Tyres, wheels and suspension modifications

Submitted: Tuesday, Jun 06, 2006 at 22:38
ThreadID: 34685 Views:2302 Replies:7 FollowUps:11
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Hi all,
There is much angst regarding tyres in particular and what is legal and what is not appearing on the site. There is a government site which give lots of details on what is and is not legal and any additional requirements should you change tyres. It is 71 pages long and bears reading if you wish to change to tyres which have been deemed of dubious legality by some. Did you know that 4WD off road tyres may be up to 50mm larger than the largest fitted by the manufacturer to one of their vehicles - not 15mm as for passenger cars? The site is the main site for future reference. It is dated 1st February 2006 so is the latest I have found. Go to NCOP11, in particular Section 4. Section 4.1 and 4.2 on pages 14 to 16 and the checklist on page 66 refer to the 50mm limit. NOTE - This details changes which may be made without engineering approval. You may also need to have your speedo modified to fit the requirement.

Site Link

Read it as you will - the government said all this, not me.

Rusty
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Reply By: Plantman - Tuesday, Jun 06, 2006 at 23:20

Tuesday, Jun 06, 2006 at 23:20
Does anyone know what the maximum percentage is that your speedo can be out by?
AnswerID: 177131

Follow Up By: disco driver - Tuesday, Jun 06, 2006 at 23:53

Tuesday, Jun 06, 2006 at 23:53
Hi Plantman,
As far as I'm aware, the Australian Design Rules allow a new vehicle speedo to be accurate to +/- 10%.
Add to this the difference between brand new and barely legal tyre tread depth and you are looking at another 5%.
Change to bigger tyres and there is about another 5-10%, depending on size fitted.

Confused???

Only safe way is to use GPS to check speeds, the other option is to run the gauntlet of the fund raising cameras, if it flashes you your speedo is out.

Cheers

Disco
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FollowupID: 433139

Follow Up By: robak (QLD) - Wednesday, Jun 07, 2006 at 10:07

Wednesday, Jun 07, 2006 at 10:07
I remember seeing somewhere on paper that it's not +/-10% but rather
+10% and -0%.
So it can show up to 10% more then your speed but never less.

R
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FollowupID: 433177

Follow Up By: Plantman - Wednesday, Jun 07, 2006 at 11:29

Wednesday, Jun 07, 2006 at 11:29
So that's not real good when 99.9% of the time we are changing the tyre size to a bigger tyre meaning that our speedo is going to read low - that is that it may read 95 km/hr when you are actually doing 100 km/hr. Does anyone now how much roughly it costs to get an electronic speedo adjusted? And what are the inplications of having a speedo that reads 95 km/hr when you are physically doing 100 km/hr - i.e. is it some insurance issue or legal issue. Would you be more liable in accident or something like that?

Cheers
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FollowupID: 433190

Follow Up By: Haza - Wednesday, Jun 07, 2006 at 16:32

Wednesday, Jun 07, 2006 at 16:32
I believe Jaycar sell a speedo adjuster kit. I think it's around the $50.00 mark.
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Reply By: mechpete - Tuesday, Jun 06, 2006 at 23:27

Tuesday, Jun 06, 2006 at 23:27
rustytruck,
in answer to your question about speedo acuracy,
the manufacturer only has to be with in 10% to meet ADR,s
if you get booked for speeding its up to you to have it checked for acuracy
cheers mechpete.
AnswerID: 177133

Reply By: Member - Troll 81 (QLD) - Wednesday, Jun 07, 2006 at 00:06

Wednesday, Jun 07, 2006 at 00:06
Some good info there. I read under the section Modifications requiring certification under LS approval codes "Raising the vehicle behond 50mm but not more than 150mm" does that mean you can go to 150mm without a mod plate? or does that mean you can't go over 150 even with a mod plate?
AnswerID: 177134

