Ln106 33”s and vehicle longevity

SFA hilux

Active Member
Hi all. I’m probably going to be ready for a new set of tyres in the next 6 months.
I’ve been slowly making my hilux more capable, while being road legal.
its twin locked, pretty soft flexy two inch suspension with 31” km3s.
seems to have really good traction, main thing is keeping the diffs and tail shafts away from rocks, also rock steps I’m sure would be better with a taller tyre.
My model (1997) came from factory with 4:55 gears.
Sits on just over 3000rpm at 100kms.
My question is how would 33s effect how hard the engine is working and fuel economy with this gearing (obviously be doing a few less revs, maybe a good thing?) even the extra weight of the tyres must have a big effect? Anyone have any 1st hand experience? What about wheel bearing service life?
Most information I can find is just how to fit 33”s and the legality’s. (would engineer it)
Im not sure if I should just stick with 31”s as it is my daily and I want this Ute to just keep going forever.
 

Lost1?

Well-Known Member
33" tyres will affect acceleration and your ability to maintain road speed on slight inclines. The engine will continuously be under load and run hotter. If this is a must have, then I would consider fitting a turbo to increase torque and turn the taller tyres.
 

typhoeus

Well-Known Member
And, the 33's will also affect braking detrimentally, and as you may already know, the brakes are not the best around. All that rubber is heavy when spinning fast. Depending on how much time it spends on road, compared to offroad, maybe some under body protection would be a better option. . reinforced diff housings etc
 

SFA hilux

Active Member
33" tyres will affect acceleration and your ability to maintain road speed on slight inclines. The engine will continuously be under load and run hotter. If this is a must have, then I would consider fitting a turbo to increase torque and turn the taller tyres.
I can appreciate that having gone from 29”s to 31”s. On a a previous hilux
I do have a turbo already, still a slow Ute, I don’t really care about that though.
i Do care about running hotter though.
I’ve seen/read most people with hilux s with 33”s change there diff gears to the gearing that I have. (4:55)
With 31” I’m pushing 3400rpm at 110km which I very rarely do. That’s why I’m not totally convinced that 33”s will be detrimental to my reliability and economy by bring the revs down a little bit but not too much?
 

Lost1?

Well-Known Member
If the increase in tyre diameter does not reduce your cruising speed rpm to below where your engine generates its peak torque value, it won't be as bad as you think. Noting you are pulling 3400rpm, going to 33" tyres you will drop to 3200rpm at the same road speed. But the additional load will make the engine run hotter.
 

SFA hilux

Active Member
If the increase in tyre diameter does not reduce your cruising speed rpm to below where your engine generates its peak torque value, it won't be as bad as you think. Noting you are pulling 3400rpm, going to 33" tyres you will drop to 3200rpm at the same road speed. But the additional load will make the engine run hotter.
That was my line of thought too. Just had a Dyno tune and peak torque is 2700rpm and peak power is 3400rpm.
So it makes me think the tyres would almost help fuel economy. But I understand there putting more load at the same time.
If I could legally just go 32”s I would just get them next time, but if a have to get an engineers cert it’s not really worth it for 15mm of diff clearance.
 

Albynsw

Well-Known Member
Don’t forget the taller gearing will be in the lower gears too, your crawl speed will be up if that is an issue to you?
 

Lost1?

Well-Known Member
I went from 29.5" to 33" tyres on a 3.2L triton. The difference on road was noticeable. Acceleration is slower and I now reach for fourth gear when fifth always did the job at highway speeds. I am slightly over geared in low range. This is most obvious when I use the engine and gearing to maintain road speed descending spur lines in the high country. Mitsubishi low range gears are around 2:1 rather than around the roughly 2.5:1 gearing in Toyotas and Nissans, so that is another contributing factor. If you rock crawl it is likely gearing will become an issue. If not you should be ok.

Other things to consider are braking requires more effort, so you might want to ensure you are using brake parts that have a proven reputation when operating closer to the extremes of their limits. I have fitted DBA T4 rotors and ceramic front pads. They have worked well to date. Due to the reduced RPM at all road speeds I am considering giving my ute a tune or changing the turbo to improve low end torque as I tow sometimes.
 

SFA hilux

Active Member
Don’t forget the taller gearing will be in the lower gears too, your crawl speed will be up if that is an issue to you?
Yes I don’t like that. But I do seem to have a very low low range compared to a lot of 4wds I’ve been in. I think it would be an acceptable trade off.
 

SFA hilux

Active Member
My dad has a 3.2 triton. It has a LOT more power than my hilux. It yes the low range in my Ute and in my Dads is very different. But I think I have low enough gearing to get away with it.
I’m presuming to get it engineered I would need some kind of brake test anyway? There’s a bit of info online about beefing up hilux brakes.
 
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