20” Unimog rims on a Mercedes 814 DA

[charlieaarons]

I am pretty sure all 4x4 Varios have a rear locker. What about the front? The replacement, 4x4 Sprinter 3500 (or 4500?) has a crappy low range ratio (~1.3), and no lockers anywhere in the drivetrain, even in the center. Unless one shells out mega $$$ to Aigner.

 

[Tiktaalik]

Mine has pneumatic center diff lock as well as rear diff lock. Full time 4x4 with low range engagement. Not sure about the low range ratio as I need to hook up the system.

I am pretty sure all 4x4 Varios have a rear locker. What about the front? The replacement, 4x4 Sprinter 3500 (or 4500?) has a crappy low range ratio (~1.3), and no lockers anywhere in the drivetrain, even in the center. Unless one shells out mega $$$ to Aigner.

 

[Mattyk]

How do you guys get away with running the mpt81s when the rear axle on 4x4 Vario is rated at 5600 kg? In your home country does it require engineering approval to run this wheel and tyre combo and do you have to down rate the gvm of the vehicle?

 

[Tiktaalik]

That's country dependent. I imported my GABO wheels to the US and I did a lot of research to make sure they would be road legal. I went as far as talking to the Tire and Rim Association of America. US employs self-certification, which means that if a wheel manufacturer stamps the appropriate markings for FMVSS requirements, then the wheel manufacturer implies that the wheel meets the regulations.

How do you guys get away with running the mpt81s when the rear axle on 4x4 Vario is rated at 5600 kg? In your home country does it require engineering approval to run this wheel and tyre combo and do you have to down rate the gvm of the vehicle?

 

[bulya]

Mine has pneumatic center diff lock as well as rear diff lock. Full time 4x4 with low range engagement. Not sure about the low range ratio as I need to hook up the system.




View attachment 668585

Do you know what is the #2 switch for, Is it a switch between AWD and RWD?
I assume #1 is a reduction gear

 

[Tiktaalik]

That’s the PTO, if it’s equipped with one.

 

[bulya]

Sorry for highjacking the thread, but it is a related discussion. For 1993 814DA 4x4 with OM364LA (136hp) and 5-speed manual, does super singles 285/70 r19.5 require gearing change?

I am currently in the process of buying a truck and it has a 17.5", dually at the rear. I would prefer single tires and am thinking of putting them on before shipping the truck to the US.

 

[Tiktaalik]

That depends. What truck are you buying?

My 814DA did not need a gearing change.

 

[charlieaarons]

How do you guys get away with running the mpt81s when the rear axle on 4x4 Vario is rated at 5600 kg? In your home country does it require engineering approval to run this wheel and tyre combo and do you have to down rate the gvm of the vehicle?

6150kg is more than 5600kg, according to my calculations.
As far as Bulya’s question, the 19.5s he wants to use are ~35.2” diameter, I trust everyone knows how to calculate that. The stock 17.5s are ~32”. Since the vehicle, particularly set up as a camper, will always be loaded, it depends on whether rpm (only 2200 with OM904) limits top speed and cruising speed excessively for use on your country’s highways. For EU and other non North America/Australia use, I would do a gearing change. If it’s going to NA, try leaving it and see what happens (recalibrate speedometer).

 

[Tiktaalik]

It depends. I don't have any numbers here but the 4x4 T2 is geared very low. Mine is not built out yet but I regularly start in second gear so there is no reason for me to believe that I will need to re-gear with my 20" rims.

6150kg is more than 5600kg, according to my calculations.
As far as Bulya’s question, the 19.5s he wants to use are ~35.2” diameter, I trust everyone knows how to calculate that. The stock 17.5s are ~32”. Since the vehicle, particularly set up as a camper, will always be loaded, it depends on whether rpm (only 2200 with OM904) limits top speed and cruising speed excessively for use on your country’s highways. For EU and other non North America/Australia use, I would do a gearing change. If it’s going to NA, try leaving it and see what happens (recalibrate speedometer).

 

[bulya]

That depends. What truck are you buying?

My 814DA did not need a gearing change.

have not bought it yet, sorting out documents at the moment. It is a former fire brigade truck, a box truck, not a van. 1993 814DA 4x4 with OM364LA (136hp) and 5-speed manual. Has permanent 4x4, low gear, central and middle differential lock, and PTO.

My other concerns with 19.5" is whether the engine will be able to handle it and if it is going to add significant stress on the drivetrain. Since currently truck has 205/15 r17.5 and they are way smaller than 285/70 r19.5.

 

[Tiktaalik]

I have a 1992 814DA with OM364LA and 5-speed manual.

In my experience of owning and driving it for the past 7 months I do not foresee needing gear change.

have not bought it yet, sorting out documents at the moment. It is a former box fire truck, 1993 814DA 4x4 with OM364LA (136hp) and 5-speed manual. Has permanent 4x4, low gear, central and middle differential lock and PTO

 

[bulya]

I have a 1992 814DA with OM364LA and 5-speed manual.

In my experience of owning and driving it for the past 7 months I do not foresee needing gear change.

6150kg is more than 5600kg, according to my calculations.
As far as Bulya’s question, the 19.5s he wants to use are ~35.2” diameter, I trust everyone knows how to calculate that. The stock 17.5s are ~32”. Since the vehicle, particularly set up as a camper, will always be loaded, it depends on whether rpm (only 2200 with OM904) limits top speed and cruising speed excessively for use on your country’s highways. For EU and other non North America/Australia use, I would do a gearing change. If it’s going to NA, try leaving it and see what happens (recalibrate speedometer).

Thank you for replies. If I will go with 19.5, won't do gearing change then, just speedometer recalibration.

 

[Mattyk]

Hi Charlie how did you work out this figure of 6150 kgs? Interested to know ?
Thanks Matt

 

[charlieaarons]

It’s axle load capacity of a pair of 335/80R20 Conti MPT81s.
Latest iteration of Michelin XZL in that size are even more (load index 150).
275/80R20 are much lower, but only ~36.5” instead of ~40.7”