Suggest a 'C'

DrewE wrote:
Everything else being equal, a wider tire will reduce gas mileage, not increase it; the wider tire has greater rolling resistance (and greater traction due to a larger contact patch), and also a greater rotational inertia that takes more energy to speed up and slow down. For smallish changes in tire size, the differences are small, and other factors can also come into play such as the composition of the rubber and often the overall diameter of the tire.

There are good reasons why you don't see anything other than skinny tires on Tour de France bicycles.

Hmmmm .... most likely a larger contact patch area carrying a given amount of weight as compared to a smaller contact patch area should have worse traction on a road surface.

The larger contact area will have less pounds per square inch of contact area pressing down against the road surface - hence each square inch should provide less lateral holding force from friction with the road surface.

I believe narrow tread areas (for any given weight) do better on slippery surfaces than wide tread areas (for any given weight) because the greater pounds per square inch of narrow treads means they can "punch through" to a hard surface. Of course wide tread areas due better at not getting stuck on soft surfaces because less pounds per square inch means thay can float weight up higher on soft stuff.

I once had a Mustang that I retrofitted with big ole' wide tires. In general it handled terrible with the wide tires - but it sure "looked good"!

Everything else being equal, a wider tire will reduce gas mileage, not increase it; the wider tire has greater rolling resistance (and greater traction due to a larger contact patch), and also a greater rotational inertia that takes more energy to speed up and slow down. For smallish changes in tire size, the differences are small, and other factors can also come into play such as the composition of the rubber and often the overall diameter of the tire.

There are good reasons why you don't see anything other than skinny tires on Tour de France bicycles.

Hi Phil,

Yes 2.5 inches--but I only get 1.25 inch increase in height.

I did get a little boost in mileage again in the fall of 2019. I added a leaf to the rear springs and did new shocks. I was most pleasantly surprized.

It is a good job that I did--as one leaf was actually broken.

It will only take about 4000 years of this improved mileage to pay for the costs LOL

pianotuna wrote:
new 235/85R16 tires which will give me 1.25 inches more height; essentially they will lower the 4:56 to some other number which makes a slight difference for (better) mileage on the flat. Wider tires = lower rolling resistance = slightly better mileage. Taller tires and different side wall construction = improved ride.

Don ... raising RV height by 1.25 inches requires a 2.5 inch larger diameter tire.

Since so many Class C motorhomes come stock with 225/75R16 tires ... I guess you're saying 235/85R16 tires are 2.5 inches taller?

If so, that sounds about right because my non-stock 215/85R16 tires have a 1.2 inch larger diameter than the stock 225/75R16 tires that came on our Class C.

Interesting what you say about lower rolling resistance (i.e. wider) tires providing slightly better mileage. What that means is that when I increased my tire diameter ... that somewhat offsets the 4.56:1 differential ratio to provide slightly better mileage ... at the same time I slightly reduced mileage by going to a higher rolling resistance (i.e. narrower) tire. :h

I didn't realize the difference involving the F450. Having a little extra height is nice . You have given me something to think about.
Great info, thank you.

new 235/85R16 tires which will give me 1.25 inches more height; essentially they will lower the 4:56 to some other number which makes a slight difference for (better) mileage on the flat. Wider tires = lower rolling resistance = slightly better mileage. Taller tires and different side wall construction = improved ride.

The distance between dual tires is called the offset. For a 225/75R16 it is 10.2 inches, center to center--so the wheel offset is 5.1 inches. For 235 one needs 10.7 inches so the wheels have to be 5.35 offset. Without sufficient space between the duals they will "kiss" and wear very fast. That's why it is so important to keep the pressure in the rear wheels at the makers specification. I thought for a while I might be able to improve ride with a lower rear pressure now that I will have higher load capacity tires. That turns out to be a big fat NO!

This would not be an issue on an F-450--which has a different "hub" with enough clearance for even a 245/75R16 with the stock rims.

The wheels are coming from Southwest Wheels Co

http://www.southwestwheel.com/store/showproduct.aspx?ProductID=1841&SEName=29578

Here is the thread where someone finally found the solution!

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27002484/srt/pa/pging/1/page/1

pianotuna wrote:
I solved it by getting new rims (wheels) and a taller and narrower Toyo tire. That gave me more ground clearance and more tire weight capacity.

I think some people would be interested in a little more ground clearance, myself included.

What sizes did you use ? wheels and tires .

Bob

Jerseydevil wrote:

pianotuna wrote:
Why are you upgrading?

Bottom line is we need more space. I have a basic starter C for 4 years now, no slides, it gets tight with two teens in tow, especially if they bring a friend along.

What about simply remodeling the inside of what you already have? A house reno on wheels.

Jerseydevil wrote:
Looking to possibly upgrade next year so starting to research now. Since there are so many layouts and models could use some help.
Here is some of my requirements-
-Need bunkhouse- have two teens
-Able to comfortably sleep 6
-At rest stop would still like to use bedroom, restroom, pantry without sliding open
- restroom and shower seperate
- 30 foot minimum
-2010-2017 year range

What are you driving?

I've got a 2016 Leprechaun 260QB that meets most of your criteria.

28.5 feet long (so just 18" shorter than your target size!), with a slide out in the front.

It technically sleeps up to 8, but the couch that folds into a bed is a little lumpy for 2 but good for one, the dinette is ok for 2 if you're not too tall. the over cab bunk can fit 2, and the RV queen in the back is good for 2.

Toilet and shower is separate (sink is in with the toilet).

It's mostly usable with the slide in, but the kitchen gets cramped - you can't open the oven (the 3 burner cooktop and Microwave are accessible) and you can't open the undersink cabinet, but if you're just trying to make a quick meal on the road, it's fine.

I can't remember how many seatbelts it has, at least 4 (driver+passenger) plus 2 in the dinette. I'm pretty sure the couch has 2 seatbelts, and the dinette may have 2 on each side. So total capacity is either 4, 6, or 8 people. We only use it for 2 so I've never really checked.


Here's the floorplan and specs:

https://www.rvusa.com/rv-guide/2014-coachmen-leprechaun-class-c-floorplan-260-qb-tr18925