National Code of Practice for Modification as of Feb 2006

[bluemu]

Hi All,

I found this today, could this be the guidlines we have been waiting for?

http://www.dotars.gov.au/transport/safe ... _ncop.aspx

In relation to just tires sizes, how big can we go, this is what it says.

See the link for all other specifications.

[mudmacaca]

Well aint we all up the creek

[Cliffy]

Yep thats the new bible......... My build up is based on the NCOP.... you will fin Engineers in vic are using this..... There is still some room to move, but the killer is 33's are the max size

[RB zook]

33 suit me good

[bigbennymq]

this is bullshit f##kin goverment

[ISUZUROVER]

The definition of "any tyre designated by the manufacturer for that model" is going to come under a lot of scrutiny...

e.g. is the model "hilux" or are all the model variants classed as different models.

But it seems reasonable. Both my vehicles came out with a smallest size of 7.50x16 (32"). So that means at least 34's are legal. If the "one-ton" land rover that came with (Michelin) 9.00x16 tyres (36") is classed as a different model, then that means 38's are legal on a "one-ton" !!!!!!!!!!

[ronoor]

rb zook that means 28'' on a zook

[Beastmavster]

Depends on interpretation of what max size is too.... a 7.50R16 is nominally a 31" tyre (7.5 x 2 + 16 = 31) but actually is a 32" tyre (this is to do with the different standards to do with it being a light truck tyre rather than a passenger car tyre).

Dont think you can put 34" on because you have a 7.50R16 option - you still might be limited to 33" and 255/85/16 and 285/75/16 may be illegal.

[ISUZUROVER]

Depends on interpretation of what max size is too.... a 7.50R16 is nominally a 31" tyre (7.5 x 2 + 16 = 31) but actually is a 32" tyre (this is to do with the different standards to do with it being a light truck tyre rather than a passenger car tyre).

Dont think you can put 34" on because you have a 7.50R16 option - you still might be limited to 33" and 255/85/16 and 285/75/16 may be illegal.

No you are wrong AFAIK. Tyre sizes are based on the sizes in the "tyre and rim association standards manual for that size". AFAIK the standard for 7.50x16s is around 32" - anyone have the manual to confirm?????? Ryano???

But this is a bit of a grey area...

btw - how could 255/85/16 or 285/75/16 be illegal on a vehicle originally equipped with 7.50's???

[Shadow]

In the Standards Manual the size of a 7.50R16LT tyre are listed to be
804mm Highway Tread(31.65"), 812mm Traction Tread(31.96").

[ISUZUROVER]

In the Standards Manual the size of a 7.50R16LT tyre are listed to be
804mm Highway Tread(31.65"), 812mm Traction Tread(31.96").

Thanks a lot Shadow - are 9.00x16 wheels listed as well???

The next question will be which diameter to use... 804 or 812 - which gives either 854 (33.6") or 862 (33.9"). Since it is a 4x4, I think there is a good argument for being able to use the traction tread values.

[Shadow]

In the Standards Manual the size of a 7.50R16LT tyre are listed to be
804mm Highway Tread(31.65"), 812mm Traction Tread(31.96").

Thanks a lot Shadow - are 9.00x16 wheels listed as well???

The next question will be which diameter to use... 804 or 812 - which gives either 854 (33.6") or 862 (33.9"). Since it is a 4x4, I think there is a good argument for being able to use the traction tread values.

no 9.0R16 tyre listed, but ive got a 9R15LT , 744mm Highway, 752 traction

10R15LT 773 781
11R15LT 777 785
12R15LT 823 831

7.50R16LT 804 812
8.25R16LT 862 870

they then go up to like 9x22 etc. I only have a 2002 copy though so maybe more R16's are listed in newer ones.

[ISUZUROVER]

no 9.0R16 tyre listed, but ive got a 9R15LT , 744mm Highway, 752 traction

10R15LT 773 781
11R15LT 777 785
12R15LT 823 831

7.50R16LT 804 812
8.25R16LT 862 870

they then go up to like 9x22 etc. I only have a 2002 copy though so maybe more R16's are listed in newer ones.

