Larger Tyres

Submitted: Thursday, Mar 25, 2004 at 00:45
ThreadID: 11533 Views:1816 Replies:5 FollowUps:9
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Hi all,
I'm looking for advice on fitting larger diameter tyres to my recently acquired T/Diesel Landcruiser (IFS). The current 'road going' Dunlops are at the end of their life and I want to fit BFG A/T as fitted to my on-the-market Explorer.
My question is what upsides and/or downsides (engineering, power, steering, insurance, legalities) there are to fitting larger (285/75R16) tyres to my Cruiser.
Any advice would be appreciated.

Cheers
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Reply By: Roachie - Thursday, Mar 25, 2004 at 15:35

Thursday, Mar 25, 2004 at 15:35
James,
My understanding of the rules in most states are that it is quite okay to go up one tyre size above the manufacturer's largest recommended size. I am guessing thae cruiser would come out with 265/75R16 in which case the 285/75R16 would be okay.
You are lucky in that your vehicle has ample power & torque to cater for this size increase. I was thinking of putting that size on my 4.2T/D Patrol, but with it's gearing being higher than the cruiser, I would really have been working the drive-train too hard in my opinion.
Other things to consider are, more stress on wheel bearings and braking capacity could be slightly affected. Also, your speedo will be out about 5% (you'll be doing around 105k/h when your speedo shows 100), so watch out for the double-bubble-trouble.
Cheers,
Roachie
AnswerID: 51921

Follow Up By: Topend - Thursday, Mar 25, 2004 at 15:49

Thursday, Mar 25, 2004 at 15:49
Standard tyre on the Cruiser is 275/70R16. Cooper quote the 285/75R16 being a 40mm increase in diameter.

Topend
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Reply By: Member - Rohan K - Thursday, Mar 25, 2004 at 15:45

Thursday, Mar 25, 2004 at 15:45
Gidday James. Do an archive search and you'll find all you need on this topic.

In short, while Roachie is not technically correct, he still comes up with basically the right answer.

You may fit a wheel/tyre combo that is not more than 15 mm larger in overall diameter than the largest wheel/tyre combo specified on the vehicle's trye placard. Find the tyre placard, select the largest combo then come back here and I can give the exact maximum diameter you can fit (which may be satisfied by a variety of width/profile/rim combinations).

Cheers.
AnswerID: 51922

Follow Up By: Jimbo (WA) - Thursday, Mar 25, 2004 at 17:18

Thursday, Mar 25, 2004 at 17:18
That's only in NSW, Rohan.

In WA there is NO increase allowed - although you can decrease slightly! Stupid isn't it? just another reason why we should have National laws and standards.
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Follow Up By: Member - Rohan K - Thursday, Mar 25, 2004 at 19:32

Thursday, Mar 25, 2004 at 19:32
Yes, it is dumb Jimbo. QLD, NSW, Vic and SA all share the same standards on this one. I don't know what NT, ACT and Tas have.

National stds - now that would grand but a little too sensible for politicians to understand. LOL.
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Follow Up By: Truckster (Vic) - Thursday, Mar 25, 2004 at 21:38

Thursday, Mar 25, 2004 at 21:38
Jimbo, national laws are not all they are cracked up to be.

Imagine if we all took on Qlds rules? there would be a glut of 4wds forsale that were worthless...
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Reply By: Wil - Thursday, Mar 25, 2004 at 19:40

Thursday, Mar 25, 2004 at 19:40
Hi James
I am not sure about 100 series, but on my 80 series TD I run BFG A/T 285/75R16 and it has been awesome. Better ground clearance etc. Engine runs at a lower rev on long trips & fuel economy is not adversely affected either way.
Andrew(Dozer) & a few other guys also uses that or bigger on their 80s. Hopefully you could get a reply from them. Read somewhere that the Yokos are pretty good and BFGs are crap. Mine is still rather newist to comment about wear so pay to do a search on which brand. As for state/insurance, you will have to look it up properly. :)
Cheers
AnswerID: 51942

Follow Up By: Member - Rohan K - Thursday, Mar 25, 2004 at 20:06

Thursday, Mar 25, 2004 at 20:06
Wil, just because you can and have, doesn't mean it is either legal or that you haven't voided your insurance.

