Rims size legality

Old Dude · Postby **Old Dude** » Fri Mar 01, 2013 7:31 pm

I have a question for the legal eagles out there.
My son has a Mazda 3 base model with 15inch rims that he wants to put bigger rims on, now the more upmarket model came out with rims up to 18inch on the MPS, my understanding was that he could put on rims legally up to that size if the cars were virtually similar.
But I was told today that what he could put on was determined by what ever the tyre placard that was on his particular car! :shock:

this was buy a reputable tyre company

Now my question is does any one know if this information is correct or have they got wrong

This is in QLD so I don't know if its different in other states

Thanks for your help guys

Cheers
Dale

Jeo · Postby **Jeo** » Fri Mar 01, 2013 8:07 pm

Ignore the internet, call your local governing body.

sailaholic · Postby **sailaholic** » Fri Mar 01, 2013 8:40 pm

Only rolling diameter and track changes matter. Even these are allowed within permissible limits. Google the new code of practise for light vehicle modification to get the gory details.

MattR · Postby **MattR** » Fri Mar 01, 2013 11:09 pm

The tyre placard is a starting point for you,

Overall rolling diameter must be within a certain limit, can't remember off the top of my head, but the old plus 1 or plus 2 rule works for getting that pretty right.

For width, a maximum of 1" wider than standard fo rthe model used, check the placard and you can go 1" wider than the widest oopption shown on that. For offset you can change the track by a maximum of 1", so that means a maximum change in offset of 12mm per wheel, that is if standard offset is +35 then you can go to +23 to keep within the track change allowed for the same width rim. Different width rims will change the allowable offsets you can run.

Hope this helps.
Matt

Old Dude · Postby **Old Dude** » Fri Mar 01, 2013 11:30 pm

Thanks guys
He wasn't planning to change the rolling diameter at all, just the size of the rim and was going to keep pretty much the same offset or as close to it as possible. His placard says 195/65x15, the next model up is 205/55x16, the next is 205/50x17 and the MPS is 225/45x18.
We have just bought some good cheap rims on ebay that are 205/55x16 and he's happy with them at present and they are Mazda rims so there is only 3 mm difference in the offset, but he did want to get a different style of rim later on when finances permit, but I was just doing some research now and I've got conflicting info from 2 different dealers.

Cheers
Dale

project.r.racing · Postby **project.r.racing** » Sat Mar 02, 2013 8:51 am

You are allowed a 15mm increase in tyre rolling diameter.
You are allowed a 25mm increase in wheel track. So 12.5mm offset change per rim.
You are allowed a 30% increase in tyre width.

http://www.infrastructure.gov.au/roads/ ... 1%20v3.pdf

KevGoat · Postby **KevGoat** » Sat Mar 02, 2013 10:02 am

project.r.racing wrote:You are allowed a 15mm increase in tyre rolling diameter.
You are allowed a 25mm increase in wheel track. So 12.5mm offset change per rim.
You are allowed a 30% increase in tyre width.

http://www.infrastructure.gov.au/roads/ ... 1%20v3.pdf

1st paragraph: "Users of VSB 14 need to be aware that this document needs to be used in conjunction with the
appropriate administrative requirements of the jurisdiction in which they wish to either register a
vehicle or to obtain approval for a modification for an already registered vehicle."

As Jeo said, pays to check with your local authorities if you want to be certain ...

Old Dude · Postby **Old Dude** » Sat Mar 02, 2013 10:04 am

Thanks Project
That info makes a lot of sense in the link, the tyre guy got it wrong :wink:

thanks for all the answers :beer:

Cheers
Dale

BLU-125 · Postby **BLU-125** » Sat Mar 02, 2013 10:40 am

Just ensure that the load index of the replacement tyres is not lower than the lowest LI shown on the placard.

Sent from my grey thing using electrons, I think.

project.r.racing · Postby **project.r.racing** » Sat Mar 02, 2013 2:34 pm

KevGoat wrote:
project.r.racing wrote:You are allowed a 15mm increase in tyre rolling diameter.
You are allowed a 25mm increase in wheel track. So 12.5mm offset change per rim.
You are allowed a 30% increase in tyre width.

http://www.infrastructure.gov.au/roads/ ... 1%20v3.pdf

1st paragraph: "Users of VSB 14 need to be aware that this document needs to be used in conjunction with the
appropriate administrative requirements of the jurisdiction in which they wish to either register a
vehicle or to obtain approval for a modification for an already registered vehicle."

As Jeo said, pays to check with your local authorities if you want to be certain ...

Just to put it out there for those not informed. That link came from the Queensland transport website, the same state the OP is in. When you go to the Queensland transport website, since the state is no following the NCOP, you will be linked to the website shown above.

http://www.tmr.qld.gov.au/Safety/Vehicl ... tions.aspx