Pajero Owners Club of South Africa

Hi All Fellow Pajero fans

I'v just bought an 2002 SWB 3200 Di D Pajero. I've seen that the standard tyre size on these vehicles is 265/70R15. The vehicle I boaght came with BFG 285/75R16 tyres that will have to be replaced within the next 5000km

Firstly, must I revert back to the 265/70R15 size with the extra cost of mags I presume?
Secondly what is the advantages and disadvantages of the larger tyre?
Thirdly, i've read alot on this forum about tyre brands, but once again, must I stick to BFG?

I still cannot believe i'm actually a Pajero owner...a dream come true!!!!

Hi Skillie,
A lot of people have personal preferances

But; you should keep the following in mind in no particular order

BFG is a good brand and a lot of people use it; there is a lot of differant models within every brand thou...

The more rubber between the rim and the road the softer the ride should be and the more floatation you will have on sand after deflating

I am not a specialist but I believe 16 is better than 15 inc as there are more tyres in 16 available which leads to an important point in that you should stay with a popular size ...if need a replacement you do NOT what to sit with an odd size in the bush

Hope this helps a bit

Enjoy you ride!

Skillie wrote:I've seen that the standard tyre size on these vehicles is 265/70R15.
...
Firstly, must I revert back to the 265/70R15 size with the extra cost of mags I presume?

Skillie, the standard tyre size is actually 265/70R16, so no need to change rims, should you decide to go for this size.

Skillie wrote:The vehicle I boaght came with BFG 285/75R16 tyres that will have to be replaced within the next 5000km
...
Secondly what is the advantages and disadvantages of the larger tyre?

One of the great features of the Gen3 is that you can fit 285/75R16 tyres without butchering the vehicle.

The standard 265/70R16 tyres have a nominal diamter of about 30.6", whereas the 285/75R16 tyres are nominally 32.8". The larger diameter means that you have slightly increased ground clearance (to the value of 25mm or so) and that the vehicle's gearing becomes a little taller (7% in fact). Taller gearing means less tractive effort at any engine speed (i.e. less acceleration) and less engine braking on downhills (especially relevant off the tar).

I am guessing that your vehicle has a manual transmission, but had it been automatic, the taller gearing would have spoilt the engine-drivetrain match (auto already has very tall gearing), which would have caused the transmission to run in torque converter mode (as opposed to running with the torque converter locked) much more frequently than before, which would increase fuel consumption and generate more heat in the transmission.

I suppose the real question is how do you like the vehicle at the moment with the big tyres. Do you find it sluggish? Is the downhill engine braking to your liking in steep off-tar descents? If you like it, then you can fit 285/75R16 tyres again.

If you would like to fit tyres that are a little smaller, but still taller than standard, you could go for 265/75R16s. These nominally have a 31.6" diameter, so you would have 13mm more ground clearance than standard and 3% taller gearing.

I think 255/85R16 tyres are a great size (33" diameter, but not too wide), but these are difficult to find in SA.

Another alternative to the standard tyres would be 245/75R16s, which are just about the same diameter as standard at 30.5", but are narrower.

Skillie wrote:Thirdly, i've read alot on this forum about tyre brands, but once again, must I stick to BFG?

BFG tyres have an excellent reputation. You won't go wrong there, but there are other good brands as well...

Skillie wrote:I still cannot believe i'm actually a Pajero owner...a dream come true!!!!

Congrats!

Hi

Thank you very much for the replies. It is very helpfull.

One of Gerrit's comments worries me a bit:

Gerrit Loubser wrote:
I am guessing that your vehicle has a manual transmission, but had it been automatic, the taller gearing would have spoilt the engine-drivetrain match (auto already has very tall gearing), which would have caused the transmission to run in torque converter mode (as opposed to running with the torque converter locked) much more frequently than before, which would increase fuel consumption and generate more heat in the transmission.

I do have the A/T box. Please explain what the above means, I am not familiar with torque converter mode and the rest. I'm new to this game....

Does this then mean that the smaller tyres would be better for the A/T box?

Thanks again

Hi Gerrit,
Thanks for the good explanation

Where would the 275/70R16 fit in?
Overall diameter?
Thanks

Skillie wrote:I am not familiar with torque converter mode and the rest.

The torque converter is a type of fluid coupling in between the engine and transmission. It works a bit like a close-coupled hydrodynamic pump and motor. Inside the torque converter there is an impeller (driven by the engine), which imparts motion to the transmission fluid inside. This transmission fluid is then redirected onto the turbine by stator vanes, where the fluid imparts energy to the turbine vanes. This results in the generation of torque. Due to the hydrodynamic nature of torque converter operation and due to the presence of the stator vanes that redirect flow, the torque converter output torque can be higher than engine output torque, which means that the vehicle can be very flexible in operation, even with very tall overall gearing.

