Wheel sizes

Submitted: Monday, Oct 11, 2021 at 09:30
ThreadID: 142705 Views:4991 Replies:7 FollowUps:4
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I’m looking at buying some 33 inch mud terrain tyres and rims for my hzj78 troop carrier. I’ve tried to figure out the limitations of offsets on rims to keep the car legal but still can’t figure out the perfect size. I would much appreciate some help.
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Reply By: Member - John - Monday, Oct 11, 2021 at 09:55

Monday, Oct 11, 2021 at 09:55
Maybe try LCOOL online, lots of info for Toyota vehicles.
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Reply By: RMD - Monday, Oct 11, 2021 at 11:09

Monday, Oct 11, 2021 at 11:09
With independent front suspension the limit is 12.5 mm or around 25mm total. Can't remember the solid axle amount but not much more. Legal and actual physical limits are different. Any negative rim offset makes the rim/tyre centre, not in line with the steering axis as was designed and the wheel noticeably rotates if turned to lock while stationary. The offset makes the scrub radius different.
Is yours Negative scrub radius? where the steering axis is outside tyre centreline, "the usual", or Positive scrub Radius? where the steering axis point at road is inside the tyre/rim centre contact.
Either way, having more outward offset makes the steering become more unstable and road shocks immediately try and turn the wheels off their normal centre tracking paths.

The less greater outward offset you can achieve is best. When going for the perfect size, bigger ain't better, necessarily! You will use more fuel with larger dia tyres, especially if towing, although a sweet spot/speed can be achieved.

With larger offset rims the weight of the vehicle is NOT taken down through the steering axis anywhere near as much. The result of that, is, the lower and upper swivel hub bearings have to take a far more radial load than previously, they are small anyway. The weight is then transferred LESS to the inner hub bearing, ie, the large one for that task, and MORE force is placed on the outer, smaller hub bearing which is not designed to take that degree of load. AS you corner with weight on, the outer bearing increasingly has more load on it than ever before. Probably quite a bit less bearing life too, OR sudden failure if the bearings get damaged from looseness hammering the surfaces and catastrophically destruct. Way more to consider than just which rim tyre combination you want.
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Reply By: Chris J16 - Monday, Oct 11, 2021 at 15:23

Monday, Oct 11, 2021 at 15:23
Hi Mack,

As RMD has said the main issue with different offset rims from standard is the change to the scrub radius.

Rather than explain it on here, look up "Scrub Radius" on the internet there are some good sites that explain the pro's and con's and how it will change handling and braking, generally for the detriment.

This is a good link for trying out different rims and tyre sizes and how it changes things.


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Reply By: Gary W3 - Monday, Oct 11, 2021 at 20:56

Monday, Oct 11, 2021 at 20:56
I guess it begs the question of why you want muddies?
Often a topic in my 4X4 club, but the consensus is to stick to AT's. Reasons offered are that muddies are expensive, noisy and less stable - particularly on blacktop. Unless you have a burning reason to fit muddies, it might be worth canvassing opinions from experienced 4X4ers, a reliable tyre dealer or other experts. Also listen to the sound advice you have been given on this forum by other posters.
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Follow Up By: Member - McLaren3030 - Tuesday, Oct 12, 2021 at 08:03

Tuesday, Oct 12, 2021 at 08:03
Hi Guys,

I have to agree with Gary, I cannot see a justification for aggressive Muddies on a vehicle that is not regularly driven in muddy conditions. There are however tyres that have a slightly more aggressive tread pattern than AT’s, but not as aggressive as MT’s. Toyo Open Country RT’s (Rugged Terain), or Coopers ST’s, Mickey Thompson also have a similar tyre. Personally, I am no longer a fan of either Coopers or Mickey Thompson, have had too many side wall splits.

As far as Off Set Wheels, as someone else has mentioned, go on line to the LCOOL site, Landcruiser Owners On Line, there is a section for 70 Series owners to ask questions. Not to denigrate anyone on this forum, it is just that LCOOL, is a dedicated Landcruiser forum.



