Wheel Tracks & Offsets

Includes handbrake, cylinders, shoes, discs, rims and rubber.

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Coopa
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Wheel Tracks & Offsets

Post by Coopa »

Ok i need VSB14 advise I am re doing my modification documents, I am a little stuck.

It states 'all rims fitted to a front axle or a rear axle must be of the same diameter, offset, width and mounting configuration' & 'Where non-original axle or suspension cross-member components are fitted, the offset of the wheel in relation to the axle or hub assembly used must not be increased by more than 12.5mm each side of the vehicle based on the specifications of the axle components used.

So my question is what happens when you use different non original axles from front to back that both have different OEM offsets that vary 37mm? (I have VN commodore diff with HR drum stubs up front)

Maybe I shouldn't have had that last beer and it all my have been clearer.


Cheers Coopa :sickk:
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Devilrod
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Re: Wheel Tracks & Offsets

Post by Devilrod »

Sounds like a question for your engineer!
Speed and Style........... One day I'll get the speed bit.
Coopa
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Re: Wheel Tracks & Offsets

Post by Coopa »

Yep i was thinking that :)

I think a phone call tomorrow, i knew about the 25mm offset but did think about differents between front to back..
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Harv
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Re: Wheel Tracks & Offsets

Post by Harv »

G'day Coopa,

I went through the same drama, as I have a CRS modified HR front end, with a narrow VP LSD rear end. I run Holden Commodore steel wheels from a VQ Statesman Series 1 (26mm positive offset, fitted with 205/65/15 tyres). The info below is part of the write up draft that I gave to the engineer at the "approval in principle" meeting - he had no issue with it.

The detail is drawn from NSW Vehicle Standards Information Sheet No.9 requirements, very similar to NCOP. It may be useful when discussing with your engineer.

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.
The original rear axle assembly was sourced from a VP Commodore. VP Commodore offset varied from 26-43mm (positive offset in all cases). The offset of the proposed wheels (26mm) is within the range originally fitted to VP Commodores. The front spindle assemblies were originally from a HR Holden, modified by the Castlemaine Rod Shop to suit Commodore bearings. HR Holdens originally had 6mm positive offset. The proposed wheels have 20mm more offset than the original assembly, in the positive direction (less axle load). Additionally, the Castlemaine Rod Shop indicates that the modified stub axles have been designed for a maximum track of 1455mm. The proposed vehicle track is 1436mm (when measured as per the Casltemaine Rod Shop to the centre of the tyre).
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.
The rear axle assembly has been shortened. The original rear axle assembly was sourced from a VP Commodore. VP Commodore offset varied from 26-43mm (positive offset in all cases). The offset of the proposed wheels (26mm) is within the range originally fitted to VP Commodores (i.e. the wheel track is identical to the axle manufacturers original track dimension, less the amount the assembly has been narrowed).
The maximum permitted rear rim width for a particular vehicle is determined by its unladen weight (10 litres of fuel, no occupants or luggage) in accordance the tables given in Vehicle Standards Information Sheet No.9.
The vehicle was built in 1961, and hence was not built to comply with ADR 24 (prior to 1973 for passenger cars). With a kerb weight of 1183kg, the maximum permitted rear rim width is 204mm (8 inches). The proposed wheels are 178mm (7”).
Front wheels shall be:
• No wider than the maximum permitted for rear wheels on your vehicle or 204mm (8 inches).
• No narrower than 70% of that fitted to the rear wheels.
• No narrower than a standard wheel fitted to the your vehicle as original equipment.
The proposed 178mm (7”) front wheels are:
• The same size as the maximum permitted for rear wheels on the vehicle.
• Wider than the standard wheels fitted to the vehicle as original equipment (5¾”).

The wheel rim width must not be less than the minimum width fitted by the vehicle manufacturer for the particular model.
The proposed 178mm (7”) wheels are wider than the standard wheels fitted to the vehicle as original equipment (5¾”).
The wheel and tyre must be contained within the body work or mudguards (including any flares) when the wheels are in the straight ahead position.
The wheels and tyres are contained within the body work when the wheels are in the straight ahead position.
The wheel and tyre must not foul any part of the body or suspension under all operating conditions.
The wheels and tyres do not foul any part of the body or suspension under all operating conditions.
All wheels and tyres fitted to an axle must be of the same carcass construction, diameter, offset, width and mounting configuration (except for spare wheels used in an emergency situation).
All wheels and tyres fitted to an axle are of the same carcass construction, diameter, offset, width and mounting configuration.
The wheel must not prevent the wheel nuts from fully engaging their studs.
All wheel nuts fully engage their studs.
The wheel rim must not have a circumferential weld other than that which attaches the rim to the wheel centre.
The wheel rim does not have a circumferential weld other than that which attaches the rim to the wheel centre.
The wheel must be one designed for the particular hub/axle in respect to bolt pitch circle diameter and wheel nut tapers. Wheels with slotted stud holes are not permitted.
The proposed wheels are designed for the proposed Commodore hub/axles in respect to bolt pitch circle diameter (120mm) and wheel nut tapers (60º). The proposed wheels do not have slotted stud holes.
Speedometer accuracy must be maintained for the selected tyre and rim combination.
Speedometer accuracy will be ensured by changing the transmission drive and driven gear combination. Calculations indicate the combination of red drive gear and black driven gear will come close (speed indicated 0.47% slower than actual), with an alternative of green/green or grey/orange (both of which will indicate 0.37% faster than actual).
The fitment of wheel spacers (or adaptors for dual wheel conversions) between the wheel mounting face and the road wheel is not permitted unless fitted as original equipment by the vehicle manufacturer.
Wheel spacers are not fitted.

