35" vs 37" Tires

[aschafer14]

Is anyone running 35" Tires and regret not going bigger. Or running 37" tires and wish they went smaller?

We just got out super singles on order are leaning towards 35's mostly due to weight, power/gearing of the vehicle and hopefully better fitment in our FG649 (trying to avoid moving the AC condenser). Our rig currently sits at 10,500 lbs dry so I was looking at the Falken Wildpeak AT4W which have a 125R load rating (3640lbs)

 

[GR8ADV]

37 all day long. Easy cruising at 65 mph (gps actual speed) at 3k rpm.

 

[gator70]

My rig got 37s on 20 inch rims. Truck is not delivered yet. The stock tire was 31. How do I adjust the speedo, or do I use a GPS device?

 

[SkiFreak]

Given that you have a FG649, I would think that 35's would be more appropriate. That truck is definitely not a powerhouse, so 37's might make going up hills a bit more painful.
Where do you plan on taking the truck? Will it mainly stay on the blacktop or fire trails, or is your intent to go on more extreme terrain?

Just because someone says this one is better than that one is not really relevant when it comes to YOUR truck.
What you intend to do with the truck needs to be taken into account in order to make the appropriate tire choice for YOUR situation.

 

[Peter_n_Margaret]

My OKA has 305/70R19.5s with a lot less power than that FG649. Yes, it is slow up hills. I live with that. The benefits outweigh the down sides. That is the diameter it was built new with, but on 16" rims.
I would consider 37s on 20" rims a poor choice. 37s on 17" rims would be far superior.
Tyres are also part of the suspension and how well they do that part of their job is about how much wall there is and 37s on 20" is reducing that too much, in my view.
Cheers,
Peter
OKA196 motorhome

 

[mog]

I agree with @GR8ADV. I went from stock to 37/12.5-16s ( Falken Wildpeak) on my 2002 FG and it was the single best improvement. The cruising speed RPM dropped to a level where the engine was not at max RPM and normal conversations were possible in the cab. No noticeable change in 'power' as the FG was underpowered before swap, so still underpowered after. (And ya, that was a while ago when you still could get 37s in a 16 inch rim size..... now 17 is the go to rim size.)

 

[aschafer14]

@mog , Glad to hear others are running the Wildpeaks. It seems most people were referencing the Toyo MT's. but I'm looking for something that will still perform in the snow. How are they performing off road for you. Here in central Oregon we don't come across much mud.

Capability wise I'm not too worried about 35's, I have 33's on our current camping rig and haven't had any issues getting where we want to go. I know the Diff hangs lower on these but I also have huge spring under leaf packs on my Scout that hang pretty low too.

So here are the gearing calc's I did based on the numbers in the repair manual. I'm not sure if the final drive gearing is any different in the newer models but I'm going to see a big jump in cruising speed either way. I just need to weigh weather 3mph is going to be worth a hit to power and would probably net out once i hit a 1% grade.

Stock Tires


35" Tires


37" Tires

 

[BigSkyBrad]

The 125 load rated tyres are maxed at 1650kg - that's 3300kg for the rear axle. Our rig sits fully loaded at 3000kg at the rear, so there's not much margin. Putting a motorbike (and it's rack) on the back would take us over at that load rating. But the 35's would be better geared than 37, especially uphill - it's a shame no-one makes 35 with a 129 or 131 rating.

For those with a Euro-spec Canter (FGB71), the diff ratio is 4.875 instead of the rest-of-world 5.285, which means even 35's are a performance sucker. I found that there is a couple of random 295/70-17's with 128 (1800kg) load rating though - but they are equivalent to a 33, so a blessing for gearing and a blight on ground clearance.

Life is a compromise!

 

[lanceatm]

Quick chime in here - all of the fist Ec`s we made where on Michelin XZL ( ~37 ) . With our need as a second stage manufacture passing the brake test ( in particular created fault of no vacuum assist ) was the most difficult. That much of an increase in rolling mass was noticeable without vacuum assist on those tiny little FUSO drum brake shoes. Passing the emergency hand brake stop was both smokey and smelly as one would expect. I bring this up because weight calculations are as mentioned critically important but there are other considerations as well. If the truck is running heavy down hill and loses vacuum ( engine dies ) it going to be a handful stop.
As side note we stayed with 35`s for the USA built trucks because of the transmission, we repragmed them specifically for our application. A 37 inch tyre was just to much if we wanted to keep a warranty with FUSO. Of course when we build our own 4x4 on FUSO or Isuzu we start with 37 and work out the gearing and brakes from there, not the other way around.
Always found it best to start any build up of a trucks from the tyre and build up from there, way less drama.

Lance

 

[charlieaarons]

Do 16” wheels still work on these vehicles?

 

[SkiFreak]

Do 16” wheels still work on these vehicles?

For the FG84/FG140 and earlier, the OEM rim size was 16" x 6.00"
Models newer than that now have 17.5" x 6.00" rim by default.

Given that the newer models still use the same axles as the older models, it is logical to think that a 16" rim will still fit on the current model trucks, but I don't know why you would go down that path.

 

[Peter_n_Margaret]

The OKA came out of the factory in the 90s fitted with 9.00R16 Michelins (which became 255/100R16). The military bought them with 10.00R16s.
Some owners have more recently fitted 325/85R16 Michelin XMLs. These are unbeatable in the desert but very ordinary on the bitumen. They are a big tyre.
MY current vehicle now has 305/70R19.5, for the load capacity. My new build OKA will have 37/12.5R17s or maybe 37/13.5R17s
Cheers,
Peter
OKA196 motorhome

 

[IdaSHO]

it's a shame no-one makes 35 with a 129 or 131 rating.

For load index? 35’s are available with a load index 129. Its what we run with our heavy SRW superduty, the 285/75r18. I stick to Toyo, and just replaced our Toyo AT2’s that had near 50k on them with a fresh set of AT3’s

 

[charlieaarons]

For the FG84/FG140 and earlier, the OEM rim size was 16" x 6.00"
Models newer than that now have 17.5" x 6.00" rim by default.

Given that the newer models still use the same axles as the older models, it is logical to think that a 16" rim will still fit on the current model trucks, but I don't know why you would go down that path.

I see a bit of concern re load capacity vs rear axle weight in Isuzu and Mitsubishi super single threads.
As Peter&Margaret often points out, 255/100R16 Michelins have good flotation and better ride than something on 18” wheels that’s also 36.5”. AND, printed on the sidewall (there’s 4 brand new ones on a pallet under a tarp next to my garage) is a load capacity of 126K/134J.
The latter is 2120kg (4675 lb) per tire at 62mph. I don’t think there’s an LT tire close to that.
And when did the offroad community forget, previously mentioned in this thread, that the tire is a really important part of the suspension?
PS: if a person wants super singles, ipso facto they’re buying new wheels. If they are going off pavement, they should find the SMALLEST diameter wheel that will fit over the brakes and accommodate a tire with the HIGHEST aspect ratio to achieve the desired diameter that works correctly with the gearing they have or intend to install. Alles klar?

 

[lanceatm]

Do 16” wheels still work on these vehicles?

Greetings
We started with a 16`s wheel with the FUSO . The single biggest reason we did not start with the Isuzu was there brake drums a larger diameter (Fuso is wider - roughly the same friction surface area) than the FUSO and can not accommodate a 16 inch wheel. At the time the most common world wide tyre fitted a 16 not a 17. So we went FUSO for our EarthCruiser platforms. Testing and compliance, it is expensive and time consuming so it is a big deal and came down to tyres. 16 good for FUSO not so Isuzu on drum brakes.