33s vs 35s vs 36s on LJ70

[Gubbtratt1]

I've recently discovered that I can legally put 35s on my LJ, and I've found some 35x10.5-16 which are actually 36.2 inch tall. Are such big tyres actually practical? It would be nice to not constantly tip over, break stuff or run out of oomph.

I'll be running stock radius arms, adjustable panhards, approx. 4cm body lift, and air suspension. Caster correction bushings in the front if necessary, stock bushings in the back.

The tyre options are:

Maxxis M8090 255/85-16 (33x9.5)
Michelin XZL 8.25R16 (34x8.5)
CST Cl18 33x10.5-16
CST CL18 275/85-16 (35x10.5)
CST CL18M 285/90-16 (36x11.5)

I'd also like them to look big without looking like a monster truck.

Since I have air suspension I can have different ride heights on and off road, in case there's any trouble with caster or U-joint angles.

 

[AirheadNut]

You’ll definitely want to regear your differentials to run 36” tires with the 2L-T engine. I probably wouldn’t run any larger than 33’s with a stock engine and diff ratio.

 

[Gubbtratt1]

You’ll definitely want to regear your differentials to run 36” tires with the 2L-T engine. I probably wouldn’t run any larger than 33’s with a stock engine and diff ratio.

Interesting. I've read on other threads that 35s are the perfect size for LJs with 4.88 gears.

I'm considering swapping the 2LT for a non-turbo B series engine sometime in the future. Would it be a good idea to run 2LT, 4.88 and 33s first and then change to 3B, 4.88 and 36s in 5-10 years, or will I have to add caster correction or suspension spacers to go from 33s to 36s? I have approximately 24cm travel with the air bags and shocks I've settled on.

 

[sark]

Interesting. I've read on other threads that 35s are the perfect size for LJs with 4.88 gears.

I'm considering swapping the 2LT for a non-turbo B series engine sometime in the future. Would it be a good idea to run 2LT, 4.88 and 33s first and then change to 3B, 4.88 and 36s in 5-10 years, or will I have to add caster correction or suspension spacers to go from 33s to 36s? I have approximately 24cm travel with the air bags and shocks I've settled on.

I'm no LJ70 expert, but when @AirheadNut mentioned regearing, I doubt they were imagining 4.88's/ I think the stock is something like 4.11 or so, so if you have 4.88 then you've already done the re-gearing suggested.

That being said, I would not go higher than 33's if my cruiser had a 2L-X in it, but that's just me.

 

[AirheadNut]

4.88's were stock in LJ's, they switched to 4.30's for the KZJ. Stock gearing with 35's or 36's would be fine if you plan for a significantly more powerful engine, but a stock 2L-T struggles even with 32's (at least here on North American highways). I drove a friend's LJ73 a while back and it struggled to hit 90km/h without going over 1200ºF EGT, running 265/75R16 tires. @GTSSportCoupe has successfully run 35's on his LJ78 with stock 4.88 diffs, but that is with significant engine modifications to massively increase power and reliability.

 

[Ash Awbery]

I run 35’s on both my LJ70 (manual) and my LJ78 (automatic) both have 4.88. They both pulled ok, and once wound up would happily sit at 70 mph on the motorway. Off road was absolutely fine.

I’m a firm believer in tall tyres (35 10.50 r16) with minimal lift for a low cog.

Both now have different engines, LJ70 has a daihatsu 2.8td DL engine and the LJ78 has a 1KZ. Which makes it much better on the highway.

 

[Gubbtratt1]

They both pulled ok, and once wound up would happily sit at 70 mph on the motorway. Off road was absolutely fine.

Was that with the original 2L(T)(E) engines or with the Daihatsu and 1KZ?

Off road performance is priority. I have other cars to drive on the road, and I'm used to both underpowered (Mercedes 508D) and way too high geared (Hyundai Getz) vehicles.

I’m a firm believer in tall tyres (35 10.50 r16) with minimal lift for a low cog.

How much lift do you need to clear 35s?

Is 0 offset wheels fine with 275-285 wide tyres, or will I need spacers/new rims?

it struggled to hit 90km/h without going over 1200ºF EGT, running 265/75R16 tires.

Sounds like there's some other problem with that cruiser, 265/75 is barely bigger than stock.

Stock gearing with 35's or 36's would be fine if you plan for a significantly more powerful engine,

Is a non-turbo B series 'significantly more powerful' enough?

 

[AirheadNut]

Sounds like there's some other problem with that cruiser, 265/75 is barely bigger than stock.

Could be, it was significantly less powerful than I expected it to be, and I didn't have high expectations either!

Is a non-turbo B series 'significantly more powerful' enough?

I think it ought to be ok, I had a BJ73 with stock diffs (4.11) and 33" tires and it was just fine. Cruised at 65-70mph. 4.88's and 35's would probably not change that too much. To maintain off-road capability you might consider putting lower range gearing in your transfer case with that large of tires.

With regards to castor correction, pretty much anything over 2" of lift you'll want to correct the castor angle or the steering will get sketchy on road.

