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DIFF conversion laws for NSW (Altering Track/offset)

Started by _LE38OY_ , Aug 26 2012 10:39 PM
diff wheel offset track rim differential axle dish stud tyre

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#1 _LE38OY_

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Posted 26 August 2012 - 10:39 PM

Hi
Could someone help my brain from exploding,

i have read the (Vehical Standards Info Rev 4, Nov 2003) ,which seems to be the current one and Im a bit lost with the laws/rules for using a diff from another vehical and the effect it has on the offset and track.
As per Document::::::






An important requirement for all replacement wheels is that the wheel track must not be increased by more than 25mm beyond the maximum specified by the vehicle manufacturer for that vehicle.


Where non original axle or suspension components are fitted, the offset of the wheel in relation to the axle or stub axle assembly used shall not be increased by more than 12.5mm each side of the vehicle based on the specifications of the axle components used.


If an axle assembly is shortened then the track width limit is taken as the axle manufacturers original track dimension, less the amount the assembly has been narrowed, plus 25mm.


Plz correct me if i am wrong but from what i understand. my torana has a standard rear track of 1372mm, and if i was to use the whole axle assembly from another car in the torana i could use the track width from the other car as long as the wheel offset for the new diff is the same as the car that it came from.

Then the 3rd sentance it sounds like that if i use a diff from another car and shorten it i can use the shortened track????????
Eg.
a torana lx track is 1372mm
the new diff. the track from donner car is 1500mm
i use the diff from the donner car and shorten the diff by 25mm each side.(50mm total)
does this mean that i can use 1450mm track??????????

Please Help.

if i am wrong does this mean that every torana with the wheel sitting close to the flare is ilegal

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Edited by LE38OY, 26 August 2012 - 10:44 PM.

#2 StephenSLR

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Posted 27 August 2012 - 09:16 AM

As per the last sentence, get the car inspected by an engineer before you modify and if he certifies it as good to go you should be ok.

s

Edited by StephenSLR, 27 August 2012 - 09:16 AM.

#3 StephenSLR

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Posted 27 August 2012 - 09:45 AM

If i was to use the whole axle assembly from another car in the torana i could use the track width from the other car as long as the wheel offset for the new diff is the same as the car that it came from.


From what it states, yes it can be the same and up to an offset increase of 12.5mm each side.


Then the 3rd sentence it sounds like that if i use a diff from another car and shorten it i can use the shortened track?


I think the third sentence refers shortening the cars original axle but if you get an axle from another car then you use the original track from that axle, minus the amount it’s been shortened then add 25mm.


the new diff. the track from donor car is 1500mm, I use the diff from the donor car and shorten the diff by 25mm each side. (50mm total)

does this mean that i can use 1450mm track?


No, you shortened the diff by 50mm then however much you shorten it you have to add an extra 25mm.

So your new track width would be 1475mm ….. AND …. the offset of the wheels can’t be increased by more than 12.5mm each side.

This is how I read it but best to get this checked with an engineer before doing any mods if you want it to be legal.

Also, keep in mind the track width is measured from the centre of each tyre, not the ends (many people get this wrong).

s

Edited by StephenSLR, 27 August 2012 - 09:46 AM.

#4 _shan620_

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Posted 27 August 2012 - 06:52 PM

mate call vmc engineering. He's given me permission to get a shortened 9" in my LC and have 18x10's on the rear with 5 1/4" deep dish.

#5 _LE38OY_

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Posted 27 August 2012 - 08:46 PM

Thanks guys



mate call vmc engineering. He's given me permission to get a shortened 9" in my LC and have 18x10's on the rear with 5 1/4" deep dish.



this Sounds like what im looking for thanks mate.i will look into it.

Edited by LE38OY, 27 August 2012 - 08:56 PM.

#6 _shan620_

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Posted 27 August 2012 - 09:07 PM

no probs mate, he said if u go 10" wide on rear u cant go smaller then 7" wide at front.
He's sometimes hard to get hold of, but keep trying he'll answer sometime.

