Ranger/BT 50 Tyre Size

Submitted: Saturday, Nov 09, 2013 at 19:49
ThreadID: 105064 Views:27582 Replies:7 FollowUps:5
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Hi. I have a 2012 Dual Cab BT 50 and am thinking of upgrading my tyres from the dealer supplied 255/70/R16. I normally use BFG but I'm looking at Kumo, Toyo and Bridgestone as well. My real dilemma is size. I think I am OK going with a 265/70/R16 because this is only 15mm bigger in diameter than what I have. I would like to go with a 265/75/R16 which is 40mm bigger in diameter but have the following concerns.
1. Is it legal. A tyre dealer told me that one can increase the tyre diameter size by 50mm legally. Is this just in WA or is it less in other states? Somebody stated in this forum that the maximum increase in diameter is 15mm.
2. The other concern is that increasing the tyre diameter and lifting the suspension can have an affect on the Dynamic Stability Control program in new vehicles. Could this void my warranty.

Any comments would be greatly appreciated.


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Reply By: Andrew D. - Saturday, Nov 09, 2013 at 20:00

Saturday, Nov 09, 2013 at 20:00
Under ADR Australian Design Regulations the only legal change to tyre size is what is specified on the tyre placard inside the drivers door or manual supplied with the vehicle.
Perhaps you need to sit down and work out what "only 15mm bigger in diameter than what I have" makes to the vehicle. IMHO only a fool changes tyres size. The manufacturer matches everything to the vehicle from engine, gearbox and diff and tyre size for optimum operation of the vehicle. Changing tyre sizes will only move the vehicle from optimum specification.
AnswerID: 521191

Follow Up By: Member - Phil G (SA) - Saturday, Nov 09, 2013 at 23:29

Saturday, Nov 09, 2013 at 23:29
Ever been offroading Andrew?
And the ADRs allow an extra 50mm diameter.
FollowupID: 801860

Follow Up By: Bazooka - Saturday, Nov 09, 2013 at 23:39

Saturday, Nov 09, 2013 at 23:39
From theToyo website:

Tyre regulations

According to Stephen Burke, Tyre Technical Manager for Toyo Tires Australia, ‘Once a vehicle is sold as new, local regulations for each state apply (when it comes to fitting replacement tyres), much of which are based on ADRs.’

There are two Australian Design Rules (ADRs) covering tyres and guards: ADR 23 and ADR 42. The former covers the labelling and construction standards of tyres fitted to Aussie cars, while the latter deals with guards for both wheels and tyres.

Replacement tyres must have a load rating equal to or better than the minimum load rating stated by the vehicle manufacturer on the tyre placard.

In addition, there is a minimum requirement for a replacement tyre’s speed rating (unless the tyre placard specifically allows a lower rating). In NSW that is 140km/h for all vehicles, plus a warning label must be fitted if the replacement tyre has a speed rating lower than the minimum required by the tyre placard. In all other states and territories it is 180km/h for passenger cars, 140km/h for off-road vehicles and 120km/h for other vehicles.

State regulations also govern allowable differences for overall diameter compared to tyre sizes listed on the tyre placard. They vary from state to state (and vehicle type to vehicle type) as follows:
State Passenger Car Off-road Vehicle
NSW +15 or -15mm +15 or -15mm
VIC +15 or -15mm +50 or -26mm
QLD +15 or -26mm +15 or -26mm
SA +15 or -15mm +15 or -15mm
WA +15 or -26mm +50 or -26mm
TAS +15 or -26mm +50 or -26mm
NT +15 or -26mm +50 or -26mm
ACT +15 or -26mm +50 or -26mm
FollowupID: 801862

Reply By: Bazooka - Sunday, Nov 10, 2013 at 00:06

Sunday, Nov 10, 2013 at 00:06

This is probably what you're seeking:
NCoP discussion: Electronic Stability Control and Vehicle Modifications
AnswerID: 521196

Follow Up By: Member - Walter D (WA) - Sunday, Nov 10, 2013 at 01:00

Sunday, Nov 10, 2013 at 01:00
Hi Bazooka

Thanks very much for your detailed reply, I appreciate it.



FollowupID: 801864

Reply By: Matthew G3 - Sunday, Nov 10, 2013 at 13:23

Sunday, Nov 10, 2013 at 13:23
Hi Walter
the 265/75/16 tyres you are looking at are only 3mm bigger than the option tyres that are available for the Wildtrack 265/60/18 . So it should be no worries but check.
AnswerID: 521215

Follow Up By: Member - adriang - Sunday, Nov 10, 2013 at 16:42

Sunday, Nov 10, 2013 at 16:42
Using the tyre size calculator, on this site and the tyre size chart, on the bridgestone website (D697AT) the difference is 29mm in diameter.
My Ranger Wildtrak has 265/60/18 tyres as std and I have a spare set of steel wheels with 265/75/16 D697AT tyres for outback touring.
The larger diameter tyres do effect the fuel economy slightly and bring the speedo up to nearly correct. At 110 by the speedo, the actual speed (from GPS) with 18" tyres is 105 and 109 with the 16" tyres.
I do not notice any difference in braking or acceleration but there would actually be a small difference.
FollowupID: 801884

Reply By: 4wheeler - Sunday, Nov 10, 2013 at 17:23

Sunday, Nov 10, 2013 at 17:23
Hi Walter,
I run BFG KM2 265/75/16 tyres on my 2012 BT 50. According to VSI 08 here in Victoria, we can run up to 50mm change in diameter over standard so for me this tyre complies and so I get 20mm extra clearance under the body approx. Unfortunately all states have different regulations at present.

