Another tyre question - fitting tyres narrower than specification

Submitted: Sunday, Sep 16, 2012 at 11:34

ThreadID: 98043 Views:4752 Replies:7 FollowUps:13

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Member - Kevin S (QLD)

My Challenger is fitted with 255/70R16 highway tyres but I have a set of new (less than 1000 km) 245/70R16 A/T light truck tyres. Can they be legally fitted to the Challenger. The tyre dealer who sold the 245/70R16s says no but he wants to sell me a new set of 255/70R16s doesn't he. And will they fit the Challenger wheel anyway? Advice will be greatly appreciated.
Thanks in anticipation.
Kevin

Kevin
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Reply By: ozjohn0 - Sunday, Sep 16, 2012 at 11:50

Sunday, Sep 16, 2012 at 11:50

Kevin.
The 'minimum' tyre size if printed on the vehicle tyre placard usually located in the glove box, door, or door frame. It'll also be printed in the vehicle handbook.
At a guess I'd say the tyre serviceman is correct.
Ozjohn.

AnswerID: 495007

Reply By: Isuzumu - Sunday, Sep 16, 2012 at 11:56

Sunday, Sep 16, 2012 at 11:56

Kevin the dealer is wrong, the 245s are only 14mm smaller in diameter than the 255s, take from the tyre size calculator Tyre Size Calaulator
The legal size bigger/smaller is 15mm in diameter, so your safe by ine mil

AnswerID: 495008

Follow Up By: Member - Charlie M (SA) - Sunday, Sep 16, 2012 at 13:56

Sunday, Sep 16, 2012 at 13:56

Can not go smaller than tyre placard. Can not go lower than load index and speed can not be lower than S rated if passenger vehicle. Light truck tyre might not be S rated.
Cheers
Charlie

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Follow Up By: Isuzumu - Sunday, Sep 16, 2012 at 19:47

Sunday, Sep 16, 2012 at 19:47

Under Qld Tpt reg you are allowed 15mm higher or lower than what is stated on your placard, so Charlie you do not know squiggly.....

FollowupID: 770695

Follow Up By: Member - PJR (NSW) - Sunday, Sep 16, 2012 at 20:29

Sunday, Sep 16, 2012 at 20:29

Shouldn't that read "15mm higher or lower than what is " fitted as stanard, out of the factory. And by that I do not mean what is fitted by the dealer. Rather what is fitted at the factory.

I thought that Charlie was correct.

Anyway. I do not understand why people do not know such a small isasue. I knew this before I got my licence. We are really suffering from loss of education from our parents or grandparents. But what did I see on the TV. Some twit "U" generation said that if he doesn't know then he will "Google it". Hmmmm. And who is to say what Google finds is up-to-date as not much has a date on it.

Phil

FollowupID: 770698

Follow Up By: Member - Kevin S (QLD) - Sunday, Sep 16, 2012 at 20:38

Sunday, Sep 16, 2012 at 20:38

Thanks Bruce. Your answer makes sense to me. I expected someone to raise the insurance issue but the wording of my policy doesn't suggest that there is a problem. But if they ever started to play silly games they stand to loose coverage of 2 cars, a caravan and a house and contents.
How are your Kimberley plans going. Departure is not much more than 6 months away. It is almost tome to count sleeps.:):):):)
Cheers,
Kevin

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Follow Up By: Isuzumu - Monday, Sep 17, 2012 at 06:19

Monday, Sep 17, 2012 at 06:19

Six months yep going to come pretty quick Kev especially that I have to fit out the new D.Max. I have known about the law on tyre sizes for a long time, as I am about to fit new wheeels and tyres to the D.Max, problem finding the tyre I want in a size that is legal.

FollowupID: 770720

Follow Up By: Member - Kevin S (QLD) - Monday, Sep 17, 2012 at 07:58

Monday, Sep 17, 2012 at 07:58

You have a new D.Max? Now I am really jealous.:):):)
The premature death of the Jackaroo robbed me of a trade in so I had to lower my expectations. Still, I think the Challenger will be up to the task of towing the van into Mt Moffatt at Easter. We are looking forward to that.
Cheers,
Kevin

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Follow Up By: Member - Charlie M (SA) - Monday, Sep 17, 2012 at 19:47

Monday, Sep 17, 2012 at 19:47

To
Isuzumu
You can actually go 26mm lower BUT ALL OTHER DETAILS MUST BE MET.

Speed index, load index under any circumstances.

As for (you do not know squiggly.....), said tyres if not compliant in any one of the above would not be fitted in my workshop and other tyre dealer is right.

We have had major work done in our shop and can not lay my hands on the latest 2012 Njoy book to get Challenger speed index and not listed in the 2010 year book.

For your info I have been in tyres since 1971 and handle tyres from 4inch to 50inches in all types of vehicle fitments.

This will be my one and only reply to your message, as I have no intention of devaluing this thread.

