Speedo Re-calibration??

[Pico42]

Has anyone re-calibrated the speedo on a Vitara? Cable driven.

Did a test run the other night to find that our speedo reads 100km/h when we are travelling at 112km/h and it is likely that our certifier will need this corrected.

Any ideas - I am yet to pull the plug out again to see what runs it. Cheers.

[pagar]

A bit of a distance but Robinson Instruments in Onehunga should be able to make an adaptor to suit. (09)6365836. cheers

[UBZ]

if they are any thing like the 413 cluster , thier is a little adjustment lever on the side of the speedo cluster mechanisium .

will try and find the pic for you.

[rangimotors]

don;t worry about it. From memory you are allowed 5 percent difference. My new out of the factory mazda 6 is only doing 100 when it says 110 on the dash so do the other 11 cars we bought. Mazda have no interest in fixing it even though its outside the 5 percent tolerance. My old truck was about 30 percent out so no so legal.

[Pico42]

Ok, so how do I remove the plug from the gearbox?

Unscrew the speedo cable, remove the bolt holding the plug in and... should it come straight out? Does it rotate?

Otherwise the vehicle is pretty much ready for certification.

[nachi]

don;t worry about it. From memory you are allowed 5 percent difference.

I would.. or at least allow for it..
I was down the Old West Coast Road today and got a ticket for doing 109.. the speedo was reading 100 he issued the ticket.. only 30 bucks.. cheap way to find out the speedo reading
First ticket in over 25 years...

[chevrolux]

just chuck a gps on the windscreen

[lneil]

Yep, going to bigger tires can make a major difference. Most factory speedos are optimistic, commonly by around 10%, but once you fit the big rubber they can get very pessimistic, which is when you'll get tickets cos you going faster than the speedo says.

My scuds on 31s are around 10% pessimistic and I run a GPS to keep track of my speed.

Remember not to bother mucking around with the speedo until you've got your final diff ratios installed though, otherwise you'll have to do it all again.

[Pico42]

OK, got it sorted by pulling the speedo cluster out and tickling the spring a little. There are two fine adjustment tabs in there as well, but not enough adjustment for what was required.

Thanks for all the advice.

Photos and details to come, but probably in a separate thread for the whole vehicle. Had it's certification inspection today with only one minor change required.

[mercutio]

another idea for a speedo is go digital get a mountain bike speedo cost like $90 and some of them you can set up for 2 different wheel sizes my mate has done that on his car which he does club racing in and has road and race wheels i'm planning on doing this to my G if i ever get it going

[Pico42]

So, this is my speedo pulled out of dash. There are two fine adjustment tabs in it - one corrects the speedo reading and the other adjusts the zero stop of the needle.

In the above photo, the needle is pointing to the fine adjustment for the speedo reading. Just above that tab you can see another tab at the back of the unit - that adjusts the needle rest.

As there is not enough adjustment in these to resolve 12% speedo error, I had to come up with another way. From my web searching, I found out that the speedo is driven by two rare earth magnets in close proximity. One spins from the cable linked to the gearbox, which rotates the other magnet against the pressure of a return spring (which you can see quite clearly in the photo). The faster the first one spins, the more the other one rotates around, taking with it the needle.

So, since I couldn't adjust the magnets, I instead made a delicate high precision adjustment of the end of the return spring to put more spring into it. This is being pointed at by the screwdriver in the photo. Just used some needle nose pliers - as I said, high precision...

To check it I simply plugged the speedo back into the cable and took it for a test run with a handheld GPS. Drove up the road, checked the speed, adjusted the spring, Back down the road, checked the speed, adjusted the spring. Did that about about 6 times until it was reading right.

The result, a speedo that reads at 46km/h when travelling at 50km/h and reads at 100km/h when travelling at 101kh/h, as measured by the Certifier. Awesome.

[kernels]

That's awesome work there, very impressed Pico

[Weasel]

I just drove up road with GPS checking what I was actually doing against the speedo's claim at 50, 70, 90 and 100 then worked out how much needed to adjust by (about 5.5kmh) and simply rotated the speedo display with numbers on it a bit so points at the right place.

As long as dont mind the numbers being on very slight angle and not dead level then easiest way to do it!!