#7 _LE38OY_

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Posted 06 September 2012 - 01:24 PM

no probs mate, he said if u go 10" wide on rear u cant go smaller then 7" wide at front. He's sometimes hard to get hold of, but keep trying he'll answer sometime.


i Have been looking into this alot more. did you change the track with on you car.if so how much did he let you go.

I was told by another engineer that i can have 10s (MAX) on rear and 8s (MAX) on front buy another guy. but he said that i canot change the standard track width og my torana by more then 25mm all up. so 12.5 each side (regardless of the shortend 9 inch that i currently have). This is also what it states in the RTA VSI 9

So in NSW a torana cant have the wheels that are near the flare as the track will be too much.even with 9s or 10s the track will be way more then 1372+25mm.

My 3 options look like
1. i get wheels that look too small for the car as it has flares.
2.i get a torana without flares
3. i get the wheels, forget the certificate. and just take the risk

#8 _CHOPPER_

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Posted 06 September 2012 - 03:13 PM

You could try the following option.

Use a VL Commodore diff.
Use Falcon stud pattern front and rear
Use AU and later wheels. AU offset is +36.5, Torana is +32

Rear track is now 1453mm and front track is close to stock.

#9 _LE38OY_

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Posted 06 September 2012 - 08:54 PM

You could try the following option.

Use a VL Commodore diff.
Use Falcon stud pattern front and rear
Use AU and later wheels. AU offset is +36.5, Torana is +32

Rear track is now 1453mm and front track is close to stock.


Hi Chopper. I was just looking at some other forums and i seen this one. http://www.gmh-toran...7862-a9x-specs/ you said that a A9X and L34 had 1443.2mm track on the rear. Is this correct and what is you source.


Thanks Mate.

#10 _shan620_

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Posted 06 September 2012 - 09:28 PM

What I said is what my engineer said he'll pass, I got him to confirm it again before I ordered my wheels 3 weeks ago. I didn't ask for max width on front, I only asked him the minimum width allowed with 10" wide on rear and he said no smaller then 7" wide on front. I guess every engineer will have different ways they want it done. I even got a email off another engineer Athol Mullen and he said the same, he said I can have a 10" wide rim but 9" tire.

#11 _LE38OY_

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Posted 06 September 2012 - 11:07 PM

its not the width that is my problem.8s and 10 is fine, it is the track. the guy i called didnt say anything about the track the first time i called him so i was happy and started pricing my wheels. then my dad told me to call him again and ask about what track i have to center the wheels to.
so i called, he told me that it cant be anymore then standared +25mm and that if it does not meet this he would fail it. so my dad just saved me a few grand as i was going to order the wheels.


WHAT IS THE STANDARD TRACK OF A LX RTS. OR WHAT CAN I USE
cani use a9x track seeing that A9x is only a option that a LX RTS came out with.

#12 _shan620_

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Posted 06 September 2012 - 11:43 PM

How do u measure track?

#13 StephenSLR

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Posted 07 September 2012 - 06:10 AM

How do u measure track?


Posted Image

From the middle point of each tyre track.

s

#14 TerrA LX

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Posted 07 September 2012 - 06:30 AM

The way I read it is that you must retain the OEM track of your car (not the diff donor) plus an allowance of 25mm if needed.
If so then nothing has changed the last 30yrs.

Edited by TerrA LX, 07 September 2012 - 06:30 AM.

#15 StephenSLR

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Posted 07 September 2012 - 06:43 AM

The way I read it is that you must retain the OEM track of your car (not the diff donor) plus an allowance of 25mm if needed.
If so then nothing has changed the last 30yrs.


Yeah I think that's how it was, I recall cars with short diffs and FAT tyres but looking at the rules today there's mention of the donor vehicles track width, offsets, etc. and it becomes a bit confusing.

s

#16 _LE38OY_

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Posted 07 September 2012 - 07:13 AM

The way I read it is that you must retain the OEM track of your car (not the diff donor) plus an allowance of 25mm if needed.
If so then nothing has changed the last 30yrs.


