GU Patrol 285x75x16 tyre legality and engineering

Submitted: Monday, May 25, 2009 at 00:42
ThreadID: 69148 Views:4790 Replies:4 FollowUps:3
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Hi all,
I have recently put the above tyres on my GU patrol and would like to know if these are legal? (probably not)
If they are not legal how would one go about getting them engineered to make them legal and what would be a rough cost?
I am located near Gosford (NSW) and would like some advice.

There must be heaps of Patrol owners that have done the same and I would like to know if people have engineered or not?

Thanks
Chris.
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Reply By: Serendipity of Mandurah (WA) - Monday, May 25, 2009 at 07:17

Monday, May 25, 2009 at 07:17
Hi Chris

Try at the Patrol 4x4 forum forum - big discussion on your tyres

David




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Reply By: splits - Monday, May 25, 2009 at 10:50

Monday, May 25, 2009 at 10:50
Chris

The only way to be sure of any legal matters is to ask the RTA. If they say it is legal then your insurance company will accept it. if not then they have the right to refuse a claim. That is what the NRMA told me the last time I asked.

Those tyres should not be a problem regarding diameter. Mathematically they work out at 834 mm. One of the stock size tyres on GUs is the 7.50 x 16 and according to the MRF information on the link below, they are all between 810 and 827. That makes yours well within the maximum 15 mm increase currently allowed by the RTA. All other stock size tyres on your car will be within a few millimetres of those diameters.

I am not sure what the regulations say in regards to width. Check the maximum width on your tyre placard or in your owner's handbook then ask the RTA. They will tell you the maximum permissible increase.




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Reply By: Member - Bentaxle - Monday, May 25, 2009 at 11:34

Monday, May 25, 2009 at 11:34
I'm running 285/75R16 on my GU, as long as they don't extend out side whell flares then you are OK. But then I'm in WA and forget what the rules were in NSW 20+yrs ago

Mike
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Follow Up By: PATROL_ST_2004 - Monday, May 25, 2009 at 21:22

Monday, May 25, 2009 at 21:22
Hi Bentaxle

How is your gearing now, it must have been affected by taller tyres. I have 3.0Ltr Diesel, wife 4 kids and fully loaded POD trailer and can easily cruise all day up and down hills in 5th gear without laboring, surely thats not possible with taller tyres and would then need to drop back to 4th gear at times? This will then affect fuel economy also, I currently get 9.5km to 10km per 1 ltr consistently to and from work 60-80km p/hr stop start, over 10km on open road w/out trailer.

Cheers Rob
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Follow Up By: StormyKnight - Monday, May 25, 2009 at 22:28

Monday, May 25, 2009 at 22:28
I think its agreed that going to larger tyres will increase your fuel consumption but maybe not as much as you expect.

Yes your acceleration will be slower, you will need to drop back a gear earlier, the vehicle will be slightly higher resulting in more drag, but when crusing, the rpm of your engine should be closer to its most efficient speed. i.e. the point of maximum torque. Most cars even in top gear cruise above that rpm @ 100km/h so a larger diameter tyre is like having a higher 5th (or 6th) gear.

On a flat level road, with good pressure in the tyres, a reasonable fuel consumption can be acheived. There is probably more difference between the final drive ratio of a manual than of an auto. An auto generally has a much higher top gear resulting in a lower rpm @ 100km/h.

Also when making comparisons, users are often going from road tyres to larger AT or MT's. A larger road tyre would give a better fuel consumption difference indication, which has probably never really been documented.
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Follow Up By: Member - Bentaxle - Tuesday, May 26, 2009 at 16:57

Tuesday, May 26, 2009 at 16:57
I haven't noticed a dramatic increase in fuel consumption, the increase is very minimal. I have found that the acceleration is a slower, but at highway speed - 110km/h I fin d that the engine revs have decreased by 100rpm. As far as an increase in overall fuel consumption I haven't noticed any real change, when we head out offroad the old girl is pretty well loaded up, food water camping gear etc. and since I started to use the 285/75r16 tyres most of our offroad work has been in remote desert areas reuiring a lot of 4wd both high and low range and consequently fuel consumption had increased, my last remote trip to Carnarvon Ranges fuel consumption ranged between 4.2- 7.9km/L and was carrying at times as much as 3 Jerry cans of fuel and 100L of water pus usual gear

Cheers
Mike
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Reply By: StormyKnight - Monday, May 25, 2009 at 22:17

Monday, May 25, 2009 at 22:17
RTA has an online document to advise the current rules & regulations regarding tyres (& rims)...

http://www.rta.nsw.gov.au/registration/downloads/vsi/vsi09_rev4.pdf

An engineering certificate cost me $330 5 years ago.

If you can, print out the document & take it with you to the RTA. It will save you having to explain the exact document you are refering too.

Cheers
AnswerID: 366728

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