The end result is that drive torque is transferred to the transmission, while allowing the vehicle to pull away from a standing start. In order to do this, there must be "slip" in the torque converter, i.e. it must be possible for the engine to be spinning while the transmission is spinning at a slower speed or is even stationary. This slip results in energy loss (some of the mechanical energy that the engine inputs into the torque converter is converted to heat), which is the reason why automatic versions of vehicles typically are a little less fuel efficient than their manual counterparts. Slip losses are greatest when the speed difference between the engine and transmission are greatest, reaching a maximum at torque converter stall where the transmission is stationary while the engine is spinning. In this latter situation, all energy is dissipated as heat. At cruise, the engine speed is only a little higher than the transmission speed, but there still has to be slip (and energy losses). Maximum torque multiplication occurs at torque converter stall.

In order to reduce the slip losses at cruise, the manufacturers have added a lock-up clutch that effectively connects the input and output shafts of the torque converter directly. When the torque converter is locked, the vehicle is effectively directly driven; the torque converter is elliminated from the drivetrain. This mode of torque transmission is referred to as torque converter lock-up mode or just lock-up mode. When the torque converter is unlocked, the torque converter works as outlined above. This mode of torque transmission is referred to as torque converter mode.

Now the amount of torque that can be transferred and the amount of heat that can be dissipated by the lock-up clutch are both limited (the lock-up clutch is not very large, being packaged in an area where real estate is at a high premium). This means that the lock-up clutch can only be activated in a limited regime of vehicle operation (normally at part throttle in cruise mode only). Lock-up occurs under the command of an electronic control unit that sense vehicle speed and throttle opening (among others) and basis its decisions on electronic engine and transmission maps stored in its memory.

Skillie wrote:Does this then mean that the smaller tyres would be better for the A/T box?

Larger tyres effectively make the overall gearing taller and bias the regime where the torque converter can be locked to higher road speeds. The Gen 3 DiD Auto already has very tall gearing and bigger tyres could mean that the torque converter only really remains locked up on perfectly flat road or downhills if the vehicle is operated around the legal highway speed limits. This leads to the generation of some heat that would not have been generated in lock-up mode, but this would not be of concern; the heat generation will be minimal and will not damage the transmission.

The fact that the torque converter unlocks and locks more often obviously leads to some increased wear on the lock-up clutch (also not a great concern, I would think), but there will be a detrimental effect on cruising fuel consumption if the transmission is left in D. What fuel consumption are you currently achieving on the highway, Skillie?

With the larger tyres it might also be possible to achieve good results by manually shifting in "tiptronic mode" and simply selecting 4th gear in conditions where the torque converter would not lock up in 5th. It is highly likely that lock-up would be achieved in 4th.

The bottom line is that the bigger tyres need not cause damage. Just be aware of what is going on in the drivetrain.

JDV wrote:Where would the 275/70R16 fit in?
Overall diameter?

The 275/70R16 tyres have a nominal diameter of about 31.2", so they are also a viable alternative to the standard size. The car will run about 7mm higher and the gearing will be less than 2% taller.

Hi Gerrit,
Thanks adain
It is nice to know have some specialists on the website!

Hi

I'm must say that I'm very thrilled (for the lack of a better word) by these replies. The knowledge gained from you guys are very valuable!

Gerrit Loubser wrote: What fuel consumption are you currently achieving on the highway, Skillie?

I currently get about 8.2 km/l whether I'm driving on the freeway or in the city. One of my friends have the exact vehicle but only the manual transmission and he averages about 11km/l in the city.

Gerrit Loubser wrote:The bottom line is that the bigger tyres need not cause damage. Just be aware of what is going on in the drivetrain.

Damage is one concern, but fuel consumption is also important to me. If by putting on smaller tyres I can significantly reduce my fuel consumption, its sounds like a no brainer.

I'm now thinking of the 265/75r16 which will give me a diameter between my current tyre and the standard tyre. 3.4% slower on the speedo and 26mm higher in diameter, 13mm extra clearance.

Do you guys agree with my new choice?

Thanks a lot

Hi Skillie,

Congrats on the Pajero.

My suggestion would be to stay with the original size tyres as specified by the manufacturers since the automatic DiD Pajero's are quite sensitive to a change in tyre sizes. As Gerrit mentioned, taller tyres will result in taller gearing and there have been enough posts about this (on other forums) to realize that not everyone has been happy with the results of going bigger. If my memory serves me correctly Bostoe (who is active on this forum) went for a bigger size and then changed back to the standard size again - an expensive exercise given the price of tyres these days.

265/70R16 gets my vote.

Have fun...
Bruce