Cheers,
Harv
327 Chev EK wagon, original EK ute for Number 1 Daughter, an FB sedan meth monster project and a BB/MD grey motored FED.
Coopa
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Re: Wheel Tracks & Offsets

Post by Coopa »

Thanks Harv thats awsome
iso007
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Re: Wheel Tracks & Offsets

Post by iso007 »

I have to say it again. You guys are smarter than aliens.
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59wagon
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Re: Wheel Tracks & Offsets

Post by 59wagon »

Hi Harv,
Thanks for a great description of what you did. I'm looking at doing similar to you on my FC - using VP rear end and HR front with VP hubs/brakes. I'm thinking about dropping a mozza of hard earned on drop spindles (HR to Commodore) and have been speaking with Rod Hadfield at Stubtech, as well as CRS. According to both, using Commy brakes, the front wheel track increases between 10-15mm each side (HR front track = 1369mm, so goes out to between 1389-1399). You mentioned that your proposed front track with CRS spindles and 26p offset rims is 1436mm. I'm hoping that's a typo, otherwise I'm still confused - should it be 1336mm? This is all new to me, so still learning and trying to get it right.
Cheers,
John
Harv wrote:G'day Coopa,

I went through the same drama, as I have a CRS modified HR front end, with a narrow VP LSD rear end. I run Holden Commodore steel wheels from a VQ Statesman Series 1 (26mm positive offset, fitted with 205/65/15 tyres). The info below is part of the write up draft that I gave to the engineer at the "approval in principle" meeting - he had no issue with it.

The detail is drawn from NSW Vehicle Standards Information Sheet No.9 requirements, very similar to NCOP. It may be useful when discussing with your engineer.

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.
The original rear axle assembly was sourced from a VP Commodore. VP Commodore offset varied from 26-43mm (positive offset in all cases). The offset of the proposed wheels (26mm) is within the range originally fitted to VP Commodores. The front spindle assemblies were originally from a HR Holden, modified by the Castlemaine Rod Shop to suit Commodore bearings. HR Holdens originally had 6mm positive offset. The proposed wheels have 20mm more offset than the original assembly, in the positive direction (less axle load). Additionally, the Castlemaine Rod Shop indicates that the modified stub axles have been designed for a maximum track of 1455mm. The proposed vehicle track is 1436mm (when measured as per the Casltemaine Rod Shop to the centre of the tyre).
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.
The rear axle assembly has been shortened. The original rear axle assembly was sourced from a VP Commodore. VP Commodore offset varied from 26-43mm (positive offset in all cases). The offset of the proposed wheels (26mm) is within the range originally fitted to VP Commodores (i.e. the wheel track is identical to the axle manufacturers original track dimension, less the amount the assembly has been narrowed).
The maximum permitted rear rim width for a particular vehicle is determined by its unladen weight (10 litres of fuel, no occupants or luggage) in accordance the tables given in Vehicle Standards Information Sheet No.9.
The vehicle was built in 1961, and hence was not built to comply with ADR 24 (prior to 1973 for passenger cars). With a kerb weight of 1183kg, the maximum permitted rear rim width is 204mm (8 inches). The proposed wheels are 178mm (7”).
Front wheels shall be:
• No wider than the maximum permitted for rear wheels on your vehicle or 204mm (8 inches).
• No narrower than 70% of that fitted to the rear wheels.
• No narrower than a standard wheel fitted to the your vehicle as original equipment.
The proposed 178mm (7”) front wheels are:
• The same size as the maximum permitted for rear wheels on the vehicle.
• Wider than the standard wheels fitted to the vehicle as original equipment (5¾”).

