20” by 10 with 275/30/20 all around is it possible? Please do help

[Skylarking]

This seems to be similar to the one @panhead posted....

All I did was google 275/30X20 VF Commodore placard and the ebay link is what cropped up first that I could actually read the image

Not faulting you.

This just highlights that tyre placards are variant specific and tyre sizes are different between different variants which goes back to my belief that you can’t take a HSV tyre placard and stick it on a commodore omega.

The reasons as Holden put it to me is that ABS/ESC calibration and the physical suspension components are tunes and certified as a whole for each model variant and only for a limited selection of tyre sizes (See SPS for tyre calibration files for various modules)…

Some of this Holden view is bullshite but that’s the strict reading of model variants as they see it. And they won’t stick their neck on the line by providing any letter indicating one can go from staggered to rotatable wheels and simply say it’s your car and you can do as you please (legal or not)…

So can one simply change a tyre placard to any model variant or one from another manufacturer at will? I still think not.

 

[panhead]

Not faulting you.

This just highlights that tyre placards are variant specific and tyre sizes are different between different variants which goes back to my belief that you can’t take a HSV tyre placard and stick it on a commodore omega.

The reasons as Holden put it to me is that ABS/ESC calibration and the physical suspension components are tunes and certified as a whole for each model variant and only for a limited selection of tyre sizes (See SPS for tyre calibration files for various modules)…

Some of this Holden view is bullshite but that’s the strict reading of model variants as they see it. And they won’t stick their neck on the line by providing any letter indicating one can go from staggered to rotatable wheels and simply say it’s your car and you can do as you please (legal or not)…

So can one simply change a tyre placard to any model variant or one from another manufacturer at will? I still think not.

I often say the placards are readily available so just change it to suit your needs as no-one will know you've done so, but I've always felt doing such a thing would be illegal but I'm yet to see any evidence that says so.

But I wouldn't put a HSV placard on a non HSV vehicle as that would stand out likes dog's balls to any inspector but applying a Holden placard to a Holden may get through.

If you're smart enough to keep the rolling diameter close to stock then I don't see how increasing or narrowing the width would impact on ABS/ESC but I'm no expert.





.

 

[RevNev]

The reasons as Holden put it to me is that ABS/ESC calibration and the physical suspension components are tunes and certified as a whole for each model variant and only for a limited selection of tyre sizes (See SPS for tyre calibration files for various modules)…

The funny thing is with a '16 SV Black Maloo last of the 340's. The selectable tyre options in the programming setup doesn't include a 255/35 and 275/35. The staggered 20" setup is 245/35 and 275/30 no Gen-F was ever fitted with that tyre size. There's 19" wheel/tyre options also! The calibration numbers are different to a Redline ute but it seems tyre size isn't a major factor otherwise the taller HSV tyre sizes would be listed you'd think.

 

[RevNev]

This just highlights that tyre placards are variant specific and tyre sizes are different between different variants which goes back to my belief that you can’t take a HSV tyre placard and stick it on a commodore omega.

We used have issues with the cops in SA when staggered wheels and tyres were first introduced and fitting HSV tyre placards fixed the problem and prevented a work order. "See officer, the tyre placard shows a different tyre size front to rear!"

 

[MrBags]

Just adding to this, is it also an issue that you should have the correct tyre placard to suit the size you are running?
***I am not saying that it is required do but I am wondering if you do need to?***
I changed mine over to suit 20’s either way.
Perfect example of what I mean in this case where no 20” requirements are even present on the standard placard?

 

[Anthony121]

After 25 years and counting in the tyre game, I do know what I am talking about...The law states, load rating and speed must be equal or greater than what is stated on the tyre placard....For 20" tyres fitted to VF Commodores, the tyre and speed ratings are 100Y...Go post your tyre placard up and show everyone what it states so we all know whether what I have posted is false information or not because that's exactly what insurance companies and the transport authorities go by...

100 is the load rating and "Y" is the speed rating just in case you don't know...

To help things along, if the tyre store you had them fitted by fitted those to the car, they are responsibile for making your car unroadworthy....When tyres are fitted, the details of the car, ie the rego number, along with the owners details, combined with what is fitted are put into the computer system, so if there is a problem down the track regarding the tyres fitted...ie be in the form of an accident, the insurance company or transport dept can do through the records and find out if the wrong tyres have been fitted to the car to make it unroadworthy....If it is found, the store has fitted the wrong tyres to your can, with an accident occurring, the tyre store is deemed at fault for fitting unroadworthy tyres.

Don't believe me...Do some research buddy, because my years of experience has done it...Yours has done none

I had one tyre supplied by a tyre fitter for my redline and I queried at the time the speed rating was not the same as original. 270 instead of 300. I've now got one 98W fitted to the front of my vehicle and one 98Y on the other side. What you have written above will cause my car to be unroadworthy. The tyre has been on the car for 2 years now.

