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Old 07-27-2016, 03:20 PM   #11
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Originally Posted by HappyGuy View Post
I would steer clear of cast aluminum wheels. They will be heavier and as the other op stated, will likely not be able to carry the same load.

17 inch forged Alcoa wheels will hold more weight per wheel than the current steel wheels and the net weight gain should be negligible. A forged aluminum wheel will drop unsprung weight when holding the same size and will normally allow you to go up one wheel size without a large weight penalty and a reduction in CCC. Every pound you add in unsprung wheel weight will drop your CCC by 4 pounds. Aluminum wheels have been reported to give a smoother ride thanks to their trueness. I looked at a wheel swap myself, sticking with the same size wheel. A same size swap would net an 85 lb drop in unsprung weight. Going up an inch in size added a few pounds per wheel but the added material in the tires needed to carry the same weight would cause another bump in unsprung weight for the aluminum wheel / tire combo. The replacement inner steel wheels will add some weight on top of the added rubber weight. IMO increasing the rim size just wasn't worth the potential loss in 100 - 200 lbs of CCC.

If you're planning on upping the brakes, spring packs, axles etc to punch up the CCC capacity to the old E550 stats then the rim swap would make some sense. Of course that would be the cheap part of the work at that point

snip

The major down sides to a forged aluminum wheel are:

A lack of wheel selection

Cost (1200 - 1600 for a set of 4 16" wheels)

Added thickness of the rims prevents using 4 on the back due to a lack of wheel stud length, wheel well

Aluminum tends to fracture instead of bend. If you smack a curb hard enough to bend a steel wheel you might end up destroying the aluminum wheel. The steel wheel can be repaired, the aluminum wheel will likely need to be replaced.

I would not worry about CCC unless you are at the GAWR or GVWR of the RV. I understand the disadvantages to unsprung weight as it means something in a race car but for RV I think the unsprung / sprung weight topic will just confuse many.
When you weigh a truck or RV it is the total load on each tire as measured on the scale. The tire capacity is not affected by sprung or unsprung loading.
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I write a blog on RV tire application and safety and give seminars on tires at RV events across the US. 40 years experience as tire design & quality engineer for major tire mfg. Freelander 23QB on Chevy chassis is my RV
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Old 07-27-2016, 03:25 PM   #12
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Originally Posted by Kenny kustom View Post
Not necessarily.
I could put 19.5's on my ram, and jump up a fair bit in load capacity with g rated tired.
2016 Sabre 36QBOK
2015 Ram 3500 CUMMINS
Since it is the inflation that carries the load not the tire moving from LR-E two steps to LR-G is where the extra load capacity comes from.
The OP didn't provide his tire size (would be helpful) but I am guessing it is LT235/85R16 LR-E which is rated 3,640# @ 80 psi in single position and is about 31.73 OD.
There are no LT sizes I am aware of in 19.5" but there are Truck tires in that rim diameter with an 8-19.5 LR-F rated at 3,525# at 110 psi but it is 33.82 OD so that can't be it as the load capacity is lower.

What size 19.5 are you thinking about?
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I write a blog on RV tire application and safety and give seminars on tires at RV events across the US. 40 years experience as tire design & quality engineer for major tire mfg. Freelander 23QB on Chevy chassis is my RV
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