Tire advice needed: 225/75R16 on my stock Diesel 3.9FGR

[pavelvoivoda]

Hello everyone
I need some advice for a specific model tires for my 2000 diesel 4Runner.

The tires are toyo 225/75R16 MT which are 29.3" by 8.9" on a 16" steel wheels.

The Runner was originally 3.9 FGR. I retro fitted the 'I' shift multi-mode transfer and added a rear diff lock, but kept the FGR the same.

So what I found out during a test drive with a friend's Тoyo 235/85R16 MT (31.7by9.3R16), was that during moderate flexing and turning, aside from the strain on the diffs, the front tires would catch the mud guards and...rip em out if I am more persistent!

Originally Toyota installed the longer shocks on the UN Diesels, doesn't matter what year the car was since they were to be used in places where roads are often unpaved. So even tho the length adds an inch of lift, the tires still rub against the inside fenders and mud guards.

After reading thru posts and threads to form a believe about what tires I would like for the occasional moderate off-roading, and still keep the car close to stock for a highway travel, I ended up at the 225/75R16 MT Toyos. They are a bit taller than my winter tires (235/75R15 or 28.9 by 9.3 on 15s) which is still OK for 3.9 to hold well, when the car is loaded and climbing.

Here is a pic of the regular sized 225/75R15 which are a standard tire size installed on runners (28.3") and it was a good time then, but it was not a great performer tire for the occasion. A lift is a future project.

"Coming down a mountain goat trail..."

I chose these Toyos because they are bigger than the stock tires, but not as big as the original 265/70R16 (30.6 by 10.4 on 16s which are installed on 4.1 FGRs). They should be less of a strain on the diffs during low4x4ing.
I think they are a good mix between a bit bigger tires the fast diffs can handle without problem, with great off-road traction, and OK highway/noise performance and fuel economy.

Any opinion and advice is appreciated. I did look at the 245/75R16 which are pretty much the same as the original 265/70R16s, but I think they are better on 4.1 gear ratios and up.

Let me know...

 

[JZiggy]

Interesting setup you have there, it would be very cool to drive a diesel powered 3rd gen!

Looking at the specs of the 3.0 KZ I see that HP is a concern since its 125 @ 3600 rpm but you have a lot of available torque. Speaking from experience with a 3RZ which is probably similar in feel due to a 150 hp peak output -- the stock 28" tires were perfect with a 4.10 gear ratio. Stepping up to 265/70R16 made it sluggish and hard to hold hills above 60mph. I later went to 265/75R16 and regeared to 4.56 and now it's dead on.

If you went to larger tires I would not be worried about strain on the diffs. You may be surprised at your ability to fit the 235/85R16 with a little trimming on the black plastic underlayment. When loaded and climbing hills if you currently feel like you have "just enough" power to keep the speeds you want then you would indeed need to regear to be happy with 31"+ tires.

 

[phattyduck]

Is the transmission gearing different at all with the Diesel motor(s)? You want/need lower RPM operation with the diesel, so comparing to gas engine diff ratios may not be a great comparison. My 4Runner originally had the 225/75-15 tires and 3.73 gears in a V6 auto 2WD.

You should be able to fit a "metric" 32" tire under your 4Runner without modifications - was the wheel offset far off from factory? An adjusted front alignment (caster near max) should clear the rear of the front wheel wells (and any mud flaps).

-Charlie

 

[pavelvoivoda]

Looking at the specs of the 3.0 KZ I see that HP is a concern since its 125 @ 3600 rpm but you have a lot of available torque. Speaking from experience with a 3RZ which is probably similar in feel due to a 150 hp peak output -- the stock 28" tires were perfect with a 4.10 gear ratio. Stepping up to 265/70R16 made it sluggish and hard to hold hills above 60mph. I later went to 265/75R16 and regeared to 4.56 and now it's dead on.

If you went to larger tires I would not be worried about strain on the diffs. You may be surprised at your ability to fit the 235/85R16 with a little trimming on the black plastic underlayment. When loaded and climbing hills if you currently feel like you have "just enough" power to keep the speeds you want then you would indeed need to regear to be happy with 31"+ tires.

The 4Runner came with trimmed mudguards and they even bent the pinch welds behind the mud guard. Kinda dumb... But still the 235/85R16 managed to reach and rub on the inside of the mudguards. It could be from the rim's offset.

I wont regear to anything slower, but it kinda does feel like it has just enough power to go 75miles with the big tires, while with the regular ones, i have managed speeds about 100... (over here it's around 90miles speed limits on the highways). But for the 4Runner with the longer stock shocks, speeds like that are not safe at all. The other 4Runner the 3RZ, has stiffer shocks and is much more stable at higher speeds and does better on the moose test. But anyway...

As for the HP and torque, it accelerates slower than the 5VZ and may be the same or a bit slower than the 3RZ, but with good grip tires it can pull a lot more at slower speeds. It's kind of between the 3RZ and 5VZ, but I plan on inter-cooling it, hopefully it will squeeze a few extra horses or donkeys at least under the hood!

Is the transmission gearing different at all with the Diesel motor(s)? You want/need lower RPM operation with the diesel, so comparing to gas engine diff ratios may not be a great comparison. My 4Runner originally had the 225/75-15 tires and 3.73 gears in a V6 auto 2WD.

You should be able to fit a "metric" 32" tire under your 4Runner without modifications - was the wheel offset far off from factory? An adjusted front alignment (caster near max) should clear the rear of the front wheel wells (and any mud flaps).

-Charlie

It's not a great comparison indeed, as my 3RZ has W59 transmission, with 3.7 diff(also 2WD) and diesel is 3.9, R150F, and it's like maybe 400 lbs heavier than the gasoline.

The rims in these 235/85R16s were from TLC80, don't know the offset, could be because of that, as you said. Here are a few pics with the tires:

I think that these 225/75R16 MT TOYOs will be perfect.

 

[phattyduck]

The LC80 wheels push the tires pretty far out, so that would increase rubbing issues. Also check out your front end alignment, like I said. Increasing the caster moves the (front) wheels forward, giving more clearance there for tires.

-Charlie

 

[pavelvoivoda]

The LC80 wheels push the tires pretty far out, so that would increase rubbing issues. Also check out your front end alignment, like I said. Increasing the caster moves the (front) wheels forward, giving more clearance there for tires.

-Charlie

Thanks for the advice! I will check those things out, and will most likely settle down for the Toyos as they are available and on sale here!