Attention 80 Series Owners

Hi TJ the another way to go about it is to use an online calculator.Its gives you the ability to input different tyres sizes,diff ratios and gear ratios and compare the results.
Before you start you need the 5th gear ratio,t/case ratio and diff ratio.
My guess is 33 inch will be the closest

http://www.csgnetwork.com/tirerevforcecalc.html

I have 31 and 29.5in tyres for my Rodeo. The tacho changes very little with the different diameters.

However fuel economy differs. I get better highway and worse around town with the bigger tyres.

Better to ask peoples fuel economy changes with the bigger tyres I would think. Perhaps a better 'real world' indicator as your vehicle has more than 5th gear.

With the website mentioned above you should use your actual tyre diameter not the one written on the sidewall as all brands are different.

You might also check out this calculator .

31x10.5x15?
3000RPM
1990 Model with 3F Petrol engine

From memory, 100kms/hr in5th is 2500 rpm . Doesnt matter what size tyre u have, the speedo and tacho will still read thesame, unless you convert your spedo drive to accomodate the discrepancy.
I now own an auto, and it sits on 2200 at thesame speed.
Andrew

Thanks for all your help guys.
I was trying to determine if 2800 RPM was too high for the 4.2 T/D in 5TH gear at 110 kmh??
(seems a touch high to me???)

that sounds about right

TJ,

1991 model TD: 2600rpm at 100 kmph

Twigiee