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Follow Up By: Member - John - Tuesday, Oct 12, 2021 at 11:19

Tuesday, Oct 12, 2021 at 11:19
Gary, an interesting comparison of MT/AT. MT vs AT
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Follow Up By: AlbyNSW - Tuesday, Oct 12, 2021 at 17:53

Tuesday, Oct 12, 2021 at 17:53
Just for clarification there are different grades of mud terrains and hybrid versions as well which are still referred to as mud tyres but are not overly aggressive and my preferred option of tyre type over an AT
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Follow Up By: Member Kerry W (Qld) - Wednesday, Oct 13, 2021 at 11:59

Wednesday, Oct 13, 2021 at 11:59
Mack, Just adding a few thoughts that came up as I read this thread ......Im not assuming you don't already know your stuff but I personally like to hear others experiences, and learn from them...so maybe this will be helpful...Once you sus out what you need re tyre size and offset - the only thing I can add to the MT/AT debate is how worthwhile Muddies are for your vehicle.
Having said that, I have run Muddies on a slightly lifted and diff lock equipped GQ for 20 years - yes I do live in the bush and yes I use them, been all over the country plus, snigging logs, exploring, and moving around my place when wet. My determining factor is that its pointless having a capable 4WD and at some point being let down because I have no traction on the odd occasion. Most of the time I have no need nor is the vehicle challenged enough to require them.
I (and my friends) have tried most brands and levels of "perceived quality" of MTs and have been reasonably scientific in weighing up the pros and cons (eg Cost, how often we used em fully, wet weather grip, noise, useful life, puncture and damage resistance etc etc) - If you are paying $4-500 per tyre then the "worthwhile-ness" is lessened. If you are paying $200-$300 for a safe and reliable tyre then OK. If you have good suspension, ground clearance and traction assistance (LSD difflocks etc) even better.
There is little difference in the "air down" question between MTs and ATs as a lot depends on the sidewall and height of the tyre, ATs are less "boggable" in sand if you are not accustomed to sand driving. MTs will dig holes faster if you have a heavy foot but will go further in sand "IF" you know what your wheels are doing. (a debate we won't go into)
The other consideration is driving in the wet you really need to slow right down and be aware that MTs will lose traction easily on some bitumen surfaces- especially in the wet and can be lethal in an emergency.
I have never regretted having MTs on the vehicle - but my other 4wd has ATs and has easily conquered the Cape York, CREB track, Vic High Country, Fraser island and many beach drives.
I know you didnt ask for opinions as to wether to buy MTs - its certinly your choice. If you asked me - I'd say go for it but dont spend too much on them and drive carefully with them. After all my trials I am running Westlake MTs - a brand commonly used in the Pilbara by many mining companies in various formats. I pay under $250 each for them and have found them far better allround (even in the wet) than the overpriced popular $300-$500 well marketed brands. Hope this adds same balance to the discussion... cheers
Kerry W (Qld)
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Reply By: Phil G - Wednesday, Oct 13, 2021 at 12:39

Wednesday, Oct 13, 2021 at 12:39
For a HZJ78, for 33" a lot of people run zero offset and either 285/75R16 on 16x8 rims or 255/85R16 on 6.5 or 7" wide rims.
I expect you will need flares.
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Reply By: Nick C13 - Thursday, Oct 14, 2021 at 17:08

Thursday, Oct 14, 2021 at 17:08
I'd suggest ringing a local automotive engineering place a chat to them regrading offset/track width as most states are different
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Reply By: Member - DOZER - Saturday, Oct 16, 2021 at 18:09

Saturday, Oct 16, 2021 at 18:09
Just to add to whats already been said, your 1hz, if not turbod, will struggle at highway speed, thats alot of resistance your adding. You may wish to weigh this up, as a turbo would be next on your list.
b4 you bag me out, walk a mile in my shoes, then your a mile away and have my shoes :)

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