Replacement Tyres from OEM Continentals

[Sydneykid]

We can agree to disagree, that's cool. But if you want to have some fun ask the TMR if you can "run a 215/45/17 with a diameter of 625 mm if your car originally comes with 215/40/17 with a diameter of 628 mm"?

It doesn't matter what size is stamped on the tyre 'cause that's not what the regulation says, it's the actual diameter that makes it legal or illegal.


Cheers
Gary

[BenT]

I still think it’s worth considering that insurance company might reject your claim if they discover you had non-standard size tyres fitted.


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[Hillbilly]

We can agree to disagree, that's cool. But if you want to have some fun ask the TMR if you can "run a 215/45/17 with a diameter of 625 mm if your car originally comes with 215/40/17 with a diameter of 628 mm"?

It doesn't matter what size is stamped on the tyre 'cause that's not what the regulation says, it's the actual diameter that makes it legal or illegal.


Cheers
Gary

Actually we were answering the OP until you hopped in and hijacked the thread so do what you like.
What you can do in NSW may be different to what we can do in QLD so just leave it at that

[Sword_Dude]

OK so getting back on thread, what is everyone recommending to replace these Bridgestone MY02 215/40/17 tyres with.

I was happy with the ContiContactSport2 that the VW came with but was just wondering if there is another option that others are finding worth a look.

cheers

Michael

[feenix74]

Try the Bridgestone Potenza Adrenalin RE003, they are doing a get the 4th tyre free deal at the the moment (Buy 3 tyres and get the 4th free November to 2018 Specials).

[Sydneykid]

Actually we were answering the OP until you hopped in and hijacked the thread so do what you like.

I didn't hijack it, I answered the question, I'm running Michelin Pilot Sports in 215/45/17 because I consider them to the best all round tyre. Then I was told I wasn't allowed to run them, which is plainly not true, yes even in Qld.

Cheers
Gary

[Hillbilly]

I didn't hijack it, I answered the question, I'm running Michelin Pilot Sports in 215/45/17 because I consider them to the best all round tyre. Then I was told I wasn't allowed to run them, which is plainly not true, yes even in Qld.

Cheers
Gary

Can you please post the part of the ADR that says diameter can be plus 4% because i have just read it and can only find 4% referrring to width.

It would be common sense for tyres of the same size to be a very close match in diameter or why bother having regs and sizes We should just chuck aything on and to hell with tyre placards

In the meantime I have asked TMR to explain the rule about diameter to me so await a reply

[Sydneykid]

Can you please post the part of the ADR that says diameter can be plus 4% because i have just read it and can only find 4% referrring to width.

6.1.5. Tyre outer-diameter specifications
The outer-diameter of a tyre must not be outside the values Dmin and Dmax obtained from the following formulae:
Dmin = d + (2H . a)
Dmax = d + (2H . b)
where:
6.1.5.1. for sizes listed in Annex 5, and for tyres identified by the "tyre to rim fitment configuration" (see para. 3.1.10.) symbol "A", the nominal section height H is equal to:
H = 0.5 (D-d), for references see paragraph 6.1.2.
6.1.5.2. for other sizes, not listed in Annex 5, "H" and "d" are as defined in paragraph 6.1.2.1,

6.1.5.3. Coefficients "a" and "b" are respectively:
6.1.5.3.1. Coefficient "a" = 0.97
6.1.5.3.2. Coefficient "b" Radial, Run flat tyre Diagonal and Bias Belted
for ordinary
(road type) tyres 1.04 1.08
6.1.5.4. for snow tyres the overall diameter (Dmax) established in conformity with the above may be exceeded by 1 per cent.

It would be common sense for tyres of the same size to be a very close match in diameter or why bother having regs and sizes We should just chuck aything on and to hell with tyre placards

The tyre size labels on cars are an ADR requirement and the dimensions can (and do) vary according to that ADR. The limiting of actual dimensions is uniquely a Qld thing, I haven't noticed it for other States, they stick to the ADR's.

In the meantime I have asked TMR to explain the rule about diameter to me so await a reply

I'm genuinely interested in the reply, I asked a NSW RMS Inspector friend of a friend at a race meeting last weekend and he laughed at the dimensions requirement. Pretty much said the same as I did, it's technically unenforceable.

