Question on speedo recalibration

[Pizzaz]

I've gone for 245/70R17s on the dub jay (ouch - weird wheel size = expense!) and was just wondering what others have done regards speedo recalibration. From the reading I've done on JU it seems that the dealer should be able to set to that tyre size... can anyone verify that?

The whole Truspeed thing seems to be a huge amount of ca$h to correct about a 5% change...

Welcome any thoughts - helpful suggestions such as changing the transfer case not really neede at this time but thanks anyway Bill :D

[billsta]

i know that dealers can do up to a certain % in variation...
they certainly couldnt do mine...

the truspeed?
i never investigated it...
but i think i might sooner or later..

or plug the GPS in and work off that...

how much you off anyway??
cant be more then 5%...

[Pizzaz]

From what I've been reading Bill, by swapping your transfer case you should be pretty much right - it's dead simple to change the speedo gearing on a ZJ / TJ / XJ... it's only the WJ(G) & KJ that have issues - fully electronic speedo you see.

[billsta]

yeah i should, but im still running the leckky speedo at the moment..

im not sure if its as simple as putting sppedo gear in transfer case and hook up the wires from the back or i have to get a T/Z/XJ speedo..

i never took too much time thinking about it...

[Steve F]

Dont forget about this - http://www1.jaycar.com.au/productView.asp?ID=KC5380&CATID=&keywords=speedo&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

Cheers
Steve

[BDASH]

Steve, that Jaycar one looks pretty good...but a couple of weeks ago I asked a mate who's a dealer here in Melbourne whether I could get the adjustment done, he said just go to a Jeep service centre and get them to plug it into the computer to adjust it...apparently it is that simple...but of course they may want to charge a full hour which will be more expensive than buying the Jaycar unit...(bloody Jeep :wink: )

[BDASH]

Pizzaz, in the mean time, rather than guessing (which I did) you can check out the percentage with this http://www.miata.net/garage/tirecalc.html. I only went from 245/70/16 to 245/75/16 and this shouwed me that I was out by 3.3%...and these days with the coppers having little or no margin for error, knowing that you're a few km's an hour out is pretty important.

[froop]

Pizazz,

If you haven't sorted out your speedo yet, certainly check out the site that BDASH has linked to. I took my KJ in for its first service last week, and asked them to re-calibrate my speedo for the 245/75R16 (factory are 235/70R16).

I certainly hope that the mechanic knows more about the rest of the car than he does about the tyres, because since the DRB-III scan tool doesn't have settings for 245/75R16, so he plugged in 205/75R16 - coz they both had a 75 profile :S

If your new tyre size isn't one of the presets in the DRB-III scantool, they can calibrate the speedo by a drive test using a GPS, or by simply entering a new value for revs per mile or revs per kilometre, which the Miata tyre size calculator page will give you.

Unfortunately I wasn't armed with that info when I had my service done, so my speedo still reads 5% too slow. But the annoying thing is that I need to do 5% more driving to get the km's up for my lease!