Thanks again...
If anyone has 9.00R16LT standards anywhere I would be interested. Michelin "traction" patterns were 926mm (have specs), so that means just over 38 with the +50mm rule!!!

[cj]

I have heard and was wondering if someone can confirm that in the Standards manual that it quotes a nominal dimension and there is also a tolerance like 4% on the section height that could be applied.

[GRINCH]

at least its better for us up here in qld

[Ezookiel]

So. To sum up:
Some mealy mouthed little bureacrat trying to impress a boss with how much he's doing to improve road safety, so that boss can impress some Minister with how much he's doing to improve road safety, so the Minister can look like a road safety hero to the ignorant, and the total twat he is, to those who actually know how little change these rules will make to road safety.

Does that just about sum up the situation?

How many accidents and deaths can they prove were the result of tyres that were too big or too small?
I'd say it would be sweet fanny adams, but it would want to be a hell of a lot to justify legislating AWAY the ability to use larger tyres.
What is this country coming to that they feel the need to legislate every square flamin inch of our lives?

Born and bred here to parents who were born and bred here, and yet starting to HATE this frigged up country's government, and it wouldn't matter which polly was in power, I don't think anything would change.

[Cliffy]

So. To sum up:
Some mealy mouthed little bureacrat trying to impress a boss with how much he's doing to improve road safety, so that boss can impress some Minister with how much he's doing to improve road safety, so the Minister can look like a road safety hero to the ignorant, and the total twat he is, to those who actually know how little change these rules will make to road safety.

Does that just about sum up the situation?

How many accidents and deaths can they prove were the result of tyres that were too big or too small?
I'd say it would be sweet fanny adams, but it would want to be a hell of a lot to justify legislating AWAY the ability to use larger tyres.
What is this country coming to that they feel the need to legislate every square flamin inch of our lives?

Born and bred here to parents who were born and bred here, and yet starting to HATE this frigged up country's government, and it wouldn't matter which polly was in power, I don't think anything would change.

I hear you loud an clear..... We are a minority, to which the majority, think that we are responsible for a majority of accidents in 4x4's, How many 4x4 are involved in accidents with 35's on them????? bugger all, how many accidents occur in standrd 4x4's .... a majority blah blah blah makes me mad.... stomp around alot.... and kich things!!!!

[cj]

I have heard and was wondering if someone can confirm that in the Standards manual that it quotes a nominal dimension and there is also a tolerance like 4% on the section height that could be applied.

Went to a Tyre shop today and had a look in their book. Not the actual Standards manual but the following information is based on it so I would still like to confirm what the Standards manual says exactly. What I did find was that for the Nominal Diameter for a stated tyre size that there is a tolerance. For Bias ply tyres it is + or - 8% and for Radial tyres it is + or - 3% to 4%.

Given the above then I wonder if the following arguement is applicable. Take a 7.50-16 in a Traction tyre at a nominal 812mm then add 8% making it 877mm being the largest size within tolerance for a 7.50-16 and then adding the 50mm allowance to it in the NCOP making it 927mm that would mean a 36" tyre could be allowed. Now need to find an Engineer that agrees with this approach.

[cj]

The definition of "any tyre designated by the manufacturer for that model" is going to come under a lot of scrutiny...

e.g. is the model "hilux" or are all the model variants classed as different models.

Yes, I would like to know the answer to this one.

[Shadow]

The definition of "any tyre designated by the manufacturer for that model" is going to come under a lot of scrutiny...

e.g. is the model "hilux" or are all the model variants classed as different models.

But it seems reasonable. Both my vehicles came out with a smallest size of 7.50x16 (32"). So that means at least 34's are legal. If the "one-ton" land rover that came with (Michelin) 9.00x16 tyres (36") is classed as a different model, then that means 38's are legal on a "one-ton" !!!!!!!!!!

the vehicle make is toyota
the vehicle model is HJ60RG. Landcruiser is just a "family" name.