Charlie Milton

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FollowupID: 770755

Follow Up By: Isuzumu - Monday, Sep 17, 2012 at 20:32

Monday, Sep 17, 2012 at 20:32

No worries Charlie but you should tell us your the guru on tyres and instead of making sure you put up the right facts first and yes if you want to go on with it pm me cause I have heaps of experience in tyres and 4Wds to.

FollowupID: 770760

Reply By: member - mazcan - Sunday, Sep 16, 2012 at 13:10

Sunday, Sep 16, 2012 at 13:10

hi kevin s
the insurance companies will find any excuse to make your claim null and void if you have under size/over size tyres so just be aware of that important fact
if your unlucky and are involved in a bingle
its your call
cheers

AnswerID: 495011

Reply By: Member - Phil G (SA) - Sunday, Sep 16, 2012 at 21:49

Sunday, Sep 16, 2012 at 21:49

The diameter is 14mm less, so still legal. (But I'd never fit an undersized tyre to a 4wd)
The width is OK for a 7" wide rim.

The big issue is the load index. Is the load index of the 245/70 greater or equal to what is stated on your tyre placard.

AnswerID: 495051

Follow Up By: Member - Phil G (SA) - Sunday, Sep 16, 2012 at 21:59

Sunday, Sep 16, 2012 at 21:59

Just found the Qld regs here:
Qld regulations

"The rim diameter may be varied from the standard size
but the overall diameter of the tyre must not vary by
more than +15mm or -26mm."

FollowupID: 770713

Follow Up By: Member - Kevin S (QLD) - Monday, Sep 17, 2012 at 07:53

Monday, Sep 17, 2012 at 07:53

Thanks for the input and the link Phil. Good stuff. The 245/70R16 ATs are on my recently deceased TD Jackaroo which has much higher load carrying specifications than the Challenger, e.g Jackaroo front 1250 kg rear 1450 kg. Challenger 1030 kg all round. I think there is a bit of scope there.
Cheers,
Kevin

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Follow Up By: Member - Kevin S (QLD) - Monday, Sep 17, 2012 at 08:36

Monday, Sep 17, 2012 at 08:36

Hi Phil G. I've had a look at the small print of the regulations and I think the last paragraph on page 11 cooks my goose. It says
"The nominal width of the narrowest tyre fitted to a
vehicle must not be less than 70 per cent of the nominal
width of the largest tyre fitted and never less than the
vehicle manufacturer’s narrowest optional tyre as
indicated on the manufacturer’s tyre placard".
Since the only tyre on the placard is the 255/70R16 it seems that I can go wider but not narrower.
Thanks for the input people. Much appreciated.
Kevin

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Reply By: olcoolone - Monday, Sep 17, 2012 at 08:55

Monday, Sep 17, 2012 at 08:55

Maybe the best thing to do is phone the "transport department" in the state where your vehicle is registered...... the would be able to tell you yes or no and you might also be able to get a copy of the document covering this.

Asking legal based questions on a forum is hit and miss.

AnswerID: 495069

Reply By: Andrew - Monday, Sep 17, 2012 at 15:53

Monday, Sep 17, 2012 at 15:53

Hi Kevin

VSB 14 Link here

Is the national standard for modified vehicles and is pretty much accepted everywhere.

it says

4.1 REPLACEMENT TYRES ON STANDARD (OR MANUFACTURER’S OPTIONAL) RIMS
Some tyre sizes have become obsolete and are no longer available. Equivalent replacement tyres with different size designations may be fitted without specific certification under this Section.
Every passenger car manufactured after 1972 (ADR 24) is fitted with a tyre placard that contains information on original and optional tyres and rims for that vehicle model.
A motor vehicle under 4.5 tonnes GVM which is required to comply with ADR 24 may be
equipped with tyres other than those listed on the tyre placard provided that:
? the load rating of the tyres is not less than the lowest load rating listed on the tyre placard of the vehicle or equivalent variant of that model vehicle;

It also says

4.2.4 Overall Nominal Diameter
The overall diameter of any tyre fitted to a passenger car or passenger car derivative must not be more than 15mm larger or 26mm smaller than that of any tyre designated by the vehicle manufacturer for that model.
The overall diameter of any tyre fitted to:
• 4WD passenger vehicles specifically designed for off-road use (typically MC ADR
category). All wheel drive (AWD) vehicles including those AWD vehicles that may be
certified as MC ADR category, (also commonly known as soft roaders) are not
included in this category;
• 4WD goods vehicles and their 2WD equivalents if the chassis and running gear are
essentially the same as the 4WD version (N ADR category); or
• any medium weight goods vehicle (NA2, NB ADR category).
Must not be more than 50mm larger or 26mm smaller than that of any tyre designated by the vehicle manufacturer for that vehicle.

Hope this helps

regards

A

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AnswerID: 495093

Follow Up By: Isuzumu - Monday, Sep 17, 2012 at 16:03

Monday, Sep 17, 2012 at 16:03

Hi Andrew, I like this "standard" but does it cover 4WDs in all States? I would imagine my insurance broker would be the best to ask this question to I think.

FollowupID: 770743