Not that it snows in Qld much, but how do they handle snow tyres that are allowed to be 5% larger in diameter? Probably similarly applies to most of the off road 4WD's, particularly the beach drivers, they use much larger diameter tyres.

Cheers
Gary

[Hillbilly]

Replacing a worn out tyre with a new one isn't a "modification" it's normal maintenance. The first fact is sizes get discontinued all the time by the tyre manufacturers. For example, my M3 from the factory runs Michelin Pilot Sports 235/40/17 fronts but they aren't available any more and no one else sells that size in Australia with the appropriate speed rating. But there is a 235/45/17 Michelin Pilot Sports, so I either run a 40 series tyre with a lower speed rating or a larger diameter tyre with the appropriate speed rating. What you are suggesting is that I would have to park my car and not drive it because the right spec tyres aren't available?

The other issue is that tyre size is not absolute, for example all tyres marked 225 are not 225 mm in width. Since the aspect ratio is a % of the width that number is also not absolute. So taking a 225/40/17 from one company and comparing it to a 225/45/17 from another company may not result in the theoretical change in diameter.

An example, a 225/50/15 Yokohama A050 is 235 mm wide and a 225/45/16 is 227 mm wide. But they are both 225's, aren't they supposed to be the same width? The 225/50/15 is 606 mm in diameter whilst the 225/45/16 is 605 mm in diameter. Plainly their quoted aspect ratios are not exactly accurate. Advan A050 (Semi-Slick)

If I remember correctly the regulation doesn't specify a tyre pressure, so is a 225/45/17 at 10 psi more than 15 mm larger in diameter than a 225/40/17 at 60 psi? The reason why I remember is because a number of automotive engineers were asked to comment on the regulation when it was proposed and it was pointed out that it was next to unenforceable on technical grounds. Plus it varies from State to State which in itself is a breach in the application of the ADR's, which are of course National.

Speaking of ADR's Vehicle Standard (Australian Design Rule 23/02 – Passenger Car Tyres) 2007 the act specifically refers to "nominal section height", "nominal section width" and "nominal aspect ratio". Nominal means "existing in name only" in others words they aren't absolute and can vary. For example the ADR allows a tolerance of 4% in the overall diameter as well as tolerances in width and hence aspect ratio. Unless my maths is way off 4% would mean a 24 mm in the A050's above. So the ADR's in fact allow a larger change in diameter for the same sized tyre than the Qld regulations (ooops).

Bottom line, it's a pretty damn easy defense, if by some miracle an over zealous HWP decided to pick on you because of some "nominal" (ie; inaccurate) numbers written on the side of your tyre. The new tyres comply with the ADR's ie; they are within 4%. The "old" tyre size wasn't available at the time I needed tyres. If necessary, I had the "new" tyres measured and they aren't more than 15 mm larger in diameter, because the ADR's allow 225/40/17 tyres to be 24 mm larger and still be that "nominal" size.


Cheers
Gary

Here is the reply from QLD TMR which says you are wrong as the 4% DOES NOT APPLY TO DIAMETER

The limits of 15mm larger and 26mm smaller are documented within VSB14 – National Code of Practice for light vehicle modifications and applies to passenger cars of category MA.

The 4% rule that is documented within ADR23 applies only to width. The ADR"S are applicable nationwide


To understand the overall diameter tolerance allowed, you could use one of the many online tyre size calculators to understand the difference or refer to the Australian Tyre and Rim Guide for further information.

From the information you have provided, and using the ADR23 calculations to calculate, a tyre designation of 235/45/17 would have an overall diameter of 643.5mm.

[sambb]

Storm in a tea cup I reckon. If you are that worried that going a smidge above the recommended tyre then how do you even leave the house in the morning. Do you follow every speed limit all the time, do you have a burbly cat back that they could say is a power mod, have no flash tune loaded, wont go near aftermarket bushes or an alignment that pushes the angles a bit beyond what the factory suggested, have a non standard DV that would be classed as a power mod? Do you measure your tread depths and buy a whole set at only the whiff of a tread wear indicator coming up. Do you go above the recommended tyre pressures to give it a bit more side wall for spirited driving? An insurance company could probably pull you across the coals for all of those things if they were prepared to pull you up for going up an aspect ratio size up in a sensible tyre choice. If you are that worried about the repercussions of the tyre size suggested then I assume none of that other stuff I've mentioned is done to the car either. Each to there own but I say live life on the edge if that's the cliff we are talking about.