[bluemu]

I have a sticker on my inside door frame which specifies the tyre size for my vehicle, dont all vehicles have one of these, or is there more to it?

[Shadow]

I have a sticker on my inside door frame which specifies the tyre size for my vehicle, dont all vehicles have one of these, or is there more to it?

all vehicles as from about 1982 are required to have a tyre placard

there is more to it though. Your tyre placard will show the wheel/tyre combination which was fitted to your vehicle, but there may have been other tyre combinations fitted to the same model.

IE: landcruiser base model came with 7.50R16 and tyre placard says 7.50R16
GXL came with 31x10.5R15 and tyre placard shows 31x10.5R15

now, 7.50R16 is taller, so even a GXL can use this tyre to obtain the tallest possible tyres.

[Charlie]

I understand your thinking Shadow but the off the record comment I received from a member of the RTA was this is exactly the type of thing they are sick of, people have pushed this too far until “we need to remove the discretion the engineers have”.

[ISUZUROVER]

Rather than just speculating I asked the horse's mouth - got the following reply:

Question:

Dear Robert,

I have a question regarding the NCOP for light vehicle modification. (I
currently live in Germany, however will be returning to Australia in 2
weeks to live.)

I refer to section LS, page 16/LS71 - specifically the section headed
"Overall Diameter" (first 2 paragraphs). If possible I would like some
clarification on the wording "...than that of any tyre designated by the
vehicle manufacturer for that model". The clarification is specifically in
regards to which diameter to use. As I understand it - the "standard" or
"nominal" diameters for a given tyre size are listed in the "Tyre and Rim
Standards Manual" (and also ARD23?), and these are the diameters to be used
for calculating allowable diameter changes - is this correct?.

However for 4x4 tyres there are two different diameters listed. For
example, if we take a size of 7.50x16LT (commonly fitted to many 4x4
vehicles), the "Tyre and Rim Standards Manual" lists 804mm Highway Tread
(31.65"), and 812mm Traction Tread (31.96"). Which of these sizes should be
used when determining allowable diameter changes?

I feel that it would be advantageous to state explicitly in the NCOP,
exactly which diameter to use and from what source (ADR 23, etc.), as this
would save a lot of confusion.

One last point - I assume from the wording, that if a model of vehicle was
fitted with 2 optional tyres of different diameter, then the smaller
diameter should be used to determine allowable increase and the larger for
diameter decrease???

Thanks in advance,

Ben.

Answer:

Ben,

at present the NCOP for light vehicle modification is not called up in
Queensland legislation and therefore the content of the code can not be
used in Queensland. I believe that the situation is similar in other
transport jurisdictions.

The present situation remains the same, vehicles must be modified to comply
with Queensland's COP and legislation. Reference to the brochure about
modifying light vehicles on QT's website gives more detail.

The brochure can be down loaded from:

http://www.transport.qld.gov.au/qt/LTAS ... an05v2.pdf

QT is working towards implementing the NCOP in the later part of next year;
however, the outcomes of the Road Safety Summit (RSS) take precedence over
this.

It is also possible that QT may asked for amends to the NCOP following
outcomes of the projects resulting from the RSS.

About tyre size permitted, the tyre size to be used, in deterring
alternative tyre sizes is the tyre size designated on the tyre placard
fixed by the vehicle's manufacturer. The maximum size on the tyre placard
can be used. The brochure explains where alternative tyres are permitted.
Regards

Robert Gibson
Business Manager (Vehicle Standards and Safety)
Policy Advice
Land Transport and Safety
Queensland Transport

[PJ.zook]

Even a suzuki will get nowhere these days on a 28" tyre, this sux.

As for the tolerance mentioned before in tyre size percentage as specified by tyre manufacturers, wouldnt they actually measure the tyre diameter at a specific PSI and calculate it that way so the tolerance wouldnt matter, or would they go by whats written on the tyre by the manufacturer?