Speedo correction.

that "gadget" could be a couple of stickers at relevant points (50, 60, 110kph).

If you are after something more fancy if would help to provide more detail to ascertain whether it has an electronic or mechanical speedo.

Hi Kirk,
There is gadgets that can be bought to calibrate the speedo, however it is probably easier to buy a scangauge II and have the benefit of water temp and other numerous gauges with it. Also something like a Navman gives you your speed regardless of which tyres you have on and also will tell you what speed zone you are in.
If you calibrate your speedo to a certain size tyre, if you ever change size again the calibration is out.

Cheers, Tony

If your spedo is like the one in My D40 then any oversize tyre will just bring it closer to correct. Mine is also not very linear in its accuracy, its out by a larger percentage at the lower speeds. Suggest you check it with a GPS/navigator to calibrate it before and after the tyre change.

Kirk
I Have done it to my 80 series. It was out by 3kmh, not much but when your looking for traks it can be a lot. I took it to a speedo correction place in Shepparton Vic, it was out at the gear box and in the speedo itself. I now have a correction module at the g/b which the speedo cable runs through. It is now spot on with my gps.
Matt

The Polaris HUD will give accurate speedo reading on your windscreen, just like the flash European cars.

Kirk


Most speedos are out. Check your speedo against a GPS (or time it with a stop watch over 100 m) to ascertain if it is out.

I generally use my GPS rather than the speedo. My speedo 3kms out at 110. In other words if my speedo is showing 110 I am actually doing 107. This also varies through the speed range.

If you speedo is out the oversize tyres may correct it.


Tjilpi

Nissan used to supply optional speedo drive gears, we used to do it for patrols a lot.
See if they still do it. Was around $50 from memory.

Steve

Hi Kirk. As has already been said, the standard speedos have an error in them. In my case with a GU Patrol with standard 265/70x16 it was near 5% overreading. I changed to 265/75x16, and now error is less than 1%. If you're making a bigger change than this, get a check of the error by using a GPS then look up the tyre size chart on this site or do a search. The best chart is one with circumference, then a bit of maths and a calculator may find that the error is cancelled out. That could you save you adding unnecessary bits if your change is similar to mine. Monster tyres will probably need corrections.
Maybe if you post the current and proposed size someone may have already done it. I'll try to post a link to the tables when I find them.

Marks Adaptors do a plug in module that you can use to set your speedo back to the correct reading as it has multiple settings you can get it close to spot on. Will need to see if they have one for your model. I have one on my Patrol works well and can be used for two different tyre sizes.
Other option as stated is swapping out the cog.

Craig

So how accurate are GPS units in general? I'm assuming that satnavs in 4WD don't have access to military satellites ( which have much more accurate positioning).

Kirk,

I am with the others on this. I have a D40 Navara STX (Spanish) which came with 255/65x17 tyres and according to my GPS I needed to read 108 kph to be doing a true 100 kph.

I fitted 265/70x17 AT tyres and now it only reads 2 kph slow (a good safety margin).
Note that I needed to fit a 40mm lift kit for clearance on these tyres.

The odometer is also this 2% out

As suggested make sure you sure you know your true speed and you probably will not need any adaptor.

Regards
Peter

Do a search on ebay for a gps speedo. Will be about $150.

Best thing about it is that it will be accurate regardless of the tyres you put on. Especially if you switch between road tyres and the muddies to save the tread on the muddies

Works a treat.

Electronic speedo corrector from jaycar, $55

Thanks all.