 

[Gubbtratt1]

I found stock hub to wheelarch measurements on an old thread. Doing some quick calculations I believe 8cm front and 7cm rear lift would be pretty close to perfect for everything between 33s and 36s. As I'm planning a 3.8cm body lift for unrelated reasons (clear the PTO winch shaft from the radiator and get the fuel tank a bit higher) I'm left with less than 2 inches of suspension lift. This leaves engine power as the only concern.

I've been looking at some regearing and engine swap options. 3:1 low range gears and 5.29 ring and pinion are both around 700€ for a set. B series engines are quite rare, but 2Hs are cheap and plentiful. I'm not sure if one of those will fit in the engine bay though. Another option is to go with stock gears and stock engine and if I find it too weak do a quick axle regear on the finished vehicle. Then of course I could just go with 33s.

 

[AirheadNut]

Another option is to go with stock gears and stock engine and if I find it too weak do a quick axle regear on the finished vehicle. Then of course I could just go with 33s.

This is an excellent plan. Do incremental modifications based on what you need from the vehicle.

 

[Felde]

Is 0 offset wheels fine with 275-285 wide tyres, or will I need spacers/new rims?

I'm running 31x10.5x15 (267x76 R15) wit 0 offset on my BJ73 3B, OME springs, so nominal 2" lift.
My wheels are touching the inner fender at full articulation. So, for 33s, spacers or different offset rims, or a narrower tyer would be required.
I wouldn't go bigger than 33s. The 3B does just fine with that size, but anything bigger imho impairs performance (wow, what a word on a 3B ) and increase wear.
Cheers Ralf

 

[Gubbtratt1]

I'm running 31x10.5x15 (267x76 R15) wit 0 offset on my BJ73 3B, OME springs, so nominal 2" lift.
My wheels are touching the inner fender at full articulation. So, for 33s, spacers or different offset rims, or a narrower tyer would be required.
I wouldn't go bigger than 33s. The 3B does just fine with that size, but anything bigger imho impairs performance (wow, what a word on a 3B ) and increase wear.
Cheers Ralf

Clearance at full articulation depends on the bump stops, not the springs or shocks. Interesting observations though, most threads I've read says that 33s fit with no lift on leaf sprung 70s.

 

[Gubbtratt1]

I made a sketch of the rear suspension in FreeCAD to see how 35s, the wheelarches and the air suspension will cooperate. 275/85-16, zero offset and 9.5cm lift should work pretty good.
That's 18.5cm from top of the tyre to the wheelarch and 63cm hub to wheelarch.
Since the air bags are quite long even at full compression, 20cm, the tyres will be 9cm from the wheelarch at full compression. This is with 2.5cm body lift. Suspension wise zero body lift would be best, but I have the PTO shaft and fuel tank to consider.
This leaves 7cm suspension lift (in the back).

I haven't calculated the front yet and I won't be able to do it accurately as I have the wheelarches removed, so I can't use them as a reference.
According to my previous estimates though the front should be lifted 1cm more than the back to sit level, which would be 10.5cm, or 8cm suspension lift. This should require caster correction. Rubber correction bushings are expensive and according to this thread not very durable. There's three other options:
1. Modify axle mounts, either by moving them around the axle or drilling new holes.
2. Polyurethane correction bushes which will limit articulation a lot, but they're cheap and durable.
3. Leave the caster as it is, lower the ride height a bit if it's too unstable. I would actually prefer slightly lower ride height, but as it is I have 10cm of uptravel, and I feel like less than that will be too little even for on road driving. The source for that is just me sitting at my desk and looking at a tape measure though, so I might be very wrong.

There is about 3.5cm interference between the rear tyre and the inside wheelarch at full articulation based on the 29cm travel of the springs, but according to this thread I won't get more than 20cm difference between the wheels, and in that case I have more than enough clearance. I should be able to get slightly more travel though since the air suspension will put equal force on both sides regardless of position, while coil springs puts much more force on the higher side.
The rear axle will also get stock rubber bushings for maximum articulation. Three link would be fun and I'm sure I could make one, but I don't want the hassle of getting one through inspection.

I recently got the opportunity to test drive a way too high geared 4x4. It was terrible. If I can afford 3:1 or 4:1 low range gears when I have easy access to the transfer case I will definitely get them, but if I don't I'll start with stock gearing and if I don't like it save up some money and regear the axles to 5.29 along with some air lockers.

 

[bj70bc]

i run 35's trepadors occasionally on a bj70 with the 2.5" old man emu and 2" longer shackles ( 1" more lift half way down the leaf at the axle) no rubbing, never comes close to the bump stops.... ever
these things just dont flex really

 

[Gubbtratt1]

i run 35's trepadors occasionally on a bj70 with the 2.5" old man emu and 2" longer shackles ( 1" more lift half way down the leaf at the axle) no rubbing, never comes close to the bump stops.... ever
these things just dont flex really

I'd hope the coil sprung variant has a bit better flex, especially with air bags.

 

[Zorlac]

33" will work perfectly without modification

It will be good for the 2LT...