The wheel rim width must not be less than the minimum width fitted by the vehicle manufacturer for the particular model.
The proposed 178mm (7”) wheels are wider than the standard wheels fitted to the vehicle as original equipment (5¾”).
The wheel and tyre must be contained within the body work or mudguards (including any flares) when the wheels are in the straight ahead position.
The wheels and tyres are contained within the body work when the wheels are in the straight ahead position.
The wheel and tyre must not foul any part of the body or suspension under all operating conditions.
The wheels and tyres do not foul any part of the body or suspension under all operating conditions.
All wheels and tyres fitted to an axle must be of the same carcass construction, diameter, offset, width and mounting configuration (except for spare wheels used in an emergency situation).
All wheels and tyres fitted to an axle are of the same carcass construction, diameter, offset, width and mounting configuration.
The wheel must not prevent the wheel nuts from fully engaging their studs.
All wheel nuts fully engage their studs.
The wheel rim must not have a circumferential weld other than that which attaches the rim to the wheel centre.
The wheel rim does not have a circumferential weld other than that which attaches the rim to the wheel centre.
The wheel must be one designed for the particular hub/axle in respect to bolt pitch circle diameter and wheel nut tapers. Wheels with slotted stud holes are not permitted.
The proposed wheels are designed for the proposed Commodore hub/axles in respect to bolt pitch circle diameter (120mm) and wheel nut tapers (60º). The proposed wheels do not have slotted stud holes.
Speedometer accuracy must be maintained for the selected tyre and rim combination.
Speedometer accuracy will be ensured by changing the transmission drive and driven gear combination. Calculations indicate the combination of red drive gear and black driven gear will come close (speed indicated 0.47% slower than actual), with an alternative of green/green or grey/orange (both of which will indicate 0.37% faster than actual).
The fitment of wheel spacers (or adaptors for dual wheel conversions) between the wheel mounting face and the road wheel is not permitted unless fitted as original equipment by the vehicle manufacturer.
Wheel spacers are not fitted.

Cheers,
Harv
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Harv
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Re: Wheel Tracks & Offsets

Post by Harv »

Could be a typo, though I was fairly careful when I measured it. Could be the difference in the way that track is measured though... some places measure to the inside rim edge, some places the outside rim edge, and CRS measure to the middle of the tyre. Took a lot of discussion with CRS before I twigged to that.

My front-end is having a little holiday at Dave's place for paint and panel... will try to remember to take a tape measure with me when I go and take a look next week.

Cheers,
Harv
327 Chev EK wagon, original EK ute for Number 1 Daughter, an FB sedan meth monster project and a BB/MD grey motored FED.
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59wagon
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Re: Wheel Tracks & Offsets

Post by 59wagon »

Thanks, Harv.

Cheers, John
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Harv
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Re: Wheel Tracks & Offsets

Post by Harv »

59wagon wrote:Hi Harv,
Thanks for a great description of what you did. I'm looking at doing similar to you on my FC - using VP rear end and HR front with VP hubs/brakes. I'm thinking about dropping a mozza of hard earned on drop spindles (HR to Commodore) and have been speaking with Rod Hadfield at Stubtech, as well as CRS. According to both, using Commy brakes, the front wheel track increases between 10-15mm each side (HR front track = 1369mm, so goes out to between 1389-1399). You mentioned that your proposed front track with CRS spindles and 26p offset rims is 1436mm. I'm hoping that's a typo, otherwise I'm still confused - should it be 1336mm? This is all new to me, so still learning and trying to get it right.
Cheers,
John
G'day John,

I checked my front end out at Dave's today. It's 1215mm inside the tyres (inner sidewall to inner sidewall), and 1630mm outside the tyres (outer sidewall to outer sidewall). These are rough as guts tapemeaurements, but would give about 1423mm track when measured like CRS (between tyre centres). This is close enough to the 1436mm I noted above (given how rough I measured), ie. I think my original post was right and I have 1436mm CRS-measured track, not 1336mm.

Cheers,
Harv
327 Chev EK wagon, original EK ute for Number 1 Daughter, an FB sedan meth monster project and a BB/MD grey motored FED.
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59wagon
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Re: Wheel Tracks & Offsets

Post by 59wagon »

G'day John,

I checked my front end out at Dave's today. It's 1215mm inside the tyres (inner sidewall to inner sidewall), and 1630mm outside the tyres (outer sidewall to outer sidewall). These are rough as guts tapemeaurements, but would give about 1423mm track when measured like CRS (between tyre centres). This is close enough to the 1436mm I noted above (given how rough I measured), ie. I think my original post was right and I have 1436mm CRS-measured track, not 1336mm.

Cheers,
Harv
Thanks for doing that, Harv. So, does that mean, to satisfy the rules, you can use almost any track width you like up to the CRS design limit for their stubs, rather than the original FB or HR track width (1384 or 1369mm + 25mm maximum)?
Thanks again,
John
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Harv
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Re: Wheel Tracks & Offsets

Post by Harv »

59wagon wrote: So, does that mean, to satisfy the rules, you can use almost any track width you like up to the CRS design limit for their stubs, rather than the original FB or HR track width (1384 or 1369mm + 25mm maximum)?
That's how I interpret the rules - I can go up to the CRS limit +25mm. If I was using original GMH components (say a standard HR front end), it would be GMH factory track + 25mm.

My engineer was happy with that interpretation, though other engineers may have a different view.

Cheers,
Harv
327 Chev EK wagon, original EK ute for Number 1 Daughter, an FB sedan meth monster project and a BB/MD grey motored FED.
bat53retro
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Re: Wheel Tracks & Offsets

Post by bat53retro »

g'day all
in wa it is 25mm wider than the crossmember used
and wheel size depends on the stubs used
as long as they fit in the original body line
no modifying of the guards :thumbsup:
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