Yet another tyre thread

[Grizzly_Adams]

G'day all,

Been looking for some tyres for my new 7" rims lately.

Of course I've been given the speil about how good Coopers are etc. Then I saw the price. Then I remembered the past warnings and what I've seen from others who had Coopers. Then I read the thread currently in the technical section

Suffice to say Coopers won't be on my shopping list.

I like the BFG's and someone said they had success with the Goodyear Wranglers as well.

As I've got a lot of kit and fully comprehensive insurance on my baby I don't want to give the insurance company an out so I'm restricted by Qld legislation - that is tyres are not to be any more than 15mm taller than what comes standard (though I would REALLY like a set of the BFG 255/85R16's ).

In my research I've found 2 useful sites.

This one contributed by a member on another thread recently:

Miata.net tyre size calculator (metric only though from what I can see)

Because it was metric though I wanted to see what my original 750R16's were (ok ok everyone says they should be the same / similar to 235/85R16's but I wanted to see it in writing). Eventually I stumbled across this link (heaven forgive me though, it's on the Coopers website!):

Cooper 4wd Tyre Size Guide

This link is quite handy as I can zoom down to my vehicle type and see which tyres came with it from the manufacturer and it tells me their diameter - which is needed so I can work out how big I can go (legally) on the Defender..

As it stands the 750R16's are apparently 810mm tall (according to Cooper), which means I can go up to a maximum tyre height of 825mm tall.

So if I want to go taller and still be legal that leaves me with

- 235/85R16's
- 806mm diameter
- roughly same height as 750R16's, but left in here for completeness

- 245/85R16's
- 823mm diameter
- non-existant size from what I can see

- 255/80R16's
- 815mm diameter
- non-existant size from what I can see

- 275/75R16's
- 819mm diameter
- haven't looked for this size yet but not interested - too fat for me

Considering I don't particularly want to go fatter it'll be one of the top 2 for me (if I can find a 245/85R16). It looks like it'll be the good ol' 235/85R16's though.

Anyways just thought I'd post this information and hope it helps someone.

Of and if anyone knows of a manufacturer who makes 245/85R16's in Mud Terrains, drop me a line please

EDIT: Also there is an interesting discussion on the ExplorOz forum here

[incisor]

interesting

seeing you are being pedantic about the legality of the tyre size, are you sure the rim itself will be covered under your insurance, does the offset of the rim keep it within QLD laws and is increasing the rim width 1.5" legal as well ?

the std defender rim is 5.5" on the vehicles fitted with 750R16

the std defender rim is 6" on vehicles fitted with 235/85/16 ?

you are fitting 7" therefore the tyre will not sit as high as it is fitting a wider rim, is that enough to drop a 255/85R16 back into contention seeing yours orig had a 5.5" rim?

[Tusker]

Defender Boost alloys are 16x7 aren't they?

I'd suggest you avoid the rare, maybe non-existent tyre sizes. You're asking for trouble outside the major metro areas. If you're doing any big trips then stick to a size that's commonly available. The 235/85/16 is popular for good reason, it has the highest load rating around.

And there's a new BFG mud pattern coming this year, if BFG is your thing.

Regards
Max P

[Bigbjorn]

Glen, slip down to Greenslopes Mall & the Qld. Transport office there, and get a copy of "Modifications-All about modifications to motor vehicles". This booklet sets out the detail of the Dept's. requirements for rims, tyres, offsets, track alterations. Having the book is quicker and easier than using their infernal web site.

[LRHybrid100]

Go the 255 / 85 x 16 BFG Mts - you will not regret it!!!

For me it just gives the best gearing, height and traction on a D110.

Just my 10c

Oh and for insurance - just tell them the mods and get them to list them on the policy and you should have no worries.

LRH

[Turtle61]

Hi, This is from the QLD Transport Motor vehicle modifications booklet:

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...

...The maximum tyre width for a car or car derivative must not be more than 1.3 times the vehicle manufacturer’s widest optional tyre.

However, for an off-road passenger vehicle fitted with front and rear beam axles, the maximum tyre width must not be more than 1.5 times the vehicle manufacturer’s widest optional tyre...

Looking at the AT tyres and sizes at Coopers website (easiest to find info), 235/85 are 810mm (your max would be 825mm) and their next size up is 833mm so you're out of luck there. STTs, for comparison, 235/85 are 808mm (your max 823) and their next size up is 265/75 which are 813mm.
You would need to have a look at various tyre manufacturers' specs to see what fits and suits your needs. Width is not much of an issue as your max would be 352.5mm.

[Grizzly_Adams]

Yeah Inc. I meant to add the link to the Qld Transport modification document and some relevant out-takes but I've been beaten to it.

The Qld Transport modification document can be found here (PDF).

It outlines the following:

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.

The rims and tyres must not protrude beyond the bodywork of the vehicle, including flares, when viewed from above with the wheels facing straight ahead.

There's suppose to be some sort of national standard on the way but apparently it's been in the books for years - whether we'll actually see it in our lifetime is debatable

[Grizzly_Adams]

interesting

seeing you are being pedantic about the legality of the tyre size, are you sure the rim itself will be covered under your insurance, does the offset of the rim keep it within QLD laws and is increasing the rim width 1.5" legal as well ?

the std defender rim is 5.5" on the vehicles fitted with 750R16

the std defender rim is 6" on vehicles fitted with 235/85/16 ?

you are fitting 7" therefore the tyre will not sit as high as it is fitting a wider rim, is that enough to drop a 255/85R16 back into contention seeing yours orig had a 5.5" rim?

As far as I was aware my rims were 6" - not 5.5? Maybe I'm wrong, I'll have to re-check now

[Grizzly_Adams]

interesting

seeing you are being pedantic about the legality of the tyre size, are you sure the rim itself will be covered under your insurance, does the offset of the rim keep it within QLD laws and is increasing the rim width 1.5" legal as well ?

I've had a look through the vehicle modification document and it definitely does not say anything about rim size except for what I mentioned above. Based on that (and the fact the rims are properly certified and stamped etc.) I read that as legal so shouldn't have any problems there.

the std defender rim is 5.5" on the vehicles fitted with 750R16

the std defender rim is 6" on vehicles fitted with 235/85/16 ?

you are fitting 7" therefore the tyre will not sit as high as it is fitting a wider rim, is that enough to drop a 255/85R16 back into contention seeing yours orig had a 5.5" rim?

Unfortunately I don't believe it would come to that. The insurers (or even the boys in blue if I would be unfortunate enough to be pulled up) would look at the new tyre specs and base their legality on that, not the reality of how high it sits because it's a wider rim etc.

Thanks anyway, it was a nice glimmer of hope

[Grizzly_Adams]

Go the 255 / 85 x 16 BFG Mts - you will not regret it!!!

For me it just gives the best gearing, height and traction on a D110.

Just my 10c

Oh and for insurance - just tell them the mods and get them to list them on the policy and you should have no worries.

LRH

Trust me LRH I'd love to get the 255/85's but whether or not the tyres are listed on my insurance doesn't get me out of the fine print which says the tyres must be legal. Putting those tyres on a Defender in Qld would make it officially unroadworthy, it's quite clear in the Qld transport modifications document - doesn't even give you an option to get them engineered

All listing them on my insurance would mean is that if someone nicks them I can claim the tyres - if I'm in an accident the insurance company can turn around and refuse my entire claim because of illegal tyres