incorrect pillar label (tire size and pressure)

[glas1700]

To further muddy? the waters, Tire Rack lists a "rim width range" of 6.5" to 8" for a 245/75-16 tire, with a measured rim width of 7". So the wheels are at the minimum range of widths for this size tire, but would still be safe.

[sailquik]

NAFTA Sprinter Specs (per the "B" pillar sticker; the owners manual; and what mostly shows up on the
new Sprinters) are different between the 2 weight classes.
NAFTA NCV3 2500 series Sprinters with single rear wheels are specified with 245/75R16 tires that are 30.5" in diameter (683 rev/mile).
NAFTA NCV3 3500 series Sprinters with dual rear wheels (DRW) are specified with 215/85R16 tires that are also 30.4" in diameter (685 revs/mile.
Comparison was made on Continental Vanco Four Seasons which are the most common OEM tire.
So, the difference is the load carrying capacity of the wheels due to differences in wheel width, not necessarily in tire size.
2500 NCV3's use one kind of wheel (6.5J x 16 I believe) that can only be installed with the
offset inboard from the ends of the axles.
3500 NCV3's use a more universal wheel that can be mounted universally (offset inboard on the inner rears and fronts....offset outboard on the outer wheels (DRW).
NCV3 3500 Cab/Chassis for box truck/service body and RV conversions use a wider 16" wheel with a bit more offset.
Hope this clears up a little confusion.
Roger

[autostaretx]

30.5" in diameter (683 rev/mile).

Just a note regarding diameter and revs per mile...
If you carry out the calculation (5280 ft/mi * 12 in/ft) / (683 rev/mi * Pi) = 29.53 inches effective diameter (or 14.76 radius, axle-to-road)

--dick

[sailquik]

Dick,
Noted!
The 30.4" and 30.5" diameters came straight off Tire Rack.com/specs for Continental
Vanco 4 seasons (identical tires....different size and aspect ratios).
I suspect the revs/mile may loaded @ normal inflation pressure, so the radius could
be less as the tires flatten a bit on the weighted side.
Might explain the discrepancy.
Roger

[talkinghorse43]

Originally Posted by sailquik

Dick,
Noted!
The 30.4" and 30.5" diameters came straight off Tire Rack.com/specs for Continental
Vanco 4 seasons (identical tires....different size and aspect ratios).
I suspect the revs/mile may loaded @ normal inflation pressure, so the radius could
be less as the tires flatten a bit on the weighted side.
Might explain the discrepancy.
Roger

Load/inflation pressure shouldn't affect circumference. Circumference determines revs/mile.

[autostaretx]

Load/inflation pressure shouldn't affect circumference. Circumference determines revs/mile.

Radius determines *effective* circumference.
Load requires (load divided by pressure) square inches to contact the road to carry that load. (more or less, with arm-waves for tire pattern and rubber/belt strengths)
The tire has to squish down (shorter radius, more turns per mile) to bring the load-determined number of square inches in contact with the road.

During all of that, the *circumference* (if you measure it) doesn't change, but the revs/mile do...

At some super speed the tire would be brought out to near-circular, but then it would be the centrifugal force carrying the Sprinter's weight, not the tire's internal pressure.
If you don't believe load/pressure change the revs per mile, think of the "flat tire" situation.. .the road-side tire radius shrinks (to the metal wheel), but the above-wheel radius doesn't change.

--dick

[talkinghorse43]

Originally Posted by autostaretx

Radius determines *effective* circumference.
Load causes (load divided by pressure) square inches to contact the road to carry that load. (more or less, with arm-waves for tire pattern and rubber/belt strengths)
The tire has to squish down (shorter radius, more turns per mile) to bring the load-determined number of square inches in contact with the road.

During all of that, the *circumference* (if you measure it) doesn't change, but the revs/mile do...

So, you agree the 1-rotation tread length (circumference) is constant. If the 1-rotation tread length is constant, then how can the rotational speed change when the tire is deformed? I don't think the tread looses contact with the road or skids a little every rotation to make up the difference.

[CJPJ]

Comparative comparability comparison! [quote=cjpj;171083]
tire size____________ 215/85-16__________ 235/85-16
section width _______ 8.46" ________________ 9.25"
rim width range______ 5.5"-7" ________________ 6" -7"
overall diameter______ 30.38"________________ 31.72"
circumfrence________ 95.44"_________________ 99.65"
actual speed________ 60mph_________________ 57.4mph
spedometer diffrence_ 0%____________________ 4.407% too slow
diameter diffrence____ 0%____________________ 4.23%
revs per mile ________ 684.6__________________ 655.7

Originally Posted by cjpj

I see that the sprinter 3500 rim width of 5.5" is 1/2" under the recommended range of the 235/85-16 tire.

Being that the tires sidewalls are .67" taller and more askew to the rim, using a 235/85-16 tires on 5.5" rims will slightly slow the steering, and a reduction in stability will show up in cross winds as more sway, How much less stable, with slower response? Comparatively little, but noticeable!

I'm still considering the taller tire. I like the appearance in the wheel well of a larger tire. I like a small increase in the final drive ratio. I don’t like clearance between the drw being small. Larger circumference tires last longer,shortens brake life, a small increase stress increase to power train and mother inlaw will have to step .67" higher to get into the sprinter. Good and bad to everything... I think I’m over thinking this!....

.

[sailquik]

CJPJ,
Did you calculate all your values here, or is this from a particular brand and model
from one of the tire companies?
The OEM Continentals wear pretty well, but seriously lack traction in snow/ice/sand/mud.
The Michelin LTX MS2's I'm using will easily go 100k miles, and provide excellent traction
in all of the above low traction categories. I get better mileage with the MS2's as well.
(approx. 1 mpg better).
Roger

[CJPJ]

....... At the time I posted those figures 02/18/12,..Michelin is the tire manufacture, and the LTX M/S2 was the tire choice. Those figures:....... I believe....... were from a Michelin pamphlet, I got at Costco.
BTW... I found Snow chains that fit tight clearance duellies!