Quote:I have drawn my info from the "Tyre & Rim Association Australia. Standards Manual."

These are the people who set the standards in cohorts with global regulatory bodies, & who manufacture tyres & rims.
I have assumed that they would know the diameters of various tyre sizes.

There are also a number of tyre size calculators available online, so a quick check there will help confirm the sizing.

The original sizes for the 1200 were ....
Standard/original fitment.
6.00x12x4 ply. diagonal ply [574mm, highway tread, Page S-03 of the 1988 book]
Optional fitment.
155SR12 [554mm, highway tread, page S-06]

My 1972 sales brochure lists only the 6.00x12 tyre but my 1973 owners manual lists both sizes in the 'recomended tyre inflation pressure' chart on page 31.
It clearly describes the radial as "optional"

If your Ute is moving around with the 13's then you're running on half flat tyres. I run mine up around the 30psi mark & don't have a problem, but then perhaps I drive a little more smoothly these days.

Besides, even girls are more fun when they have a little 'wiggle in their walk'
So are our cars.

well i find running the smaller rims (13") with larger side walls that my car drives a little like a boat and sort of sways a little bit in the rear end and when your tearing through windy roads in the hills at 100k's thats not the best feeling. the 15's handle much better and offer less understeer, with my driving style. so im not saying that this is the way to go for everyone, its just what works for me.

this all explains why the cars today are so hopelessly undergeared on the original rims.
original cross ply tyres gave a decent final drive, but 12" radials available today dont.
early ford escorts with 12" wheels have the same problem, 4th gear feels like 3rd.

pretty sure all the 195/50/15s i have have stood the same height as the 155 12 on most stock rims

Quote:Yep.

If you had gone to a 205/50/15 on the rear only, they would measure out at 586mm diameter. The slightly wider tread loooks just that little bit more tough from the rear & the extra 10mm of diameter translates to roughly 30mm more traveled distance every time the wheel goes round.

I run 185/60/13's on the front of my 1200 coupe [552mm] & 205/60/13 on the rear [576mm] That way it steers well with no body rub anywhere & the tyres cost less, while the rears fill the wheel arch nicely & maximise my gearing. The big 'n' little look apeals to me & I get a little 'rubber rake' into the bargain which gives it a little bit of attitude.

I have not run the same size tyres front & rear for about 30 years.

Quote: Actually you are absolutely right about the early, alloy carrier H165's. I must have had a senior moment & forgotten.

The H150 differential shares the mounting gasket with the H145, so it will fit into the h145 housing, however there seems to be a misalignment problem with the centerline of the differential, so a 2mm spacer & a second gasket [one each side of the spacer] should fix that little problem & a wider range of ratios then become available to the 1200 owner.

the 195/50/15 is accually a 576mm diameter tyre so it is running at approx the same size as the original cross ply tyre

Yes they all bolt in but not all axles are the same. Unless ive pulled a brain fart the old P411 bluebirds ran a H165 with a different axle spline to any other H165.

Also isnt there some sort of a mod(spacers) to adapt a H165 centre into a H145 or is that a 1200 thing due to axle size?

All H165 differentials will fit into all H165 rear axle housings. The 1200 ute has a H165 & so does the series 1 & 2 Bluebird.

The 155R12 was not the original tyre size but was in fact the the radial 'option' & at 554mm diameter it's 20mm smaller than the original 600x12 tyre which was 574mm.

The 195/50/15 is 556mm in diameter, just 2mm larger than the stock 'original' 12" tyre size.

do these bolt up in the same housings? im running a 15" 195/50 wheel so it has a larger circumference than the original 12" 155/80.