increasing tyre size from 31s to 33s

going to 33's will make your speedo read 10% less, will make your engine drink more fuel, will only give you 1 inch higher vehicle but it does get your diff higher from the ground which a suspension lift or body lift cant do, will lose horsepower, will make it hard to get tyres when you are out on a trip so take plenty of spares, ...
I have done the reverse to you,,, i have 33's in A/T's for the highway and sand driving and 31's M/T's for mud and rocks..

Gday Shaun 17

DukeAtty is right. You will get 1 inch in height and you Speedo will be out by 10%.

But the extra fuel will be bugger all and the gearing shouldn’t be a problem.
What type of 4WD is it?

My mate had 33inch muds on his Ute back cruiser and the fuel, gearing and loss of power was not even noticeable.

If you think about this stuff to hard it all becomes to difficult and the what ifs go on for ever!

What vehicle is it?

If it is a Cruiser or Patrol then 31s would be too small anyway. 33s would be much better.

If it is a medium size vehicle then it would be borderline to fit 33s. Depends on what motor and they may or may not even fit. You would probably want to look at gearing changes.

It will affect your speedo but are you positive it is reading correctly at the moment? Going up two inches would make it under read either way I'm sure.

Point 1. They will only make you 1" taller (1" at top - irrelevant, and 1" at tyre contact point)

Point 2. You will be 33/31 (6.5%) times faster than your present speedo i.e. 100 km/h indicated = 106.5 km/h actual, in effect probably "corrects" the inaccuracies you already have in the speedo (speedos normally tend to read above the actual anyway). This is all theoretical as tyres rarely measure up to their advertised diameter.

Point 3. As for M/T very much depends on what sort of terrain you normally drive on (DO NOT do it for "looks"). M/T are loud on the road, have poor roadhandling characteristics, and wear rapidly on road. You need to work out if these compromises are acceptable. Maybe A/T would be more appropriate, with a set of chains?

Shaun, I had a 60 series cruiser which had 31 x 10.5 R15 tyres on it when I got it. Seemed to be the norm, everyone had em.

But when I compared the overall height of the tyres and vehicle with my brothers cruiser which has 750/16 skinnies, my tyres were a fair bit smaller and my axles were not as high off the ground.

I went out and bought five 33 x 10.5 R15 BFG AT's and was very happy with the decision. Low down torque suffered very slightly (bugger all) but beach and general 4WDriving was noticably better. Speedo was out a bit but thats only a problem for anyone who isn't aware of it. Also, this size tyre has a lower speed rating.

I didn't get the 33 x 12.5 cos I'm not a fan of overly wide tyres. I don't beleive big fat tyres have any benefit for normal forby's, and they aquaplane more easily.

In BFG tyres you can also get 32 x 11.5 R15, which I still find a little too wide.

Cheers'

Muzz

Thanks for that all.

Ive got a 1990 hilux 4runner which is in the process of having a lot of money spent on it!!! Im looking at getting a live axle conversion on the front, just for the fact I have great wheel travel. Eventually in due course this 4runner will be a tourer which will take me anywhere that I can possibly take it.

Its got the 3VZ-E motor under the hood and the torque on it is amazing! Now Im not to sure whether or not the gearing and torque will be affected dramatically but if so then that isnt really an issue, it would just mean I would have to work around the fact that my gearing is a bit out of wack. Isnt there a saying out there that has to do with learn to adjust to different conditions? I believe so.

I think I can handle having to adjust to the slightly different conditions, shouldnt be to much of an issue. Moving up to the 33s would be a benefit when on gravel etc and specially in the mud just so I have that little bit of extra height. For me the 4wd isnt a daily driver so I wouldnt be to worried about the tyres as they would only be driven on roughly 3 times a week; Friday, Saturday and Sunday.

Ive got 31x10.5xr15 so movin up to the 33x10.5xr15 would be nice or even the 33x11/11.5 (cant remember which one).

Hi Shaun,

I currently have a 75 series landcruiser and the speedo is now accurate since fitting 33's. It is Turbo diesel and any loss in power has not really been noticed.

But 2 years ago I had a 2.8 diesel dual cab Hilux with 33's on it. Power loss was significant. Forgot what it was like to overtake for a couple of years. There were also some spots off-road that I used to get through easily in high range and after fitting 33's had to use low-range more often. Fuel consumption also increased by at least 10%

I hope this helps mate.

Brett

You will need to spend $500 on an engineers certificate just for the tires to be legal if you go 33's...

hey mate,
Just got new tyres this morning on a 1995 4runner rv6. Went up to a 32x11.5R15 MTR. Found this is the biggest size tyre I could go as I have the standard alloy rims that are 15x7inch. I considered getting other rims for it but thought it'd be a waste of money. Got the MTR's at a good price to ring around and tell people you got a cheaper quote elsewhere bout 30bucks cheaper each time till they tell ya to nick off.

As I've only had them for a day limited testing has shown with a GPS that the speedo now is accurate and that height has increased a little.

Whatever you choose as your'e not driving them daily you could consider the 33's in maybe a more serious tyre like a Simex or something........

also to fit 33's on a 4runner you need at least an 8inch rim and a 2 inch body lift and 2 inch susp lift to avoid major tyre rubbing.

Hope this helps,
Cheers.

Hi Shaun

We have just gone from 31's to 33's on the Patrol. At this stage fuel usage is about the same and the speedo is correct and ( unlike using the 31's ).' The driver' is so impressed that he is considering selling the 31's.

Just another point of view

mrs slave

Thanks for the feedback there guys.

A few weeks ago I was quoted $300 for 33x12.5x15 including rims as well for the BFG MT but from what I have been hearing around the streets, the BFG arent exactly the best tyres. Now I am going to get tyres and rims and then keep the road tyres and rims as purely road/sand use.

Now with the lift yes I have got the 2" lift around so that shouldnt be to much of a problem. What I will do though is when the time gets closer for the tyres then Ill ask the tyre dealers if I can take the new tyres for a test drive as where I was quoted offered me that option.

All i can really do for the time being is way up my options then when the time comes around then I can check out what rim size etc.

I would like continual feedback as well if people are happy with doing so as that way I can really way up the options and see what choices I will have.

Thanks so far.

Shaun

had 7.50x16's on the patrol when we bougt it then put 31x10.5x15's on. fuel consumption went up & speedo was 10%out, went to 33" BFG muddies fuel consumption went down, speedo now corect. 33,s seem to measure about 5-7mm more in diamator than 7.50x16.