 

[Skylarking]

Yeah @RevNev, bluffs can go a long way until reg authorities take a harder line and create a new doc the explicitly spells out the new way of looking at the rules and the cops have something concrete forcing their hand. Once that occurs then bluffing cops with self fitted tyre placards just won’t cut it as the rules will be clear ( and they’ll likely have quick links to the RVD itself which clearly specifies the standard and optional tyres allowable for that model variant so won’t need to look at the tyre placard Luckily we are not there yet )

And since the tyre placard is a legal requirement that must be fixed by the manufacturer, just like the complience plate, I don’t believe it can be replaced for something else by the owner that the manufacturer didn’t fit to that model variant.

As for the last of the 340 Marlo’s, there must be some calibration for the optional 255/35 & 275/35 20” tyres otherwise the speedo would be out. In any case, Holden tow the “we don’t recommend you modify our stuff“ line as do all manufacturers and that is a self serving view as it forces prospective buyers to shell out for the more expensive variant (which is part of the goal around “model variant” interpretations, compliancing and RVD of mod rules…. The establishment is wanting to move towards reduce modification to fluffy dice and soft toy figures on the dash.

@MrBags, modification rules in most states allow you to increase wheel track marginally and increase rim diameter by some margin as long as rolling diameter doesn’t change too much. But your not allowed to degrade load and speed ratings in the process. And IIRC, the mod rules themselves don’t require you to change your tyre placard to reflect the mod you’ve made.

As long as your within the base tyre mod rules, think of it as a mechanical mod that doesn’t require engineering approval and mod plate affixed to the car.

@Anthony121, yes technically your vehicle is now unroadworthy but you could always ring up the technical section of vicroads and ask 2 different people but get 3 different answer as one guy changes his mind

 

[RevNev]

Just adding to this, is it also an issue that you should have the correct tyre placard to suit the size you are running?
***I am not saying that it is required do but I am wondering if you do need to?***
I changed mine over to suit 20’s either way.
Perfect example of what I mean in this case where no 20” requirements are even present on the standard placard?

I always change the tyre placard and did so when fitting 20" wheels, the standard Redline placard had the staggered 19's. I used the HSV one showing 255/35's on the front although my rear tyres don't match, it's closer than 19's. I got an export tyre placard for my old VE showing the staggered fitment when fitting the 9" Redline rear wheels and 275's.

As for the last of the 340 Marlo’s, there must be some calibration for the optional 255/35 & 275/35 20” tyres otherwise the speedo would be out.

Speedo calibration's in the ECM represented as revolutions per km. That's different than the Redline and can't be altered with GM programming, but of course can be changed in HP Tuners along with diff ratios. Tyre size selection is in the BCM and chassis control module setup. I don't think it's in the ABS module by memory. There's a selectable Police Pack option on something too and I'm not sure what that does. It's not in the ECM for an extra 10kw's!

 

[RevNev]

But I wouldn't put a HSV placard on a non HSV vehicle as that would stand out likes dog's balls to any inspector but applying a Holden placard to a Holden may get through.

I've tested this before with vehicle inspectors and HSV is "Holden" Special vehicles and you tell them it's an option or accessory, factory go fast gear like all the BMW M Performance parts you can buy. Most of the SA vehicle inspectors will let something go with a plausible explanation I've found, it's more if you're rude or argue with them too much they'll dig deeper into the rule book. A few times they haven't measured the track with decent offset wheels and HSV centre caps, "are they Clubsport wheels mate?", yeah that's it!

My ute would fail being too low, I'd have to raise it a bit to pass a rego inspection but surprisingly, I did get it through with film 20 tint on the side windows as it had QLD rego when buying it and had to be inspected for SA rego.

 

[Skylarking]

Tyre size selection is in the BCM and chassis control module setup.

I posted some sps stuff about tyre sizes in another thread but there are calibrations around tyre sizes within k20 Engine Control Module.
For one tyre size example for my motorsport edition redline, there are more, see the speed calibration module in the following:

Software Description Module Part Number CVN Main Software Calibration Module 12673958 93E3 System Calibration Module 92285952 4A30 Fuel Calibration Module 92285950 C65A Speed Calibration Module 92285984 B4BE Engine Diag. Calibration Module 92285947 13EA Engine Calibration Module 92285946 4204 MHC Software Calibration Module 12625892 36F2 MHC Calibration Module 92279826 BE4E

Selected Options: VIN: 6G1FE5EW3HL33xxxx Salesmake: Holden Model Year: 2017 Model: VF COMMODORE Engine: 6.2L (LS3) Controller: K20 Engine Control Module Function: Programming Tire Size: 5CF=245/35R20 (FRONT) and 275/30R20 (REAR)

Isn't there something similar of the Marloo?

PS: The SPS data for my VIN also lists R3V=245/45R18-100V as a selecable tyre size which wont fit because of the brembos (unless GM has a forged 18" rim that would)