mileage meter and larger tires

Jim,

Thanks.

Steve

SteveAE wrote:
A couple dumb questions but here goes anyway:
- Can you really tell the difference in either ride or tire wear between 78 and 80 psi?
- How can you set a pressure this accurately when ambient temperature swings throughout the day (and from day to day) is likely to change the tire pressure by almost this amount alone?
Thanks in advance for the "education" I am sure to receive.

Steve

I cannot tell if all are at 80 or all are at 78, but it was really easy to tell on my C if they were all the same cold (meaning the inners had higher pressure hot) or the outsides were a little higher cold. I is the same as being able to tell a small toe in from a small toe out on tires when going around a corner in your car. It's the difference between stable and a big move toward conditionally stable.

You cannot. You just follow the rules about cold pressure being in the morning before the sun hits the tires and after many hours resting. You can measure at close to hot if you are quick (or have tire pressure sensors), but as soon as you add air to a hot tire, it is just warm.

Just my experience and discussions with some OEM guys here and there over the years. Treat it like any other free advice.

Jim

Hi Don, maybe the extra diameter will get you through the flooding! Just saw on the news this morning that Saskatoon is getting it now. Take care.

Hi Jim,

I'm set to 65:80:80 so I'll go with that. Thanks. I might not have check the pressures--if not for this thread.

A couple dumb questions but here goes anyway:
- Can you really tell the difference in either ride or tire wear between 78 and 80 psi?
- How can you set a pressure this accurately when ambient temperature swings throughout the day (and from day to day) is likely to change the tire pressure by almost this amount alone?
Thanks in advance for the "education" I am sure to receive.

Steve

Sounds good. Or try 80:80, then after getting a feel for the new tires, try 80:78 and compare. But yeah ditch that 75 all around ASAP.

Jim

Hi Jim,

So I'll try 65:80:78 and see how it works?

A lot of my weight is on the drivers side. 7 batteries, 2 water tanks, and the waste tanks "favor" the driver's side.

1 because Ford spec allows it (up to 5 psi different among tires)
2 because a little more pressure on the outside creates a toe in effect, adding stability (Toyota implemented this as an official OEM practice on their tiny motorhomes to fix poor handling)
2 because you will never get exactly the same pressure on sister dualie tires, so my argument is have a little more on the outside rather than risk a little more on the inside
3 because the inners run hotter at speed, inflate more hot, and create an undesirable toe out effect
4 because I speculate that it lets the shortest lived tires of the 7, the inner dualies live longer
5 because it worked well for me, is within spec, and what's it hurt to see if you notice a difference?

:)

Regardless you should see a driveability improvement from dropping the fronts closer to the right inflation for the weight, and a durability improvement putting the rears closer to the proper inflation for weight.

Jim

Hi Jim,

I just checked the pressures....and am slightly miffed

They did 70 in the front and 75 in the rear, so I've gone down to 65 in the front and up to 80 in the rear.

Are you suggesting different pressure on the inner duals? If so , why?

Nice margin gain!

So where would 78 psi on the inner duallies and 62 psi on the fronts put you in tire weight carrying capacity? Still be ahead of where you were on the old tires with a little added control and comfort?

Jim