Nothing beats having a design that tucks the vital parts up high!
Family camper / overland build thread T2 V6 TDI
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In the overland situation getting from A to B is the goal. A little precaution is way better than bashing away until something breaks. Even the OE is better than nothing and there are enough sensors etc up there to warrant thinking about them.
Tire pressure math! For offroad tires I run BFG A/T KO2 LT245/70R17 30.6" tires, and for on-road tires I run Goodyear Eagle LS2 265/50R19 110H, which are slightly bigger and much cheaper than stock. The KO2s are worth swapping out for non-offroad use, because they are loud, and handle poorly on twisty paved roads.
First, I figure out the psi/lb weight approximately for the factory tires by using the spec in this size for a Goodyear Eagle Touring 275/45R19/XL 108V:
2,205 lbs @ 50psi max pressure
50/2205 = 0.02267574 psi / lb
Next, I apply this to translate the factory pressures into approximate load weights:
Front factory spec is 39 psi:
41/0.0226757 = 1719.9 lbs
Rear factory spec is 46psi:
46/0.0226757 = 2028.603 lbs
Then, I find the psi/lb for the KO2 from BFG specs:
3000 lbs @ 80psi max
80/3000 = 0.02666667 psi / lb
Then I convert the factory weights to pressures for the KO2, rounded to the nearest psi:
Convert factory front spec:
1801.1 * 0.02666667 = approx 46 psi
rear spec:
2028.603 * 0.02666667 = approx 54 psi
Let's double check this load rating based method, and see what we get if we use math to keep the same length contact patch, in a narrower tire:
Front: 39psi*265/245 = approx 42psi
Rear: 46psi*265/245 = approx 50psi
So 4psi lower vs the load rating method... probably close enough either way.
Lastly, I do the same calculation for my Goodyear Eagle LS2 265/50R19 110H street tires:
2337lbs @ 50psi
50/2337 = 0.02139495 psi/lb
Front: 1719.9 * 0.02139495 = approx 37psi
Rear: 2028.603 * 0.02139495 = approx 43-44psi
Finally, I apply some common sense and decide that the spec of 2psi lower for the narrower LS2 tires doesn't make intuitive sense, and I will stay at the factory 39/46 value, especially since I tend to corner hard, and wear tires on the outside edges really quickly at low pressures. For the KO2s on road use, the 46/54 pressures do make a lot of sense to me- since they are narrower tires they will need more pressure at the same weight to keep about the same length contact patch. Offroad I will run these at 18-20psi.
First, I figure out the psi/lb weight approximately for the factory tires by using the spec in this size for a Goodyear Eagle Touring 275/45R19/XL 108V:
2,205 lbs @ 50psi max pressure
50/2205 = 0.02267574 psi / lb
Next, I apply this to translate the factory pressures into approximate load weights:
Front factory spec is 39 psi:
41/0.0226757 = 1719.9 lbs
Rear factory spec is 46psi:
46/0.0226757 = 2028.603 lbs
Then, I find the psi/lb for the KO2 from BFG specs:
3000 lbs @ 80psi max
80/3000 = 0.02666667 psi / lb
Then I convert the factory weights to pressures for the KO2, rounded to the nearest psi:
Convert factory front spec:
1801.1 * 0.02666667 = approx 46 psi
rear spec:
2028.603 * 0.02666667 = approx 54 psi
Let's double check this load rating based method, and see what we get if we use math to keep the same length contact patch, in a narrower tire:
Front: 39psi*265/245 = approx 42psi
Rear: 46psi*265/245 = approx 50psi
So 4psi lower vs the load rating method... probably close enough either way.
Lastly, I do the same calculation for my Goodyear Eagle LS2 265/50R19 110H street tires:
2337lbs @ 50psi
50/2337 = 0.02139495 psi/lb
Front: 1719.9 * 0.02139495 = approx 37psi
Rear: 2028.603 * 0.02139495 = approx 43-44psi
Finally, I apply some common sense and decide that the spec of 2psi lower for the narrower LS2 tires doesn't make intuitive sense, and I will stay at the factory 39/46 value, especially since I tend to corner hard, and wear tires on the outside edges really quickly at low pressures. For the KO2s on road use, the 46/54 pressures do make a lot of sense to me- since they are narrower tires they will need more pressure at the same weight to keep about the same length contact patch. Offroad I will run these at 18-20psi.
Thorough. I do it differently, totally avoid the factory recommendations and stick to the tyre manufacturer specs. There is an ideal tyre pressure for a specific tyre at a certain wheel weight. For me that is it. I hear from insiders that the factory errs on the side of the lowest acceptable pressure to help with the impression of ride comfort. In the end it is all about the donut on the rim, particularly when you are towing with a fully laden car and max tow ball weight.
If you have plenty of lee way between measured and max permissible weight on a corner then the tyre tricks can come into play where you can vary the pressures to help with over and understeer, comfort and the like. You could write a book on it and some have.
If you have plenty of lee way between measured and max permissible weight on a corner then the tyre tricks can come into play where you can vary the pressures to help with over and understeer, comfort and the like. You could write a book on it and some have.
That is a great idea, if the manufacturer publishes the chart and you have access to an accurate scale... I could not find that for any of the above tires. I hear people say on here "in Europe we don't rotate tires and they wear evenly." This makes me wonder if in some countries the Touareg pressure specs are equal for all 4 tires? I find that my front tires wear a lot faster on the outside edges only (with correct alignment), and that is likely due to the lower pressure. I would guess using the rear pressure all around would make the ride stiffer but improve fuel economy and tire life.
The single rated pressure on my Touareg is certainly nonsense, as a fully loaded vs unloaded vehicle will have very different optimal tire pressures. My old RWD Volvos all had lightly loaded vs heavily loaded pressure specs. I will err on the side of higher pressures for on road use of offroad tires, as my vehicle is always heavily loaded when heading out for long offroad trips.
Tyre pressures on the rear are usually slightly higher than those on the front to encouarage gradual understeer which most drivers can deal with rather than sudden oversteer which most drivers - apart from good ones like ourselves - can't.
And, yes. we don't rotate and tyres normally wear pretty evenly.
And, yes. we don't rotate and tyres normally wear pretty evenly.
Can you please share what the pressure specs were for your Touareg? Do your vehicle specify lower in the front also?
I much prefer a car to oversteer at the limit, it feels much safer to me. A little bit of opposite lock and you're right on track, vs plowing off the road w/ understeer. It would cause spins though in people that don't know to do opposite lock.
TOTSTT
The Overlander Track Scalpel Touareg TDI
The Overlander Track Scalpel Touareg TDI
Are you saying that the US delivered Touareg has only one tyre pressure specified??? Personally I would have no idea how they are delivered to you guys but here we have a range of tyre pressures for light and max load for all the wheel options.
Oh no... Metric units.... The poo has hit the fan now 
Indeed, we only have one specified pressure, and interestingly, it is even higher than even your fully loaded pressure. Mine, came with 275/45R19 tires and the spec was 39/46 front/rear psi, which would be 269/317 KPA.
Edit: Also interesting (and agreeing with my theory), your unloaded front and rear pressures differ by a smaller percentage (230/260=0.885) compared with our pressures (39/46=0.848), which may account for the reduced need for tire rotation.
It makes life a little difficult when we have to say we have "Rest of the World" models on a US centric site but then again, Metric is the Rest of the World measurement system.
Now that is interesting. Another new fact. There is bound to be someone on here that has a handle on this, it sure isn't me.
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