Running my FG on standard 16" rims with BS 7.50's on my speedo has an 8% deficiency
that is at 100kph on the dial my road speed is 92Kph (GPS)
If I fit 19.5s when I put singles on will the larger diameter wheel tyre rectify this problem or will I have to fit a compensator to the speedo drive
those ive talked to with 19" singles on dont think so
Any ideas???


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Hi Stu,

ADR Rules allow up to 13% error (amazing I know) if your speedo indicates above true speed but zero% if your speedo reads less than true speed. If you run 285/70/19.5" s which is the G.O. then your standard speedo will run slighty lower than true speed therefore it technically won't be legal. Sorry. That's just the way it worked out. If you were only fitting 265/70/19.5's you might just get away with it. However if you are looking at one of our ADR compliant single wheel kits then of course a speedo correction unit has to be included. We have designed these to read approximately 2% (depending on which FG model) below true speed with 285/70/19.5 Toyo M608z's which should cover any slight differences in tyre diameters between brands if retrofitted later.

BTW, it is common to find speedos reading 8% out as in your case on a standard truck with OEM wheels and tyres
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Cheers John
after meeting up with a couple of ATW fitouts on Isuzus along the track Ive come to the conclusion its gunna happen sooner than later
Going to look into it when we get to Darwin
Both wheels and springs

BTW have you started clearing space in the yard for Alans new bedford bus project :Wow1:


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Yeah....I've got no doubt you'll see Alan up there soon cause I know how much he likes your travel snaps and cause it's so nice in Vic right now...so when you see him tell him I'll clear some space out the back yard for him....out my front yard looks like a Porsche and a boat exploded and my garage floorcovering is a shade of Vstrom with Mazda rotary highlights.

I guess the important thing here is that Alan still needs another project.
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