manufacturer's GQ tyre diameter (at factory)

[shantillylais]

can anyone give me a link to the original manufacturer total wheel / tyre diameter for the Patrol 15" wheels? Reason I am asking is the constantly talked about issue of speedo/odo relationship to tyre size. I have 2 new tyres, both "labelled" the same, 31/10.5/15LT, yet the Michelin is about 27mm bigger in diameter than the B/S D/Dueller. I have searched the forums with no sucess, but have noted that some say the tray tops had taller tyres than the wagons. I was going to change my 16's for 15's on my camper to match my wagon, but when checking tyre diameter, the 15" Michelin was exactly in between the new Desert Dueller 31/10.5/15, and the 265/75/16 A/T Dueller. After listening to a presentation about 4wd's and legalities of our vehicles, especially tyres, I am simply confused at which way to go.

[fnqcairns]

I bought my 95 gq three years ago with still the original spare on it so after reading the date i changed it out, tried to remember the brand but couldn't anyway I now have Yokohama superdiggers with half tread on the rear and the GPS says the speedo is spot on at 100km/h.

hope this helps.

[nastytroll]

Try this. This covers 5 different gq models. Tyre size does change considerably between type and manufacture.

http://i452.photobucket.com/albums/qq246/nastytroll/tyreplacard.jpg

[shantillylais]

thanks, I have all that from my manual, what I am referring to is that some on here and the GU forum have mentioned the max over size that Main roads/transport dept will allow legally. So my question related to what is THEIR referrence point size wise. It cant be just a nominated tyre size, eg 31/10.5/15, because already I have found quite large differences in actual diameter.

[shantillylais]

ok, thanks to the tyre sheet in the glove box (same as what nastytroll posted), a phone call to SA Transport modifications branch, and the below calculator, I have now sorted the issue. Transport SA, said it is a gray area, but said in their regs, we cant go over 2" in wheel/rim size, so 15 to 16 is fine. BUT the OVERALL diameter cannot be bigger than plus 15mm. What they DID say was that it is the owners responsibility when sourcing tyres to be aware that different makes can be different in diameter and to check that BEFORE fitting. Hence my dilemma with the Michelin tyre, in reality and by the strict letter of law, the Michelin is actually illegal because even tho' it is 31/10.5/15, its diameter is above 15mm bigger. The calculator works that out. So for legality (insurance included) I cant use Bridgestone A/T's 265/75/16's because the overall diameter is 40mm bigger than the Desert Duellers 31/10.5/15. Perhaps that will help others who want to stay within the law. http://www.exploroz.com/Vehicle/Tyres/SizeCalc.aspx

[mav-i]

Thats y u should run 4 tyres of the same brand. I had a set of coppers atr thay had printed on the side wall 31 inch. when i put the tape on them, thay were worn out but thay only come up at 28 inch.So i dont reckon thay where ever 31;s. Go 2 your local tyre shop & u will find that most 4wd tyres dont measure up

[vinesy92]

Firstly a 265/75/16 will always be bigger then a 31/10.50R15. A 265/70/16 is roughly the same as the 31

[Selous]

the only way your are accurately measure your actual roadspeed vs indicated speedo reading is to gps measure it, see if u can borrow some ones if u dont have one, there are penty of phones out there that do it these days

ive got 33" muddies and my speedo reads 5% above actual roadspeed

[Burra boy]

I've found this site to be very useful

http://www.tyresave.co.uk/tyresiz2.html

[shantillylais]

originally this thread started because I wanted to sell/swap my tyres from my camper so I could match the camper and car. Nobody was interested.
So then I started looking at what I actually had, namely the duellers, michelin and B/S a/t's.
That led to a call to transport SA and they said they get their info from Nissan as to standard tyre size for legality. So thats when I wanted to know exactly what Nissan say.
I found that, I found a tyre calculator. I sorted the issue with that information.
It was never about what speed I am doing, (I have 2 GPS units), or not knowing that the 265's were different to the duellers, I already said that I knew that.
There just didnt seem to be any factual information on the original fittment tyres other than the tyre plaquard in the glovebox which is posted above. Then I found the exploreoz calculator, which helped me crossreference, and made my choices easy.