speedo 15-30% out - any ideas? Options

[alex1981]

I have a 95 Celica GT4 ST205. It was imported from Japan to UK, and someone has changed the clocks to MPH. However, for quite some time now, the speedo reads between 15 and 30% out (too high). Which tbh I would not mind if it was just a case of the speedo, as I pretty much know what speed I am doing anyway...but of course the miles go up quicker as well (I assume) so I am going to end up servicing the car more than I need!

I am guessing it has some sort of converter from km to mph? Is there any adjustment in this? Or jsut a case of I need a new unit? Or is there normally any other way of calibrating the speedo? Could it be anything else like a dodgy speedo cable or gauge?

Thanks for any help

Alex

[Rav4Race]

oh i think i had the same problem with my speedo. it climbs up too quick. Its a quite common problem for cars in general. It can be caused by a different tire size or variances in wheel sizes or simply the speedo is going crazy due to lack of servicing or getting out of date. The best solution i fouund for this was getting n electronic speed meter like n Apexi RSM or AVC-R. I needed a boost control so i opted for n Apexi Avc-r with which i can have the exact reading of rev n speed while calibrating my boost.

[alex1981]

Its not wheel or tyre size as I have had the same for several years and it seems to get worse over time! Electronic ones sound interesting but I would much rather my speedo work than go to the effort of buying and fitting something else!