Sprinter Tire Pressure

[Boxster1971]

Originally Posted by 3bcamper

It is a 2008 chassis,2009 AI build.

OK - thanks. I recall the 2009's were prior to Alcoa wheels becoming standard equipment.

[3bcamper]

Originally Posted by Teamaron

I still have the original contis with 20k miles, they are now 4 years old and tread is still good, just wandering about age and would love to soon put new Michelin’s on especially if it improves ride quality.

We bought Defenders earlier this year and the ride quality is fantastic compared to the Continentals.

[Protagonist]

Originally Posted by 3bcamper

It is a 2008 chassis,2009 AI build.

Brings up an excellent point: For the T1N Interstates— those built on a Sprinter 2500 van, the tire pressures are different than on the later models built on the Sprinter 3500. For the 2500 Sprinter, front tire pressure should be 47psi, and rear tire pressure should be 70psi. This is directly from the Sprinter operator's manual (though admittedly my 2011 edition, but the numbers for the earlier editions should be close to this), and is based on the lower gross front axle weight of 3970 pounds, as well as the lower gross rear axle weight of 5360 pounds but carried on only two wheels.

That gives a tire-to-road contact surface of 42.2 square inches per front tire, and 38.2 square inches per rear tire. Should be noted that the tires listed for the Sprinter 2500 in the manual are speed range N, not speed range Q as for the Sprinter 3500, which probably accounts for the higher contact surface.

[Titus]

CAS138 Your experience is identical to mine. I had front outside wear that I thought indicated an alignment issue but tire/alignment shop thought it was due to under-inflation. I had religiously maintained 61 psi and told him so. He thought the continentals should be run higher - which I did and no more front tire outside wear. I know that some on this forum believe that under-inflation would result in wear on both edges. Their reasoning makes sense - but my (and perhaps your) experience proves them wrong.

[Protagonist]

Originally Posted by Titus

Their reasoning makes sense - but my (and perhaps your) experience proves them wrong.

Not really. You presume that there is a cause-and-effect relationship between tire inflation and outer-edge wear. In actual fact, over-inflation would eliminate edge wear by causing center-tread wear, whether the front end alignment was correct or not.

Recall that I said that under-inflation typically causes edge wear on both the outer and inner edges, and on all tires, not just the front tires. So if you saw outer-edge wear only, and only on the front tires, that is not due to under-inflation.

[Titus]

Pressure was 61 psi for the first 22,000 miles. Lots of wear on the outside of the front tires (both sides). Tires were rotated. Alignment was not adjusted. 'New' front tires (ones rotated up from the rear) had even wear when put up front. Increased pressure to appx 75 psi and front tires maintained even wear until all 6 tires were replaced at 40,000 miles. Anxious to see if CAS138 has the same to report after 20,000 more miles.

[Lotus54]

My 2006 T1N 2500 show 80 psi front and rear on the Airstream door sticker.

[Protagonist]

Originally Posted by Titus

Pressure was 61 psi for the first 22,000 miles.

'New' front tires (ones rotated up from the rear) had even wear when put up front.

You just made my case. 61psi in the rear showed even wear, but 61psi in the front didn't. So 61psi was not under-inflated, and the problem is not to do with tire pressure but rather with something else at the front end.

[Titus]

What? Nothing was changed but the pressure. Maybe the tire guy actually knows something about tires.

[Protagonist]

Originally Posted by Titus

What? Nothing was changed but the pressure.

That's my point, but somehow you can't see it. Same tires. Same weight carried per tire. Same pressure per tire. Should produce the same wear per tire.

I'm trying to convince you to get a front end alignment to even out the tire wear on the front end, and not just adjust tire pressure. That's why the alignment is adjustable, so you can adjust it!

I do not understand why I can't make you understand. So I give up even trying. You win. Don't get an alignment. Run with the tires 15 pounds over-inflated. And if you lose steering in slippery conditions to those over-inflated front tires not making adequate contact with the pavement, then I hope winning this argument gives you great comfort after the crash.

[Titus]

I had alignment checked at 40,000 miles when I switched to Michelin tires. To my surprise the camber was 0.1 on both sides. The specs call for 1.3 but many advise setting it to 0 because of the weight of the AI. I didn't need to reset it to 0 because it was already there. Toe was off a bit - overall toe was OK but it was not quite 'balanced' between the two sides. But all of this was 20,000 miles after increasing tire pressure. I don't understand tire dynamics any better than you do, I am simply reporting on my experience.

[CapriRacer]

Originally Posted by Protagonist

That's my point, but somehow you can't see it. Same tires. Same weight carried per tire. Same pressure per tire. Should produce the same wear per tire. .......

Ah ..... Mmmmmm ....... not exactly.

It seems there are other things more important than pressure with regards to tire wear - and while you've mentioned one of them - alignment - there is another that is also important - wheel position.

Steer tires tend to wear the shoulders and drive tires tend to wear the center. This sometimes leaves folks to falsely conclude that they have a pressure problem.

The fix for this is regular tire rotation - BUT - some vehicles aren't set up for that. Some duallies have alloy wheels where the outside face is polished, but on a dually, that is a different side for the fronts tires compared to the rears! WORSE: They sometimes have a steel inner wheel!

IMHO, if that situation exists, the right move is to just live with it. Messing with the pressure just changes the size of the footprint and that changes the grip level.

[hmason72]

Since this thread is about tire pressure, I posted this question here.

I must be doing something wrong. I follow the menu options to see tire pressure on my 2018 Interstate with key in position 2. But I see oil pressure OK, the coolant temp, and back to the milege display. No option with up down arrows goes to tire pressure. And in the settings there is a place to opt for PSI says the manual, but I have no such option. Is this suppose to work? I have no idea how to monitor tire pressure or if this system is even installed.

[Pahaska]

Tire pressure monitors are not installed on the 3/4 ton chassis, only on the half-ton chassis as required by law.

[hmason72]

Thanks for the info. The users manual that came with the coach from Mercedes shows it, I guess incorrectly. Appreciate the clarification.

Hank

[3bcamper]

Originally Posted by 3bcamper

I'm finding that I have to inflate tires every few days on all the tires, but especially the inner duallies. Pressure is dropping to 30 psi. I had them checked twice since we bought them in Feb. (Michelin Defenders), but it's still happening. Is this normal? What are you finding with your AI?

I had this type of valve installed on all six wheels (I have all steel wheels). These seem to be doing the job so far.

[3bcamper]

Originally Posted by 3bcamper

I had this type of valve installed on all six wheels (I have all steel wheels). These seem to be doing the job so far.

I'm trying to post a photo, but cannot figure it out...

[Air99]

Originally Posted by 3bcamper

I'm trying to post a photo, but cannot figure it out...

You have 3 choices to attach, first from left is taking a new picture via your device camera, next is selecting a picture from your photo library, or attaching a file or link. Choose OK for next pop up asking for your permission. You can test run them all and choose Cancel to back out, no harm no foul will result. Good luck,

[3bcamper]

Okay, thank you. This is the tire valve I had GCR install on all six wheels. So far, they're working great. Best performance I have had so far.

[3bcamper]

Another photo of my new tire valves.