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05-25-2016, 12:52 AM
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#41
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Rivet Master
2015 Interstate Ext. Coach
Lake Mary
, Florida
Join Date: Jan 2016
Posts: 504
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Today I weighted the vehicle, and scale shows:
Front is 3,520 lb (with myself)
Rear is 6,510 lb (with wife and the entire trip luggage)
On the time of wheighting the vehicle was with full tank of diesel, half-tanks of water/fluids and gas, full kitchen stuff, and full fridge of food and beverages. This is how I usually use it.
Now, following Protagonist's math, we can count my tires pressure by his table:
Front - 3,520 lb : 2 wheels : 32 sq. in. = 55
Rear - 6,510 lb : 4 wheels : 32 sq. in. = 50
It is coming the figures of:
Front tires pressure as 55 PSI in each tire,
And for the rear is 50 PSI in each of four tires.
Protagonist, please confirm??
However, the Michelin site table says for rear is even lower pressure, i.e. for my rear weight is 45 PSI in each of dual wheels. Table is below.
So, Gentelmen, I am confused of which the lowest pressure in rear wheels I can use safely?
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05-25-2016, 10:32 AM
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#42
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Rivet Master
2014 Interstate Ext. Coach
Sedona
, Arizona
Join Date: Jul 2008
Posts: 1,084
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Quote:
Originally Posted by Mr. B
Today I weighted the vehicle, and scale shows:
Front is 3,520 lb (with myself)
Rear is 6,510 lb (with wife and the entire trip luggage)
On the time of wheighting the vehicle was with full tank of diesel, half-tanks of water/fluids and gas, full kitchen stuff, and full fridge of food and beverages. This is how I usually use it.
Now, following Protagonist's math, we can count my tires pressure by his table:
Front - 3,520 lb : 2 wheels : 32 sq. in. = 55
Rear - 6,510 lb : 4 wheels : 32 sq. in. = 50
It is coming the figures of:
Front tires pressure as 55 PSI in each tire,
And for the rear is 50 PSI in each of four tires.
Protagonist, please confirm??
However, the Michelin site table says for rear is even lower pressure, i.e. for my rear weight is 45 PSI in each of dual wheels. Table is below.
So, Gentelmen, I am confused of which the lowest pressure in rear wheels I can use safely?
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Mr B, the chart you attached is for XPS RIB tires, and they are probably not recommended for the rear axle on a Sprinter since they are extra heavy duty and probably won't make the rear ride softer under any circumstances. Also the tire dimensions are non-standard: should be 215.85 x 16 I believe.
Incidentally, that chart shows the total rear axle weight, no dividing by 4 is necessary here.
Sent from my iPad using Airstream Forums
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05-26-2016, 07:23 AM
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#43
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by Mr. B
Now, following Protagonist's math:
Rear - 6,510 lb : 4 wheels : 32 sq. in. = 50
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I calculate 50.8 which rounds up to 51psi for the rear to keep the same contact area between tire and ground. Going any lower will cause additional sidewall flex and raise the tire temperature, increasing the possibility of a blowout.
__________________
I thought getting old would take longer!
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05-26-2016, 12:11 PM
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#44
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Rivet Master
2024 Interstate 19
Fulton
, Maryland
Join Date: May 2010
Posts: 3,867
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Improve the ride from Sprinter Interstate
Quote:
Originally Posted by 73shark
Or the camber is too positive which is usually the case unless the AI has been aligned since it left the factory. After reading how a lot of folks were experiencing outer edge wear and noticing the same thing, I had the front end aligned and rotated the tires/wheels. Front tire wear is now uniform. YMMV
My theory is that the extra weight added to the rear causes the front to raise slightly which would increase positive camber.
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I had my front realigned about 40,000 miles ago when I was getting more wear on the outer edges of front tires. I got new Michelins then. Now the wear is on both inner and outer edges with more wear on inner edges. Likely the pressure at 55 psi is a bit low for proper tire wear on front tires.
- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter
__________________
- - Mike
--------------------------
2024 Airstream Interstate 19e AWD
Previous: 2013 Airstream Interstate 3500 Ext Lounge
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05-26-2016, 10:16 PM
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#45
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Rivet Master
2015 Interstate Ext. Coach
Lake Mary
, Florida
Join Date: Jan 2016
Posts: 504
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Quote:
Originally Posted by UKDUDE
Mr B, the chart you attached is for XPS RIB tires, and they are probably not recommended for the rear axle on a Sprinter since they are extra heavy duty and probably won't make the rear ride softer under any circumstances. Also the tire dimensions are non-standard: should be 215.85 x 16 I believe.