No i dont think it has been the same in the last 30 years as the standards im looking at are Rev 4 , November 2003.

if you look at my first post the 2nd sentance. From what i understand is if you use a non original axle you have to use the track (+12.5mm each side if you want) and offset of the donor car it came from .
if this in not the case then why didnt they put if you use a diff from another car you have to shortn the diff to match the original track of the car it will be going into..

i am going to call up today and see if someone can make any sence of this

Edited by LE38OY, 07 September 2012 - 07:14 AM.

#17 TerrA LX

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Posted 07 September 2012 - 07:49 AM

An important requirement for all replacement wheels is that the wheel track must not be increased by more than 25mm beyond the maximum specified by the vehicle manufacturer for that vehicle.


Where non original axle or suspension components are fitted, the offset of the wheel in relation to the axle or stub axle assembly used shall not be increased by more than 12.5mm each side of the vehicle based on the specifications of the axle components used.


If an axle assembly is shortened then the track width limit is taken as the axle manufacturers original track dimension, less the amount the assembly has been narrowed, plus 25mm.



Basically what this is saying is if you have a torana with a track of 1372mm you can increase it by 25mm. You cant find a car with a 1500mm track and expect to use that.

#18 _LE38OY_

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Posted 07 September 2012 - 08:31 AM

i just called and i confirmed what i said. BUT THE GUY I WAS TALKING TO SAID THAT HE COULD NOT GIVE ME A REFERENCE.

The way i have written these is the way the he explained it to me.

First sentance- you use an original diff 9Not modifyed) and can only increase the track by 25mm all up.

Second- you use a non original diff from a donor car and do not change the lenght of the diff. you have to use the original track of the donor car and the original offset. (shall not increase the track by more then 12.5mm each side.25mm all up)

Third- you use a diff from a donor car and shorten the diff. the track to be used is the original track of the donor car MINUS the amount the diff has been shortened and PLUS 25mm (at first he didnt say this but then i pointed out that is says AXLE MANUFACTURERS ORIGINAL TRACK. ) NOT CAR MANUFACTURERS ORIGINAL TRACK. Meaning the Track that the axle was made and tested to use.

But he said the engineer still have to sign off on it.

Edited by LE38OY, 07 September 2012 - 08:34 AM.

#19 _LE38OY_

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Posted 07 September 2012 - 08:34 AM

Unless this guy had no idea what he was talking about. HAHA

#20 _LE38OY_

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Posted 07 September 2012 - 08:51 AM

BTW the guy i was talking to was

RTA Technical Enquiries at Parramatta
1300 137 302
email: [email protected]




its the same as the rim width increase.
it say (Allowable rim width increase above the widest optional wheel available for the axle assembly used is)

1inch up to 800kg
1.5inch 801-1200
2inch 1201 and over

NOT THE WIDEST OPTIONAL WHEEL AVAILABLE FOR YOUR CAR.

Edited by LE38OY, 07 September 2012 - 09:01 AM.

#21 _CHOPPER_

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Posted 07 September 2012 - 12:55 PM

Hi Chopper. I was just looking at some other forums and i seen this one. http://www.gmh-toran...7862-a9x-specs/ you said that a A9X and L34 had 1443.2mm track on the rear. Is this correct and what is you source.


Thanks Mate.


It is correct, I used figues from GMH. The track change is due to the difference in rim offset, nothing else.

#22 _ass308_

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Posted 11 September 2012 - 08:33 AM

i Dont know how the recent law changes,have affected this issue

but i can say the new wheel track,rim offset,did go off the replacement AXLE and not the OEM axle.

here it is writing,allowing me to use a commodore diff,and modify that.u cannot change the offset of the donner wheel buy more than 12.5 each side though

Posted Image

Edited by ass308, 11 September 2012 - 08:42 AM.

#23 _ass308_

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Posted 11 September 2012 - 09:14 AM

the right way up

Posted Image

#24 _CHOPPER_

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Posted 11 September 2012 - 01:27 PM

Well they got the tyre specs wrong, but that's better for you. A DR70H14 is the equivelant of a 195/70R14 with a diameter of 625mm. I'd rather run a slightly taller tyre if it would pass.
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