General Query on rim to tyre sizes

Hi All,
Think I asked this question some time ago and never really got a definitive answer.
Concerns what size tyres are both legal as well as practicable on two and three piece rims.
Bit of history, my Karrier Bantam was originally imported in CKD form and was shod with 13 inch X 4 inch two piece rims, someone told me made by Sankey-Benson to comply with Aussie content.
Changed all mine up to 16 inch X 6.5 and some 7.0 inch (all rim sizes measured from inside flanges), after having 6 stud Leyland wheels centres machined out to take Karrier bosses. Have since found two rims with hair line cracks across from stud hole to centre boss hole.
Since all this happened, had shod the larger wheels with standard new 7.50 X 16 inch tyres, easy to get, relatively cheap etc.
Bought another Karrier for spares, but this one came with 16 inch tyres and rims standard, but all tyres are cactus. Just received my long awaited workshop manual and it is telling me that standard wheels/tyres ex factory were 4.5inch rims with Nylon 6.00 X 16 Tyres.
I don't want to spring for all new tyres, nor go to any fancy radials, the 7.50 X 16's will do me nicely, but I'm a bit worried that the rims themselves may be too narrow for them.
I must point out that I am hopeless doing any sort of Google search, tried several times and keep getting sent to ads for radials and being short on patience, throw in the towel.
Maybe some one can give me a straight yes/no answer on this, or put up a link pertaining to older Nylon/Rubber tyres when thet were measured in inches instead of metrics?
Thanks
Dave_64

Hi Dave, glad to hear you have obtained a workshop manual. Were you successful in getting the one we talked about?

As far as your wheels and tyres go, i'd be tempted to just fit one up and see what it actually looks like fitted up. I don't know what tyre on what rim is legal, but if it looks wrong, fair chance it is. If it looks ok, then you might have narrowed down your search for a yes/no answer to a specific tyre on a specific rim, and a tyre dealer would likely then have accurate information re legality.
It might be something like 10% variation from the recommended tyre size for that rim is permissable, or i could (most likely) be completely wrong.

Brett.

Yeah, thanks Brett,
The manual was the one that was detected on here, thanks.
The bloke who owns the tyre joint in the next big town to me, reckoned he had a book that gave all conversions from radials to the old rag tyres and also what rims fitted each type
Everytime I've called in there, he's either forgotten it, latest excuse is one of his fitters loaned it to a bloke who never returned it, so on and so on, think he's full of you-know-what!
Someone on here will know for sure

180wannabe wrote:

As far as your wheels and tyres go, i'd be tempted to just fit one up and see what it actually looks like fitted up.

Brett.

This would be my plan of attack

I have the Australian Tyre and Rim Association book will look for you.

The ATRA is the authorising body for tyre and rim specifications for Australian Design Rules. A thick book with every specification on rim design, tyre design and all sizes and specifications. It comes out annually and is the legal reference in every State.

This is the 2010 edition (still legal reference if not superseded) as later versions started dropping reference to bias/diagonal ply tyres.

Stand by.

Lang


Here you go. Personally I think 7.50 or 6.00 on either rim would be close enough.

Ripper, Lang!
Just what I was looking for.
Will download it onto the desktop,
Thanks again, Dave

Apart from the science behind radial tyre construction the size difference is that where rags are as high as they are wide radial have an "aspect ratio" of around 90%, So for the the same nominal size a radial has a smaller diameter and that is why they look wrong on an old car or truck

I believe you are correct

My understanding is that for example a 205/75 × 16 is 205 mm wide, wall height is around 75% of 205 and 16 is the rim diameter, is this correct ?

Paul

Mrsmackpaul wrote:

I believe you are correct

My understanding is that for example a 205/75 × 16 is 205 mm wide, wall height is around 75% of 205 and 16 is the rim diameter, is this correct ?

Paul

That is correct as I understand it. If there is no 75 or other aspect ratio number listed then 70% is assumed. The rim size in normally preceded with an R while any letters and number listed after the rim size normally denotes the speed rating.

Terry