Incidentally, that chart shows the total rear axle weight, no dividing by 4 is necessary here.
Sent from my iPad using Airstream Forums
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Yes, UK Dude, I was mistaken with the tires size - we all have originally equipped 215x85x16 of course, and there are no RIB but regular traction tires, though the tire pressure chart shows the same numbers for all in this size.
The following is the result of my deep researches and conversations in different American and Russian forums.
Below is a screenshot from the official Michelin chart for the load and pressure.
The load is indicated per axle, not per wheel.
As I've told before, my real weight is 3520 lbs on the front axle, and 6510 lbs on the rear axle.
As per the chart, pressure have to be following:
For my front axle it is recommended 45 PSI in each tire.
For the rear axle it is recommended 45 PSI in each tire.
In accordance with official Michelin recommendation, from now and on I will be safely keeping the tire pressure of 45 PSI in each of four rear tires.
In accordance with our Protagonist recommendation, from now and on I will be safely keeping the tire pressure of 51 PSI in each of two front tires.
Bingo, Gentelmen!
Comments are appreciated!
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05-27-2016, 05:29 AM
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#46
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by Mr. B
In accordance with our Protagonist recommendation, from now and on I will be safely keeping the tire pressure of 51 PSI in each of two front tires.
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Each REAR tire, not each front tire. You misread my post.
__________________
I thought getting old would take longer!
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05-27-2016, 11:53 AM
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#47
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Rivet Master
2015 Interstate Ext. Coach
Lake Mary
, Florida
Join Date: Jan 2016
Posts: 504
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Quote:
Originally Posted by Protagonist
Each REAR tire, not each front tire. You misread my post.
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Did you see the Michelin table I've attached?
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05-27-2016, 12:00 PM
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#48
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by Mr. B
Did you see the Michelin table I've attached?
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Yes I did.
But if you're going to say, "In accordance with our Protagonist's recommendation…" you need to actually use my recommendation rather than misusing it. Don't use my rear tire recommendation for your front tires.
If you want to go by the Michelin table exclusively for all six tires, that's fine by me. I'm just opposed to being misquoted.
Oh, and maintain your spare at the highest pressure you use for any tire on the ground. It's a lot easier to bleed out air from the spare to match the tire you're replacing than to pump it up to match.
__________________
I thought getting old would take longer!
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05-27-2016, 12:27 PM
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#49
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Rivet Master
2015 Interstate Ext. Coach
Lake Mary
, Florida
Join Date: Jan 2016
Posts: 504
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Yes sure )
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06-11-2016, 11:00 AM
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#50
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3 Rivet Member
2015 Interstate Ext. Coach
Chicago
, Illinois
Join Date: Mar 2015
Posts: 187
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Quote:
Originally Posted by 73shark
Or the camber is too positive which is usually the case unless the AI has been aligned since it left the factory. After reading how a lot of folks were experiencing outer edge wear and noticing the same thing, I had the front end aligned and rotated the tires/wheels. Front tire wear is now uniform. YMMV
My theory is that the extra weight added to the rear causes the front to raise slightly which would increase positive camber.
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I had that camber and alignment "fix" done at 5,000 miles. Unfortunately, I did not pay attention to tire wear at that point. Today at 14,500 miles, I notice the front tires are WAY WORN on outer edges ... shockingly so.
How often should we be aligning? Did I run through too many potholes or something? At this point I'm almost thinking about replacing the front tires, but don't want the same thing to happen again.
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06-11-2016, 11:23 AM
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#51
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3 Rivet Member
2015 Interstate Ext. Coach
Chicago
, Illinois
Join Date: Mar 2015
Posts: 187
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...SORRY, meant extremely worn on INSIDE edges of both front tires
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07-14-2016, 11:06 PM
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#52
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Rivet Master
2015 Interstate Ext. Coach
Lake Mary
, Florida
Join Date: Jan 2016
Posts: 504
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Report: Have a pleasure to ride few recent round trips Florida-NY with front tires pressure of 56, and 46 is each rear.
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