Increasing Front Tire PSI

[Sensfan]

Historically, we have set our RT 190 Ranger Michelin Defender tire pressure PSI at 65 pounds front and 80 rear. The tires are three years old with modest mileage and appear to be aging well. Due to gas prices, the plan for this summer is to increase the front PSI to 80.
Good idea/bad idea/safe idea?
Sensfan

[folivier]

Overinflating based on your front weight could cause uneven wear. Slowing down will have a greater affect on your mileage.

[booster]

I wouldn't do it myself. It will affect wear as mentioned and also cause rough ride and probably worse handling. The gain in mileage would likely be trivial.



Turn off the AC, slow down, accelerate slowly, coast downhill, etc will do much more. Our 07 Roadtrek 190P will approach 17mpg at 50mph and fall to 14mpg at 70+ so that is a big improvement.

[Sensfan]

Originally Posted by folivier

Overinflating based on your front weight could cause uneven wear. Slowing down will have a greater affect on your mileage.

[QUOTE=booster;139437]I wouldn't do it myself. It will affect wear as mentioned and also cause rough ride and probably worse handling. The gain in mileage would likely be trivial.


Thanks. 65PSI it is.

[Urlauber]

Living in a windy area, I've found that the time of day and direction I go make a huge difference in mileage. One can't always time it right, but if there is flexibility, why not. Most of the year, wind picks up around 1pm and blows from the North. Going up there in the afternoons I get about 13mpg, coming down South at the same time yields >20mpg.

[jakegw2]

I think the pressure differential is partially to ensure that you will experience the more easily controlled oversteer at the traction limits rather than understeer. You might not like the emergency handling characteristics if you have the front wheels at the same pressure as the rear ones.

[Sensfan]

Originally Posted by jakegw2

I think the pressure differential is partially to ensure that you will experience the more easily controlled oversteer at the traction limits rather than understeer. You might not like the emergency handling characteristics if you have the front wheels at the same pressure as the rear ones.

Logical for sure
Sensfan

Originally Posted by Urlauber

Living in a windy area, I've found that the time of day and direction I go make a huge difference in mileage. One can't always time it right, but if there is flexibility, why not. Most of the year, wind picks up around 1pm and blows from the North. Going up there in the afternoons I get about 13mpg, coming down South at the same time yields >20mpg.

More good logic.

[jrobe]

If you asked Michelin, they would tell you to get the van weighed with both a front and rear axle weight and then inflate the tires to exactly the pressure off of their tire pressure chart for those tires.

I have no idea what your RV weighs but I wouldn't be surprised if you aren't already over inflating the front tires at 65 psi. As I recall (I have it recorded on the door tags), our Michelin Defender pressures based on our weights are 50 psi in the front and 70 psi in the rear.

[booster]

Originally Posted by jrobe

If you asked Michelin, they would tell you to get the van weighed with both a front and rear axle weight and then inflate the tires to exactly the pressure off of their tire pressure chart for those tires.

I have no idea what your RV weighs but I wouldn't be surprised if you aren't already over inflating the front tires at 65 psi. As I recall (I have it recorded on the door tags), our Michelin Defender pressures based on our weights are 50 psi in the front and 70 psi in the rear.

I have used and never liked the Michelin chart pressures, and depending on what description/recommendation you see, the reality if you talk to them is that the chart gives the MINIMUM acceptable pressure capable of safely supporting the load. They will also say that any pressure up to the tire marking max pressure is OK, but might not be best for comfort or driveability. The chart, which is not as readily available as it used to be, probably intentionally, is confusing people at best, IMO, because pressures above the chart listed ones are not overinflated at all unless they exceed the actual max specification.

[Sensfan]

Originally Posted by jrobe

If you asked Michelin, they would tell you to get the van weighed with both a front and rear axle weight and then inflate the tires to exactly the pressure off of their tire pressure chart for those tires.
I have no idea what your RV weighs but I wouldn't be surprised if you aren't already over inflating the front tires at 65 psi. As I recall (I have it recorded on the door tags), our Michelin Defender pressures based on our weights are 50 psi in the front and 70 psi in the rear.

Maybe, maybe not. We don’t put a lot of miles on our 2012 190 Ranger. Regardless, we change our tires every five years and are currently on our third set of Michelins. We regularly conduct safety checks looking for evidence of sidewall cracking and uneven wear and have found neither. Preventative maintenance includes occasional soaking the exterior sidewalls with 303 and covering them when the RT is parked.

[SeabeckStan]

I actually have checked with Michelin on this and the response was:
- it was no problem (for tires) to run with the 65 pounds inflation
- they recommended not going to 80 PSI because of uneven wear
- they did not think handling would be a problem either way

[Lucylulu]

You already got all the input you asked for but I'll add that my tire pressure monitoring system goes nuts if my tires are under or over by a few pounds. The risk is that it has no additional way to alert me of a flat tire. The warning lights are already on.

[rtbill]

The method I have used for setting the pressure in our Roadtrek's tires starts with the manufacturer's intended contact patch area. That's the maximum weight divided by the maximum pressure. For our tires, that is

3042 lb/80 psi = 38 square inches

Weigh your van. Odds are you can only get axle weights, not individual wheel weights. Divide the axle weights in half and multiply by the contact patch. Our van's front axle weighed in at 3420 lbs so the front tire pressure should be

1710 lb / 38 sq in = 45 psi.

You should not go lower than the pressure calculated this way because the tires will flex more and get hotter. Higher pressure is ok although as others have said you may get uneven wear and I can tell you the handling will degrade if you go a lot higher. Our van was delivered with 65 psi (at the factory in Kitchener)! It was pretty squirrely. The handling is much better with 45-50 psi in the front tires. Gas mileage is not noticeably affected. Highway speed makes a difference and tire brand and model also affects mileage.

Don't get obsessive about exact pressures. You don't know how accurate your pressure gauge is in the first place.