Hankook Tyre Size Warning

HI Robin,

I have just put on Federal's at 265/75R16 which are 804mm or 31.6".

I would check your compliance plate and if the tyres supplied are more than 50mm bigger, then the tyre fitter has broken the law. If this is the case threatening to report him should be enough to get a change over.
I believe the standard tyre for your vehicle is 275/65R17 which is 789mm. The tyre supplied at 831mm is 42mm bigger, so legal provided you have had no suspension lift. It is legal (in Vic) to raise your vehicle a max of 75mm with a combination of suspension lift and bigger tyres with no single element being greater than 50mm. So therefore provided you have not had a suspension lift of greater than 33mm (75 - 42) then you are still legal.
I understand that the authorities do not use manufactures specs to ascertain sizes but have a table which is probably the same as the ExplorOz chart.http://www.exploroz.com/Vehicle/Tyres/SizeCalc.aspx
If you have changed the suspension you may have to prove that it is not more than what is legal. If you are close to the legal limit I would be very friendly and courteous to anyone who should stop you, as if you get on the wrong side of them they could make life very difficult.

In terms of speedo accuracy, it is the rolling diameter which is important, not the inflated diameter.
That relationship will change slightly with profile differences, but not enough to make up that error :(

Cheers,
Peter
OKA196 Motorhome

hi
3% tire size tolerance, for speedo to still be accurate .Some also mention about the 50mm rule . There are legality issues with this subject and has varations state to state . Its a mine field .

swamp

There are a lot of misunderstandings about tyre sizes and what you can fit. It is because most people do not read past the headlines.

All states adhere to the national modification rules. If you comply with these rules, your vehicle will be legal in every state.

The national modification rules are known as VSB 14. The "LS" rules within this regulation deal with tyre sizes.

Everyone jumps to section 4.2 in these rules. This is the one that lists the 50mm increase, however, this rule applies when you are changing rims and tyres.

Section 4.1 deals with what tyre sizes you can fit if you keep the standard size rims. It states:

4.1 REPLACEMENT TYRES ON STANDARD (OR MANUFACTURER’S OPTIONAL) RIMS
Some tyre sizes have become obsolete and are no longer available. Equivalent replacement tyres with different size designations may be fitted without specific certification under this Section.
Every passenger car manufactured after 1972 (ADR 24) is fitted with a tyre placard that contains information on original and optional tyres and rims for that vehicle model.
A motor vehicle under 4.5 tonnes GVM which is required to comply with ADR 24 may be equipped with tyres other than those listed on the tyre placard provided that:
• • the load rating of the tyres is not less than the lowest load rating listed on the tyre placard of the vehicle or equivalent variant of that model vehicle;
• • the speed rating of the tyres fitted to a passenger vehicle is at least 180 km/h (S) when the tyre placard requires a higher speed rating than S;
• • the speed rating of the tyres fitted to vehicles with special features for off-road use of at least 140 km/h N when the tyre placard requires a higher speed rating than N; and
• • for all other vehicles a speed rating of at least 120 km/h.
• • In special circumstances, the speed rating may be less than the ratings specified above if the speed rating of the tyre is more than the vehicle’s maximum speed. This will need to be confirmed with the Registration Authority

I read this as you can fit any diameter tyre to the standard rims as long as they can be legally fitted to those rims. That is, tyres will have a rim size listed to what they can be fitted to. There is certainly no 50mm limit listed in these rules.

Now we can move on to section 4.2 if you are changing your rims. The biggest mistake people make is thinking that there is a specific diameter listed somewhere for each tyre size. This is not the case. You only have to look up the actual diameter of various tyres. Mud tyres tend to have a larger diameter for a specific size than say a road tyre, the diameters also vary between manufacturers. So what is the base diameter than I can go 50mm above.

ADR 23 deals with the requirements of tyres and their sizes. Up to 2009, there was only ever a minimum diameter specified for a given tyre size. So basically a given tyre size could have any diameter above a certain measurement. So if there is not requirement under the ADRs to have a certain diameter for a particular tyre size and the modification rules allow you to go 50mm above the diameter of the tyre size, it is very open ended about how large a tyre you can fit.

In 2009, ADR 23 actually brought in a range of diameters for a given tyre size. They came into line with the United Nations Regulations. These rules allow a minimum and maximum diameter for the size in question. Basically you calculate the theoretical diameter the same way as most of you do, that is, using the rim size, tyre width, and profile. The regulations state that for a 4WD tyre, the range in size can vary from 3% below the calculated diameter to 6% above.

So with a range of diameters that can easily range by 20 to 30mm, which diameter do you use in calculating how big you can go. I would suggest that you can use the maximum diameter as this is the diameter most closely related to mud tyres and if we are putting on bigger tyres, they are usually mud tyres.

But you can interpret these rules how you like. I am just highlighting that there is a little more behind the headline rules that everyone keeps on quoting

After rereading you figures, I am at a loss as to your issue. You quote a number of tyre sizes, but your calculated diameters appear wrong.
The calculated tyre size, using the profile, width and rim size, for a 285/70/17 is 831mm, exactly what you got. For a 285/75/16, the calculated diameter is 834mm, which is in line with the 285/70/17.
I thought the standard tyres on a Nissan were 265/75/16, which have a calculated diameter of 804mm.
I also doubt that you will find your new tyres are actually 831mm. As this is the default calculated diameter, it is rare that the actual diameter would line up with this. It could be up to 25mm bigger than this and still be within industry standards.

Gee's Robin, you wouldn't think such a "High Profile" company would make a blue like that.

I don't think anyone else would be looking to get hankooks anyway, would they? ;)


Cheers

A lot of Landcruisers, Nissan Patrols, and probably a heap of other 4WDs and 2WDs, mainly the workhorse versions, have come with a tyre that was quoted as being a 7.50x16 in the old imperial sizing. Personally I don't remember the numbers on the sidewalls ever stating a profile percentage.
Does anyone know what a 7.50x 16 tyre in 6 or 8 ply have as a percentage ratio? Probably some variations between manufacturers, but I would have thought most of the standard offerings would be pretty close to maybe 75 or 85%.
I think most of them went 31" or 32" diameter.

Actually after a bit more "Googling" one source seems to be of the opinion that the "average" 7.50x16 were usually 100% aspect ratio i.e. the tread width and the sidewall height were the same.

Cheers
Pop