Tyres that breach the regulations in place in the stare in which the vehicle is registered, render the vehicle legally "un-roadworthy". You'll find all insurance companies require the vehicle to be roadworthy according to those regulations. An unroadworthy vehicle may lead to insurance being void.

If the Cruiser came with 275/70/16 and doesn't allow anything bigger, according to the tyre placard, then a 285/75/16 exceeds the allowable increase (in NSW, QLD, Vic and SA) and renders the vehicle legally unroadworthy, unless you obtain an engineer's certificate.
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FollowupID: 313757

Follow Up By: Wil - Friday, Mar 26, 2004 at 07:15

Friday, Mar 26, 2004 at 07:15
Mate
If you really want something that bad..why not go ahead and get the engineer's cert done?
After all, you only live once and the truck's got to be customised to your needs. "Eat your heart out guys"...Happy driving :)
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FollowupID: 313818

Reply By: Member - StevenL - Friday, Mar 26, 2004 at 00:24

Friday, Mar 26, 2004 at 00:24
James,

I am in SA and am buying a 120 series Prado. I want some bush capable boots on it and am replacing the original equipment highway biased Dunlop Grand Trek AT20's.

I went to my Tyre Dealer and there was a big printed poster on the wall put out by Cooper Tires (note american spelling) that suggested the one alternative tyre available for my vehicle in that brand. Cooper A/T.

The original Dunlops are 265/65R17. Mathematically they have an overall diameter of 776.3mm (265mm x 0.65 plus 17 x 25.4). The Cooper A/Ts are 265/70R17 and have an outer diameter of 802mm. This is a 26mm increase. The tyre dealer, who seemed unaware of the 15mm maximum increase when asked, said "haven't heard of a problem with these, we fit them all the time".

I went to the Toyota dealer that afternoon to ask about this issue and lo and behold there was a 120 GXL Prado ready for delivery to a customer with DEALER FITTED Copper A/T 265/70R17s. I ask "Any legal issues with these tyres?" Dealer says "none that we know of".

So much for the 15mm maximum increase under National ADRs.

Steven
AnswerID: 52007

Follow Up By: Wayne (NSW) - Friday, Mar 26, 2004 at 08:37

Friday, Mar 26, 2004 at 08:37
Steven,
I know I am going back a bit but I thought that a 1" taller and a 1" wider tyre was OK
Wayne
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Follow Up By: Member - StevenL - Friday, Mar 26, 2004 at 18:43

Friday, Mar 26, 2004 at 18:43
Yeah,

I've heard that one too but to me the rules seemed quite clear. The maximum increase in diameter is 15mm. I did not see anything on width apart from the fact that the tyre must remain inside the line of the guard in the straight ahead position (presumably to stop spay in wet weather).

Guess I'll have to ask the Transport Dept.

Steven
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FollowupID: 313937

Reply By: Bob et Joëlle - Monday, Apr 05, 2004 at 21:04

Monday, Apr 05, 2004 at 21:04
James

Hope this is not too late to help - been going back a bit on the threads. We covered the same ground on post 11692 - have come to the view it is not on for us.

B & J
AnswerID: 53302

Follow Up By: Member - James H (QLD) - Monday, Apr 05, 2004 at 23:23

Monday, Apr 05, 2004 at 23:23
Thanks Bob (and everyone else who has replied),

I have read your thread tonight. First chance I've had to look at a computer screen as have been in Albury for 7 days.

My tyre dealer highy recommends 75 profile over the 70 profile in BFG as they have a tougher sidewall - more plys apparently. Probably gives a slightly rougher ride than the 70 profile which I have no experience of in BFG. I had 265/75-16 on my explorer. No flats during 80,000km. I must say that I was pleasently surprised that the ride was as good if not better than the crap (7 flats in 2yrs) Firestones that came with the vehicle which were a more road oriented tyre.

Cheers
James
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FollowupID: 315036

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