Reply By: Jugs - Wednesday, Jun 07, 2006 at 00:08

Wednesday, Jun 07, 2006 at 00:08
Reading through the NCOP11 4.2 sub Heading "Overall Diameter" the easy confusion would be
"tyre fitted to a passenger car or passenger car derivative" 15mm larger etc.
"tyre fitted to a off road passenger vehicle or commercial vehicle" 50mm larger etc
The Heading "Maximum Tyre and Rim widths for Off-road passenger and commercial vehicles" also bears reading not more than 50% etc. As does the preamble as it states local (state rules hold precedence)
The speedo accuracy mentioned in NCOP4.1 is interesting in that it states "the speed indicated by the speedometer should be NO less than the vehicles actual speed and NO more than 10% above the actual speed"

Great reference site Rustytruck thanks
Jugs
AnswerID: 177135

Follow Up By: Member - Troll 81 (QLD) - Wednesday, Jun 07, 2006 at 01:54

Wednesday, Jun 07, 2006 at 01:54
I want to know the definition of a off road vehicle. Is that just a normal 4x4 like we have with a bit of a lift and some extra stuff or is it something that is not registered and you can only drive with it on private property off road?
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FollowupID: 433142

Follow Up By: robak (QLD) - Wednesday, Jun 07, 2006 at 10:11

Wednesday, Jun 07, 2006 at 10:11
troll

if it's not registered then the you don't need conform to the rules for registration.
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FollowupID: 433179

Follow Up By: Member - Troll 81 (QLD) - Wednesday, Jun 07, 2006 at 10:19

Wednesday, Jun 07, 2006 at 10:19
That still does not answer my question. Is the normal 4x4 you see on the street classified as a off road vehicle
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FollowupID: 433180

Follow Up By: robak (QLD) - Wednesday, Jun 07, 2006 at 10:36

Wednesday, Jun 07, 2006 at 10:36
These are the rules only apply to vehicles that are to be registered . If you're not registering the vehicle then you don't have to comply. Like a go-cart for example.

So, I would say, Yes. The normal 4x4 you see on the street is classified as an off road vehicle.

R.

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FollowupID: 433182

Follow Up By: Member - Troll 81 (QLD) - Wednesday, Jun 07, 2006 at 10:39

Wednesday, Jun 07, 2006 at 10:39
Ok but then why have people been telling us that we can't go more than 15mm on tyres and if you do you are going to get booked ?
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FollowupID: 433183

Follow Up By: robak (QLD) - Wednesday, Jun 07, 2006 at 10:44

Wednesday, Jun 07, 2006 at 10:44
Because that's what the old rules said.

Now you can go +50mm on tyres and a total of 150mm max(tyres+body lift+suspension lift).

having said that, the law is never black and white. That's why lawyers drive around in $200 000 4WDs. It's all a matter of how much you're willing to pay your lawyer to argue your case.
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FollowupID: 433184

Reply By: Snowy 3.0iTD - Wednesday, Jun 07, 2006 at 07:57

Wednesday, Jun 07, 2006 at 07:57
Rusty

Again it comes down to what your interpretation of a "off-road passenger vehicle" is, most of us would like to think it means any serious 4WD, will an insurance company apply the same interpretation when assessing a claim? I have asked numerous differenct people including tyre manufacturers, transport inspectors and gotten different answers. It is a grey area.

Regards

Snowy
AnswerID: 177155

Reply By: Member - Fourplayfull - Wednesday, Jun 07, 2006 at 09:56

Wednesday, Jun 07, 2006 at 09:56
G'Day Rusty ,
Resetting your speedo to read correct is simple , from my own experience anyway . Check the reading when travelling at an indicated 100km/hr on your GPS . Advise Castlemaine Speed Shop how far out it is and they will supply a correcter box to rectify error to a spot on reading - easy to fit & has done 50000kms. so far . Good news about the 50 mm increase .
Cheers
AnswerID: 177172

Follow Up By: Jugs - Wednesday, Jun 07, 2006 at 13:10

Wednesday, Jun 07, 2006 at 13:10
Found this site the other day

Marks 4WD spedo it is a 2 position box so you can have correct speedo on town tyres and the big mud off road weekend / trip tyres site price is $160 or $175 depending on model
don't work own ect
Jugs
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FollowupID: 433206

Reply By: AS/KS - Wednesday, Jun 07, 2006 at 17:02

Wednesday, Jun 07, 2006 at 17:02
I dont believe "NCOP11" has been passed by law yet.
According to the RTA (NSW) 15mm larger is still the law.

AnswerID: 177245

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