Although some might suggest otherwise, IMHO I am not crazy to do this as the BT does not have that much clearance from stock and given that many tracks in the Victorian High Country need clearance for safety then I am happy with this increase. With the saggy suspension on the BT the body will sag down to standard height anyway once any weight is applied. At least I keep the axle clearance.

Speedo reads correctly with this tyre and it does not foul the body or suspension. I don't notice any difference in performance and possibly only a slight increase in fuel consumption.

I have run my own swerve test (not too violent) and have not been able to induce a fault MIL with the ESC so I believe that the stability system is functioning correctly with this tyre upgrade. If the increase was way too far outside the ECU parameters then a I would expect a fault to be induced. If ESC can't work properly with such a change given the different tyres and wheels available as standard from Ford and Mazda and the fact that loads are always changing and the fact that I could have a trailer attached then it is not much use is it. I am confident the increase has not compromised this system.

Regarding ESC, it would also have to cope with that fact that people might fit a roof rack with loads and the extra weight of a front bar and rear bar. These would alter the vehicle dynamics and Mazda sell these as options. Yes, I think ESC can cope with a slight increase in tyre diameter.
AnswerID: 521221

Reply By: gbc - Monday, Nov 11, 2013 at 05:57

Monday, Nov 11, 2013 at 05:57
Here in qld it is also legal to run 265/75/16. My new ranger will be moving that way when the originals wear out.
ESC is a reactive system, not pro-active. It CANNOT assume tyre size, road traction levels or any other guesses about loading etc.
It merely reacts to losses of traction at the wheel and brakes various wheels until traction is regained. You think the same sized cheap chinese mud tyre as the oe highway terrains is going to have the same grip on a wet highway?
AnswerID: 521240

Reply By: Member - Brenton H (SA) - Monday, Nov 11, 2013 at 09:36

Monday, Nov 11, 2013 at 09:36
My 2013 BT50 came standard with 265/65/17 and i was thinking about a wider tyre with a higher profile until I checked the width I had left to play with...virtually nothing. The standard alloys are a +55 offset which means the tyre fits v.close into the suspension. The optional rims shown in the Mazda brochure are CSA Jackals which are available in +20 to +35 offset which would allow the wider tyres seen in many pics around the place.

Soo...My dilemma is simply just a reminder to also check the available width to be able to run a larger tyre and not just the height.

AnswerID: 521248

Follow Up By: 4wheeler - Monday, Nov 11, 2013 at 20:03

Monday, Nov 11, 2013 at 20:03
I have contacted Mazda to see what is the maximum offset which is acceptable for the BT 50. The dealer did not know and so far I have had no reply from Mazda customer service.

In Victoria and probably other states the maximum track increase for the front axle/independent is 25mm. I think it might be different in some states if you have a beam axle which could be 50mm. Once again the regulations are not written particularly clearly. Rear axle is 50mm. So, as the standard steel or alloy rims which are supplied by Mazda are plus 55mm then the that means that the maximum track increase is to a plus 43mm positive offset rim. That is why I have contacted Mazda as the CSA style rims are a plus 35mm. It must be legal as Mazda supplies them as an option. So does that mean that as the manufacturer supplies a plus 35mm rim can we then go out to plus 23mm?

There are lots of good looking rims out there but from what I can work out they are not legal based on the regulations. Further some have very low load ratings so they might fit, but are not capable of carrying the load based on the maximum axle rating for the vehicle.

Obviously there are other limitations as have been mentioned and the wheel tyre combination must not protrude outside the guards and aftermarket flares would assist. If anyone has clear information that would help. Also increasing track puts added strain on bearings and other components. Not to mention insurance and warranty problems.

I await the reply from Mazda.
FollowupID: 801973

Reply By: Member - Walter D (WA) - Thursday, Nov 14, 2013 at 00:22

Thursday, Nov 14, 2013 at 00:22
Hi Everybody,

Thanks for all the responses, it has certainly given me some direction. It appears that 265/75/R16 tyres are legal but may not be accepted for Mazda warranty purposes. I telephoned Mazda Customer Service at Headquarters and asked them about fitting larger tyres and about modifying the suspension. They told me that they advised against ANY modifications. They said that although the mods may work they could void the warranty if they caused a problem with the vehicle. They did give me an address to write to regarding technical mods and I posted a letter yesterday. In the mean time I will run 265/75/R16 on a separate set of rims for bush work and use my normal tyres on another set of rims for touring and caravan travelling. I will have the rear suspension stiffened up but have not yet decided whether to go for a 50mm lift.


AnswerID: 521407

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